SMALL GRAIN INSTITUTEPrivate Bag X29, Bethlehem, 9700, South Africa.
M. Craven.
Preharvest sprouting occurs when physiological mature wheat starts to sprout when still in the field due to heavy rain experienced during the harvest season. Although all of the current cultivated areas of the Free State are subject to PHS, the eastern Free State generally suffers the most from this phenomenon. Because sprouted wheat negatively effects the falling number, these two factors are closely linked.
The main focus of the PHS program is the routine evaluation of all current cultivars, especially newly released cultivars, for their inherent PHS resistance. The tendency of a cultivar to sprout under favorable conditions is determined with the use of a rain simulator. Approximately 3,000 wheat spikes were evaluated for this purpose during the 2003-04 season. In addition, ARC-Small Grain Institute breeding material is evaluated for PHS resistance to ensure that cultivars with poor PHS resistance are not released. During the past season, nearly 12,000 wheat spikes were evaluated for this purpose. A separate breeding program also was initiated with PHS resistance as the main focus. We hope that in the future, protein gels will simplify this task.
Because PHS is not the only factor that influences falling number (FN) of wheat, the FN project is currently focussing on factors that might influence FN, and the possibility of managing these factors to allow for the optimum FN to be obtained within a specified season. The effect of high kernel-moisture content, fertilizer applications, and the possibility of glyphosate treatments to enhance the drying period of wheat are currently long-term projects running within the FN program.
As of April 2004, a new project will be initiated at the University of the Free State to investigate the effect of frost damage at early grain-filling stage on various quality parameters. The effect of such treatments on the FN will also be investigated. We hope that this type of research will not only supply the producer with answers to unexplained low FN, but also will help to manage FN better.
A. Barnard, W.M. Otto, and T. Walsh.
Three production systems dominate in South Africa, dryland conditions in both summer and winter rainfall regions and under irrigation on a countrywide basis. Almost 50 % of the South African wheat production is accounted for by cultivation under dryland conditions in the Summer Rainfall Region, the Winter Rainfall Region and under irrigation accounting for the remaining production in South Africa. A national, cultivar-evaluation program is conducted each year at the Small Grain Institute, which entails the evaluation and characterization of all newly classified and released wheat cultivars of all seed companies on an objective and scientific basis.
The objectives of this program are mainly to characterize cultivars in terms of yield performance and yield stability, hectoliter mass, falling number, protein content, and other parameters grain quality, over environments and years. Another major objective is to compare cultivars in terms of agronomic characteristics, such as growth period, straw strength, shattering, and yield components and to make reliable and scientifically sound recommendations to producers and others for all production regions of South Africa.
The results of the program enable producers, including small-scale farmers, to make well-informed production decisions in terms of cultivar choice. Cultivar choice is a critical production decision that will greatly affect the profitability of the producer's enterprise.
Dryland production. Almost half of the South African wheat production is accounted for by cultivation under dryland conditions in the Summer Rainfall Region. Due to the large variation in climatic conditions and soil types existing in this region, wheat production is very challenging. Not only are good cultivation and management practices essential for successful wheat production, but also the correct cultivar choice. The dryland production area is divided mainly into four homogenous areas where different cultivars, mainly winter and intermediate types, are planted. Cultivar evaluation trials were planted at 17 sites throughout the Western, Central, and Eastern Free States and parts of Mpumalanga. The trials were successful and were reported. Twenty entries were included in the trials, of which seven were from the Small Grain Institute, seven from Monsanto, and six from PANNAR.
Production under irrigation. Wheat produced under irrigation amounts to about 20 % of the total wheat production of South Africa and has a stabilizing influence on the total production. Currently, six major irrigation regions exist, although irrigation farming is expanding into new production regions.
Spring wheat cultivars are planted mainly in a total of 60
evaluation trials at 31 localities in the different irrigation
areas. Entries in these trials were from the Small Grain Institute
(7) and Monsanto (5). Three advanced breeding lines also were
included. Analyses of variance, AMMI analysis, and biplots are
used in the interpretation of results and in identifying cultivar
adaptation and stability in the different production regions.
Results from these trials are available in a detailed report.
Two wheat producing areas are in the Winter Rainfall Region
The Swartland area stretches from Durbanville in the south to the Sandveld area around Elandsbaai in the north and from Saldana Bay in the west to the mountain ranges in the east.
