Agronomic characteristics of durum wheat stocks possessing the chromosome substitution T1BL-1RS.

R.L. Villareal, O. Banuelos, A. Miranda, and A. Mujeeb-Kazi.

Translocations involving the short arm of rye chromosome 1R have been of particular interest and are widely used in winter and spring wheat breeding programs worldwide. Cultivar comparisons have suggested that the T1BL-1RS chromosomal translocation enhances agronomic performance and environmental stability of wheat. However, there are concerns that the T1BL-1RS translocation has an adverse effect on end-use quality of bread wheat and genetic and disease vulnerability that is associated with the 1RS segment. Stable cytological transfer of the T1BL-1RS translocation from bread wheat to durum wheat has been demonstrated. No studies are known of the effect of this translocations in durum wheat. The objective of this study was to measure the effect of the T1BL-1RS chromosome on grain yield and other agronomic traits using 22 related durum lines (11 homozygous for chromosome 1B and 11 homozygous for T1BL-1RS). The test lines were produced by substituting the T1BL-1RS chromosome in durum wheat cultivar Altar 84 (homozygous for 1B) through backcrossing.

All field trials were evaluated at the Mexican National Institute of Forestry, Agriculture and Livestock, Campo Agricola Experimental Valle del Yaqui (CAEVY) Research Center, Sonora, Mexico, during the 1993-94 and 1994-95 crop production cycles. Analysis of variance showed significant differences between translocation group on all traits except harvest index and plant height (Table 23). The T1BL-1RS genotypes had 3.5 % increased grain yield, 3.3 % higher aerial biomass at maturity, 11.7 % heavier kernels, more grain volume weight, longer spikes, delayed heading, and an extended grainfilling period and took longer to reach physiological maturity than the 1B genotypes. However, the 1B lines produced more kernels/m² than the T1BL-1RS lines in all tests. The expression of the 1RS may vary in other durum backgrounds, primarily because of recombination events that occur when chromosome 1BL wheat arms associate during meiosis. These results require wider validation and T1BL-1RS substitutions in other durum genetic backgrounds are in progress.

Table 23. Means for the 1B and T1BL-1RS substitution lines of durum wheat cultivar Altar 84 during the 1993-94 and 1994-95 crop cycles at CAEVY, Sonora, Mexico.

* and ** denote F-test significant at P = 0.05 and 0.01, respectively; NS= not significant.

Utilization of alien Triticeae germplasm resistant to barley yellow dwarf virus for wheat improvement.

M. Henry, V. Rosas, and A. Mujeeb-Kazi.

Seven bread wheat-based, tissue culture-derived lines developed in Australia with Th. intermedium chromatin (TC 5, 6, 7, 8, 9, 10, and 14) were analyzed for BYDV resistance. Susceptible families of these lines also were included. The BYDV-resistance status of these lines was established by ELISA and immuno-dot blot analyses. Additional germplasm similarly evaluated was comprised of Th. bessarabicum- and Th. elongatum-wheat amphiploids, their disomic chromosome addition lines (2n = 6x = 42 + 2), Zhong 1 to 7 germplasm from China, a BC₁ fertile amphiploid of the cross `T. turgidum/P. juncea//T. turgidum' (2n = 6x = 42; AABBNN), and an Agrotricum 56-chromosome line (OK 7211542). Use of the above alien germplasm in wheat improvement is projected based upon data obtained through the above diagnostic evaluations.

In the TC families, the Thinopyrum exchanges for three families (TC6, 7, and 9) had a Robertsonian translocation, whereas the TC families 5, 8, and 10 had one alien chromosome arm that extended partially to the other chromosome arm. Of these two exchange types, those entries with Robertsonian translocations are preferred for wheat improvement, because of their lower amount of alien chromatin.

FISH analyses on the TC14 lines obtained subsequently indicated a reduced alien exchange on chromosome 7D of wheat. This line will be of a higher priority than the TC6, 7, and 9 Robertsonian translocation families for wheat improvement, because of its reduced alien chromatin.

Only one Agrotricum (OK 7211542) plant had a ELISA value higher than twice the healthy threshold level. All other plants were not infected and, therefore, were considered immune to BYDV under our experimental conditions. Comeau et al (1994) also observed this immunity of the OK 7211542 line. The Agrotricum partial amphiploid has 56 chromosomes. Occasionally aneuploidy does occur, but can be selected against. Meiosis is regular with bivalent formation. FISH analysis indicated the presence of 14 alien chromosomes and a translocated pair in 56-chromosome plants. Some plants had a pair of telocentric chromosomes. The OK 7211542 line is our current preference for BYDV resistance transfers to wheat and has been subjected to ph manipulation strategies to facilitate DNA introgression into wheat.

