BHABHA ATOMIC RESEARCH CENTRE
Nuclear Agriculture and Biotechnology Division, Mumbai-400085, India.
B.K. Das and S.G. Bhagwat, and A. Saini and N. Jawali
(Molecular Biology Division).
The HMW-glutenin subunits are important for improving the bread-making quality of wheat. We selected desirable HMW subunits such as 5+10 (coded by Glu-D1d) in early generation breeding material in a high yielding background. We also are working to recombine durable rust-resistance genes such as Sr24, Lr24, and Sr31 with good quality subunits. Intervarietal crosses were made and in the F2 generation and single-plant selections were made. Single-plant harvests from the F2 plants were analyzed for HMW-glutenin subunits by SDS-PAGE. Plants with subunits 5+10 were selected and carried forward. The F3 plant progeny were grown and their agronomic attributes are being evaluated. Resistance to rusts under field conditions in these lines is being studied by artificially injecting a stem rust spore suspension at the seedling stage. We also are developing and identifying DNA markers for quality traits and rust-resistance genes. The F2 progenies were raised by crossing suitable parents and PCR-based markers are being evaluated.
Earlier, the sphaerococcum locus was transferred in to an agronomically suitable background. From the backcross population, plants with sphaerococcum and nonsphaerococcum morphology were selected and crossed. An F2 population resulting from this cross was grown in the field. The population segregated for sphaerococcum and nonsphaerococcum types. Culm length, spike length, number of spikelets/cm of spike, and leaf type (erect/drooping) were recorded. On the basis of culm length, the segregation pattern indicated shorter culms were governed by a single, recessive locus. We currently are analyzing morphological data and DNA from individual plants using RAPDs to study variation at the DNA level associated with sphaerococcum locus.
E. Nalini and N. Jawali (Molecular Biology Division) and S.G. Bhagwat.
Most often a linkage map is prepared using populations obtained from two highly diverse genotypes. Such maps may not be best suited for practical use as the markers used in obtaining the map may not be polymorphic among the cultivars used as parents in a breeding program. The cultivars Kalyansona and Sonalika, which were extensively grown at the beginning of Green Revolution and subsequently widely used in breeding programs, showed variation for seed and plant morphology, agronomic characters, and HMW-glutenin subunits. An F2 population from a cross between the two cultivars was grown and phenotypes for the morphological traits and HMW-glutenin subunits were scored. Methods for minipreparation of DNA from wheat leaves suitable for PCR-based marker analysis and long term storage were developed and used to isolate DNA from the leaves collected from the plants in the F2 generation. Arbitrarily primed polymerase chain reaction (AP-PCR), RAPD, and ISSR primers are being screened for polymorphism in the parents and subsequently used to genotype the F2 population. Analysis of the data to determine the association of markers with morphological and agronomically important traits is underway.
S.G. Bhagwat.
Stomata/mm^2^ of leaf and leaf area are usually negatively correlated. We are studying an experimental selection that was irradiated using gamma rays. Plants in the M9 generation were grown in the winter of 2002-03. Flag-leaf blade area of five main tillers was estimated using leaf length and maximum leaf width. Stomatal frequency was estimated by making leaf impressions of the upper surface. Analysis is in progress. So far, results show that the range of stomata/mm^2^ was 100 + 2.9 to 63.6 + 8.8 corresponding to leaf areas of 11.1 + 0.4 and 27.7 + 2.61 cm^2^, respectively. An overall negative association between stomatal frequency and leaf area was observed, however, lines with less than expected stomatal frequency were observed. Results indicate that variability for leaf area and stomata/mm2 was induced.
An experimental line with sphaerococcum morphology was mutagenized using gamma rays. A mutant with altered culm and rachis length was isolated. The leaves also showed altered morphology. The data (mean of three) on pot-grown plants for culm length, spikelets/cm of rachis, flag-leaf blade area (cm2), and stomata/mm^2^ for the parent and the mutant were 31.3, 3.61, 28.4, 64.1, and 37.9, 2.43, 13.7, and 91.2, respectively. One F1 plant had taller culms and intermediate numbers of spikelets/cm of rachis, flag-leaf blade area, and stomata/mm2 values.
Two experimental lines with contrasting leaf areas showed that the larger-leafed parent had an area of 26.2 cm^2^ and a stomatal frequency 70.1/mm^2^. The corresponding values for the smaller-leafed parent were 11.5 for leaf area and 79.2 for stomatal frequency, each a mean of three observations. The mean of two F1 plants showed that the leaf area was intermediate (20.6 cm^2^) and the stomatal frequency was lower than expected (66.9/mm^2^).
S.G. Bhagwat, J.K. Sainis (Molecular Biology Division), and S.P. Shouche and R. Rastogi (Computer Division).
Image analysis has the potential for use in assessing quality and identifying cultivars in wheat. Previously, we studied Indian wheat cultivars with a 'Comprehensive Image Processing Software'. We were able to show that the cultivars could be distinguished from each other. To test the capability of the software and hardware combination, we have subjected genetically related experimental wheat lines to image analysis. The results show that out of the six possible pair combinations, four were distinguishable.
BHARATHIAR UNIVERSITY
Cytogenetics Laboratory, Department of Botany, Coimbatore-641 046, India.
V.R.K. Reddy and G. Kalaiselvi.
Seven stem rust-resistance genes (Sr24, Sr25, Sr26, Sr27, Sr28, Sr31, and Sr38), four leaf rust -resistance genes (Lr19, Lr24, Lr26, and Lr37), and two stripe rust-resistance genes (Yr9 and Yr17) present either singly or in combination (linked), were transferred from aline hexaploid wheat cultivars (K8962, HW 2034, and HW4001). A simple backcross method was used to transfer these genes, and BC2F5 and BC5F5 NILs were made from all 21 cross combinations. The transfer of rust-resistance genes into Indian wheats was confirmed through morphological, genetic, and molecular markers. Morphological markers for awnless spikes (Darf/3Ag*6//KITE; Sr24 + Lr24), lax spike (TH*8/VPM-1; Sr38 + Lr37 + Yr17), reduced yellow pigment in the flour (COOK*6/C80-1; Sr25 + Lr19), club spike (W3353; Sr27), and waxy color (VEE S; Sr31 + Lr26 + Yr9) were used. Respective NILs were crossed with the universal susceptible cultivar Agra local.
All F1 hybrids were completely resistant to rust, whereas the F2 plants were segregating as 3 resistant:1 susceptilbe. Similarly, the BC1 hybrids segregated in a ratio of 1 resistant:1 susceptible. The F2 segregation from F1 monosomics and disomic hybrids between monosomic Chinese Spring wheat and the NILs for Lr19 (K8962), Lr37 (HW 2034), and Lr24 (HW 4001) segregated 3:1 resistant:susceptible for rust-resistance genes except for lines 7D, 2A, and 3D, respectively, thus confirming the incorporation of rust resistance into that chromosome of the wheat parent.
The NILs and the parental lines for leaf rust-resistance gene Lr24 were screened at the molecular level using the previously identified RAPD primer OPJ-09 (Schachermayr 1995), which has complete linkage to Lr24. This primer amplified a diagnostic 550-bp fragment and resulted in one additional band in the resistant NILs. This band was absent in the susceptible parents.
Reference.
CH. CHARAN SINGH UNIVERSITY
Department of Agricultural Botany, Meerut 250 004, India.
P. K.Gupta, H.S. Balyan, M. Prasad (Present address IPK, Corrensstrasse 3, D-06466, Germany), J.K. Roy (Present address Department of Biology, Dalhousie University, Halifax, Canada), R. Bandopadhyay, N. Kumar, S. Sharma, P.L. Kulwal, S. Rustgi, R. Singh, A. Goyal, A. Kumar, and S.N. Prashanth.
QTL-interval mapping using the International Triticeae Mapping
Initiative mapping population.
QTL analysis for yield and yield-contributing traits. Using
QTL Cartographer, QTL-interval mapping for seven yield and yield-contributing
traits (tillers/plant, spike length, spikelets/spike, grains/spike,
biological yield, harvest index, and grain yield) was undertaken
in bread wheat using a set of 110 RILs of the International Triticeae
Mapping Initiative mapping population (ITMIpop). For each trait,
recorded values were averaged from 15 plants/genotype (five plants
from each of the three replications). Data on a set of 358 mapped
molecular markers for the ITMIpop (both genotype data and genetic
distances) were provided by M.S. Röder (IPK, Gatersleben,
Germany) and were used for QTL analysis. Composite interval mapping
(CIM) resolved 29 QTL (LOD = 2.1 to 5.5) distributed on 16 chromosomes
(six from the A genome and five each from the B and D genomes).
Seven molecular markers associated with QTL also showed significant
marker-trait association, both in regression analysis and t-tests
and can be used for MAS. The QTL effects (R2) ranged from 5.3
% to 50.6 % and, when measured irrespective of LOD score, gave
a characteristic L-shaped distribution suggesting that there are
many minor QTL that should also be taken into account during MAS.
