ITEMS FROM SOUTH AFRICA

SMALL GRAIN INSTITUTE

Private Bag X29, Bethlehem, 9700, South Africa.

Plant breeding - Winter and Intermediate Wheat Breeding Program.

H.A. van Niekerk, J.C. Aucamp, D.J. Exley, and O. Müller.

The aim of the Winter and Intermediate Wheat Breeding Program is to develop and release new, high-yielding, well adapted, and stable cultivars for dryland conditions in the eastern, central, and western Free State. These cultivars must comply with the quality criteria set by the processing industry and have resistance to diseases (such as leaf, stem, and stripe rusts) and RWA.

The new intermediate cultivar Elands was released in 1999. Elands is a well-balanced bread wheat with excellent milling and mixing characteristics and good protein quality. The cultivar completely meets all the quality requirements that rule the 'new market environment' in South Africa. Elands also has excellent RWA resistance, very good preharvest sprouting resistance, and exceptional hectolitre mass. Elands is resistant to stem rust, but unfortunately, it is susceptible to leaf and stripe rusts.

Stripe rust occurred in South Africa for the first time during 1997. At this time we have two pathotypes. Because resistance to this disease is a major concern to us, we are looking at the possibility of screening for yellow rust and the possibility of shuttle-breeding at Adana in southern Turkey.

Plant breeding - spring wheat breeding.

H.A. van Niekerk, F.P. Koekemoer, A.D. Barnard, T.G. Paxton, M.S.S. Jordaan, R. Brits, F.J. Groenewald, and E. Vermeulen.

Line KBSP95/26 will be sent in for final classification. KBSP 95/26 is a early maturing, semidwarf, spring wheat line that is adapted for irrigated and rain-fed conditions.

The following aspects were evaluated during the previous season:

1. The raised-bed planting system developed by CIMMYT as a normal planting procedure. The data still need to be analyzed statistically. The main aim is to eventually lower irrigation and farmer's input costs to increase profit margins. Dr. Ken Sayre from CIMMYT proved that seeding rates, fertilization, and water requirements can be lowered by this technique.

2. A total amount of 150 kg nitrogen was applied at the second node stage. An application of 100 kg of nitrogen before planting, two topdressings of 50 kg of N 6 weeks after planting, and 30 kg N at the flag leaf stage were applied. Most lines in the trial had increased yield, hectolitre mass, and protein content.

Two lines that showed take-all resistance in 1997 were planted in the field in 1998, and both lines were less susceptible than all the commercial cultivars currently planted, except SST 57, a solid-stem cultivar released by Sensako (Table 1). Line 1 was less susceptible than line 2. The F2 population originated from crosses between lines 1 and 2. Other parents from the irrigated spring wheat crossing block were planted at the same locality. Five spikes were selected from rows that had less than 15 % white spikes. These spikes were bulked for further evaluation in the F3 generation in the next season.

The biannual Southern African Plant Breeding Symposium will be held in Harare, Zimbabwe, from 16­19 March, 2000.

Plant breeding - triticale and oat breeding.

O. Müller.

During 1998, a mild to warm autumn caused a severe crown rust infestation on the majority of oat cultivars and lines. Only 14 % of the evaluated oat entries had good resistance. A promising new forage oat line was selected and will be tested under grazing conditions in 1999.

Crown rust (Puccinia coronata) reduces the ability of young oat plants to harden at low temperatures. The loss of cold resistance is proportional to the severity and length of exposure to the disease and explains why the cultivar Maluti, which is generally tolerant to low temperatures, was susceptible to cold damage during the winter months.

Crown rust also effects the yield and quality of forage production. Contrary to general opinion, crown rust does play a significant part in forage oat production. Cultivars meant for inclusion in fodder flow programs must be stable, with regard to disease and cold resistance, under an ever-changing environment. New releases in the future will be based on yield and disease resistance and not on dry material production alone.

Plant breeding - quality laboratory.

H.A. van Niekerk, F.P. Koekemoer, C.W. Miles, K.B. Majola, and M.L.T. Moloi.

Wheat quality has become very important in South Africa. A new, liberal, marketing environment lends itself to buying on an individual cultivar basis, as is the common practice in many countries that have deregulated wheat marketing systems. The wheat quality laboratory at the Small Grain Institute is currently analyzing the relative milling and baking worth, including bran-carrying capacity, of the South African wheat cultivars on a scientific and selection-index basis. This information will create clear market signals as to what the market requires and lead to concomitant higher prices for improved quality. Therefore, this laboratory has become an integral part of the breeding programs at the Small Grain Institute. Other departments at the Small Grain Institute, wheat producers in the area, and small millers make use of this laboratory and contribute to the more than 50,000 analyses that are performed here each year.

Plant breeding - preharvest sprouting.

A.D. Barnard.

The major objective in preharvest sprouting research is to solve the problems experienced by the cereal producers and the cereal industry. This study aims to characterize newly released cultivars, determine their sensitivity to the environment (G x E), and evaluate advanced breeding lines for their preharvest sprouting tolerance.

