SMALL GRAIN INSTITUTEPrivate Bag X29, Bethlehem, 9700, South Africa.
J.C. Aucamp, O. Müller, D.J. Exley, and H.A. van Niekerk.
The winter and intermediate wheat breeding program has the exclusive aim of supplying new cultivars to the dry land winter wheat producer of the Free State. The development and release of high-yielding, well-adapted and stable winter and facultative wheat cultivars for the Eastern, Central, and Western Free State can be accomplished by breeding for cultivars with long coleoptiles and tolerance to drought and heat stress. To help the farmer make a profit from wheat production, these cultivars must have a high falling number, very good preharvest sprouting resistance, disease resistance (especially for the yellow, stem, and leaf rusts), and Russian wheat aphid resistance. Bread wheat quality characteristics of the newly released cultivars have to comply with the quality criteria set by the processing industry. Cultivars with all these features will help the farmer to reach maximum yield and keep input cost as low as possible.
During 2000, five new lines were identified that will be submitted to the Wheat Technical Committee for provisional classification. All these lines (T98/5, T98/7, T98/8, T98/21, and T99/10) have improved resistance to yellow rust, compared to the previously released cultivar Elands. Good preharvest sprouting resistance is another feature of these lines. Russian wheat aphid resistance is proven in T98/5, T98/7, T98/8, T98/21, and T99/10.
Because resistance to yellow rust is of prime importance in the winter wheat program and natural infections do not occur to the same extend each season, we are investigating the possibility of screening for resistance to yellow rust in the Lesotho Mountains during the summer months.
F. Middleton and P. Delport.
The aim of this breeding program is to generate and then manage genetic variation in such a way that an assortment of desired traits are fixed in a single plant. We will achieve this by attaining a segregating plant population via hybridization and then improving the desired gene frequency in subsequent generations by use of a modified pedigree selection method. Genotypes generated in other breeding programs are also introduced and evaluated in the program.
Because the breeding is aimed at the identification of generally adapted cultivars, specific adaptations also are select for because of the heterogeneity in climactic and ecologic conditions within the Western Cape. Promising cultivars are evaluated at 11 sites that were preselected to sample typical commercial conditions. In addition, the facilities at the two state-owned experimental farms also are used to evaluate advanced nonsegregating lines and to screen segregating material. The 2000 trials included the evaluation of 30 elite, 160 senior, and 715 junior entries.
Ultimately, the main objective is the improvement of resistance to rust (stem, leaf, and yellow) and baking characteristics, the 2000 material also was characterized by resistance to eyespot and Septoria and aluminum tolerance. Diversity, particularly in respect to baking quality, was extended further by the addition of several CIMMYT genotypes. The impact of these introductions will most certainly be realized when the material from crosses between these and the more adapted local varieties are evaluated.
Baviaans and Steenbras, and one advanced line have been earmarked for final classification in the winter rainfall region. In addition to several years of evaluation for agronomic suitability, which they have passed, these lines also have been subjected to rigorous quality testing. Quality data collected over at least 3 years have proven them to be suitable, if not better, than the available cultivars. Several first-year lines also have proven themselves to be suitable for commercial production but will have to be subjected to more quality tests.
F.P. Koekemoer and F. Groenewald.
During the 2000 season, the new cultivar Baviaans was released. Baviaans is a semidwarf spring wheat cultivar with a good yield potential and extremely good tillering capacity. Furthermore, this cultivar reacts differently to certain nitrogen applications. Baviaans is currently being multiplied and seed will be available commercially during 2002.
Take-all evaluations at Potchefstroom showed good infection. Two lines that were identified with good resistance during the previous three seasons were evaluated with all the spring wheat cultivars currently produced in South Africa. Crosses were made during the 1998 season between tolerant lines and genotypes with good quality characteristics. These lines will be tested as F3 lines during the 2001 season.