Multitrait, composite-interval mapping (MCIM) for two groups of
correlated traits (1. tillers/plant, biological yield, harvest
index, and grain yield; and 2. spike length, spikelets/spike,
and grains/spike) detected 41 QTL for seven individual traits.
Several QTL could be pleiotropic, influencing more than one trait.
In some cases, for the same QTL, LOD scores in MCIM were generally
higher than those in CIM, thus placing a higher level of confidence
and reducing the possibility of false positives in the QTL identified
in both CIM and MCIM. This study is being extended by growing
the mapping population at three locations for 2 years, so that
'QTL x environment' and the epistatic interactions can be worked
out.
QTL analysis for growth and leaf characters. Using QTL Cartographer, QTL-interval mapping for four growth characters (early growth habit, days-to-heading, days-to-maturity, and plant height) and associated studies for two leaf characters (leaf color and leaf waxiness) were conducted utilizing a set of 110 RILs of the ITMIpop. CIM for all the four growth characters and MCIM for three correlated traits also were made. The framework map and the genotypic data for the molecular markers used for yield and yield-contributing traits also were utilized for the QTL analysis of these traits. Sixteen QTL detected by CIM using LOD scores ranging from 2.0 to 12.7 were spread over eight chromosomes. The individual QTL effects ranged from 6.838.08 %, giving an aggregate of 17.81-91.04 % for individual traits. MCIM was done separately for three correlated metric traits, i.e., early growth habit, days-to-heading, and days-to-maturity. MCIM and CIM together detected 26 QTL for the above three correlated traits. Of these, only six were detected by both CIM and MCIM, 12 were detected by MCIM alone, and the remaining eight were detected by CIM alone. Fourteen molecular markers that were closest to 14 of the 16 QTL identified by CIM also were tested for marker-trait association using regression and t-tests. Five markers showed significant association and, therefore, are recommended for use in MAS.
QTL analysis for preharvest-sprouting tolerance (PHST). QTL-interval mapping for PHST also used the ITMIpop. At crop maturity, data for PHST were recorded on each of 110 RILs belonging to ITMIpop. At the time of physiological maturity, 15 spikes from each of the 110 RILs (five each per genotype per replication) were harvested separately and scored for tolerance to preharvest sprouting following Baier (Ann Wheat Newslet 33:40, 1987). Observations on sprouting were recorded 10 days after harvest and spikes were kept wet by regular spraying with water. For PHST, the RILs were evaluated in four different environments involving three different locations. Data on PHST were scored on a scale of 19. Although there was a narrow range of variability for PHST between parents of ITMIpop, a wide range of variability was observed among the RILs derived from the cross, encouraging us to conduct CIM enabling the identification of 12 QTL on eight chromosomes (1A, 2A, 1B, 2B, 3B, 7B, 2D, and 7D). Individual QTL effects ranged from 6.05-16.47 %.
QTL interval mapping using three intervarietal mapping populations.
QTL analysis for grain-protein content. Continuing
our earlier studies, we did QTL-interval mapping (using QTL Cartographer)
for grain-protein content (GPC) on a set of 100 RILs derived from
the cross 'WL711 (low GPC)/PH132 (high GPC)'. GPC data on the
RILs evaluated in five different environments involving three
different locations and 2 years was used for this purpose. QTL
analysis included single-marker analysis (SMA), simple-interval
mapping (SIM), and CIM. A framework genetic map was prepared using
the above population. The map had 173 loci involving 171 SSR primer
pairs. As many as 13 QTL with a LOD score > 2.5 were detected
on eight different chromosomes. As many as 10 QTL were detected
by CIM, followed by SMA and SIM (five each). These 13 QTL included
seven QTL identified by CIM at a LOD score higher than the threshold
LOD (ranging from 3.21 to 3.57) calculated for each environment
after 1,000 permutations. Two of these seven QTL also were identified
by all the three methods.
More markers are being added to the above framework map to increase the precision of QTL analysis. For this purpose, genotyping of RILs with 105 SAMPL markers (using 12 primer combinations involving two SAMPL primers, i.e., SAMPL 6 and SAMPL 7) and 87 AFLP markers (using eight EcoRI-MseI pairs) already is completed, utilizing a semi-automated multifluorophore technique (at the University of Delhi South Campus). Using this saturated map, QTL-interval mapping will be used to estimate main effects and epistatic and 'QTL x environment' interactions. QTLmapper, developed in China, will be used for this purpose.
QTL analysis for PHST and grain weight (GW). The ongoing project 'Marker assisted selection for some quality traits in bread wheat', funded by National Agricultural Technology Project (NATP) of Indian Council of Agricultural Research (ICAR), also involved preparation of framework linkage maps for two other grain-quality traits, PHST and GW. We have two independent intervarietal-mapping populations (each comprising of 100 RILs) for these two traits. The data on these traits at three different locations were recorded in the year 2001 and 2002. Data on these two populations also were collected on other traits including early growth habit, days-to-heading, days-to-maturity, leaf color, leaf waxiness, plant height, tillers/plant, spike length, spikelets/spike, grains/spike, grain yield, and harvest index. This data, collected over environments, will be used for finding 'genotype x environment' interactions. Genotyping data of the RILs for both the populations using 15 SAMPL and 15 AFLP primer combinations have been recorded using the multifluorophor technique. Using the molecular genotyping data, framework maps will be prepared, which will be used for QTL-interval mapping, not only for PHST and GW, but also for other traits.
Genomic SSRs for DNA polymorphism in Triticeae. Genomic SSRs also were used to study polymorphism in 14 species of the Triticum-Aegilops group using in-gel hybridization and PCR-based approaches. For in-gel hybridization, 13 probe-enzyme combinations were tested that gave 520 (0.40 kb to >23kb) bands in each of the 14 individual species. In addition, 15 SSR primer pairs amplified SSR loci in both species containing A, B, and D genomes and in other species that contained other genomes, suggesting ubiquitous distribution and interspecific polymorphism of SSRs among different species of Triticum-Aegilops group. The available polymorphism also proved helpful in discriminating not only the species with different ploidy levels and possessing different genomes, but also those with similar or very closely related genomes. Thus, wheat SSRs might have been derived from the corresponding SSRs in an ancestral genome and are conserved across a number of species in the Triticum-Aegilops group. The present study suggests that genomic SSRs can be used to evaluate DNA polymorphism, genetic diversity, gene mapping, and synteny conservation across different species of Triticum-Aegilops group.
ESTs in wheat genomics: mining SSRs and SNPs.
Development of ESTSSRs. A large number of SSRs
can be obtained by mining EST databases. We conducted in silico
mining of SSRs in 15,000 wheat ESTs representing 8,250 kb of cDNA
sequences using a modified form of the software developed and
used by Dr. N.D. Young, of the University of Minnesota, U.S.A.,
which identified 897 EST-SSRs. A subset from these EST-SSRs was
used for a detailed study involving, first, the diversity estimates
in 52 elite wheat genotypes, and second, their transferability
to related species and genera. Some of the results of our EST-based
study are posted at the ESTSSR coördination site available
on the GrainGenes web page (http://wheat.pw.usda.gov). This project
is a collaboration between laboratories working on the Triticeae
ESTs for SSRs in order to reduce duplication in the efforts between
laboratories working on wheat ESTSSRs.
Seventy-four primer pairs of a subset of above EST-SSRs were synthesized on contract and used by us to study (i) the polymorphism between the parents of the four mapping populations available, (ii) their transferability to related wild species and five cereal species (barley, oat, rye, rice, and maize), and (iii) the genetic diversity in a collection of 52 elite exotic wheat genotypes using a subset of 20 EST-SSR primers with a view to compare their utility compared to other molecular markers, including genomic SSRs, AFLPs, and SAMPL.
Detection of polymorphism between parents of four mapping populations. Sixty-four of the above 74 EST-SSR (86.48 %) primer pairs were functional but only nine (14.06 %) detected polymorphism in the parents of the mapping populations for GPC, PHST, and ITMI (none of the EST-SSRs was polymorphic for the parents of mapping population for GW) with PAGE. The level of polymorphism observed is lower than the polymorphism (~30 %) detected by genomic SSRs in various studies. The nine EST-SSRs with polymorphism already have been used for genotyping the mapping populations, and the data on genotyping have been collected for mapping of these nine ESTs.
Diversity analysis using 20 EST-SSR primers. A set of 20 EST-SSR primer pairs also was used to study diversity in 52 elite and exotic wheat accessions. Eleven of these 20 primers detected polymorphism and the remaining nine were monomorphic. Out of 11 polymorphic primers, two primers showed length variation, seven primers showed presence and absence (null allele) of the band of the expected size, and the remaining two primer pairs showed polymorphism due to length variation as well as due to null alleles. The number of alleles detected by each of these 11 polymorphic primers varied from 2 to 5.
Transferability of wheat EST-SSR to other cereals. All 64 primers that were functional in wheat were tested for their transferability to the five cereal species rice, oat, maize, rye, and wild barley. Fifty-nine (92.18 %) of these primers showed transferability. Twenty-four (40.68 %) of the 59 successfully amplified fragments in all the five cereal species; the remaining 35 (59.32 %) primers showed transferability to one or more of the five species. This information suggests the possible transferability and utility of EST-SSRs in other cereal species.
