SMALL GRAIN INSTITUTEPrivate Bag X29, Bethlehem, 9700, South Africa.
J.C. Aucamp, D.J. Exley, and H.A. Smit.
During 2002 Small Grain Institute released a new bread wheat
cultivar named Komati. Komati is a facultative cultivar with
moderate vernalization requirements. The lodging resistance of
this tall cultivar is good. Komati has a long coleoptile (±
9.3 cm) and excellent resistance to preharvest sprouting, which
has been confirmed successfully. Another advantage is the high
level of resistance against RWA infestations. Komati is susceptible
to stripe rust. Though susceptible, the application of a fungicide
is only necessary when conditions are optimal for disease development.
The cultivar has no aluminium tolerance and planting on soils
with low pH and high levels of acidification is not recommendable.
Komati is suitable for planting on low to high potential fields.
Yields are stable and competitive with the best cultivars available.
Komati has an excellent hectoliter mass and falling number and
good protein characteristics and, thus, produces grain of a supreme
grade. The cultivar meets with the set standards for flour extraction,
protein quality, water absorption, and mixing quality required
by the milling and baking industries.
W.H.P. Boshoff and H.A. Smit.
The Wheat Technical Committee accepted BSP98/8 for final classification. The line will be marketed as Olifants. Olifants yields above average, which appears stable over environments. Important agronomic characteristics of Olifants are a medium growth period, good tillering, and strong resistance to lodging. The cultivar has excellent quality characteristics that comply with requirements of the milling and baking industry. Olifants has high levels of resistance to local foliar diseases including the currently prevailing pathotypes of stripe rust.
T. van A. Bredenkamp and M.V. van Wyk.
The success of a breeding program depends mainly on the genetic diversity available. A constant need exists for the incorporation of new germ plasm to improve locally adapted lines. Activities of the Small Grain Institute Germplasm Collection consist of the conservation of small grain crops, namely wheat, barley, oats, triticale, and rye. This collection is maintained in a cold room facility with a mobile shelving system for medium-term viability at ± 4 C.
International collaboration is of extreme importance because
no breeding program can function effectively without sufficient
heritable diversity. Over the years a working relationship has
been established between South Africa and CIMMYT (Mexico), ICARDA
(Turkey), Uruguay, and other countries. Wheat, barley, and triticale
nurseries and trials, segregating material, and interspecific
crosses are imported annually. These lines are evaluated under
quarantine. Microenvironments conductive to disease development
are created artificially ensuring high selection pressure. The
three quarantine sites are Bethlehem in the Free State, Riviersonderend
in the Western Cape, and Vaalharts in the Northern Cape.
A.F. Malan and H.A. Smit.
During the 2002 wheat season, several combinations were handled
in the DH program. The main purpose of the program is to enhance
the development of pure breeding material of promising combinations
identified in the different breeding programs. The DH process
is involved in the spring, winter, and prebreeding programs and
assists in development of lines with good disease resistance,
superior quality aspects, and minor gene characteristics.
In the spring wheat-breeding program, cross combinations were
made with special emphasis on stripe rust resistance. A potential
winter breeding lines' progeny will be tested for agronomic traits,
bread-making quality, and disease resistance. Material from the
prebreeding program includes combinations for RWA and leaf rust
resistance. All these DH lines will be tested in extensive field
trials during the 2003 season.
R. Prins, V.P. Ramburan, and W.H.P. Boshoff (ARC-Small Grain Institute, RSA); L.A. Boyd (Department of Disease and Stress Biology, John Innes Centre, UK); Z.A. Pretorius (Plant Pathology Department, University of Free State, RSA); and J.H. Louw (Genetics Department, University of Stellenbosch, RSA).
Adult-plant resistance to stripe rust in the South African wheat cultivar Kariega was assessed in a DH-mapping population made from the F1 of a cross between Kariega and the susceptible cultivar Avocet S. A partial linkage map covering all 21 chromosomes was developed with 208 DNA markers and four alternative loci.