We decided to evaluate local germ plasm at a suitable site for exposure to more than the two stripe rust pathotypes currently found in South Africa. Uganda was identified as this screening site. The first cycle was from 6 June, 1999 until 14 January, 2000. The second cycle was completed by June 2000. A second devastating disease, Karnal bunt, was identified in South Africa during the 2000 wheat production cycle. The area where the outbreak occurred currently is under quarantine. his quarantine will affect the irrigation program to a large extent, because most of the evaluation sites are present in the quarantine area.
A.D. Barnard and M.V. van Wyk.
The incorporation of new and advanced germ plasm and breeding material are important to prevent genetic narrowing. Annually, wheat, barley, triticale, and rye are imported form CIMMYT (Mexico), ICARDA (Syria), and Uruguay. These lines undergo intensive, daily evaluations at two localities namely Bethlehem, in the Free State, and Tygerhoek, in the Western Cape, for agronomic adaptability, disease resistance, yield potential, and quality characteristics. During the 1999-00 season, a total of 18 nurseries and 11 trials were planted and evaluated. Outstanding lines were selected and designated directly to the different breeding programs, whereas good lines were incorporated in a specialized crossing block for improvement of undesirable characteristics with the focus on future releases. This material will aid breeders in developing improved cultivars for both the commercial and small-scale farmers.
R. Prins, V.P. Ramburan, and W.H.P. Boshoff; L.A. Boyd and T. Worland (Cereals Research department John Innes Centre, UK); Z.A. Pretorius (Plant Pathology Department, University of Free State, RSA); and J.H. Louw (University of Stellenbosch, RSA).
The 'Kariega/Avocet S' doubled haploid mapping population was characterized for its yellow rust phenotypes in a field trial consisting of randomized complete blocks with four replications and six control plots per replication of the susceptible parent, Avocet S. All plots were scored independently by three experienced plant pathologists. Preliminary analysis of associations of AFLP and SSR markers using single marker, marker regression, and interval mMapping methods suggest the presence of at least two adult-plant resistance (APR) genes in Kariega. Field trial analysis of the genetic material derived from Cappelle Desprez confirmed the effectiveness of Yr16 (APR) against the South African pathotypes (6E16 and 6E22).
A. Barnard, F. van Niekerk, M. Blaauw, and P. Craven.
The three dominant production systems in South Africa are dryland conditions in both summer and winter rainfall regions and irrigated conditions on a country wide basis. Almost 50 % of the South African wheat production is accounted for by cultivation under dryland conditions in the summer rainfall region, whereas wheat production in the winter rainfall region and under irrigation accounts for the remaining production in South Africa. A national cultivar evaluation program is conducted each year at Small Grain Institute that 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 grain-quality parameters 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 other role-players 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.
Frost and cold weather conditions cause sporadic but major crop losses in especially the irrigation and dryland wheat production regions (±70 %) of South Africa. Various spring and winter wheat cultivars were evaluated for their cold resistance by using the whole plant method and a conductivity test. Forty-three frost-risk areas were investigated for possible patterns in the occurrence of frost. In these areas, the incidence of temperatures below 0°C and a long-term record of minimum temperatures were followed. The high-risk areas will be characterized according to this climactic information. Cultivars will have to be evaluated for their susceptibility to frost and cold damage using 2-year data, whereas a short-term solution will be agronomic strategies to limit the risk of frost damage to wheat production in high-risk areas.
More and more producers are saving seed from season to season for planting. The problem of carry-over seed seems magnified in the light of the high seed prices. According to a SANSOR (South African National Seed Organization) estimate, up to 37 % of all seed planted in the summer rainfall area may be carry-over seed. Many a producer has suffered by planting poor quality carry-over seed rather than good quality seed, because this seed is not tested and not protected by law. Other agronomic problems are a greater contamination of weeds and possible problems with green, unripe kernels among the ripe grain. In addition, bakers and millers set quality prerequisites with regard to the grain they purchase in the deregulated wheat trade. Therefore, producers must decide on the most suitable cultivars and plant high quality seed to prevent production losses and to ensure a marketable product.
