ITEMS FROM SOUTH AFRICA

SMALL GRAIN INSTITUTE
Private Bag X29, Bethlehem, 9700, South Africa.

Winter and intermediate wheat breeding.

H.A. van Niekerk, N. Edwards, M. Brunkhorst, U. Bornman, D. Exley, O. Müller, M. Ncala, and R. Pretorius.

During 1998, subsequent to the discovery of RWA resistance, we decided to discard about 80 % of our breeding program because of RWA susceptibility. At that time, we decided that any future cultivar releases will have RWA resistance. The effect on the release of new cultivars was significant. However, again in 1998, we now are going through the same cut-back exercise because stripe rust has appeared for the first time in the winter wheat production area of South Africa.

Two lines, T95/7 and T95/14, were selected for release in 1997. Although these lines are susceptible to tripe rust, we plant to continue with their release. These lines probably will be the last that will be susceptible to stripe rust.

The pyramiding of different RWA-resistance genes is progressing according to plans but obviously will be affected by the high level of stripe rust susceptibility.

Triticale and oat breeding.

H.A. van Niekerk and O. Müller.

The Small Grain Institute does not own a triticale and oat-breeding program, although specific crosses are being made on a small scale. New lines are obtained from international nurseries and included in an evaluation and development program. This program serves a dual purpose. First, we can identify and develop new, high yielding triticale and oat cultivars sown mainly in the winter rainfall region, and second, this program focuses on the development of winter forage cultivars. Because of this dual approach, more often than not, new winter forage cultivars tend to be high yielding grain cultivars as well. It is important to stress that, because of their vernalization requirements, winter forage cultivars are suited only for grain production in the summer rainfall region.

Five new cultivars were released from this program during the past 5 years. The first one was the triticale cultivar Kiewiet, with a high grain yield and good quality for grain production in the winter rainfall region. Two triticale cultivars Arend and Falcon, with high grain yields and exceptional dry material production, were released in the summer rainfall region for winter forage production. In addition to these two cultivars, an oat cultivar, Maluti, with excellent cold tolerance and high dry material production was released to be included in a fodder flow program alone or in combination with triticale as winter forage. The fifth release was the oat cultivar Drakensberg with a high yield and good hectolitre mass. Drakensberg was released for grain production in the summer rainfall region with average forage production capability.

The long-term aim of this program is the development of new triticale and oat cultivars to serve both the grain and stock production industries. The program will still make use of imported lines, but crosses will be made to fill specific shortcomings in imported lines. (H.A. van Niekerk, O. Müller)

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, E.Vermeulen, and H. Botha.

No new cultivars were released from either breeding program, which focuss on developing lines adapted under irrigation or rainfed conditions. A total of 12 lines was sent for provisional classification.

The breeding programs currently are investigating the possibility of using the Raised-Bed Planting System developed by CIMMYT as a normal planting procedure. Preliminary trials showed that same yields can be obtained with lower seeding rates for lines that showed better tillering capacities.

Two lines that proved to have take-all resistance last season were planted again in field conditions, and both the lines showed lower susceptible percentages than all the commercial cultivars currently used except SST57, which is a solid stem cultivar released by Sensako (see Table 1). However, line 1 has better resistance than line 2.

The biannual South African Plant Breeding Symposium was held in Golden Gate, Bethlehem, South Africa from 16­19 March, 1998. The invited guest speakers were M. Goodman, A. Fernandez, I. Vasil, R. Cooper, S. Baenziger, and C. Bornman.

Wheat Quality Laboratory.

H.A. van Niekerk, F.P. Koekemoer, L. van Rooyen, H. Nel, K.B. Majola, M.L.T. Moloi, M.M. Radebe, N.E.M. Mtjale, C.N. Matla, M.M. Mofokeng, and M.L. Dhlamini.

Wheat quality has become very important the last few years in South Africa. The Wheat Quality Laboratory at the Small Grain Institute, therefore, has become an integral part of the breeding programs. Early generation, junior, senior, and elite phases from the spring wheat breeding programs for irrigated and dryland conditions and the winter and intermediate programs are analyzed. Although the laboratory's main service is to breeders, other departments at the Small Grain Institute and wheat producers in the region use the laboratory and contribute to the more than 50,000 analyses that are performed each year.

Plant pathology.

H. Smit, B.D. van Niekerk, W.H.P. Boshoff, and S.O. Meintjes.

Stem rust. Rust samples are collected annually by means of surveys, cooperators, farmers, and trap nurseries throughout the small-grain producing areas of southern Africa in an effort to determine the prevalence and the virulence/avirulence spectrum of P. recondita f. sp. tritici. During 1997, the pathotypes 3 SA132, 3 SA 133, 3 SA 140, 3 SA 126, and 3 SA 123 were identified. Pathotype 3 SA 133 dominated this season, comprising 80.6 % of the isolates, followed by 3 SA 132, 3 SA 140, 3 SA126, and 3 SA 123 with 15.3 %, 2.8 %, 1.4 %, and 1.4 %, respectively. This represents a significant shift in virulence, because the period 1989 to 1993 was dominated by 3 SA 132 and 3 SA 140. A buildup of 3 SA 133 occurred from 1994 to 1996, with 3 SA 132 and 3 SA133 dominating this period.