Interesting features of the linkage map include the low polymorphism observed in the D genome and a region showing segregation distortion on chromosome 4A. The Ltn and Sr26 genes also were mapped in this study. Two major QTL, together explaining about 55 % of the variation in the trait, were identified on chromosomes 2B and 7D, whereas minor QTL explaining about 14 % of the variation were identified on chromosomes 1A and 4A. The QTL on 7D appears to correspond to Yr18, a gene for APR to stripe rust. Markers fairly close to the QTL have been identified and these may be used to detect the presence of these QTL regions in marker-assisted selection. The APR to stripe rust of Kariega appears to be controlled by major QTL, in combination with other minor QTL, which is characteristic of APR in general. The DH population developed and the linkage map constructed are valuable resources for future genetic studies that may include studying APR, plant-pathogen interactions, and the mapping of additional traits polymorphic in this population.
Previous field trials of genetic material derived from Cappelle Desprez (CD) and Palmiet confirmed the effectiveness of Yr16 (APR) against the South African pathotypes (6E16- and 6E22-). We know that CD also carries a T5BS-7BS translocation that is a complicating factor in studying Yr16. Chromosome 2D SSR markers, previously thought to be associated with Yr16, were tested on various resistant and susceptible lines. The molecular data suggest that the position of Yr16 on chromosome 2D needs further verification. Various resistant plants were used in backcrosses to Avocet S and Palmiet and the resulting F1s were used to produce DHs to simplify future genetic studies. These DH lines will be evaluated for their stripe rust phenotypes in a field trial in 2003.
A. Barnard.
The South African wheat-producing areas, especially the Eastern Free State, are highly subject to the risk of preharvest sprouting because of summer rainfall that occurs just prior to or during harvest. Because preharvest sprouting is closely related to falling number (FN), a substantial amount of research is done on both topics.
Thousands of wheat spikes obtained from various commercial and newly released cultivars are evaluated for preharvest sprouting tolerance with the help of a rain simulator. This information is handed down to the commercial farmer to enable him to make the right decision regarding his cultivar choice for the coming season. Recently, more attention also was given to breeding programs for sprouting resistance with the help of the rain simulator and protein electrophoresis. This technique is still in developmental and its usefulness still uncertain. Should this technique prove to be useful, direct crosses can be made and the progeny screened for the presence of the necessary electrophoretic bands, ensuring that, as sprouting resistance is a polygenic trade, none of the genes will be lost during the breeding program.
Since the incorporation of the FN method within the grading
regulations, attention has been given to the possibility of managing
FN within a wheat production system. The effect of early termination
of kernel development (early harvest) on the FN of wheat and the
effect of fertilizer on FN are being investigated.
Because of the importance of cultivar choice in the Summer Rainfall Region, an extensive cultivar-evaluation program is followed for each of these areas. Different cultivars are planted in each region and these cultivars are evaluated and characterized in terms of yield reaction and stability in the different areas. Other characteristics that also are evaluated in this program include important quality specifications such as hectoliter mass, protein content, and falling number. These characteristics are used in recommending cultivars best suited for each area in the region.
Dryland production. Almost half of the South African wheat production is in cultivation under dryland conditions in the Summer Rainfall Region. Because of 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 primarily into four homogenous areas where different cultivars, mainly winter and intermediate types, are planted. All cultivar-evaluation trials planted at 18 sites throughout the Western, Central, and Eastern Free State were successful and reported. Eighteen entries were included in the trials, seven were from Small Grain Institute, six from Monsanto, and five 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 regions.
Mainly spring wheat cultivars are planted in a total of 44
evaluation trials at 23 localities in the different irrigation
areas. Entries in these trials originated from Small Grain Institute
(7) and from Monsanto (4). A durum cultivar also was included.
ANOVA, AMMI analysis, and biplots are used in the interpretation
of results and identifying cultivar adaptation and stability in
the different production regions. Results from these trials are
available in a detailed report.
There are mainly two wheat producing areas in the Winter Rainfall Region:
Spring wheat cultivars are grown in these two regions. These cultivars do not require the same amount of cold to break their dormancy as that of the winter wheats grown in the rest of South Africa. Cultivar choice in the Winter Rainfall Region is of extreme importance because of the varied climatic differences between cultivation areas. The yields of available cultivars differ relative to the changing yield-potential conditions that exist in the Winter Rainfall Region. Other important factors that also need consideration are grain quality, hectoliter mass, and disease susceptibility.