The Rûens or South Coast area stretches from Botrivier in the west to the Albertina-district in the east and from Aghullas in the south to the Langeberg mountain range north of Greyton through to Riversdal.
The Winter Rainfall Region is well suited to the production of spring wheat cultivars, which do not require the same amount of cold to break their dormancy as that of the winter wheat cultivars grown in the rest of South Africa. Cultivar choice in the Winter Rainfall Region is of extreme importance due to the varied climatic differences between cultivation areas. The cultivars available differ in their yield reaction to the changing yield potential conditions that exist in the Winter Rainfall Region. Other important factors that also have to be taken into consideration are grain quality, hectoliter mass, and disease susceptibility.
The Western Cape experienced extreme weather pattern differences during the 2003 season resulting in a significant reduction in overall yield for the area. The Swartland area of the Western Cape had the lowest rainfall in decades, with the average rainfall for the period April to October being 27.5 % less than the long-term average for the area. The Rûens area, although wetter than the Swartland, recorded an averaged of 2.4 % less rain than the long-term average for the area.
Because of drought conditions in the Swartland during the 2003 production period, many lands were not cultivated or planted. Land that was planted yielded 50 % less on the average than that of a normal season. Weed and disease control was cut to the minimum. The result was a visible increase in weeds and also a decrease in grain quality due to low hectoliter mass.
The Cultivar Evaluation Program in the Winter Rainfall Region is run jointly by the Small Grain Institute and The Directorate of Agriculture of the Western Cape. The program consists of 13 sites in the Swartland and 13 sites in the Rûens, with 14 cultivars included in the trials. The cultivars, from ARC-Small Grain Institute, Monsanto, and PANNAR, are annually tested for yield potential, quality, disease resistance, and adaptability. However, because of the drought conditions that prevailed in the Swartland this past season, only three trial sites were harvested and appraised. These three sites were all located in the Sandveld area of the Swartland. The trials in the Rûens-area were harvested and reported.
S. Ramburan.
As part of the National Cultivar Evaluation Programme, the Small Grain Institute has introduced a related program in 2003 that involves the screening of wheat cultivars suitable for production in resource limited agriculture. Differences in production practices and resources of small-scale enterprises in comparison to commercial situations necessitated the introduction of cultivar-evaluation work in the resource limited areas of the country. A large proportion of resource-limited farmers in the major wheat producing regions of South Africa have the potential for commercialization and correct cultivar choice is sure to assist them in reaching this ultimate goal.
In 2003, cultivar-evaluation trials were planted at various small-scale farms that were representative of specific wheat-producing regions. A total of four dryland trials (15 cultivars) and three irrigation trials (16 cultivars) were planted. Cultivars originated from three different institutes, Small Grain Institute, Pannar, and Monsanto. During the season, the adaptability of the cultivars to the production environments were evaluated through observations of emergence problems, growth period, and disease damage. Statistical analyses were used to determine the yield and quality performance of the cultivars in the different environments.
The data obtained from the project will be used to ultimately characterize the different cultivars in terms of their suitability for production in different resource-limited areas. These results, together with those expected in 2004 and 2005, will eventually be used to assist small-scale wheat producers with reliable recommendations that are based on applicable scientific research.
G.J. Prinsloo.
Research on the control of different wheat insect pests is continuing. Our focus is on developing and using different kinds of alternate control methods. Besides the major use of plant resistance to control the RWA, other control agents like predators, parasitoids, entomopathogenic fungi, and the usefulness of plant volatiles are researched in collaboration with national and international partners. All these control options are being used in a integrated control program which, together with a diverse environment, are aimed at the prevention of the development of a resistant-breaking biotype of RWA. At the same time, these environmentally safe methods also are being used to control the minor insect pests of wheat in the country.
B. Khubeka.
Fusarium head blight has become a serious disease of both wheat and barley in South Africa. Regular yield losses varying from 5 to 40 % on wheat produced under center-pivot irrigation have been recorded. Research on the evaluation of fungicides and different cultivars is conducted in South Africa to control FHB.
J.S. Komen.