The Small Grain Institute has an accredited Seed Testing Laboratory that uses international methodologies (ISTA methods) to determine the quality characteristics of seed. The genetic purity analysis, determined visually, has accounted for a few hundred tests in the past year. Unfortunately, the Small Grain Institute has lost this expertise during the past year due to the resignation of the coördinator. Grading of small-grain seed as a result of low falling numbers has become a more popular test, with the producer looking for verification. The germination and purity testing over the past year resulted in 500 analyses, in which the quality of each seed lot was tested to ensure that poor quality seed would not be planted. Several seed lots did not comply with the Plant Improvement Act because of poor quality. The laboratory provides a unique service, having the infrastructure and experience, and seed analyses are conducted objectively on a commercial and need driven basis for the seed industry.
Preharvest sprouting research addresses problems that are currently being experienced by cereal producers and the cereal industry. Farmers have to earn a living and bakers can not afford to buy wheat that does not comply with international baking standards. Therefore, answers need to be found for low falling numbers. This season, no serious rain was reported, yet some farmers had serious problems with wheat that was downgraded because of low falling number.
Many projects are currently underway in an effort to find answers, one being the effect of early harvesting (14-22 % moisture) on falling number. Further studies entails the evaluation of cultivars of all localities planted on a national basis in all wheat producing areas in South Africa (40 in total). With all this data, we hope to gather more insight into the problem. Emphasis also is placed on the inherent a-amylase activity of newly released cultivars.
Because preharvest sprouting (PHS) is such an important research area, we have combined efforts with the Cereal Research Non-Profit Co. in Szeged, Hungary. In such a combined effort, various factors are evaluated such as the screening of cultivars from both South Africa and Hungary for elevated PHS tolerance. The aim is to broaden the existing genetic breeding material from both countries, which will eventually lead to cultivars with better resistance.
V.L. Tolmay, G.J. Prinsloo, J.H. Hatting, and R. Maré. [p. 195]
The ARC-Small Grain Institute now has six wheat cultivars with resistance to RWA in commercial production, Tugela-DN, Betta-DN, Gariep, Limpopo, Caledon, and Elands. Other RWA-resistant cultivars also are available from commercial seed companies. An estimated annual total of more than 70 % of the wheat producing area of the Free State is planted to RWA-resistant wheat.
Aphelinus hordei a host-specific parasitoid of the RWA. Although never released in Lesotho, is has crossed the border from the Free State Province to Lesotho and has become established in the wheat-producing Mokhotlong Valley of the Mountain Kingdom. We have hope that establishment will take place in the mountainous regions of the eastern Free State to the benefit of wheat producers in South Africa as well. At present, attempts are being made to import more natural enemies in order to increase and diversify the natural enemy spectrum.
Chemical control of RWA by means of insecticide sprays has been dramatically reduced. The average area treated with insecticides decreased from 85 % in 1990 to 30 % in 1997 and was projected to decrease to only 16 % in 2000 with the percentage of farmers using insecticide sprays decreasing by 43 % from 1990 to 1997. The number of sprays per year decreased from four during the 199092 seasons to only one in the years after 1996. The RWA-resistant cultivars released by ARC-SGI for commercial use are tested under field conditions with and without chemical control methods to determine the efficacy of these cultivars. All resistant cultivars tested so far give a yield and hectoliter advantage and in almost all instances, applying either an insecticidal seed dressing or foliar spray for improved control is not an economically viable option. A backcross program is still used to transfer RWA resistance to agronomically acceptable lines for use in the winter and intermediate wheat breeding programs.
Entomopathogenic fungi are simultaneously being investigated for development as mycoinsecticides against the cereal aphid-complex. Two indigenous hyphomycetous species, Beauveria bassiana and Paecilomyces farinosus, were isolated from RWA and are being screened for their virulence against the RWA and other important cereal aphid species. Techniques for mass production of suitable indigenous isolates by both solid substrate fermentation and liquid fermentation are currently being investigated in collaboration with a private company in KwaZulu, Natal. Field trials with an exotic strain of B. bassiana (Mycotrol ®) indicates that a commercial preparation of this pathogen is capable of significantly reducing RWA numbers on resistant wheat. Entomopathogenic fungi also will be screened against the oat aphid, an important aphid pest of wheat in the winter rainfall region of South Africa.