In the Winter Rainfall Region, the cultivar-evaluation program 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 11 cultivars included in the trials. Cultivars, from ARC-Small Grain Institute, Monsanto, and PANNAR, are annually tested for yield potential, quality, disease resistance, and adaptability.
K. Naudé.
Karnal bunt was identified for the first time in South Africa in December 2000 in the Douglas irrigation area. Karnal bunt is caused by the quarantine organism, Tilletia indica, and according to South African regulations, the occurrence thereof should be reported to the National Department of Agriculture (NDA).
To date, the South African wheat industry has been protected against wheat imports from countries where KB already occurs. After the identification of KB in South Africa, a KB Task Team was founded with the objective to compile protocols to limit the spread of the disease in South Africa. These protocols include the testing of all registered seed units and all commercial grain for the presence of teliospores produced by the fungus. Using quarantine regulations and permits for the transportation of grain to intake points and mills also are included.
Karnal bunt occurrence in South Africa. As was the case with the 2001-02 wheat-production season, official surveys were made by the NDA-Directorate Plant Health and Quality (NDADPHQ) to test seed and grain for the presence of KB spores and infected kernels. All seed units of the 2001-02 season tested free of spores and infected kernels. Karnal bunt spores and infected kernels, however, were found in grain from the Douglas and Koffiefontein areas. Infection also was found on four farms in the Douglas district, and these farms were placed under quarantine. Results of the 2002-03 season will be available at a later date.
Control of Karnal bunt. At this stage wheat producers are making use of seed free of KB spores. The treatment or nontreatment of seed with chemical fungicidal seed dressing is done at the producer's own discretion. In areas where KB has been identified, spraying twice with Triticonazole is recommended. A first application is done at 25 % ear emergence, followed by a second application 10 days later. This spraying system is used by most wheat producers in the Douglas area with the purpose of limiting KB infection to levels lower than 2 %.
The role of ARC-Small Grain Institute (ARCSGI).
The latest information regarding KB and its control is transferred
to producers, agents, and advisors at farmers' days and during
courses on a continual basis. ARC-SGI tests all its seed and
grain at the KB Laboratory at Bethlehem. All ARC-SGI seed required
for planting at the more than 90 localities country wide is washed
at the KB Washing Facility according to procedures used by CIMMYT.
Fifty lines and cultivars of ARC-SGI were evaluated by CIMMYT
in the 2001-02 season for KB resistance. These lines and cultivars
will be evaluated by CIMMYT again during the 2002-03 season.
Planting of less susceptible or resistant cultivars in the affected
areas is regarded as the only sustainable solution for the control
of KB.
W.M. Otto.
The objective of this research was to measure the yield and protein response of irrigated wheat cultivars to nitrogen (N) management options. Furthermore, the effect of split N applications combined with residual soil mineral N on grain yield and quality also is determined. The contributions of soil mineral N, plant uptake of N, and biomass development to N management of the crop also were calculated. The aim is to develop an N management system that the producer can implement to optimize all the relevant production factors.
The yield and grain protein responses to split applications of N applied at planting, late tillering, and flag-leaf stages of six commercially available wheat cultivars (SST 876, SST 822, Kariega, Olifants, Baviaans, and Steenbras) were measured. The trials were planted at Riet River, Vaalharts, Loskop, and Bethlehem.
The tested cultivars differed in response to split applications of applied N, with the magnitude of yield and protein response linked to the adaptability and growth period of the respective cultivar. Measured residual soil mineral N influenced yield response to N. A high level of soil mineral N (205 kg N/ha) decreased the response to applied N, whereas where a low soil mineral N of 60 kg N/ha was measured, significant responses to applied N were found.
Protein percentage of the grain increased with an application of 40 kg N/ha at the flag-leaf stage. A decrease in yield of all the tested cultivars was found when the total N rate was applied at planting. The split application of N, where 80-120 kg N/ha applied at planting was followed by 40-80 kg N/ha at late tillering and 40 kg N/ha at the flag-leaf stage, resulted in the highest yields and protein percentage of the grain. Plant N analysis at the measured growth stages indicated that the split application of N increased plant N concentration to within the optimal N analysis range, showing the potential use of this measurement in N management of the crop.