Reference.

Comeau A, Makkouk KM, Ahmad F, and Saint-Pierre CA. 1994. Bread wheat x Agrotricum crosses as a source of immunity and resistance to the PAV strain of barley yellow dwarf luteovirus. Agronomie 2:153-160.

Agronomic performance of some advanced derivatives of synthetic hexaploids (T. turgidum x T. tauschii).

R.L. Villareal, O. Banyuelos, J. Borja, A. Mujeeb-Kazi, and S. Rajaram.

Since 1989, CIMMYT has been concentrating on exploiting goatgrass (T. tauschii), because of its wide range of resistance/tolerance to biotic/abiotic stresses. This wild grass also appears to be a potent source of new variability for important yield components such as 1,000-kernel weight, increased photosynthetic rate, and improved bread making quality. Introgression of genes from diploid T. tauschii into hexaploid wheat via crosses with durum wheat is an effective way of developing stable, hexaploid lines with unique and useful genes for bread wheat improvement. The synthetic-hexaploid bridge allows not only the T. tauschii genes to be exploited, but also incorporates the genetic diversity of the A and B genomes of the respective improved durum cultivars.

Synthetic hexaploids have been used extensively in our bread wheat hybridization program (e.g., synthetic x bread wheat). For example, during the 1995-96 wheat cycle at Yaqui Valley, Cd. Obregon, 40 % of the program's bread wheat F₂ populations involved a synthetic hexaploid in the cross. Crossing methodologies employed to incorporate this germplasm include single crosses, top (three-way) crosses, and backcrosses. Advanced lines from this breeding effort have been produced and are being evaluated for yield. The main objective of this study was to evaluate the yield potential of the `synthetic hexaploid x bread wheat' derivatives developed by CIMMYT's wheat breeding program.

The yield trials were conducted at the Mexican Agricultural Research Center in the Yaqui Valley, Ciudad Obregon, Sonora, during the 1994-95 and 1995-96 wheat production cycles. Grain yield, yield components, and other agronomic characteristics of the 10 highest-yielding, advanced bread wheat derivatives are shown in Table 24 (p. 176). None of the entries yielded significantly better than the bread wheat check cultivar Bacanora 88. Two lines, `Chen/T. tauschii (205)//Kakuz' and `Chen/T. tauschii (224)//Opata' showed comparable yield potential over the check cultivar. Improved 1,000-kernel weight was significant on most of the synthetic derivatives.

Over 600 synthetic hexaploids have been developed by the Wide Crosses Program at CIMMYT with a majority from a unique T. tauschii accessions. These germplasms are spring types and, hence, offer an easier route for their practical utilization and global distribution. As screening data on biotic/abiotic conditions of synthetics become available, we anticipated that the hybridization effort of elite synthetics with our current high-yielding advanced lines will increase.

Table 24. Agronomic characteristics of ten high yielding advanced bread wheats derived from 'synthetic hexaploid x T. aestivum' crosses at Yaqui valley, Sonora, Mexico, during the 1994-95 and 1995-96 wheat seasons.

Table 25. The crossability data of Triticum turgidum/A-genome diploid species (T. boeoticum, T. monococcum, and T. urartu) accessions.

Production, cytogenetics, maintenance, and breeding implications of A-genome amphiploids (2n = 6x = 42, AAAABB).

S. Cano, A. Cortes, R. Delgado, and A. Mujeeb-Kazi.

The A-genome primary gene pool diploid species (T. boeoticum, T. monococcum, and T. urartu) and their accessions provide genetic diversity that can be utilized by bridge crosses where AAAABB amphiploids produced by `T. turgidum/A-genome diploid species' accession hybridizations are exploited. All F₁ hybrids (2n = 3x = 21, AAB) are low- to high-frequency crosses and require embryo rescue and colchicine treatment for inducing fertility (2n = 6x = 42, AAABB). Meiotic analyses of F₁ hybrids gives evidence of A-genome recombination. Derived C₀ fertile products predominantly express bivalent associations. The AAAABB hexaploids express diversity that facilitates stress screening and provide a means for durum wheat improvement. One hundred seventy such AAAABB stocks are available and are described.