Transferability and polymorphism of wheat EST-SSRs in 18 alien species. The above 64 EST-SSR primers were checked for their transferability in 18 alien species of Triticeae possessing different genomes (A, B, D, M, N, and U) and representing three ploidy levels (2x, 4x, and 6x). Out of 64 primer pairs, 31 (48.43 %) primer pairs amplified DNA in all 18 species; the remaining 33 (51.56 %) primer pairs did not show amplification in one or more (114) species. Out of 64 primer pairs, only nine (PK3, PK11, PK10, PK24, PK27, PK42, PK45, PK47, and PK62) gave products of expected size in all of the 18 species. The primers PK5, PK17, PK29, PK69, and PK74 gave species-specific products of expected size in Ae. geniculata, Ae. cylindrica, Ae. uniaristata, T. timopheevi, and T. turgidum subsp. durum. Of interest were two pairs of primers, PK24 and PK32, which also showed genus-specific bands. Primer PK24 gave product of expected size (275 bp) even in different species of genus Aegilops, i.e., Ae. crassa (DM), Ae. vavilovii (DMS), Ae. triaristata (UM), Ae. biuncialis (UM), Ae. peregrina (US), and Ae. geniculata (UM), and primer pair PK 32 gave product of expected size (280 bp) only in the different species of genus Triticum, i.e., T. monococcum subsp. aegilopoides (Am); T. urartu (Au); T. turdigum subspp. durum (AB), dicoccum (AB), and dicoccoides (AB); and T. timopheevii subsp. timopheevii (AG). Therefore, these two primers can be used to distinguish Triticum and Aegilops genera.
Development of SNPs in bread wheat. As a member of International Wheat SNP consortium, we have identified 326 SNPs using 53 EST contigs that were allocated to our group. A density of one SNP every 220 bp was found, although the local density of SNPs varied from gene to gene, some genes having more SNPs than others. Consensus sequences for each of the above contigs also were annotated through BLASTing them against annotated wheat sequences available at TIGR (The Institute of Genome Research), many of these contigs were found to belong to functionally important genes. Therefore, the SNPs also will allow us to map ESTs of known function on the available map. Primers have been designed for the above SNPs and would be used for SNP genotyping using SnuPe (single nucleotide primer extension) reaction at MegaBACE automatic sequencer facility available at NCPBR, IARI (in collaboration with Dr. N.K. Singh).
Estimates of genetic diversity among 55 wheat genotypes using data on AFLP, SAMPL, SSR, and phenotypic traits. Data on AFLP (eight primer pairs) and 14 phenotypic traits, collected on 55 elite and exotic bread wheat genotypes, were utilized for estimations of genetic diversity. We earlier used these 55 genotypes for a similar study using SSRs and SAMPL. As many as 615 scorable AFLP bands visualized included 287 (46.6 %) polymorphic bands. The phenotypic traits included yield and its component traits and physiomorphological traits such as flag-leaf area. Dendrograms were prepared using a cluster analysis based on Jaccard's similarity coefficients in case of AFLP and on squared Euclidean distances in case of phenotypic traits. PCA was conducted using AFLP data and a PCA plot was prepared, which was compared with clustering patterns in two dendrograms, one each for AFLP and phenotypic traits. The results also were compared with published results that included studies conducted elsewhere using entirely different wheat germ plasm and our own SSR and SAMPL studies based on the same 55 genotypes used in the present study. Molecular markers were shown to be superior to phenotypic traits and that AFLP and SAMPL are superior to other molecular markers for estimation of genetic diversity. Based on AFLP analysis and keeping in view the yield performance and stability, a pair of genotypes (E3876 and E677) was recommended for hybridization in order to develop superior cultivars.
Proposed future work.
Mapping of QTLs for certain agronomic traits. QTL analysis
will be conducted for a number of agronomic traits with emphasis
on the estimation of nonallelic epistatic interactions and 'QTL
x environment' interactions, which may result in identifying QTL
with or without major main effects. The raw data on agronomic
traits recorded in several environments will be used for QTL analysis
with the help of framework genetic maps that are being prepared
using four mapping populations including ITMI.
Digital gene expression. To study tissue specific
and correlated pattern of genes expression between different tissues,
we are conducting digital gene expression studies using putative
gene sequences available in the form of EST contigs and various
cDNA libraries of wheat available at the NSF website. This study
will allow us to (i) identify genes with tissue specific expression,
(ii) identify genes with correlated expression pattern in different
tissues/organs, and (iii) assign putative biological function
to specific gene sequences.
Physical and genetic mapping of available genomic and EST-SSR markers. Physical and genetic mapping of available wheat SSR markers such as wmc, gwm, psp, cfa, and cfd (some are already genetically mapped by different workers whereas others are not yet mapped) using terminal deletion stocks of wheat has been initiated. Besides the above, the physical mapping of EST-derived SSRs from wheat and rye that are yet to be mapped genetically, also is underway.
Construction of a wheat database. A comprehensive database (Gramene) for rice already is available. However, a similar database for wheat is not at present, although enormous information on ESTs, physical and genetic maps, and markers and proteins is available. Therefore, we are planning to develop a structurally built, wheat database where all the available information on wheat can be accessed through available hyperlinks.
CHAUDHARY CHARAN SINGH HARYANA AGRICULTURAL UNIVERSITY Department of Plant Pathology, Hisar125004, India.
Rajender Singh, S.S. Karwasra, and M.S. Beniwal.
Sixty-two entries with field resistance to flag smut after 5 years of tests were found susceptible to loose smut after artificial inoculation for two crop seasons. These lines were HS207, HS240, HS271, HS361, HS365, HS369, HPW56, HPW62, HPW93, HPW143, HPW155, HP1657, HP1658, HP1744, HW971, HI1077, HD2189, HD2501, HD2607, HD2620, HD2624, HD2667, HD2701, HUW467, HUW468, HUW485, HUW1043, K8565, K8705, K8806, K9305, K9453, K9533, K9606, KLL19, KRI28, NI9075, NIAW5439, NW1038, NW1043, GW173, GW190, GW236, JOB173, MACS2496, VL711, VL730, VL773, VL791, VL798, PBW316, PBW320, PBW435, PBW438, PBW443, PBW452, PBW299, PL975-1, UP2418, WH573, and WH601.
Another 42 entries have been evaluated for 5 years and are resistant to loose smut. These lines include KW3924, CPAN1418, CPAN6117, CWI6081, CWI6840, CWI6838, CWI7462, CWI7463, CWI7471, CWI8635, CWI8636, GW1066, HPW42, HW517, HW657, HW888, HW1081, HS355 HUW20, HUW44, HCM901, HCM903, HCM906, HCM915, HCM919, HCM920, K825, K9227, MACS3065, NP796, PBW213, PBW218, PBW65, RW733, VL646, VL682, VL705, VL743, WL2082, WL410, and WL1803.
These lines may be exploited as donors for disease-resistance genes in improving breeding material.
DIRECTORATE OF WHEAT RESEARCH
Karnal-132 001, India.
G.P. Singh (Division of Genetics, IARI, New Delhi, India), Ravish Chatrath, S. Nagarajan (Indian Agricultural Research Institute, New Delhi, India), Jag Shoran, Gyanendra Singh, and S.K. Singh.
India has achieved impressive progress in wheat production during the last 35 years and now ranks as the second largest wheat-producing nation in the world after China. Wheat production increased from 11 x 10^6^ tons in 1960-61 to 76.37 in 2000-01, and India is carrying a surplus of ~ 28 x 10^6^ tons (Anonymous 2002).
The newly released cultivar DBW 14, is intended for the North Eastern Plains Zone (NEPZ) of India, which contributes about 30 % of the total wheat production and boasts a predominantly ricewheat cropping system. Out of the total 11 x 10^6^ ha under rice-wheat production in India, nearly half is in the NEPZ and has a yield gap of nearly 1.5 t/ha between what is achieved and what can be harvested. This gap mainly is because of complexities arising due to late harvesting of rice and subsequent delays in sowing wheat, which exposes the wheat crop to unfavorable temperatures.
Cultivars intended for northeastern India, besides having high-yield potential, should also have good early vigor, early maturity, and heat tolerance for late-sowing conditions and resistance to brown rust and foliar blight. The shuttle-breeding approach followed at DWR, Karnal, has successfully developed the cultivar DBW 14, which incorporates all the desired features and, therefore, meets the requirements of the ricewheat cropping system of the NEPZ.
Yield potential. DBW 14 has had a superior and stable yield under late-sown conditions in various locations of northeastern India over the past 3 years in the coördinated trials when compared to the best checks. The frequency that DBW 14 occurs in the top nonsignificant group is highest among all the checks and other varieties in the AVT I and AVT II, scoring 11/20 in 2000-01 and 17/19 in 2001-02 (31/45 on overall basis of 3 years). The performance stability of DBW 14 is attributed to the shuttle-breeding approach used in breeding of the genotype. The yield potential of DBW 14 under AVT was as high as 54.7 q/ha at Faizabad during 2000-01. The most commonly grown wheat variety in this region, HUW 234, which was developed for such late-sown conditions, has become a low yielder in recent years due to susceptibility to brown rust under field conditions. Therefore, the need of another early-maturing variety coupled with high yield and resistance was considered imperative for wheat breeders to meet the challenge of environmental constraints.