The mechanism of dormancy also will be characterized for the roles played by certain sugars, amino acids, proteins, and enzymes. The oxidative pentose phosphate pathway might be the process involved in the loss of seed dormancy.

The effects of seed treatment and preharvest sprouting seed on the emergenceence and yield of winter wheat in South Africa were studied during the past two seasons. Seed treatment had no significant effect on germination, although germination and emergence were reduced relative to the sprouting severity of the seed.

The South African wheat crop was generally characterized by low falling numbers this season, which were not necessarily due to preharvest sprouting. More emphasis will be placed on falling number and a-amylase activity in the future.

Plant breeding - frost damage.

Dryland winter and intermediate wheat cultivars were screened and evaluated for frost resistance by a conductivity test. This evaluation method will be correlated with field results. Wheat producion in South Africa in areas of frost risk was characterized, and the results will be processed in order to develop and improve management strategies to avert risk.

Weed control - the influence of surfactant concentration on sulfonylureas.

B.L. de Villiers, R.C. Lindeque, J.J. Smit, and H.A. Smit.

Preliminary glasshouse studies indicate that surfactant concentration is vital to sulfonylurea performance. Thifensulfuron and metsulfuron needed at least 0.1 % nonylphenol ethoxylate surfactant to reach optimal performance in 310 l H2O/ha. Rates of 0.01 and 0.05 % were insufficient in certain instances. Higher rates of the surfactant probably increased both spreading and penetration of the sulfonylureas.

Weed control - herbicide resistance.

J.J. Smit, H.A. Smit, and B.L. De Villiers.

Herbicide resistance has been discovered in wheat production in South Africa. This phenomenon is well-known in Australia, Europe, and the U.S. and is now confirmed in South Africa for the first time. During the past 2 years, several tests were made on suspected resistant seed to confirm herbicide resistance and estimate the extent of the problem. Herbicide resistance to the aryloxyphenoxy propionic acids and cyclohexanediones was confirmed, and the grassy-weed species involved are Avena fatua L., Lolium rigidum Gaud, and Phalaris minor Retz. The only broadleaf weed species involved is Raphanus raphanistrum L., which is resistant to the sulfonylureas.

Soil management - resource-limited farmers in South Africa participate in on-farm wheat research.

J. Tolmay, L. Serage, and L. Lesufi.

Wheat is the second most important grain crop after maize in South Africa. Produced in various provinces, wheat is grown in either irrigation or rain-fed conditions. Many resource-limited and developing farmers are interested in wheat as a crop because they believe that it could fit successfully into their production systems. Most small-scale farmers are well acquainted with maize growing, but very few have sufficient knowledge about wheat production.

To alleviate this problem, the Small Grain Institute initiated a program to facilitate technology transfer to previously disadvantaged producers. When researchers get involved in a community, all role-players (extension, Co-Ops, unions, and tribal authorities) are encouraged to participate and take ownership of the research work. After particular needs have been assessed, a trial is designed and an action plan drawn up with the community. Farmers, researchers, extension staff, students, and even school children take part in the planting, maintenance, and harvesting of the trial plots. A field day is held at every trial site during the growing season to demonstrate varieties, fertilization effects, and pest management problems.

During 1998, 17 demonstration trials were planted at communities in different wheat-producing regions. Successful field days were held at 10 communities, but a severe drought at some sites destroyed the trials and prevented collection of data. More than 600 farmers and hundreds of school children were interested in receiving information. As part of the technology transfer program, farmers also were introduced to a small threshing unit suitable for their use.

Soil management - soil tillage.

J.T. Steyn and W.H. Kilian.

The influence of three primary cultivation methods, chemical and mechanical weed control and burning versus no burning of yield plots, and the influence of three nitrogen levels on the productivity of soil under wheat have been investigated in a field trial after 19 seasons of continuous wheat production in the eastern Free State.

Tillage costs have risen drastically in the last few years, especially between 1996 and 1997. The weakening of the rand against the overseas currencies and the elimination of the diesel subsidy to farmers are the most important reasons. Trial results indicate that input costs can be reduced when chemical weed control is used together with mechanical weed control practices. Furthermore, nitrogen levels should be increased during wet seasons to composite for nitrogen loss through leaching. Leaving the stubble unburnt resulted in higher yields during 1997.

Entomology.

V.L. Tolmay, G.J. Prinsloo, J.H. Hatting, and R. Maré.

An integrated program for control of the RWA is being implemented by the Small Grain Institute. The basis of this program is the use of RWA-resistant cultivars. These cultivars are supported by natural enemies of the aphid and cultural practices. Chemical control is intended to be used only when extremely high infestation levels occur. The RWA-resistan cultivar Elands was released. Other wheat cultivars with RWA resistance released by the SGI for commercial production are Tugela-DN, Betta-DN, Gariep, Limpopo, and Caledon. Sources of RWA resistance are being studied with regard to the inheritance and mechanism of the resistance. A backcross program is aimed at transfering RWA resistance to agronomically acceptable lines for use in the winter and intermediate wheat breeding programs. Resistant cultivars released for commercial use are tested under field conditions with and without chemical control methods to determine the value of these cultivars. All resistant cultivars tested so far have a yield and hectolitre advantage. The parasitoid Aphelinus hordei is being released in the field for the third year. More than 1.8 million individuals were released on six farms in the eastern Free State. The developmental threshold and thermal constant were determined for this parasitoid. Field trials with A. hordei show that this parasitoid is able to significantly reduce RWA populations on both susceptible and resistant wheat cultivars if present early in the season. Bioassays were conducted to test the compatibility of two fungal species with Triazole-based fungicides and certain herbicides that are used in wheat. A field trial with Mycotrol ® was conducted during October and November, 1998, on an RWA-resistant cultivar.