Karen Naudé.
In December 2000, Karnal bunt was identified for the first time in the Douglas area in South Africa. The farm where the disease was found and the municipal area of Douglas were placed under quarantine. Although the disease does not cause major yield or quality losses, it affects flour color, and dough strength and grain with an infection level of more than 3 % is not fit for human consumption. Although South Africa has not exported wheat during the past decade, the presence of the disease may affect exportation of other crops.
A Karnal Bunt Task Team, chaired by Dr. Cobus le Roux of ARC-Small Grain Institute, was founded with the objective to determine the extent of the infection through a national survey and to identify control measures to contain the disease as quickly as possible and in the most economical way. Other team members include the National Department of Agriculture, the Grain Silo Industry, Grain South Africa, and the South African National Seed Organisation. A well-known Karnal bunt expert from CIMMYT, Mexico, Dr. Guillermo Fuentes, was invited to South Africa for discussions with these organizations. Topics discussed included quarantine regulations, control measures, and future research.
W. Otto, W. Kilian, H.C.S.A. van der Merwe, E. van der Merwe, B. van Rensburg, and C. Fourie.
Trials were planted in the Vaalharts, Riet River, Brits, and Loskop irrigation schemes to evaluate the influence of split applications of nitrogen on the growth, yield, and grain quality of wheat cultivars. Several of the currently released cultivars were planted. Nitrogen was applied at planting, at early and late tillering, and at flag leaf/ear emergence growth stages. A total N application of 200 kg N/ha at Vaalharts and Riet River, and 180 kg N/ha at Loskop and Brits, was applied. Cultivars were tested at seeding densities of 60, 120, and 180 kg seed/ha.
The average yield levels in the trials in 1998 were on average 5-6 t/ha at Loskop and Brits and 7-8 t/ha at Vaalharts and Riet River. The split application of N resulted in significant yield responses. The split application of 100 kg N/ha applied at planting, 30-50 kg N/ha applied at late tillering, and 30-60 kg N/ha at flag leaf stage produced the highest yield. This treatment also produced the highest hectoliter mass of the grain, which indicates the positive effect of N applications during the later growth stages on kernel size and weight. Protein content of the grain was increased by the application of N at flag leaf stage. These results indicate that the management of N up to the late tillering stages is aimed at optimizing yield potential, and N applications during the later growth stages will benefit grain-protein content. Only small yield differences were measured between the tested seeding densities, although lodging increased at the highest level, especially in combination with high, early N applications. The lowest seeding density also yielded the lowest yield at all localities, indicating that the recommended range of seeding density of 100-120 kg seed/ha is still applicable for the cultivars tested.
The results from this project are of great importance to the wheat producer in the current marketing system. We now can aid the producer with N recommendations regarding the amount and split applications of N to reach yield potential levels and produce acceptable levels of grain quality.
During the last year, six new personnel joined Small Grain Institute. Pieter Craven replaced Dr. Sierk Ybema as researcher. Maryke Blaauw was appointed as researcher in Annelie Barnard's position who was promoted to Program Manager after Dr. John Purchase resigned. Michelle van Wyk was appointed as technician, replacing Antoinette Otto. Felix Middleton was appointed as wheat breeder in the Western Cape. Godwin Khorombi and Jan Ramalepe were appointed as researcher and technician after Johan Smit and Robbie Lindeque resigned.
UNIVERSITY OF STELLENBOSCH
Department of Genetics, Stellenbosch 7600, South Africa
G.F. Marais, F.L. Middleton, and A.S. Marais.
Two advanced triticale lines were selected for preliminary release in the winter rainfall region in 2001. These are (1) a selection from CIMMYT's 28th ITYN-48 (SUPI 3//HARE 7265/YOGUI 1) and (2), a selection from the local cross 'KIEWIET/4/W.TCL83/HOHI//RHINO 4/3/ARDI 1'.