Suitability for late sown situations. The sowing span of wheat in the NEPZ is from first week of December to mid January. In low-lying areas, sowing also is delayed till first two weeks of January. DBW 14 has shown superior performance under late as well as very late-sown conditions in the NEPZ. Agronomic trials (2001-02) on late sowing has shown that DBW 14 had the lowest reduction in grain yield under very late-sown conditions when compared to all checks. The 1,000-kernel weight is a crucial yield component being affected by late sowing in eastern India. DBW 14 had the highest mean 1,000-kernel weight and also showed low reduction under very late-sown conditions.
Better disease tolerance. DBW 14 has shown tolerance to brown rust (Table 1) and is comparable to all checks except HUW 234, which is highly susceptible. The cultivar also has resistance to all the prevalent pathotypes of brown rust. For yellow rust, DBW 14 is highly resistant when compared to the checks and other test cultivars. The AUDPC values of DBW 14 was 11-100 in 2000-01, which indicated presence of adult-plant resistance in addition to vertical resistance. Such genotypes exhibit better field durability over the years.
| Cultivar | Zone yield (t/ha) | Rust reaction | |||||
|---|---|---|---|---|---|---|---|
| Year 1 | Year 2 | Year 3 | Brown | ACI | Yellow | ACI | |
| DBW 14 | 4.83 | 4.12 | 3.87 | 30S * | 4.30 | 0 | 0.0 |
| HUW 234 | 4.25 | 3.91 | 3.47 | 100S | 35.20 | 0 | 0.0 |
| NW 1014 | --- | 3.97 | 3.75 | 40MS | 9.00 | 40S | 15.3 |
| PBW 373 | 4.47 | 3.93 | --- | 20MR-MS | 3.60 | 5MR | 0.4 |
| HW 2045 | --- | --- | 3.64 | 5S | 0.70 | 40S | 8.50 |
| NW 2036 | 4.72 | 4.15 | 3.87 | 10S | 1.40 | 80S | 33.3 |
| HUW 543 | 4.79 | 4.10 | 3.57 | 10S | 1.40 | 80S | 33.2 |
| PBW 499 | 4.79 | 4.06 | 3.55 | 60S | 28.30 | tR | 0.0 |
| CD | 0.3 | 0.1 | 0.09 | --- | --- | --- | --- |
| * Maximum reaction at one location only. | |||||||
Leaf blight is an important disease in northeastern India and DBW 14 has shown average leaf blight score of 35, which indicates resistance. The flag leaf rating on a 09 scale is only 3 and, therefore, it may not suffer losses. For other diseases, DBW 14 scored better in resistance to flag smut and Karnal bunt when compared to all qualifying entries and checks.
Good quality. DBW 14 has a high protein content (11.6 %) and is comparable to the checks. Grain appearance of DBW 14 also is good with an achapatti quality (6.75/10.0), the best bread quality (7.56/10), and highest bread loaf volume among the checks and qualifying entries.
Conclusion. DBW 14 has a total balance of traits that makes it a more profitable cultivar for farmers. With high yield potential and better disease resistance, DBW 14 is amenable to late sowing thereby indicating heat tolerance, high grain weight, and appropriate industrial applications. These qualities will optimize the investment, yield for maximum return, and gives maximum economic return to the farmers of NEPZ.
Reference.
INDIAN AGRICULTURAL RESEARCH INSTITUTE REGIONAL STATION
Wellington - 643 231, the Nilgiris, Tamilnadu, India.
R.N. Brama, M. Sivasamy, and Aloka Saikia.
Unique wheat plant types possess stout stems, long spikes with multiple spikelets and florets, and large broad leaves. Such plant types are unfit for commercial cultivation, because they lack other desirable agronomic traits. However, these plant types could serve as a useful resource for robust habits in a wheat-improvement program, particularly for developing new plant types with a slightly reduced robust plant habit through further hybridization with other conventional wheat cultivars.
A cross was made between the robust wheat stock PH 137, with the rust-resistance genes Lr9, Lr19, and Lr24, and the premier Indian wheat cultivar PBW 343 with Sr31, Lr26, and Yr9. This cross resulted in an improved robust plants type (IRPT) with good agronomic traits. The IRPT, though not as robust as PH 137, had more tillers, strong stems, broad leaves, and long spikes with around 110 seeds/spike. However, the seeds were semihard and dull in appearance and without acceptable shape and texture. In order to improve the seed quality, the IRPT was crossed with other Indian wheat stocks having hard seeds, PW 529, PW 556, AP 850, AP 860, KYZ 9801, KYZ 9812, KYZ 9852, KYZ 9873, KYZ 9932, W 4530, W 8770, WG 9899, W 9917, VW 9814, VW 9875, VW 9876, VW 9879, VW 9880, VW 9904, RSP 379, RWP 9710, RWP 9718, WBM 1260, UP 34, UP 41, UP 51, HS 364, HS 365, K 9107, K 9527, MP 3110, MP 3111, MP 3117, Lok 7/99, WG 6596, TR 758, TR 761, HG 993, HUWL 99004, HM 99160, LBP 98 -10, LBP 98-35, GW 244, and Ind 9130.
All the crosses between the IRPT and Indian wheat stocks resulted in new robust plant types (NRPT) that were less robust in appearance when compared to PH 137 and IRPT. The NRPTs were taller (90-110 cm) than PBW 343 (85 cm). Similarly, the NRPTs had longer spikes (13-17cm) with 70-80 grains/spike than PBW 343 (11 cm) with 55 grains/spike. The NRPTs also had a higher 1,000-kernel weight (48-54 gm) than PBW 343 (46 gm). All NRPTs had hard, amber seeds of the proper shape and texture. The NRPTs matured earlier, at least by 15 days, compared to PBW 343 (120 days). The NRPTs were resistant to all three wheat rusts under the heavy epiphytotic conditions at Wellington. The resistance observed in these new robust wheat lines could be attributed to Sr31 for stem rust, to Lr19 and Lr24 for leaf rust, and to Yr9 for stripe rust. The resistance genes Lr9 and Lr26 do not seem to have contributed for the resistance, because these genes are no longer effective in India.
K.A. Nayeem, S.G. Bhagwat, and P.J. Kulkarni.
In the marketplace, the customer judges the quality of wheat grain by visual appearance with respect to shape, color, luster, and plumpness. Every genotype has specific traits, however, all these visual characters are qualitative; they cannot be quantified. Morphology is a method by which image analysis can measure precisely the variation among seeds/grains of various shapes, sizes, and perimeters, quantitatively.
We looked at 15 genotypes of bread wheat, including seven stable, induced-mutant lines, three hybrid derivatives, two landraces, and three checks, HD 2189, C306, and PBNS 1666-1. This research was a collaborative project with the Bhabha Atomic Research Center, Mumbai, India, who supplied the hardware, a 100-Mhz Pentium III computer with 16 MB RAM and a SNGA monitor and a digital monochrome CCD camera with high resolution (1,134 x 972 pixels and a 12.5-75 mm lens). BIOVIS Image Plus Program software, version 1.3, was used for measurement of grain dimensions. Twenty grains from a single-plant harvest were placed under the CCD camera. The grains were arranged with the crease down. An image of the grain was taken and observations recorded for grain area (mm^2^), major axis (mm), minor axis (mm), radius ratio, perimeter (mm), roundness, compactness, and elongation.