Since the first outbreak of Puccinia striiformis f. sp. tritici in 1996, wheat fields were surveyed periodically by researchers of the Small Grain Institute to monitor the occurrence, development, and distribution of stripe rust in South Africa. Disease nurseries are planted annually in all the important wheat-production areas of South Africa. Surveys also are carried out in Lesotho were wheat is grown in the summer. Samples were taken at the end of February from the disease nursery in Lesotho and pure isolates were inoculated on the world and European differentials. New virulence for Yr1 was detected in Lesotho during stripe rust surveys. The new pathotype has shown no new virulence on the commercially cultivars planted in the production areas of South Africa. The new pathotype 7E22A differs only from pathotype 6E22A (found in 1997) by its virulence to Yr1.
H. Hatting.
Seed plays a vital role in the potential crop yield of each small grain producer. Small grain seed must comply with legal requirements with regard to the purity and germination percentage before it can be marketed. The Small Grain Institute has a registered Seed Testing Laboratory in which international methodology (ISTA (International Seed Testing Association) methods) is used to determine the quality characteristics of seed. Germination and purity testing over the past year resulted in 456 analyses, in which the quality of each seed lot was tested to ensure that poor quality seed would not be planted. The laboratory provides a unique service. Having the infrastructure and experience, seed analyses are conducted objectively on a commercial and need-driven basis for the seed industry.
The laboratory was visited by several schools. This work contributes favorably to the income of the Seed Testing Laboratory. The services are client-specific and extended the commercial services of the laboratory.
C.W. Miles.
The Wheat Quality Laboratory plays an integral part in the breeding process and accurate and reliable data for researchers must be ensured. To accomplish accuracy and reliability, the laboratory takes part in ring tests sent out monthly by Sasko and quarterly by the South African Grain Laboratory.
During the past year, a total of 66,083 analyses were performed for researchers at the Small Grain Institute and 5,003 analyses were performed for external clients.
The laboratory experienced a very prosperous 2003-04. In spite of a dry season and the fact that farmers in the laboratories operational area planted 25 % less wheat, the external income was increased by five percent.
During the year the following activities took place:
- Lientjie Visser received training at different USA laboratories,
- Marie Potgieter attended an ICP-course at the Pretoria Technicon,
- a new Compact Titrator was purchased,
- the database was upgraded with information on rural areas in the Eastern Cape and Thaba 'Nchu, and
- laboratory personnel attended two meetings of Agri-LASA, the national control scheme of South Africa's laboratories.
The main objective of the laboratory will always be to provide clients with accurate and reliable results, upon which they can make the necessary management decisions.
Ms. Una Aucamp has resigned as a breeder and Ms. Rachel Oelofse
was appointed to replace Ms. Anri Barnard. Anelizwa Makhathini
joined the Small Grain Institute as a research technician in Plant
Breeding. Dr. Hussein Shimelis has been appointed temporarily
at Plant Protection as a rust expert. Iona Basdew replaced Karen
Naudé to handle the Karnal bunt laboratory, washing facility,
and take-all research. Bongani Kubheka replaced Khaya Ntushelo
as a researcher on Fusarium. Cedric Baloyi, Lucas Serage, Nora
Mokoka, and Tshepo Maeko were appointed at Soil Management as
researchers. Kenneth Mokoena joined Soil Management as a research
technician.
UNIVERSITY OF PRETORIA
Department of Genetics, Forestry and Agricultural Biotechnology Institute, Hillcrest, Pretoria, Gauteng, South Africa.
http://www.up.ac.za/academic/genetics
A-M. Botha, M.T. Matsioloko, F.B. du Preez, L. van Eck, K. Muller, R. van Zyl, A.C. Laubser, E. Swanepoel, Z.A. Swanevelder, and R. Walters.
M.T. Matsioloko, L. Van Eck, R. Walters, and A-M. Botha.
The RWA is a major factor hampering the production of wheat. In the present study, wheat NILs Tugela DN (Dn1; SA1684/*Tugela), Tugela Dn2 (SA2199/*5 Tugela), Tugela Dn5 (SA463/*5 Tugela), and Tugela were employed to study differential gene expression induced by aphid infestation using cDNA-AFLP analysis. cDNA was synthesized using mRNA extracted from leaf material collected at 0, 1, 2, 6, 12, 24, 48, and 120 hours post infestation (HPI) with RWA. cDNA-AFLP profiles were obtained after analysis on a LICOR automated analyzer. Differentially expressed, transcript-derived fragments (TDFs) were identified following an in silico subtraction of the measured band intensities of Tugela from the Tugela DN. The data were further analyzed using Hierarchical Cluster Analysis and Spearman Rank Correlation. Subclusters of TDFs (Table 1) indicated genes putatively involved in conferring resistance to the RWA.