The implementation of a recurrent selection procedure for wheat was continued. We believe that a wheat breeding program can be based solely on recurrent selection using genetic male sterility and that this can be done very cost effectively. Marais et al. (2000) described the use of a hydroponic system to pollinate and ripen male sterile spikes cut at flowering. The technique could be improved by the use of larger galvanized iron trays each of which accommodate about 230 female spikes and up to 70 male spikes. Male spikes were placed in two narrower trays positioned on both sides of the main tray and raised about 600 mm. The main tray was provided with inlet and outlet holes making it possible to rapidly change the nutrient solution without moving the female spikes. This improved the seed set to about 80 % and the 1,000-kernel weight to 16 g. Seed quality could be improved still further making use of hormone treatment, however, the already high germination percentage made it unnecessary to expend the extra time and effort. Since 1998, we are expanding a genetically diverse base population segregating for the dominant male sterility gene, Ms3, and rich in genes for adaptation, quality, yield, and pest resistance. Selection is done on both the male-sterile and male-fertile components, however, only the male-fertile populations are field tested and selected. The F2-F4 populations are grown as bulks at representative localities within the production area. The test location can be selected to differ for generations. Although selected F4 spikes are harvested singly, F2 and F3 spikes are harvested in bulk. Thus, there are no pedigrees to keep, no F2-F4 field books and tags, and planting and harvesting operations are simple. From the F5 onwards, the program has the shape of a regular breeding program for a self-fertilizing crop, namely, progeny testing and selection of the F4-derived lines. Following the evaluation of F5 ear rows for yield and quality, the superior selections are used as male parents for hybridization. During the crossing cycle, both the male and female parents can be selected (seedling disease resistance or molecular markers) before intercrossing them. Annually the best selections from our pedigree breeding program is used as male parents, this strategy will be continued until the first cycle of male sterile selections have progressed to the F5 and can be used as male parents. Although the population will be closed at this stage, it will still be possible to continuously introduce new genes to the base population following pre-breeding. This can be done through subcycles of recurrent selection in which the introduced germ plasm is used to pollinate male sterile spikes taken from the base population.
Following the induction of allosyndetic recombination, four Lr19-149 recombinants were recovered. When an attempt was made to select double recombinants following the hybridization of the proximally shortest recombinant (Lr19-149-299) with a distally shortened recombinant (Lr19-149-478), data were obtained which suggested multivalent formation during meiosis. Thus, all exchanges did not necessarily involve chromosome 7B. An attempt is therefore being made to determine which group-7 chromosomes were involved in each exchange.
Two AFLP fragments were found to be linked to the presence of the VPM1 translocation carrying the Pch1 resistance to eyespot. One of the polymorphic fragments was cloned and sequenced. Appropriate primers were designed and tested on a set of NILs. They were shown to amplify a codominantly inherited fragment of approximately 200 kb that includes a highly polymorphic microsatellite area. The marker is presently being tested for cosegregation with the Ae. ventricosa derived endopeptidase marker, Ep-D1b.
Attempts to find molecular markers associated with Th. distichum chromosomes having genes for salt tolerance were continued. For this purpose, populations differing with respect to salt tolerance and combinations of addition chromosomes they retained were selected among Th. distichum / 4x rye // 2x rye progenies. A total of 29 putative disomic additions and 13 putative monosomic additions of Th. distichum chromosomes to triticale also were selected and an attempt is being made to determine their homoeology relationships. The material also includes plants showing degrees of apomixis and perennial growth.
Backcrosses to transfer leaf and stripe rust resistance from
several Triticum species to common wheat were continued.
Also, NILs differing for the presence or absence of group-3 wheatrye
translocations were developed in three wheat varieties (Inia 66,
Condor, and SST3). The translocations included the noncompensating
T3AS·3RS translocation of Acosta (1962) and two compensating
translocations with constitutions T3AL·3RS and T3BL·3RS
developed by us. The NILs were yield tested at the Welgevallen
Experimental Farm in 2000. Each translocation appears to be associated
with a sizeable yield (17-54 %) and hectoliter mass (3-8 kg) penalty
and that it is unlikely to be of use in breeding in its present
form.