A. Barnard, C.W. Miles, K.B. Majola, M.L.T. Moloi, M.M. Raderbe, N.E.M. Mtjale, C.N. Matla, M.M. Mofokeng, M.L. Dhlamini, and N.M. Mtshali.
One of the main objectives of the Quality Laboratory is to maintain a cost-effective, highly scientific, and objective quality assessment of Small Grain Institute breeding lines, to incorporate contract work for milling and baking industries and private companies, and to provide an objective service to wheat producers. To ensure accurate data to researchers and external parties, the laboratory takes part in quarterly and monthly ring tests. A total of 57,410 analyses were performed during 2002.
L. Visser.
Soil analyses form an essential part of a producer's success. The laboratory provides this service and plant and water analyses to external clients and researchers.
During the 2001-02 financial year, the laboratory performed 111,032 tests on 9,329 samples. Fifty-four percent of these samples were received from external clients such as producers, advisors, and representatives of different fertilizer companies. During December 2001, the laboratory bought a new Inductive Coupled Plasma Emission Spectrometer. The instrument is known for accurate, reliable, and fast results. With this instrument the laboratory can handle a larger amount of samples/year and also analyze for elements such as sulphur and boron.
The laboratory is also involved in a research project to evaluate the soil fertility status of resource poor areas where Small Grain Institute operates. The database will help identify trends like increases in soil acidity and also improve the quality of technology transfer in future.
In order to ensure an accurate and reliable service to all clients, the laboratory runs internal control samples and also belongs to Agri-LASA, a national control scheme.
During the past year the external income of the laboratory increased by 10 %. The main objective of the laboratory is to improve on this by rendering an accurate and efficient service to all clients.
Ms. Vicki Tolmay was appointed program manager of Plant Protection
replacing Dr. Hugo Smit. Ms. Anri Barnard has resigned to pursue
household duties. Labious Masike replaced Godwin Khorommbi as
a researcher of Plant Protection. Sanesh Raburam joined Crop
Science as a research technician. Willem Otto was transferred
to Crop Science to handle the Cultivar Evaluation Programme under
irrigation. Pieter Craven and Danie van Niekerk resigned from
Small Grain Institute.
UNIVERSITY OF STELLENBOSCH
Department of Genetics, Stellenbosch 7600, South Africa
G.F. Marais, H.S. Roux, A.S. Marais, and W.C. Botes.
Three new triticale cultivars will be available for commercial
production in 2003, these are Bacchus, a selection from CIMMYTs
28th ITYN-48 (SUPI 3//HARE 7265/YOGUI 1); Tobie, a selection from
the local cross KIEWIET/4/W.TCL83/HOHI//RHINO 4/3/ARDI 1; and
Ibis, also derived from a local cross FLORIDA 201/17th ITSN 238
(= DURUM WHEAT/BALBO//BOK"S"). Tobie is a very early
maturing triticale with high grain yield and excellent hectoliter
mass, whereas Bacchus is a high-yielding, later maturing cultivar.
Ibis is a late-maturing, tall straw cultivar selected specifically
for the production of fodder. Two cultivars released at Stellenbosch,
Tobie and USGEN19 (late maturing), also have been released in
Ethiopia under the names Sinan and Maynet, respectively, as part
of a collaboration with the Ethiopian Bureau of Agriculture, Amhara
Region, and the German G.T.Z. (Technische Zusammenarbeit) program
coördinated by Dr. K. Feldner.
A recurrent-selection procedure for wheat based on genetic
male sterility and hydroponic culture of cut tillers was continued
and further improvements of the technique were made (Figure 1). The breeding cycle could be reduced
to 4 years (1 year for making crosses and 3 years for inbreeding
and field evaluating the F4 and F6 male parents). Single-seed
descent steps were introduced to advance from the F1 to the F6
in the course of 2 years. To accomplish this, two additional
plantings (F2 and F3) are made during the summer months in an
uncooled greenhouse. The F4 is again planted in the normal growing
season (winter) and the F5 planted under irrigation during the
summer. The F6 is used for the first yield trials (plots) in
the third winter. This modification has several advantages.
The shorter breeding cycle allows for a more rapid increase in
the frequency of desirable alleles of disease resistance loci.