| Subcluster Number | Hours post infection | |||||||
|---|---|---|---|---|---|---|---|---|
| 0 | 1 | 2 | 6 | 12 | 24 | 48 | 120 | |
| 1 | -- | + | 0 | 0 | -- | + | -- | + |
| 2 | + | + | -- | 0 | -- | -- | -- | + |
| 3 | -- | + | + | -- | 0 | 0 | + | -- |
| 4 | -- | 0 | 0 | -- | + | + | + | -- |
| 5 | -- | + | -- | -- | + | + | -- | -- |
| 6 | -- | + | -- | -- | -- | -- | + | + |
| 7 | -- | -- | + | + | -- | -- | -- | -- |
| 8 | + | + | + | -- | -- | -- | -- | -- |
| 9 | + | -- | -- | + | + | -- | + | -- |
| 10 | + | 0 | -- | -- | -- | + | + | + |
| 11 | -- | -- | + | -- | -- | + | + | + |
| 12 | 0 | -- | -- | -- | -- | + | + | + |
| 13 | + | + | -- | -- | -- | + | + | -- |
| 14 | -- | -- | 0 | -- | + | + | + | + |
| 15 | -- | + | + | + | -- | -- | -- | -- |
F.B. du Preez and A-M. Botha.
Our current research focuses on the identification and classification of R-gene candidates from the wheat genome; more specifically on the NBS-LRR gene family for which a large number of members and their avirulence complements have been cloned across multiple plant genera. Using initial Position-Specific Iterated Blast searches (PSI-Blast), many putative members of this gene family for species of the Triticeae tribe were identified and used to build a Hidden Markov Model (HMM) of the nucleotide-binding-site domain of this gene family. Using this model, many high-scoring, EST sequences generated by among others the International Triticeae EST Cooperative (ITEC) were obtained.
Phylogenetic analysis of the gene family members obtained for
wheat and its putative genome-donor species was performed. A comparative
analysis between the wheat group, barley, rice, and Arabidopsis
confirmed previous observations with regard to the domain structure
distribution observed over large taxonomic groups. NBS-LRR RGA
sequences have great utility in marker design for mapping the
position of localized clusters of this resistance-gene family
and for identification of candidate open-reading frames in mapped
R-gene containing regions.
K. Muller, A.C. Laubser, E. Swanepoel, and A-M. Botha.
Two thousand wheat ESTs, including 156 wheat NBS-LRR sequences were obtained using degenerate primer sets designed from the consensus NBS region from other genome studies (e.g., Arabidopsis and rice), RACE-PCR, suppression subtractive hybridization (SSH), and cDNA libraries. Previously, we confirmed the cosegregation of a SSH clone, AMO00SSHL1 (GenBank accession # AF4446141.1; e-125) and NBS-RGA2 (368 bp; GenBank accession # AF326781; 7e-13; NBS-RGA2) with the RWA resistance gene Dn1 at a linkage distances of 7.41 cM and 3.15 cM, respectively. We presently are constructing a framework map using SSRs and AFLP analysis, and a F2/3 segregating population composed of 184 individuals that derived from a 'Tugela/Tugela DN' cross in an effort to map all the ESTs obtained through our study. The genetic map will provide information to be used in the physical mapping of these genes using BAC libraries.
R. van Zyl, Z.A. Swanevelder, and A-M. Botha.
RWA feeding causes the induction and down regulation of proteins as well as the appearance of novel proteins, as the plant attempts to defend itself against attack. The exact function of these proteins is unknown, but they appear to be involved in the defense of the plant against aphid feeding. RWA-induced proteins are found in the apoplast (along the stylet route) and it has been shown that aphid feeding on resistant plants turn to nonphloem feeding to survive. Induction of proteins was confirmed during RWA infestation of the resistant cultivar Tugela DN.