The mean performance of the genotypes is given in Table 1. Image analysis was used for pattern recognition to assess the physical properties of the kernel. Because a kernel is a 3-D object, various morphometric parameters can be measured and the data subjected to biometrical analysis. Visual assessment plays an important role in identification and judgment of quality of wheat grains. Image analysis can help in performing these tasks, particularly relevant in India where a large section of wheat consumers prefer grains possessing large size with a lustrous appearance. In the present investigation, PBN 4501 had the highest grain area and Sharbati the lowest. The range observed was large and corresponded with 1,000-kernel weight. All the genotypes in trial II showed a slight decrease in grain area when compared with trial I. Late sowing may have resulted in exposure of the crop to adverse temperatures during flowering and grain filling.
| Genotype | Grain area (mm^2^) | Major axis (mm) | Minor axis (mm) | Perimeter (mm) | Radius ratio | Roundness | Compactness | Elongation |
|---|---|---|---|---|---|---|---|---|
| TPBN 1 | 15.41 | 5.95 | 2.72 | 14.73 | 2.69 | 0.84 | 14.95 | 2.21 |
| TPBN 2 | 15.44 | 6.01 | 2.73 | 14.61 | 2.70 | 0.84 | 14.83 | 2.17 |
| TPBN 3 | 15.26 | 6.21 | 2.84 | 15.09 | 2.65 | 0.84 | 14.81 | 2.14 |
| TPBN 4 | 15.35 | 5.88 | 2.79 | 15.26 | 2.78 | 0.81 | 15.22 | 2.23 |
| TPBN 5 | 15.44 | 6.14 | 2.82 | 14.60 | 2.56 | 0.85 | 14.77 | 2.10 |
| TPBN 6 | 15.32 | 6.16 | 2.87 | 15.18 | 2.65 | 0.84 | 14.87 | 2.17 |
| Kalyansona | 15.00 | 6.16 | 2.72 | 15.12 | 2.86 | 0.80 | 15.35 | 2.27 |
| TPBN 1-1 | 15.59 | 6.06 | 2.87 | 15.04 | 2.64 | 0.84 | 14.94 | 2.15 |
| TPBN 2-1 | 15.51 | 6.14 | 2.83 | 15.19 | 2.70 | 0.84 | 14.94 | 2.17 |
| TPBN 3-1 | 15.66 | 6.07 | 2.93 | 15.14 | 2.52 | 0.85 | 14.65 | 2.08 |
| TPBN 4-1 | 15.14 | 5.96 | 2.70 | 14.73 | 2.69 | 0.83 | 15.06 | 2.20 |
| TPBN 5-1 | 15.30 | 6.12 | 2.73 | 15.06 | 2.80 | 0.82 | 15.22 | 2.25 |
| TPBN 6-1 | 15.49 | 6.18 | 2.82 | 15.28 | 2.70 | 0.82 | 15.14 | 2.20 |
| HD 2189 | 15.49 | 6.20 | 2.66 | 15.00 | 2.87 | 0.80 | 15.59 | 2.38 |
| C 306 | 19.41 | 7.47 | 2.96 | 17.94 | 3.12 | 0.75 | 16.71 | 2.71 |
| PBNS 1666-1 | 15.53 | 6.20 | 2.76 | 15.26 | 2.65 | 0.79 | 15.18 | 2.19 |
| Mean | 15.58 | 6.17 | 2.80 | 15.20 | 2.72 | 0.82 | 15.14 | 2.22 |
| Standard error | 0.19 | 0.12 | 0.03 | 0.11 | 0.03 | 0.003 | 0.05 | 0.02 |
| CD at 5 % | 0.60 | 0.36 | 0.08 | 0.31 | 0.09 | 0.01 | 0.15 | 0.05 |
PBN 4025 had the highest major axis, minor axis, and perimeter. These results suggest that the major and minor axis influence perimeter increase considerably. Kalyansona had the lowest minor axis and Sharbati had the lowest major axis. Kalyansona had the lowest perimeter value and highest radius ratio, however, revealing that among all the genotypes, Kalyansona and Sharbati have round grains; confirmed by their roundness values. Roundness is an important parameter for flour extraction because it helps with the precise crushing of grain during milling and less bran is mixed in the flour.
Parbhani 51 had the highest compactness value and PBN 4501
the lowest. A low compactness value may be due to larger grain
size as revealed through test weight and perimeter. The roundness,
compactness, and elongation values showed a narrow range of variation
among genotypes. Environmental variation had the least effect
on these parameters. Thus, roundness, compactness, and elongation
are important for identifying particular genotypes, similar to
results from other researchers.
K.A. Nayeem.
A major goal of plant breeding is the induction of maximum genetic variability of genetic sources for securing a wider scope for selection of desirable traits. Bergner produced the first haploid plants in Datura stramonium in 1921. Haploids can be produce in vitro (anther culture and embryo rescue), however, using in vivo techniques, haploids can be produced by gynogenesis, androgenesis, genome elimination by distant hybridization, semigamy, chemical treatment, temperature shock, and irradiation.
We used maize pollen to eliminate one genome produces haploids in wheat. In this method, haploids are produced to the selective elimination of one of the parental genomes during the process development after fertilization. Consequently, the embryo is formed with only one genome and the plant arising from such an embryo is expected to be haploid.
While producing haploids by using maize at the Wheat Research Unit, Marathwada Agriculture University, Parbhani, mango pollen was used in fertilizations. The results are in Table 2. The seeds were small in size and shriveled when compared to the normal. The seeds possess one genome, and haploids can be produced. Mango pollen is generally available in the months of December and January and these months are most favorable for emasculation and seed set. The availability of an abundance of pollen from mango trees can benefit haploid production in wheat.
| Cultivar | Maize pollen | Mango pollen | ||
|---|---|---|---|---|
| No. emasculated spikelets | Seed set | No. emasculated spikelets | Seed set | |
| HD 2189 | 24 | 5 | 23 | 4 |
| MACS 2496 | 26 | 4 | 27 | 4 |
| PBN 51 | 19 | 4 | 19 | 5 |
| PBNS 1666-1 | 15 | 6 | 16 | 4 |
| Sonalika | 17 | 3 | 15 | 2 |
INDIAN AGRICULTURAL RESEARCH INSTITUTE
Division of Genetics, New Delhi - 110012, India.
B.S. Malik, A.P. Sethi, V. Tewari, R.K. Sharma, and V.C. Sinha.
Wheat is cultivated in very diverse agroclimatic situations in India. For the benefit of testing varietal performance, the country has been divided into six agroecologic zones. The Indian Agricultural Research Institute (IARI) has the privilege of having a Regional Station in five of these zones. The cultivar-development program encompasses a number of projects, which are involved in developing cultivars suitable for different cultural conditions, both rainfed and irrigated. The Common Varietal Trial has been designed for the multilocation testing of new cultures evolved in various projects at the Delhi center and at regional centers. This approach has proved very effective in selecting suitable strains for coördinated trials, which are conducted under the auspices of the All India Coordinated Wheat Improvement Project. The varietal trials have paid rich dividends to breeders of IARI in getting cultivars released for various wheat-growing regions in different agro-ecologic zones. Recent cultivars developed by the breeders at IARIDelhi are elaborated below.
Ganga (HD2643). This cultivar was identified for the irrigated, late-sown conditions of the North Eastern Plains Zone and was developed from the cross 'VEE 'S'//HD2407/HD2329'. The cultivar has distinct superiority in yield over all the commercial cultivars of the area with yield potential of 5 t/ha and average production of 4 t/ha. Ganga is tolerant to brown rust, which is the major disease of the zone, and is resistant to a new, virulent race (46S119) of yellow rust that attacks Yr9. Ganga has broad leaves and has high number of effective tillers. Long, lax ears with amber, hard, and lustrous grains give Ganga superior quality traits, protein (13.1 %), grain-appearance score (6.0), and hectolitre weight (76 kg).
Shresth (HD2687). Developed from the cross 'CPAN2009/HD2329' combining diverse gene pools of winter and spring wheats, Shresth was released for timely sown, high-fertility conditions of North Western Plains Zone. Shresth has a yield potential of 6.5 t/ha with an average of 5 t/ha and outyields the popular cultivar HD2329 by a margin of over 10 %. The cultivar has durable resistance to leaf and stripe rust and is tolerant to Karnal bunt, leaf blight, and powdery mildew pathogens and insect pests such as aphids and the shoot fly. Shresth has broad leaves, is waxy, and has a mid-dense spike supported on a slightly wavy peduncle. The amber, hard, lustrous, and attractive grains have a 12 % protein content and good chapati-making qualities.
VSM (HD2733). Released for the timely sown, irrigated conditions of North Eastern Plains Zone, VSM was developed from the cross 'Attila/3/HUI/CARC//CHEN/CHTO/4/Attila', which involves both bread and durum wheat parents. The cultivar is double-dwarf, medium-early in maturity with erect leaves and profuse tillering. The spike is mid-dense and tapering. VSM has a yield potential of 6.2 t/ha with an average of 5 t/ha and outyields the popular cultivars by a margin ranging from 15 to 26 %. VSM provides stable resistance against all the three rusts (more specifically against leaf rust) and leaf blight, which are the major diseases of the zone. VSM is widely adapted across various management practices. The grains of VSM are medium-bold (41g/1,000 grains) with excellent chapati-making qualities.
S.S. Singh, J.B. Sharma, P. Bahadur, Anita Baranwal, and J.B. Singh.
The stability of wheat production and productivity is influenced greatly by biotic stresses, among which the rust pathogens pose an important threat to stable wheat production in various environments. Although more than 47 leaf rust-resistance genes have been catalogued, only a few have been exploited in commercial wheat cultivars. Long-lasting or durable resistance has obvious advantage over race-specific, seedling-resistance genes that eventually lead to evolution of new pathotypes when exploited in commercial cultivars. Durable resistance is complex in nature and little is known about the genetic diversity for this type of resistance. This report presents the genetic analysis to wheat leaf rust in five commercial cultivars HS 240, PBW 343, HD 2687, UP 2425, and Raj 3765 grown in India.
The five wheat cultivars along with differentials were tested against 11 pathotypes of leaf rust and the leaf rust-resistance genes present in these wheats were postulated. The F1, F2, and F3 populations of crosses of these wheats with Agra Local, a susceptible parent, were analyzed at adult-plant stage against three highly virulent, leaf rust pathotypes 77-2, 77-5, and 104-2. The F2 populations and NILs with the adult-plant resistance gene Lr34 were tested with three pathotypes.