The vernalization procedure resulted in very vigorous growth of all A-genome diploid accessions with a flowering range of 90-135 days. Thus, a majority of the accessions were able to be crossed with the T. turgidum cultivars. Embryos were rescued at 16 days postpollination from all crosses. Embryos were small, translucent, generally ill-defined, and floating in a watery endosperm cavity. Crossability data for some combinations indicating the general trend observed for seed set, embryos recovered, and plants regenerated are presented in Table 25 above.

All genuine F₁ hybrids were stable for 2n = 3x = 21 (AAB) chromosomes. The C₀ amphiploid seed generally possessed 42 chromosomes after colchicine doubling. Some hypo- or hyperploidy did exist, but was subsequently purified by additional cytology and seed increase. C-banding elucidated the AAAABB chromosomes as some amphiploids so analyzed.

Field plantings were utilized for establishing descriptive parameters and for a seed increase from the wide array of AAAABB wheats produced. Extensive genetic diversity for plant height, flowering date, grain-fill duration, awn color, days to physiological maturity, and 1,000-kernel weight was demonstrated. Utilization of this germplasm for durum wheat improvement will presumably be at an advantage if the more agronomically desirable amphiploids that further express high levels of resistance to biotic/abiotic stresses are exploited as opposed to using resistant, but poor, agronomic types.

F₁ hybrids are generally the first step leading to a gene introgression program and may be advanced directly by backcrossing followed by selection. However, production of amphiploids-where possible-forms a crucial second step, because it allows for a more reliable evaluation of the genetic value of the alien genes (Jiang et al. 1994) in the derived background through a permanent germplasm base. Though amphiploid instability is a frequent occurrence, all the 170 AAAABB C₀ amphiploids produced generally were cytologically stable. The predominance of bivalents with a high seed set/amphiploid has enabled adequate production of seed for distribution and stress testing. We contend that the maximum exchanges from the diploid accessions into durum wheat occur at the F₁, with the reduced tri- and quadrivalent associations extending these arrangements further. Anaphase separation normalcy exists in the amphiploids.

Publications-Wide crosses, 1995-96.

Ma H, Singh RP, and Mujeeb-Kazi A. 1996. Resistance to stripe rust in durum wheats, some diploid A genome accessions and their synthetic hexaploids. Euphytica (in press).

Mujeeb-Kazi A, Sitch LA, and Fedak G. 1996. The range of chromosomal variations in intergeneric hybrids involving some Triticeae. Cytologia 61:125-140.

Mujeeb-Kazi A, William MDHM, and Islam-Faridi MN. 1996. Homozygous 1B and 1BL/1RS chromosome substitutions in Triticum aestivum and T. turgidum cultivars. Cytologia 61:147-154.

Mujeeb-Kazi A. 1996. Cytogenetics of hybrids Thinopyrum elongatum (2n=2x=14, or 2n=4x=28) with Hordeum vulgare, Secale cereale and Triticum turgidum. Cytologia 61:141-146.

Mujeeb-Kazi A, Islam-Faridi MN, and Cortes A. 1996. Genome identification in some wheat and alien Triticeae species intergeneric hybrids by fluorescent in situ hybridization. Cytologia 61:307-315.

Mujeeb-Kazi A. 1996. Apomixis in trigeneric hybrids of Triticum aestivum/Leymus racemosus/Thinopyrum elongatum. Cytologia 61:15-18.

Mujeeb-Kazi A and Riera-Lizarazu O. 1996. Polyhaploid production in the Triticeae by sexual hybridization. In: In vitro haploid production in higher plants, Vol. 1 (Jain SM, Sopory SK, and Veilleus RE eds). Kluwer Academic Publishers. p. 275-296.

William MDHM and Mujeeb-Kazi A. 1996. Development of genetic stocks and biochemical markers to facilitate utilization of Aegilops variabilis in wheat improvement. Cytologia 61:7-13

Mujeeb-Kazi A, William MDHM, Cortes A, Islam-Faridi MN, and Rosas V. 1996. Some disomic Thinopyrum elongatum (2n=2x=14) chromosome additions to wheat produced by the wheat x Zea mays polyhaploid induction methodology. (Submitted).

Villareal RL, Del Toro E, Mujeeb-Kazi A, and Rajaram S. 1995. The 1BL/1RS chromosome translocation effect on yield characteristics in a Triticum aestivum L. cross. Plant Breed 114:497-500.