However, properly selecting for agronomic and quality characteristics
of lower heritability is still possible. Inbreeding to the F6
has the same effect as the use of DH technology but can be achieved
at considerably reduced costs. When inbred male parents are selected
for marker or disease-resistance loci, very rapid shifts in the
frequency of desirable alleles occur. Once the frequency of the
favorable allele of a number of genes has been raised to 0.70
or higher, a significant proportion of inbreds will have these
genes fixed in their genotypes, i.e., the procedure facilitates
gene pyramiding. The advantage of pyramiding genes in this manner
is that there is no yield ceiling as is the case with backcross-based
procedures and numerous diverse genotypes with pyramided genes
can be generated over time.
n 1993, we initiated a program for transferring leaf rust-resistance genes identified in a collection of wild Triticum species. We have developed advanced material of 11 sources that show effective resistance to all known local pathotypes of one or more of the diseases leaf, stem, and stripe rusts. These include a subset of six lines in which resistance (derived from T. turgidum subsp. dicoccoides, Ae. sharonensis, Ae. speltoides, Ae. peregrina, and Ae. kotschyi) appears to occur on wheat chromosomes and five addition lines with added chromosomes from Ae. peregrina, Ae. umbellulata, Ae. biuncialis, and Ae. neglecta. In several instances, promising stem rust and/or stripe rust resistance genes were co-transferred with leaf rust resistance. The stripe rust resistance genes (from T. turgidum, Ae. sharonensis, Ae. speltoides, Ae. peregrina, Ae. kotschyi, and Ae. biuncialis) also were effective against four Australian pathotypes and appeared to be novel (evaluations done by Dr. Colin Wellings, University of Sydney). Leaf rust-resistance genes in 10 of the sources showed promising resistance to commonly occurring Western Canadian pathotypes of the disease (evaluated by Dr. Brent McCallum, Cereal Research Centre, Winnipeg, Canada). Stem rust-resistance genes from two Ae. speltoides sources were tested with Western Canadian stem rust pathotypes (Dr. Thomas Fetch, Cereal Research Centre, Winnipeg, Canada). One source showed resistance to all pathotypes whereas another was susceptible to one of the pathotypes. All the genes appear to have a wide spectrum of resistance to justify continued introgression into wheat. Preliminary results would suggest that the Ae. kotschyi-derived genes (leaf and stripe rust resistance) occur on chromosome 2D, whereas leaf and stripe rust-resistance genes from Ae. sharonensis are on 3B. Resistance from Ae. biuncialis and Ae. neglecta appears to be on group-3 chromosomes of these species. Some of the resistance genes have preferential transmission and the Ae. speltoides-derived genes may involve gametocidal effects.
A unique, Th. distichum/ 4x rye hybrid (95M1) with genomes J1dJ2dRR allowed us to identify four Thinopyrum chromosomes apparently involved with salt tolerance. When 95M1 was pollinated with diploid rye it yielded F1 offspring with primarily 21 chromosomes (two complete rye genomes and seven Thinopyrum chromosomes). Apparently, the closely related homoeologous chromosomes of the J1^d^ and J2^d^ genomes regularly formed bivalents during megasporogenesis, and egg cells mostly received a random, yet balanced set of seven Thinopyrum chromosomes. F1 plants were tested for salt tolerance and a set of 15 highly salt-tolerant F1 plants were selected and maintained as clones for several years. These plants were C-banded and the Thinopyrum chromosomes in each line were determined. By comparing segregation patterns, the Thinopyrum chromosomes were grouped into seven homoeologous pairs. For each of four homoeologous pairs, one of its members occurred at a higher than expected frequency, implying that these chromosomes are primarily being expressed under salt-stress conditions. The results could be confirmed by backcrossing two of the most tolerant F1 plants to diploid rye. Although the critical chromosomes can be identified through C-banding, an attempt also was made to find an RFLP marker for each. RFLP probes, diagnostic for the group 2, 3, 4, and 5 homoeologues of wheat, detected polymorphisms on the respective critical Thinopyrum chromosomes. However, the preliminary allocation of the critical chromosomes to homoeology groups needs to be confirmed using more and varied markers. An attempt also was initiated to develop triticale plants with disomic additions of the respective critical Thinopyrum chromosomes. Disomic addition lines producing the group-3 and 5 RFLPs of two of the target chromosomes have been recovered and are being used in attempts to induce translocations to triticale chromosomes.