SMALL GRAIN INSTITUTEPrivate Bag X29, Bethlehem, 9700, South Africa.
J.C. Aucamp and D.J. Exley.
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 Province. 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 that also have 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 yellow
rust, stem rust, and leaf rust) and resistance to RWA. 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.
F. Middleton and P. Delport.
Although the breeding effort is aimed at the identification of generally adapted cultivars, specific adaptations also are selected for due to the heterogeneity in climatological and ecological conditions of regions within the Western Cape. For this reason, promising cultivars are evaluated at 11 sites that have been preselected to sample typical commercial conditions. In addition, the facilities at two state-owned experimental farms also are used to evaluate advanced nonsegregating lines and screen segregating material. Although our main objective is ultimately the improvement of rust (stem, leaf, and yellow) resistance and baking characteristics, the 2001 material also was characterized by resistance to Septoria and aluminium tolerance. Diversity, particularly in respect to baking quality, was further extended by the addition of several CIMMYT genotypes. The impact of these introductions will be evident when the material from crosses between these and the more adapted local varieties are evaluated.
Biedou, a spring wheat cultivar specifically adapted to the
climate in the Western Cape production area, was released during
2001. The cultivar is resistant to the prevalent races of stem,
leaf, and yellow rusts and provides moderate to good resistance
against Septoria. Biedou exhibits a moderate to high yield potential
and excellent yield stability across years and environments.
W.H.P. Boshoff.
Breeding objectives for the irrigation areas are concentrated
to two major regions, the warmer (Mpumalanga, North West, and
Northern Provinces) and cooler (Northern Cape) areas in the summer-rainfall
region. Another, though smaller, region in KwaZuluNatal also
is covered.
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 oats are imported form CIMMYT (Mexico),
ICARDA (Syria), and Uruguay. These lines undergo intensive, daily
evaluations at locations in Bethlehem, in the Free State, and
Tygerhoek, in the Western Cape, for agronomic adaptability, disease
resistance, yield potential, and quality characteristics. During
the 2000-01 season, a total of 23 nurseries and 15 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 the improvement
of undesirable characteristics with the focus on future releases.
These materials aid breeders in developing improved cultivars
for both the commercial and small-scale farmers.
A.F. Malan and M. Ncala.
During the past 5 years, a protocol was developed to suit the needs of the Small Grain Institute for doubled haploids of wheat. Maize-wheat crossings were used to achieve the goal. Several maize pollinators and hormone treatments were tested, but the best results were achieved with the U.S. cultivar Miricle, followed by two consecutive treatments with the hormones 2,4-D and gibberellic acid.
This technique was standardized and currently is applied as a routine protocol in the tissue culture laboratory at the Small Grain Institute. The technique is used extensively on the early generation, segregating material to produce large amounts of pure breeding lines for selection purposes.
Furthermore, this laboratory is responsible for generating double-haploid material for the SGI barley breeding program. Between 15,000 and 20,000 anthers are placed on medium per year.
A. Barnard.
The South African wheat-producing areas, especially the Eastern Free State, are highly subjected to the risk of preharvest sprouting due to summer rainfall that occurs just prior to or during harvest. Because preharvest sprouting is related closely 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.
The previous season saw the release of the Falling Number Report, which investigated various factors affecting FN as well as the need for such an analytic test in the South African-grading system. Although a lot of questions regarding FN were answered, many still remain unanswered. Research on the effect of temperature changes during certain stages of grain filling and the effect of kernel size on FN are just some of the areas to be investigated.
The ensuing season also marks the second year of cultivar evaluation from all localities planted on a national basis in the wheat-producing areas in South Africa (40 in total).
Small Grain Institute continues to combine efforts with the
Cereal Research Non-Profit Co. in Szeged, Hungary. Research areas
include the screening of both South African and Hungarian cultivars
for elevated, preharvest-sprouting tolerance with which we hope
to broaden the genetic breeding material from both countries.
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 also 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 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 mainly into four homogenous areas where different cultivars, mainly winter and intermediate types, are planted. All the cultivar evaluation trials planted at 18 sites throughout the Western, Central, and Eastern Free State were successful and were reported on. Twenty entries were included in the trials, of which five were from Small Grain Institute, ten from Monsanto, and five from PANNAR.