From the multipathotype tests, leaf rust-resistance genes Lr1 and Lr26 were postulated to be in HS 240, whereas Lr26 is in PBW 343; Lr1, Lr23 and Lr26 are in HD 2687; Lr1, Lr23, and Lr26 are in UP 2425; and Lr10 and Lr13 are in Raj 3765.
Inheritance studies using Agra Local as a susceptible parent at the adult-plant stage suggest the dominant, monogenic control of resistance to leaf rust pathotypes 77-5 and 104-2 in four cultivars HS 240, PBW 343, HD 2687, and UP 2425. Because these four wheats were susceptible to pathotypes 77-5 and 104-2 in seedling tests, we concluded that the resistance gene(s) present in these four cultivars is/are APR gene(s) that are not effective in seedlings. The expression of two dominant genes against pathotype 77-2 in these four cultivars can be explained because these cultivars were resistant to pathotype 77-2 in seedling tests and this seedling resistance was postulated to be seedling leaf rust-resistance gene Lr26 in all the four cultivars. By definition, seedling resistance is expressed throughout the plant's life, so the expression of two genes to pathotype 77-2 in the field-inheritance study is due to Lr26 and an APR gene.
Analyzing the F2 populations from crosses among these four cultivars in a half-diallel suggested the presence of a one common APR gene in HS 240 and PBW 343 and another APR gene common in HD 2687 and UP 2425. Allelism tests of these four cultivars with an NIL (Tc6 + Lr34 (RL 6058)) identified the APR gene in HS 240 and PBW 343 as Lr34 because of nonsegregation of F2 population (all resistant F2 plants) in these crosses, although segregation for susceptible plants in the F2 population of crosses 'HD 2687/Tc6 + Lr34' and 'UP 2425/Tc6 + Lr34' suggested that the APR gene present in these two wheats is different than Lr34. We refer to this undescribed gene as APR1.
Inheritance studies with pathotypes 77-2, 77-5, and 104-2 in Raj 3765 indicate the presence of two dominant resistance genes in Raj 3765 that are effective against the three pathotypes. Because Raj 3765 was susceptible in a seedling test to these three pathotypes, the genetic control of resistance in this wheat was attributed to two APR genes. The positive test of allelism of Raj 3765 with the Lr34 NIL proved that out of two APR genes in Raj 3765, one is Lr34. Our results were further corroborated from nonsegregation in the F2 of crosses of Raj 3765 with HS 240 and PBW 343, which are carriers of APR gene Lr34.
The second APR gene for leaf rust resistance in Raj 3765 was concluded to be the same as that in HD 2687 and UP 2425, because crosses of Raj 3765 with HD 2687 and UP 2425 did not segregate for susceptible plants in F2. Because we also concluded from this study that HD 2687 and UP 2425 have the undescribed APR gene in common, it is logical to conclude that Raj 3765, HD 2687, and UP 2425 have the same undescribed APR gene. The genetic constitution of the leaf rust resistance present in five wheats is
HS 240 = Lr1, Lr26, Lr34 PBW 343 = Lr26, Lr34 HD 2687 = Lr23, Lr26, APR1 UP 2425 = Lr1, Lr23, Lr26, APR1 Raj 3765 = Lr10, Lr13, Lr34, APR1
The isolation of the undescribed APR gene present in these wheats will be pursued in the following generations. However, a close perusal of the parentage of these three wheats could not identify the common parent that is the donor of APR1 in these three cultivars.
Lal M. Ahamed, S.S. Singh, and J.B. Sharma.
Leaf rust is one of the most destructive and widely distributed diseases in most wheat-growing areas in the Indian subcontinent. Breeders commonly have relied on race-specific, leaf rust genes for hypersensitive resistance, which are very effective in reducing the epidemic buildup and easy to manage in breeding programs because of their monogenic nature. The short-lived nature and improper use of race-specific genes on a commercial scale has led to their erosion within a short time. Partial resistance is characterized by a slow epidemic buildup despite a high infection type indicating a compatible host-pathogen interaction.
In this study on slow rusting to wheat leaf rust, we hope to determine the genetics of the slow-rusting components against the leaf rust pathogen, the association among the components of the slow rusting phenotype, and the relationships of the components between slow rusting and slow disease development in the field.
Six wheat cultivars, Kundan, Galvez-87, Trap, Chris, Mango, and PBW-438, along with the fast-rusting cultivar Agra Local were evaluated for 2 years for the components of partial resistance (pustule size, pustule number, and latency period) in a glasshouse and for their AUDPC in field conditions. Three of the better performing cultivars were selected for the genetic analysis by making intercrosses and crosses with Agra Local (without reciprocals). The parents, F1s, and F2s were evaluated in the glasshouse for the components of partial resistance. Part of F2 seed was sown in the field to advance an F3 generation. In the next season, the parents, F1s, F2s, and F3s were evaluated for AUDPC in the field.
The six evaluated slow-rusting parents along with the fast-rusting line showed significant variation for all the components of slow rusting and AUDPC. Selected parents showed significant differences from the remaining parents for the components. All the parents and F1s showed significant variation for all the components and additive variance was significant for pustule number, latency period, and AUDPC, and the dominance component was significant for pustule size.
Strong associations among the components of slow rusting and with AUDPC were observed. AUDPC showed a positive correlation with pustule number and pustule size and negative correlation with latency period, whereas latency period showed a negative correlation with pustule size and pustule number. Pustule size and pustule number had a positive association, indicating the usefulness of these parameters for identifying slow-rusting types both in the field and glasshouse conditions.
The parental lines Kundan, Galvez-87, and Trap showed significant general combining ability effects for all the components of partial resistance and AUDPC. Kundan showed significant specific combining ability effects for all the components, whereas Galvez-87 and Trap showed significant values for three (pustule size, latency period, and AUDPC) and two (pustule size and latency period) components of slow rusting, respectively. Kundan may have a use in breeding programs as donor of slow rusting to leaf rust.
Transgressive segregation was observed in the 'Kundan/Galvez-87', 'Kundan/Trap', and 'Galvez-87/Trap' crosses for both the positive and negative sides for all the characters, which indicates the presence of different genes. No plant with an AUDPC value as low as the susceptible parent were observed in the F3s. The same genes with one or two minor genes involved in the expression of AUDPC, but in crosses between slow and fast rusting wheats, the F3s had mean values in the range of slow-rusting types.
Generation mean analysis of AUDPC showed that epistatic interactions were present in controlling AUDPC. Epistatic interactions were highly significant in all the crosses. The cross 'Kundan/Agra Local' was highly significant for the additive component compared to the other crosses. Kundan will be important in breeding programs for incorporation of slow-rusting resistance by using a reciprocal-recurrent selection method of breeding.
The analysis of data for number of genes, estimated by using Wright's formula, indicated more than three genes in the expression of the components of partial resistance and AUDPC in all the parents where F2 phenotypic range was used in estimating the gene number. In the case of 'slow x slow' ruster crosses, all showed variation in gene number from two to six, indicating the involvement of the same or different genes in the expression of components of partial resistance and AUDPC in wheat to leaf rust.
Javed S. Salim, S.S. Singh, and J.B. Sharma.
Genetic diversity is of paramount importance for the success of any crop improvement program. To diversify the genetic resistance, some synthetic hexaploid wheats were produced from 'T. turgidum / Ae. tauschii' crosses with the objective of exploiting new genetic variability available for resistance or tolerance to abiotic and biotic stress in genome of Ae. tauschii. Aegilops tauschii, the D-genome donor, and T. turgidum, the source of the A and B genomes, are known to be a rich reservoir of valuable genes for resistance to disease and pests of bread wheat. Both the tetraploid and diploid progenitors share chromosome homology with bread wheat and were used as resistance gene donors, either in direct crosses or via bridging crosses or as amphidiploids. Many such genes have been transferred from Ae. tauschii to wheat. Direct gene transfer of resistance genes from diploid and tetraploid species to hexaploid wheats requires cytological follow up. Therefore, synthetic hexaploid wheats provide an excellent opportunity for the easy transfer of these genes from T. turgidum and Ae. tauschii to cultivated wheats without cytological analyses.
The move-counter-move process of evolution of resistant genes and virulence of pathogens necessitates tapping different sources of resistance. The development of lines with durable resistance depends on the availability of desirable donors and understanding of genetic control of resistance. To meet this demand, we have screened the different synthetic hexaploid wheats developed at CIMMYT. These lines have shown a good amount of resistance to leaf rust when screened at the Indian Agricultural Institute, New Delhi. About 42 synthetic hexaploid wheats were screened with the most virulent stem rust race, race 40 A, under epiphytotic conditions, and six lines showing a high level of resistance were selected.