Application of molecular and tissue culture techniques to problems in disease resistance (emphasis on yellow rust) of wheat.

R. Prins, M.O. Julius, and W.H.P. Boshoff; L.A. Boyd and T. Worland (Cereals Research Department, John Innes Centre, U.K.), Z.A. Pretorius (Plant Pathology Department, University of Free State, R.S.A.), J.H. Louw (University of Stellenbosch, R.S.A.).

Yellow or stripe rust was noticed for the first time in South Africa in 1996. South African wheat farmers had to spend an additional R30 million/year on fungicides. Currently two pathotypes, 6E16 and 6E22, occur in South Africa. This pathogen mutates quite rapidly to overcome resistant sources. Because this disease was recently introduced to South Africa, only initial attempts to control the disease by identifying and utilizing resistance genes have been implemented. As part of the SGI's yellow rust-management strategy, this new project was implemented in 1999. We have taken a view that a yellow rust-management strategy is more likely to be successful if knowledge of the genetic basis and effectiveness of both the more complex adult plant resistance (APR) genes and single APR resistance genes are obtained. These data will help us to make an informed choice of which Yr resistance sources to use and how to incorporate them successfully in breeding material. The initial aims of this project are to study the unidentified APR gene(s) of the SGI yellow rust-resistant wheat cultivar Kariega and test the effectiveness of the Yr16 APR gene against the South African pathotypes for possible use in our breeding programs.

Personnel.

Benida Laubscher resigned at the end of April 1998. Chrissie Miles joined the quality laboratory as a technician. Liane van Rooyen and Hendriëtte Nel have left this laboratory during 1998. Una Bornman was married during September 1998 and is now Mrs U. Aucamp.

Publications.

Koebner RMD, Kirsch F, Thorpe C, and Prins R. 1998. AFLPs as a source of STS markers in alien introgression. In: Proc 9th Inter Wheat Genet Symp (Slindard AE ed). University Extension Press, Saskatoon, Saskatchewan, Canada. 3:118-122.

Prins R and Marais GF. 1998. An extended deletion map of the Lr19 translocation and modified forms. Euphytica 103:95-102.

Prins R and Marais GF. 1999. A genetic study of the gametocidal effect of the Lr19 translocation of common wheat. SA J Plant Soil (In press).

Smit JJ and De Villiers BL. 1998. Lolium spp. Resistance to ACC-ase inhibitors in wheat (Triticum aestivum L.) within the RSA: a preliminary study. SA J Plant Soil 15(4):158-161.

Smit JJ, Smit HA, and De Villiers BL. 1999. Differential efficacy of tralkoxydim and diclofop-methyl on a suspected resistant ryegrass (Lolium rigidum Gaud.) biotype. SA J Plant Soil (In press).15(4):158-161.

Smit JJ, Smit HA, and De Villiers BL. 1999. Differential efficacy of tralkoxydim and diclofop-methyl on a suspected resistant ryegrass (Lolium rigidum Gaud.) biotype. SA J Plant Soil (In press).

UNIVERSITY OF STELLENBOSCH

Department of Genetics, Stellenbosch 7600, South Africa

G.F. Marais, F.L. Middleton, H.S. Roux and A.S. Marais.

Breeding programs.

Low wheat prices caused a drastic decline in local durum production in recent years, and the durum breeding program was phased out as a result. However, increased demand for triticale in the southwestern Cape necessitated expansion of our triticale breeding program. No new releases were made, but promising advanced lines were selected. An attempt to introduce a recurrent-selection routine in wheat that can supplement a pedigree-selection program and is based on a dominant gene for male sterility was continued.

Genetic studies.

An attempt to further shorten the Lr19-149 translocation through allosyndetic recombination yielded four putative recombinants. Recombinants Lr19-149-252, Lr19-149-299, and Lr19-149-452 apparently resulted from the exchange of chromosome segments proximal to Lr19. Of these, the Lr19-149-299 translocation appears to be the shortest. Another recombinant, Lr19-149-478, may have a chromosome segment distal to Lr19 that includes the Wsp-1 locus. The latter recombinant is being verified. All four translocations appear to have retained the Sd2 locus. An attempt will be made to induce recombination between translocations 299 and 478 in order to produce an even shorter one.

A deletion map of the the Lr19 translocation was extended by the addition of two AFLP marker loci and three RAPD marker loci. However, none of the loci occur in the shortest recombinants, and