Production under irrigation. Wheat produced under irrigation
consists of about 20 % of the total wheat production of South
Africa. This area is divided into six different irrigation regions.
Because these regions have a very stable production area, they
are of great importance. The types of cultivars grown include
mainly spring types that are planted in the late autumn and early
winter. Thirty-five out of 38 cultivar-evaluation trials planted
at 20 sites throughout the irrigation areas of the summer-rainfall
region were successful and have been reported on in a detailed
annual report. Eight entries were included of which five originate
from Small Grain Institute and three from Monsanto.
Spring wheat varieties are grown in these two regions. These varieties do not require the same amount of cold to break dormancy as do the winter and wheat varieties 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 cultivars available differ in their 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.
In the winter-rainfall region, the Cultivar Evaluation Program is run jointly by The Small Grain Institute and The Directorate Agriculture of the Western Cape. The program consists of 12 sites in the Swartland and 12 sites in the Rûens, with 14 cultivars included in the trials. Cultivars from ARC-Small Grain Institute, Monsanto, and PANNAR are tested annually for yield potential, quality, disease resistance, and adaptability.
A. Barnard, C.W. Miles, K.B. Majola, M.L.T. Moloi, M.M. Radebe, 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; incorporate
contract work for milling and baking industries and private companies;
and provide an objective service to wheat producers. To ensure
accurate data to researchers and external parties, the laboratory
takes part in quarterly and monthly ringtests. A total of 40,341
analyses were made during 2001.
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 an accredited
Seed Testing Laboratory in which international methodology (i.e.,
ISTA (International Seed Testing Association) methods) is used
to determine the quality characteristics of seed. 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.
L. Visser.
The Soil Analyses Laboratory provides an important service to researchers, farmers, advisors, and representatives of different fertilizer companies. In addition to reliable and accurate analysis results, clients who visit the laboratory also have the benefit of exposure to research information generated at the Institute. At present, the laboratory is actively involved in a research project to evaluate the fertility status of soils from resource limited farms. There is a huge need for more information, specifically on the soils of Qwa-Qwa and the Eastern Cape.
The external income of the laboratory increased by nearly 30
% during the past year. A total of 75,532 tests were performed
on 430 plant and 9,947 soil samples. Fifty-five percent of these
samples were internal research samples. The laboratory aims to
improve these figures in the following year.
W. Otto.
Rainfed trials were planted in three of the major wheat-production areas under conventional-cultivation systems over two consecutive cropping years. A control (zero nitrogen fertilizer) and the recommended rate (per region) was banded at planting using the widely adapted cultivar Gariep. Crop development was monitored by biomass measurements, and nitrogen-uptake curves were calculated. Coinciding with these measurements, soil-mineral nitrogen (0-1,200 mm) also was measured. Multivariate analysis of measured yields, protein percent in the grain, and nitrogen-uptake values at harvest were used to determine the contribution of soil-mineral nitrogen at planting, soil-water content at planting, rainfall during the growing season, and applied fertilizer nitrogen to the changes in these values over the sites and years.
From the calculated analysis, soil mineral nitrogen, fertilizer applied, and soil-water content at planting contributed to 87 % of the variation in measured yields. Soil-water content, rainfall during the growing season, soil-mineral nitrogen at planting, and fertilizer applied explained 96 % of the changes in the measured grain-protein percentage.
Measured yield was the major contributor that explained changes in nitrogen uptake at harvest, and together with soil mineral nitrogen content and fertilizer applied, explained 96 % of the variation.
All the measured crop growth parameters were lower in the second
cropping season, which is linked to soil mineral nitrogen availability
at planting, in turn influenced by residue decomposition and soil
water availability. Residue and cultivation management during
the shortened fallow period between the cropping seasons is dependent
on rainfall during this time. From the data collected from this
project explanatory models were developed indicating the effects
of certain measurable parameters on agronomically important factors.
With further verification and refinement these models can be useful
in fertilizer planning and recommendation systems.
V.L. Tolmay and K. Naudé.
The outbreak of Karnal bunt in the Douglas area in December, 2000, caused a stir in the wheat industry. Until recently Karnal bunt has been regarded a dreaded wheat disease worldwide and also in the U.S. The U.S. currently is considering deregulation of the disease. Such a step may affect the South African wheat industry.