Villareal RL and Mujeeb-Kazi A. 1996. Exploitation of synthetic hexaploids (Triticum turgidum x T. tauschii) for some biotic resistances in wheat. In: 8th Assemb Wheat Breed Soc Austr (Richards RA, Wrigley CW, Rawson HM, Rebetzke GJ, Davidson JL, Brettell RIS eds). The Australian National University, Canberra, Australia. pp. 185-188.

Villareal RL, Fuentes-Davila G, Mujeeb-Kazi A, and Rajaram S. 1995. Inheritance of resistance to Tilletia indica (Mitra) in synthetic hexaploid wheat x Triticum aestivum crosses. Plant Breed 114:547-548.

Villareal RL, Del Toro E, Rajaram S, and Mujeeb-Kazi A. 1996. The effect of chromosome 1AL/1RS translocation on agronomic performance of 85 F₂-derived F₆ lines from three Triticum aestivum L. crosses. Euphytica 89:363-369.

Villareal RL, Mujeeb-Kazi A, and Rajaram S. 1996. Inheritance of threshability in synthetic hexaploid (Triticum turgidum x T. tauschii) by T. aestivum crosses. Plant Breed (in press).

UNIVERSIDAD AUTONOMA AGRARIA ANTONIO NARRO

Departamento de Fitomejoramiento, Programa de Cereales de Grano Pequeno, Buenavista, Saltillo, Coahuila, Codigo Postal 25315, Mexico.

Northern Mexico wheat production in 1995-96.

G. Martinez-Zambrano and M. Colin-Rico.

The 1995-96 climatic conditions were generally good in most cereal-growing areas under irrigation in the northern Mexico region, which includes the states of Coahuila, Nuevo Leon, Durango, Zacatecas, and parts of San Luis Potosi and Chihuahua. Rainfed growing areas were severely stressed by nearly 5 years of drought.

The wheat milling industry in Coahuila is very concerned about stimulating both the bread and durum wheat cultivation in Coahuila, mainly to reduce industrial costs by reducing the freightage costs. Nevertheless, grain quality may be the most important production trouble, mainly for durum wheat production in relation to yellow berry.

Development of bread wheat populations.

Gaspar Martinez-Zambrano.

In 1995, two bread wheat population were made by crossing 20 Mexican varieties: Yaqui 50, Penjamo 62, Nadadores 63, Siete Cerros 66, Tanori 71, Tanori 71M, Toluca 73, Jupateco 73, Jupateco 73M, Torim 73, Cleopatra 74, Zacatecas 74, Salamanca 75, Pavon 76, Nacozari 76, Ciano 79, Ciano 79M, Abasolo 81, Celaya 81, and CP-1 with two male-sterile donor populations. The pollination of 400 spikes of AZ-MSFRS-80RR population (Crop Sci 18:698, 1978), with a pollen mix of the Mexican varieties produced the population named ARIZONA-UAAAN (AZ-UAN). The other population, named MONTANA-UAAAN (MT-UAN), was made by pollinating 400 male-sterile spikes of the population MTMSSF-88 (Crop Sci 29:838, 1989). Both populations are under enhancement by phenotypic recurrent selection. Both bread wheat populations show high variability for plant height, days-to-flowering, and ripening. The AZ-UAN population is spike-awned and the MT-UAN population is awnless.

Development of a durum wheat population.

G. Martinez-Zambrano.

In 1995, a durum wheat population was made by hand-mating 100 pure lines selected from several CIMMYT nurseries, including four Mexican durum varieties: Mexicali 75, Yavaros 79, Altar 84, and Aconchi 89. CIMMYT nurseries were the Durum Yield Trial, High Protein Lines Trial, Drought Tolerant Lines Trial, and the 24th International Durum Screening Nursery (IDSN). The population CIMMYT-UAN is unexpectedly very uniform in maturity, plant height, grain, and plant type in spite of the number of parents involved, which may to indicate the reduced genetic base in durum wheat breeding at CIMMYT.

ITEMS FROM NEPAL

NEPAL AGRICULTURAL RESEARCH COUNCIL

National Wheat Research Program, Pupandehi, Bhairahawa, Nepal.

M.R. Bhatta, D.R. Pokharel, Ashok Mudwari, and B.R. Thapa.

Wheat crop and production statistics.