One reason for the shift may be the popularity of the yellow rust-resistant cultivars Kariega and SST57 and the yellow-rust susceptible winter wheat Gariep. All three cultivars are susceptible to 3 SA 133. However, this does not explain the high percentage of 3 SA 133 found in volunteer wheat in the Free State early in the season. A second reason for the shift in virulence may be the use of isolates from various cultivars instead of the universally susceptible cultivar Morocco. This was necessary because yellow rust killed Morocco at most of the trap locations. These findings would enable breeders and pathologists to adapt their breeding strategies in the future.

Entomology.

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

The Small Grain Institute is busy implementing an integrated program of RWA control. The basis of this program is the use of resistant cultivars, supported by natural enemies and cultural practices. Chemical control is intended to be used only when extremely high infestation levels occur. Five wheat cultivars with RWA resistance, Tugela-DN, Betta-DN, Gariep, Limpopoand, and Caledon have been released for commercial production in South Africa. We are studying sources of RWA resistance investigating the inheritance of mechanisms of the resistance. A backcross program is attempting to transfer RWA resistance to agronomically acceptable lines for use in the winter and intermediate wheat breeding programs. Resistant cultivars will be tested under field conditions to compare their efficiency with chemical control. The parasitoid Aphelius hordei was released in the field for the third year. A parasitism level of up to 67 % was measured where parasitoids were released. However, the parasitoids failed to survive the summer in the field, mainly because of low RWA numbers during summer. We are now trying to get alternative RWA host plants established in the field during summer to ensure that the RWA population will enable the parasitoid to survive. Biological studies showed that both temperature and daylength are able to induce diapause in A. hordei. The use of entomopathogenic fungi as possible biocontrol agents for the RWA is being investigated by the SGI. Five fungal species have been isolated from field-collected specimens of the RWA and are presently being evaluated at the Institute. Investigations include culturability on artificial media, storage, production of conidia, LD50 values, and application techniques. Additional surveys aimed at isolating net strains and species are being made in the Western and North Eastern Cape, the irrigation areas of Kwazulu and Natal, and the Eastern Free State region.

Preharvest sprouting and frost damage.

J. Purchase and A. Barnard.

The major objective in preharvest sprouting research is to solve the problems faced by the cereal producers and the cereal industry in this regard. The major aims of this study are to characterize newly released cultivars and their sensitivity to the environment (G x E) and to test advanced breeding lines for preharvest sprouting tolerance. The mechanism of dormancy also will be characterized in terms of the role played by certain sugars, amino acids, proteins, and enzymes. The possible role of the oxidative pentose phosphate pathway in dormancy also will be investigated. Studies to determine the effect of certain microelements, especially molybdenum, on preharvest sprouting were carried out under field conditions. A new project was initiated to characterize frost-risk wheat producing areas in South Africa and to develop and calibrate methodologies for screening for frost tolerance with a frost chamber (whole plants) and by means of a conductivity test. Wheat cultivars will be screened and evaluated for frost tolerance.

Crop management program.

W. Kilian, T. Steyn, W. Otto, K. van Zyl, J. Visser, L. Visser, V. Wessels, W. Du Toit, J. Tolmay, and L. Serage.

The crop management program consists of five divisions: soil cultivation, plant nutrition, soil analysis, modelling, and the small-scale farmer. The program develops technology and produces those services that are required for production of affordable small grains with a high quality but also tries to maximize return per unit area for the producer. The complexities of farming in the modern era with fluctuating markets contribute to the cereal producer's need for careful planning and management to optimize production and profitability. Profitable cereal farming demands higher production per unit area at lower cost per unit of production. The soil analysis laboratory gives the farmer the need-driven information for fertilizer application with planting and/or the liming needs of each production unit. The fertilizer application together with soil cultivation costs are the small grain producer's main input costs, contributing approximately 55 % of the input cost.

Small-scale farmer development program.

J.P.C. Tolmay, K.L. Serage, and T. Steyn.

The Small Grain Institute launched this program during 1996 to assist wheat producers in South Africa to improve production. Since the start of the program, the group has been involved with eight communities that grow wheat under rainfed and irrigation conditions. Many newly settled farmers and/or farming groups interested in wheat production were helped to plan their operations. Research work is mostly demonstrative, and farmers, extension staff, and researchers are involved in the project together. Communities where the Institute are involved so far include Strydkraal (Irrigation - Northern Province); Qwa-Qwa, Thaba Nchu, Hennenman (Dryland- Free State Province); Herschel and Lady Frere (Dryland- Eastern Cape Province); and Leliefontein (Dryland- Northern Cape Province). Eight field days on wheat production were held in various communities in 1997, and seven demonstration trials were planted.