Under guidance of the Karnal bunt Task Team, national surveys of all registered seed units and commercial grain were conducted. All seed units tested free of KB. KB infection of commercial grain occurred once again in the Douglas area. The Directorate has placed the Plant Health & Quality (National Department of Agriculture) under order. Regulations such as these are essential in containing the disease to the affected area. In the future, these surveys will help determine the extent of the disease in South Africa.
At the ARC-Small Grain Institute, measures have been compiled to prevent the spread of the disease through institute actions. A laboratory was established to test ARC-SGI seed-production units, seed increases, and trial material for the presence of KB spores. A washing facility currently is being built to wash seed needed for trials and seed production in the coming production season. These procedures will ensure that all seed planted at research stations and coöperator's farms are free of KB spores and other deleterious organisms.
Mr, Francois Koekemoer resigned his position as irrigation
wheat breeder for ARCSGI, effective February, 2001, to join
Monsanto, Bethlehem as a wheat breeder. Dr Willem Boshoff has
been appointed as irrigation wheat breeder in his place. Thom
Steyn, who was responsible for no-till research, resigned to accept
a post at Monsanto. John Tolmay will continue with the no-till
research project. Dr. Hugo van Niekerk retired at the end of April
after 30 years service to the wheat and barley industry. He headed
the wheat breeding section from 1983 until his retirement and
was instrumental in the release of at least 25 cultivars. Palmiet,
a spring wheat cultivar became the most widely grown cultivar
in South Africa during the mid 1990s, comprising 43 % of the wheat
crop. Dr. Hugo Smit has replaced Dr. van Niekerk as Programme
Manager of Plant Breeding. Olaf Müller resigned his position
as winter and intermediate wheat breeder to join Monsanto as a
maize breeder. Ms. Una Aucamp handles the program. Felix Middleton
has accepted a position at the University of Stellenbosch. Dr.
Hugo Smit has been assigned as interim project leader until a
replacement for Mr. Middleton can be found.
UNIVERSITY OF STELLENBOSCH
Department of Genetics, Stellenbosch 7600, South Africa
G.F. Marais, H.S. Roux, A.S. Marais, and W.C. Botes.
Variety listing and plant breeder's rights were obtained for
two new spring triticale cultivars intended for cultivation in
the Winter Rainfall Region of the Cape. Bacchus was selected from
CIMMYTs 28th ITYN-48 (Supi 3//Hare 7265/Yogui 1), and Tobie is
a selection from the local cross 'Kiewiet/4/W.TCL83/Hohi//Rhino
4/3/Ardi 1'. Two of our cultivars, Tobie and USGEN 19, also have
been released for cultivation in Ethiopia and will be the first
triticales to be grown commercially in that country. A recurrent
selection procedure for wheat that is based on genetic male sterility
and hydroponic culture of spikes was continued.
Twenty-five promising backcross populations, each derived from
a different species donor, were tested with a total of nine leaf
rust, four stem rust, and two stripe rust pathotypes endemic to
South Africa. Five lines with resistance (from T. turgidum
subsp. dicoccoides, Ae. sharonensis, Ae. speltoides,
and Ae. peregrina) introgressed into wheat chromosomes
and six disomic addition lines with added chromosomes from the
wild species (Ae. kotschyi, Ae. peregrina, Ae.
umbellulata, Ae. biuncialis, and Ae. neglecta)
had wide-spectrum resistance. In several instances, stem and/or
stripe rust-resistance genes were cotransferred with the targeted
genes for leaf rust resistance.
A previous attempt to reduce the amount of foreign chromatin associated with leaf rust resistance by replacing homoeologous Thinopyrum chromatin with wheat chromatin yielded the shortened form Lr19-149 (chromosome 7BL). This translocation has lost the deleterious yellow endosperm pigment (Y) gene and subsequently was used in a further attempt to shorten the segment. The second attempt yielded the four Lr19-149 recombinants, 252, 299, 462, and 478. Physical mapping and monosomic analyses revealed that the recombinants still are associated with chromosome arm 7BL. In addition, recombinants 252, 299, and 462 resulted from proximal exchanges, whereas 478 resulted from a distal crossover. Recombinant 299 was a proximal form that had lost the most Thinopyrum chromatin. Recombinant chromosomes 299 and 478 then were combined in a heterozygote that was test crossed with a leaf rust-susceptible tester. The testcross progeny was screened for plants with a recombinant chromosome that combines the two shortened ends. Several such recombinants were found and are being confirmed with molecular markers.