Two-dimensional gel electrophoresis has shown that bands obtained from SDS-PAGE analysis represent more than one protein. This study shows an induction of five groups of protein, which correspond to seven proteins. The first and second induced proteins (~ 36 and 26 kDa) could possibly be related to the PR-proteins, b-1,3-glucanases and chitinases. These enzymes have sizes that correspond to those of the induced PR proteins. We previously reported that RWA infestation induced b-1,3-glucanase isozymes having pI values ranging from 3.6 to 9.3, whereas feeding results in the expression of one chitinase isozyme with a pI of 5.5. Group-3 proteins are not serologically identified. Occurring close to this group was three induced proteins (all ~ 20 kDa) and two induced proteins (< 14 kDa). These proteins are not similar to the group-4 proteins. Protein sequence analysis of induced proteins would help clarify the exact nature of these proteins and their role in plant defense and, thus, the analysis of these induced proteins using MALDITOFF is under way.
UNIVERSITY OF STELLENBOSCH
Department of Genetics, Stellenbosch 7600, South Africa
G.F. Marais, H.S. Roux, A.S. Marais, and W.C. Botes.
The breeding program was continued and promising new lines
were selected. Of the six commercial cultivars, USGEN 19, Rex,
Kiewiet, Bacchus, Tobie, and Ibis, Kiewiet has become susceptible
to stem rust, whereas Rex and Bacchus have shown moderate susceptibility.
Results of the 2003 trials have shown that, on average, the better
grain yielders, Bacchus and Tobie, out-yielded the best wheat
cultivars by 27 %. Plant breeder's rights were obtained for a
new rye cultivar Duiker.
A commercial-scale, recurrent-selection program is being established.
Following each selection cycle (4 years), the Ms3 male-sterility
gene and hydroponic culture of cut tillers are being used to effect
cross-pollination of male and female spikes. Female plants destined
for crosses are selected as F1 seedlings, however, male parents
are field tested and are not used in crosses until the F7. We
managed to advance F1 male families to the F6 in only two seasons
(2002-03), making use of single-seed descent and off-season planting.
Following stringent field selection (single spikes) among and
within F4 families for leaf, stem, and stripe rust resistance
during the winter of 2003, about 450 F5 rows were grown during
the summer (2003-04). These will be evaluated as unreplicated
F6 field plots in the winter of 2004. From these nurseries, the
first set of male parents will be selected for use in crosses
in the fourth year (2005). The size of the breeding population
will gradually be expanded in the coming years. In 2004, an attempt
will be made to introduce MAS on a limited scale.
In a program aimed at the transfer of leaf, stem, and stripe rust resistance genes from wild relatives, we found two closely linked, leaf and stripe rust-resistance genes from T. turgidum subsp. dicoccoides were inserted on chromosome arm 6BS. Leaf rust resistance from Ae. kotschyi could be translocated from a group-2 chromosome addition to a wheat chromosome, probably 2D, utilizing the tendency of unpaired chromosomes to undergo centric break and fusion translocations. Aneuploid analyses to map genes from Ae. sharonensis and Ae. peregrina were continued. An attempt to shorten chromosome segments derived from Ae. speltoides through disruption of meiotic chromosome pairing was continued, and an attempt to induce translocation of target genes from unknown group-3 chromosomes of Ae. biuncialis and Ae. caudata to wheat.
We confirmed that RWA-resistance gene, Dn5, is located on chromosome arm 7DL of wheat. Telosomes 7DL with and without Dn5 could be recovered and confirmed with molecular markers. A DH mapping population derived from the cross 'PI294994/Chinese Spring' is now being characterized in an attempt to relate Dn5 to known markers on 7DL.
A recombined Lr19 translocation, Lr19-149-299, was used in an attempt to shorten it still further through use of ph1b-induced homoeologous pairing. Testcross progeny are being screened specifically for the absence of the segregation distortion gene, Sd2.
In a program aiming to transfer salt tolerance from Th. distichum to triticale, chromosomes IIJ1d, IIIJ1d, IVJ1d, VJ1d, and VIIJ1d were putatively identified as being involved in its expression. An attempt is being made to develop disomic addition lines of each target chromosome in triticale. Additions were recovered for IIIJ1d and VJ1d. The additions were crossed to triticale monosomics for the A, B, and R genomes of the corresponding homoeologous groups. For each cross, double monosomic lines were selected and testcrossed with triticale. The testcross F1 is being screened (GISH) for centric breaks and fusion translocations involving triticale and Thinopyrum chromosomes. An attempt to develop SCAR markers for the critical Thinopyrum chromosomes has produced three markers, specific for IIJ1d and IIIJ1d. Backcrosses to develop the remaining additions are being continued.