The six selected synthetic hexaploid wheats along with susceptible check, Agra Local, were screened with prevalent races of stem rust, 40-A, 40-1, 117-6, 117-3, 21A-1, 21A-2, 34, and 295, and infection data were recorded according to scale of Stakman et al. (Table 1). Of the six selected synthetic lines, two were nearly immune to all the races tested and the remaining lines, although resistant, had a slightly higher infection type, 1+. The two nearly immune lines are interesting because most of the strong stem rust-resistance genes are alien in origin. This material seems to possess new stem rust-resistance genes. We are investigating the genetic and molecular analysis of stem rust resistance.
| Genotype | Disease index (%) | Genotype | Disease index (%) |
|---|---|---|---|
| SH 4 | 0.00 | SH 42 | 12.60 |
| SH 12 | 0.00 | SH 44 | 0.00 |
| SH 18 | 8.33 | SH 46 | 8.33 |
| SH 26 | 8.33 | SH 55 | 0.00 |
| SH 39 | 12.30 | SH 75 | 8.33 |
| SH 40 | 8.33 | SH 86 | 0.00 |
| SH 41 | 24.30 | Agra Local | 66.66 |
These SH wheats also were screened for resistance against isolate 26 of Dreschlera sorokiniana because blight is a major problem and there are no good sources of resistance. Many lines were found to be resistant. Most of the lines showed resistance with a disease index ranging from 0-8.33 %. The susceptible check had a disease index of 66.66 %. Because many lines had high levels of disease resistance, we are making a genetic analysis of the resistance.
R.B. Ram, S.S. Singh, and J.B. Sharma.
Forty-two synthetic hexaploid wheats (2n = 6x = 42) derived from 'T. turgidum/Ae. tauschii' received from CIMMYT were screened for identifiable morphological characters and to cluster them for further use in wheat breeding. The observations were recorded on 22 morphological traits of agronomic importance including leaf blade color, leaf sheath color, flag leaf angle, straw strength, tiller angle, glume pubescence, glume color, spike density, awnedness, threshing behavior, culm length, leaf area, spike length, awn length, 1,000-kernel weight, number of grains/spike, and grain yield/plant. The accessions exhibited substantial variability for the traits. Data on quantitative traits were subjected to genetic divergence analysis using the Mahalanobis D2 statistic. The genotypes were grouped into three clusters with differing numbers of accessions in each cluster. On the basis of genetic divergence analysis and superior cluster means, we predict that cluster III and cluster I were important for between-cluster improvement, and cluster II was important for within-cluster improvement. Information on taxonomic description and genetic diversity of these traits in these genotypes can be utilized in the breeding programs to improve the yield and its traits.
R.B. Ram, S.S. Singh, and J.B. Sharma.
Forty-two synthetic-hexaploid wheat accessions also were tested for seedling and adult-plant resistance to leaf rust virulent race 77-5 in the glasshouse and field conditions, respectively. A high degree of genetic variability for leaf rust resistance was observed both at seedling and adult-plant growth stages. Most of the accessions were highly resistant at seedling and adult-plant stage.
The genetic analysis of APR to leaf rust in the SH accessions 18, 35, and 36, which showed seedling susceptibility and APR, indicated that the APR response in the field was governed by two dominant genes. The APR genes involved in these accessions are different. The APR genes present in these synthetic wheats can be used as a new source for resistance to leaf rust in wheat.
Reza Haghparast, S.S. Singh, K.V. Prabhu, and J.B. Sharma.
Leaf rust is the most damaging wheat disease in many wheat-growing regions of the world. Breeding for resistance represents the most cost-effective and environmentally safe method for controlling leaf rust. Aegilops tauschii, the donor of D genome to hexaploid wheat, has been identified as an important source of resistance to wide array of diseases of common wheat (Mujeeb-Kazi et al. 1995). At CIMMYT, several synthetic-hexaploid wheats were produced from 'T. turgidum/Ae. tauschii' crosses to exploit new genetic variability for resistance or tolerance to biotic and abiotic stresses in the D genome of Ae. tauschii (Singh et al. 1998). A high degree of genetic variability for leaf rust resistance has been observed at both seedling and adult-plant stages in synthetic wheats (Singh et al. 1998). In this study, a SH with a high degree of resistance against the most virulent leaf rust pathotype in India, 77-5, was selected to determine the genetic basis of its resistance.
Material and Methods. A SH wheat resistant to the most virulent leaf rust pathotype in India, 775, was selected for genetic analysis of its resistance. This SH wheat was derived from crosses between T. turgidum subsp. durum (Duergand 2) and an accession of Ae. tauschii (Ac. 221) in the wide-hybridization program at CIMMYT, Mexico. Agra Local (AL) was used as susceptible parent in crosses with the SH wheat. The NILs for leaf rust-resistance genes Lr23, Lr32, Lr39, Lr40, Lr41, Lr42, and Lr43 used for gene identification in a multipathotype test using seven pathotypes. Pathotype 77-5 was selected for inheritance studies. The SH wheat, AL, and the NILs were tested with the seven leaf rust pathotypes as seedlings in a glasshouse. Direct and reciprocal crosses were made between the SH wheat and AL. A part of the crossed seed and the parental lines were sown in the field. The F1 of cross between the SH wheat and AL was backcrossed to AL. The SH wheat and the F1 and F2 generations of the crosses between the SH wheat and AL were grown in field to assess resistance to leaf rust pathotype 77-5 at the adult-plant stage. Seeds from the F1 and F2 generation were harvested on a single plant basis to give F2 and F3 seed for further inheritance analysis. The SH wheat, F1, F2, F3, and BC1F1 generation along with differential sets were tested against leaf rust pathotype 77-5 as seedlings in the glasshouse. The urediospore inoculum of the individual pathotypes was multiplied on the susceptible cultivar AL in the glasshouse. The procedure described by Joshi et al. (1988) was followed for the multiplication of inoculum and testing of material. To test segregating populations, seedlings were grown in rectangular trays (11" x 4" x 3") and inoculated after approximately 1 week of growth. Seedlings were sprayed with the inoculum and the pots/trays were kept in a humid glass chamber for 48 hours. The average temperature of glasshouse varied between 15 and 25 C. For recording of rust reactions at seedling stage, the system of Stakman et al. (1962) was followed. Testing of material at the adult-plant stage was done in the field. Spreader rows were inoculated at boot with a uredospore suspension of pathotype 77-5 in water using hypodermal syringe. Rust severity was recorded according to the modified Cobb's scale described by Peterson et al. (1948). The Chi square test (X2) for goodness-of-fit was used for testing the validity of observed versus expected in segregating populations.
Results and discussion. In the multipathotype tests, the SH wheat was resistant to all the seven leaf rust pathotypes. The range of infection type of the SH wheat varied from 0; to X- and the mesothetic reaction (IT X-) was observed to pathotypes 12-1 and 12-4 (Table 2). Among the NILs with leaf rust-resistance genes derived from Ae. tauschii, those with Lr32, Lr39, Lr40, and Lr43 were resistant (IT = 0 to 12-) and Lr41 and Lr42 were highly resistant (IT 0 to ;) to all seven pathotypes. The NIL of Lr23 derived from T. turgidum subsp. durum was highly susceptible to the group 77 pathotypes and 104-2 (IT = 3- to 33+) but resistant to 12-1, 12-4, and 108-1 (IT = X-). AL was susceptible (IT = 33+) to all the pathotypes. Adult-plant response to pathotype 77-5 confirmed that the SH wheat was highly resistant (trace) at field conditions. AL was susceptible, exhibiting a reaction of 90S in the field. NILs with Lr32 and Lr43 had resistance reactions of 5R and 30R, respectively. NILs with Lr41 and Lr42 were observed to be immune in the field. Moderately resistant (10 RMR) reactions were shown by NILs with leaf rust-resistance genes Lr39 and Lr40. Consequently, the multipathotype test revealed that the SH wheat was resistant to all the pathotypes and produced a spectrum of ITs ranging between ;1- and X. The spectrum of ITs produced on the SH wheat differed from that of the NILs with known resistance genes derived from T. turgidum subsp. durum and Ae. tauschii. Thus, we concluded that the resistance gene in the SH wheat is not present in these NILs.
| Line | Pathotypes | |||||||
|---|---|---|---|---|---|---|---|---|
| 12-1 | 12-4 | 77-2 | 77-5 | 77-7 | 104-2 | 108-1 | 77-5 * | |
| Synthetic | X- | X- | ;1- | ;1- | 0; | ;1 | 0 | TR |
| Lr23 NIL | X- | X- | 3+ | 33+ | 33+ | 3+ | X- | 60S |
| Lr32 NIL | 12- | 1+ | 12+ | 12- | 12- | 1+2- | 1+ | 5R |
| Lr39 NIL | 0 | 12+ | 1 | 1+2- | ;1 | ;1 | 0 | 10RMR |
| Lr40 NIL | ;1+ | 12- | 1- | 12- | 1 | 12- | 0 | 10RMR |
| Lr41 NIL | 0; | ; | 0; | 0; | 0; | 0; | 0 | 0 |
| Lr42 NIL | 0 | 0 | 0; | 0; | 0 | ; | 0 | 0 |
| Lr43 NIL | 12- | 12 | 1+ | ;1 | 1+ | ;1- | 0 | 30R |
| Agra Local | 33+ | 33+ | 33+ | 33+ | 33+ | 33+ | 33+ | 90S |
| * Leaf rust resistance at the adult-plant stage. | ||||||||
In field conditions, the SH wheat showed a high degree of resistance (trace), whereas AL was susceptible (90S) to 77-5. The F1 plants of a cross between these two genotypes had a resistant response, 20MRMS, indicating the partial dominant nature of resistance in the SH wheat . Based on their level of resistance, the F2 plants were grouped into three classes, TR, the resistant-parent type; S, susceptible-parent type; and MRMS, an intermediate type. The observed ratio in all the F2s fit a 1:2:1 ratio (P > 0.05) indicating a single, partially dominant gene controls APR in the SHW.