Chromosome arm 7DL was targeted for mapping as part of an ongoing attempt to improve the utility of important genes on this chromosome, e.g., Dn2, Dn5, Lr19, and Pch1. Three mapping populations were used for this purpose.
Twenty-nine deletion mutant lines (produced by gamma irradiation) were used to extend a physical map of the Lr19 translocation. One hundred and forty-four Sse8387I/MseI and 32 EcoRI/MseI primer combinations were used to obtain 95 useful AFLP markers. The physical map confirmed that terminal deletions were the most common, however, it appears that several intercalary deletions and a number of primer or restriction-site mutations also were induced. The markers allowed for the discrimination of the deletions into 19 clusters, with seven AFLP markers mapping close to Lr19. Using the extended physical map, the size of the shortened recombinant forms could be readily deduced, and the markers identified will be very useful for further reduction of the translocation.
A doubled-haploid mapping population consisting of 94 lines was established from the F1 progeny from the cross 'Chinese Spring/PI294994'. This population was evaluated for seedling resistance to RWA (Dn5), endopeptidase (Ep-D1), and four microsatellite loci (Xgwm37, Xgwm111, Xgwm428, and Xgwm437). Several RFLP probes and two PCR-RFLP markers were tested on the parental lines, but were not polymorphic. Dn5 was linked to Xgwm111 and Xgwm437 at distances of 25.4 and 28.6 cM, respectively, but segregated independently from Xgwm428, Xgwm37, and Ep-D1.
AFLP markers associated with eyespot resistance gene. Pch1, and the endopeptidase locus, Ep-D1, were identified. One of the markers was cloned and sequenced. The sequence contained a microsatellite repeat motif and flanking primers were designed and tested on the material. The microsatellite marker, XustSS30M90AG240 could distinguish between the parental genotypes used, and a map distance of 2 cM was calculated between it and the endopeptidase locus in an extended mapping population. We also were able to physically map the marker between the Wsp-D1 and Sr25 loci. The latter may prove to be more versatile for marker-assisted selection of eyespot resistance than the presently used Ep-D1 marker.
There are two aspects to this project.
Identification of the critical chromosomes. 'Thinopyrum distichum/4x rye' hybrids with genomes J1^d^J2^d^RR were pollinated with diploid rye and yielded F1 offspring primarily with 21 chromosomes (two complete rye genomes and seven Thinopyrum chromosomes). We concluded that the homoeologous chromosomes of the J1^d^ and J2^d^ genomes regularly formed bivalents during megasporogenesis in the partially allohaploid F1. As a result, egg cells received a random, yet balanced, set of seven Thinopyrum chromosomes. The F1 plants were tested for salt tolerance and showed wide variation, implying that salt tolerance genes on some of the homoeologues may normally be suppressed. Fifteen highly salt-tolerant plants were C-banded and the Thinopyrum chromosomes in each were identified. We then assigned the Thinopyrum chromosomes to seven homoeologous pairs. We then began testing a set of diagnostic RFLP probes (John Innes Centre) on the same material to relate the Thinopyrum chromosomes to their wheat homoeologues. Up to now, it was possible to identify the chromosomes of homoeologous sets 3, 5, and 7. Dominance of certain homoeologues among the 15 selected plants was used to indicate that these chromosomes are primarily being expressed under salt-stress conditions. Up to six chromosomes may determine salt tolerance in this species.
Development of triticale lines with disomic additions of
the Thinopyrum chromosomes associated with salt tolerance.
A total of 35 putative disomic addition lines were developed,
each presumably has a set of 42 triticale chromosomes plus a random
pair of Thinopyrum homologues. As markers are found for
the five critical chromosomes implicated above, they are used
to test the disomic additions for the presence of the particular
chromosome. Thus far, two addition lines were found to have the
critical group-3 chromosome. Once the complete set of six critical
additions is available, we can begin the process of testing the
added chromosomes for complementation and plan the introgression
of some of the chromosome sections to triticale.