Personnel.

Anri de Villiers was married during October, 1997, and is now Mrs. A. Barnard. Una Bornman joined the program as a winter wheat breeder, replacing Megan Brankhorst who resigned and moved to Pietermaritsburg. Nicola Edwards resigned and moved to Durban. Elaine Vermeulen joined the spring wheat breeding program as a technician. Hendriette Nel joined the quality laboratory as a technician.

UNIVERSITY OF THE ORANGE FREE STATE
Department of Plant Pathology, Bloemfontein, 9300, South Africa.

Resistance in South African wheat cultivars to pathotype 6E16 of Puccinia striiformis.

F.J. Kloppers, W.H.P. Boshoff, and B.D. van Niekerk.

Stripe rust of wheat, caused by P. striiformis f. sp. tritici, was observed for the first time in South Africa in 1996. The disease occurred in all major wheat producing areas including the Free State, KwaZulu-Natal, Gauteng, North West, and Mpumalanga in 1997. Because stripe rust has never occurred in South Africa, no selection or breeding for resistance has been conducted in local wheat breeding programs. In collaboration with plant pathologists (WHPB and BDvN) from the ARC-Small Grain Institute, disease severity and reaction types of South African cultivars to pathotype 6E16 were determined in naturally infected field trials at Bethlehem (Free State) and Greytown (KwaZulu Natal) in 1997. Of the 50 winter and spring cultivars tested, 30 % and 45 % were susceptible, respectively. The disease ratings showed that 43 % of the winter cultivars and 25 % of the spring cultivars were moderately susceptible to moderately resistant. Effective resistance to stripe rust was expressed by 27 % of the winter cultivars and 30 % of the spring cultivars.

Markers linked to leaf rust resistance genes Lr37 and Lr41.

J-M Lottering, C. Troskie, F.J. Kloppers, A-M Botha, and Z.A. Pretorius.

In conjunction with the Department of Botany and Genetics, potential RAPD markers linked to the leaf rust resistance genes Lr37 and Lr41 were identified. Segregating populations were screened with a series of primers (OPA-OPO) from Operon Technologies. NILs and bulk segregant analysis currently are being used to analyze populations of crosses involving these genes.

Germ plasm development.

Z.A. Pretorius, C.M. Bender, and F.J. Kloppers.

One hundred sixty five 'Lr37/6*Karee' and 225 'Lr35/6*Karee' wheat lines were released under contract to the ARC­Small Grain Institute, Bethlehem for agronomic and quality evaluation and further application in wheat improvement in South Africa.

Sabbatical visit

Z.A. Pretorius spent 6 months at the Plant Breeding Institute, Cobbitty, the University of Sydney, Australia, to study stripe rust resistance in South African wheat cultivars. Stripe rust research included multipathotype testing and evaluation of disease progress in the field. Other collaborative projects focused on molecular comparison of Australian and South African wheat leaf rust isolates, the detection of Sr2 in South African wheats, improved screening techniques for adult-plant resistance to leaf and stripe rust of wheat, and genetic analysis of cultivars with resistance to Australian pathotypes of P. striiformis.

Publications.

Barnard JE, Pretorius ZA, Kloppers FJ, and Bender CM. 1997. Components of resistance to Puccinia recondita f. sp. tritici in certain Triticum species. In: Proc 11th Biennial Conf Austral Plant Path Soc. Perth, Australia. p. 285

Barnard JE, Pretorius ZA, and Marais GF. 1997. Adult plant resistance to Puccinia recondita f. sp. tritici in a collection of wild Triticum species. South Afr J Sci August 1997 93:xvi (abstract).

Bender CM, Pretorius ZA, and Spies JJ. 1997. Assessment of macroscopic components of leaf rust resistance in wheat genotypes containing Lr12 and Lr13. South Afr J Plant and Soil 14:71-80.

Bender CM, Pretorius ZA, Kloppers FJ, and Jacobs AS. 1997. Early abortion and papilla formation associated with Lr13+Lr35 resistance in wheat infected with Puccinia recondita f. sp. tritici. South Afr J Sci August 1997 93:xxii (abstract).

Kloppers FJ, Boshoff WHP, and Van Niekerk D. 1997. Wheat Stripe Rust (in Afrikaans). Information leaflet.

Kloppers FJ and Pretorius ZA. 1997. Effects of combinations among Lr13, Lr34 and Lr37 on components of resistance in wheat to leaf rust. Plant Path 46:737-750.

Pretorius ZA. 1997. Detection of virulence to Lr41 in a South African pathotype of Puccinia recondita f. sp.