In the glasshouse, the SH wheat was highly resistant to pathotype 77-5 (IT = ;1-), whereas AL was susceptible (IT = 33+). The IT of the F1 seedlings of the crosses and the reciprocal cross ( AL/SH wheat) exhibited the mesothetic IT X, indicating that resistance in SHW also is partially dominant at seedling stage. Based on the ITs, the F2 individuals derived from direct crosses (SH wheat/AL) were classified into three groups, resistant with an IT similar to SH wheat (IT = ;1-), partially resistant with mesothetic IT = X, and susceptible similar to AL (IT = 33+). The observed ratio according to this classification fit the expected ratio of 1 (IT = ;1-): 2 (IT = X) : 1 (IT = 33+) (P > 0.05). Identical F2 segregation of the reciprocal cross (AL/SH wheat) ruled out any cytoplasmic effect in controlling resistance, because the F2 seedlings of this cross were classified as above and the X2 value indicated no significant difference between observed and expected ratio, 1:2:1 (P > 0.05). Thus, the results from the direct and reciprocal crosses indicated the presence of a single, partially dominant gene controlling the resistance to pathotype 77-5, supporting the results screening at the adult-plant stage. In the BC1F1 populations, only two type of infections were observed, X and 33+, and seedlings with IT ;1-, similar to that of the SH wheat were not observed. Nonsignificant deviation in the ratio of resistant (IT = X):susceptible (IT = 33+) in the BC1F1, 'SH wheat/AL//AL', from a 1:1 ratio confirmed the presence of one partially dominant gene for resistance in the SH wheat (Table 3). The F3 families derived from seeds of individual F2 plants in field were labeled based on their reaction to pathotype 77-5 and harvested individually. According to the reaction of the original F2 plants, three families of F3 were available and were called the TR, MRMS, and S groups. The reactions of the families in each group were studied as seedlings against pathotype 77-5 in the glasshouse. No segregation was observed in the TR families, indicating that they are homozygous for dominant resistance alleles. No segregation was observed in S families, indicating that they are homozygous for recessive resistance alleles. The families that were grouped as MRMS segregated, indicating heterozygosity. The distribution of these F3 families at 1 (resistant):2 (segregating):1 (susceptible) showed a goodness-of-fit p > 0.05. This result confirms the presence of a single, partially dominant gene to pathotype 77-5 in the SH wheat. Some partially dominant, leaf rust-resistance genes have been identified already, such as Lr12 and Lr13 by Dyck et al. (1966), Lr17 and Lr18 by Dyck and Samborski (1968), Lr25 by Driscoll and Jensen (1963), and Lr21 and Lr22a from SH wheats by Kerber and Dyck (1969). The presence of Lr21 and Lr22a from SH wheats in the test is eliminated, because these genes confer APR, whereas the SH wheats have genes for seedling resistance.
| Population | No of seedlings | Expected ratio | X2 | df | P | |||
|---|---|---|---|---|---|---|---|---|
| Resistant | Susceptible | Total | ||||||
| (IT ;1+) | (IT X) | (IT 33+) | ||||||
| F1 (SHW/AL ) | 0 | 12 | 0 | 12 | --- | --- | --- | --- |
| F2 (SHW/AL) | 65 | 110 | 75 | 250 | 1:2:1 | 4.400 * | 2 | 0.111 |
| BC1F1 (F1/AL) | 0 | 38 | 36 | 74 | 1:1 | 0.054 * | 1 | 0.816 |
| F1 (AL/SHW) | 0 | 10 | 0 | 10 | --- | --- | --- | --- |
| F2 (AL/SHW) | 24 | 74 | 32 | 120 | 1:2:1 | 4.600 * | 2 | 0.100 |
Acknowledgment. We thank Drs. R.G. Saini and H.S. Dhaliwal for their valuable advice and support during the research.
References.
Nirupma Singh, Sohan Pal Sharma, and S.S. Singh.
A 1 % annual genetic gain in wheat productivity for the last several years is of great concern to wheat scientists in general and wheat breeders in particular because this level of genetic gain is too low to achieve the production target for feeding an ever increasing population. The low genetic gain in productivity mainly is due to the limited diversity used in developing wheat varieties. Genetic diversity is considered to be an important factor in choosing parents for a hybridization program for obtaining high-yielding progenies. Currently, the major concern is to augment wheat genetic diversity in order to realize another quantum jump in wheat production. The only logical approach is to tap into the huge genetic variability present in different wheat progenitors. Keeping this objective in view, synthetic wheats were developed between T. turgidum subsp. durum and Ae. tauschii. This investigation analyzes the genetic diversity present in the SH wheats received from Division of Genetics, Indian Agricultural Research Institute, New Delhi, and grown at the GB Pant University of Agriculture and Technology Research farms, Pantnagar, U.P. that can be used by the breeders in developing high yielding genotypes. We assigned these genotypes to groups and studied their intra- as well as intergroup diversities using the Mahalanobis' D2 statistic, which is very useful in selecting parents for hybridization program. Twenty-five genotypes were grouped into eight clusters using seven characters, plant height, biological yield/plot, economic yield/plot, grain weight/spike, 1,000-kernel weight, number of spikelets/spike, and number of grains/spike (Table 4). Synthetic wheats 9 and 50 were contained in clusters I and III, respectively. Cluster II constituted of synthetics 58 and 78. Three synthetic hexaploids, 8, 39, and 42, were grouped in cluster IV. Clusters V and VI were comprised of five and six genotypes, respectively. Cluster VII contained three genotypes, synthetics 19, 33, and 56. Cluster VIII had four genotypes, synthetics 31, 55, 63, and 74.
| Cluster | Number of genotypes | Genotypes included |
|---|---|---|
| I | 1 | SHW 9 |
| II | 2 | SHW 58, SHW 78 |
| III | 1 | SHW 50 |
| IV | 3 | SHW 8, SHW 39, SHW 42 |
| V | 5 | SHW 2, SHW 12, SHW 41, SHW 46, SHW 47 |
| VI | 6 | SHW 6, SHW 30, SHW 35, SHW 44, SHW 45, SHW 59 |
| VII | 4 | SHW 19, SHW 33, SHW 56 |
| VIII | 4 | SHW 31, SHW 55, SHW 63, SHW 74 |
The results of this study demonstrate the immense, unexploited genetic variability for different combination of traits that exist in this material that may be exploited through use of different breeding methodologies (single, three-way , and backcrosses). Developing wheats from this material with very high yield potential and genes for resistance/tolerance to biotic/ abiotic stresses is possible.
Acknowledgment. GB Pant University of Agriculture and Technology, Pantnagar, U.P., India.
SHER-E-KASHMIR UNIVERSITY OF AGRICULTURAL SCIENCES AND TECHNOLOGY
Division of Plant Breeding and Genetics, FOA, R.S. Pura, Jammu, India.
J.S. Bijral.
Aegilops longissima is resistant to powdery mildew and leaf and stem rust. The species also possesses a high degree of tolerance to heat and drought stress coupled with high grain protein (Kimber and Feldman 1987) and, thus, constitutes a valuable germ plasm for the improvement of bread wheat. This communication reports the cytogenetics of T. aestivum/Ae. longissima F1 hybrids.
Materials and methods. The bread wheat cultivar WW 27 and Ae. longissima (accession number 28) were used in the study. Manually emasculated wheat spikes were pollinated with freshly collected, Ae. longissima pollen under field conditions. For meiotic studies, immature F1 spikes were fixed in a 1:3 acetic acid:alcohol solution for 24 h, and meiotic preparations were made by squashing the anthers in 2 % acetocarmine.
Results and discussion. The F1 hybrid plants were completely self-sterile and resembled the wheat parent more closely in overall morphology. The hybrid status of the F1 plants was confirmed cytologically. All the plants had the expected 28 chromosomes. The mean chromosome associations in bread wheat/Ae. longissima hybrids were 25.5 univalents + 1.1 ring bivalents + 0.15 rod bivalents, suggesting a low homology between the parental genomes. The F1 hybrids were backcrossed successfully to the bread wheat parent.
Acknowledgment. Our sincere thanks to Dr. H.S. Dhaliwal, Department of Genetics and Biotechnology, Punjab Agricultural University, Ludhiana, India, for kindly providing the seed of Ae. longissima accession no. 28.
Reference.