Wheat is the third major cereal crop of Nepal, after rice and maize. A minor cereal until 1960, wheat cultivation was limited to a small area (< 1,00,000 ha) in the western hills. The introduction of Mexican semidwarf, high-yielding varieties during mid-1960s had a highly significant impact on both the area and production of wheat in Nepal. Wheat occupied an area of 653,500 ha during the 1995-96 crop season. with total production of 1,012,930 MT and productivity of 1,550 kg/ha. The total wheat area, production, and productivity have been increased by 3.0, 10.7, and 7.6 %, respectively, compared to the 1994-95 wheat season. Weather conditions during the crop season were favorable, because of frequent rains and the absence of desiccating hot winds. The low productivity of wheat was due to low fertilizer use by wheat growers, inadequate irrigation facilities, late planting due to a late harvest of the rice crop, low seed replacement, and plant diseases particularly foliar blight complex caused by B. sorokiniana and P. tritici repentis. The major wheat cultivars currently popular are Nepal 297, UP 262. BL 1022, Bhrikuti, BL 1135, and Triveni in the terai region; and Annapurna-1 and Annapurna-3 (both Vee 'S'), Annapurna-4, and RR 21 in the hills.

Wheat breeding activities. The rice-wheat cropping system comprises more than 84 % of the total wheat area. The major objectives of the wheat breeding and varietal improvement program are to develop wheat cultivars that fit well into the rice-wheat cropping pattern, with high yield potential; resistance to multiple diseases (leaf and stripe rusts, major foliar blight pathogens, and loose smut); and tolerance to postanthesis heat stress. To create genetic variability for desirable traits, a modest hybridization program with 150 to 200 crosses per year among selected parents are made. F₂ populations are space-planted, and individual plant selection is made. A modified bulk system is used in the F₃ and F₄ generations. Plant progenies in segregating generations are selected based on resistance to disease especially to the black point fungus, remaining green at high temperature regimes during grain filling, and grain plumpness. This year, as many as 1,779 advanced/fixed lines were evaluated in the form of screening nurseries and yield trials at 14 different testing sites. A total of 2,449 segregating plan-V progenies were evaluated, and some 1,910 progenies were selected for the next cycle. New genotypes identified for release are BL 1496 (PRL"S"/TONI//CHIL"S") and NL 713 (CPAN169/HD2204) for the Terai, and NL 665 (LIRA/FUFAN/NEE#5"S") and WK 685 (PGO/SERI) for the hills.

Disease situation and breeding strategy. Leaf rust and the foliar blight complex fungi are the most serious yield-reducing pathogens in the Terai areas, whereas stripe rust and loose smut are the major problems in the hills. Two species of foliar blight pathogens, B. sorokiniana and P. tritici repentis, are the causes of blight symptoms in wheat. The predominance of the two species changes with the environmental conditions. Bipolaris sorokiniana predominates when the temperatures are relatively higher.

Leaf and stripe rust incidence was less and appeared late in the season even in susceptible cultivars in 1996. Helminthosporium leaf blight has remained a serious problem in all wheat-growing environments of the Terai. Yield loss to this pathogen is estimated at 23.8 to 27 % in susceptible cultivars. Recently released wheat cultivars BL 1135 and Bhrikuti possess a moderate degree of resistance to the foliar blight complex pathogens. Virulence for Lr26 and Yr9 was detected at a moderate level. The importance of adult plant resistance gene Lr34 and its combination with other genes is greatly realized in limiting leaf rust epidemics. Our present breeding strategy is to combine these durable resistance genes into a high-yielding, better-adapted, and foliar blight-resistant genetic background.

The CIMMYT wide cross advanced lines from T. curvifolium (CHRlYA 1, CHRIYA 3, and CHRIYA 7) in addition to some Chinese, Brazilian, and Zambian lines have exhibited a moderate degree of foliar-blight resistance under Bhairahawa conditions. Some of these lines have been widely utilized in the hybridization program and have given adequate level of resistance in segregating populations. Limited studies on the genetics of foliar blight resistance involving resistant versus susceptible genotypes indicated both qualitative and quantitative types of resistance.

Zero tillage cultivation of wheat. A new technique of zero-tillage wheat cultivation recently was developed by the National Wheat Research Program for low-land rice areas where wheat cultivation was not possible because of excessive moisture following the rice harvest. This technique involves soaking the wheat seed in fresh water for 10 to 12 hours, mixing the soaked seed with fresh cow dung, and then broadcasting the seed in standing rice 1 week before the rice is harvested, or surface-seeding just after the rice harvest. Fertilizers can be successfully applied 10 to 20 days after wheat seeding. This technique is being popularized among low-land rice farmers to bring one-third of winter rice fallow under the wheat crop.

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