8th INTERNATIONAL WHEAT CONFERENCE

APPLyINg mALe STeRILITy medIATed mARkeR ASSISTed
ReCuRReNT mASS SeLeCTIoN IN A PRe-BReedINg
STRATegy foR ACCumuLATINg dISeASe ReSISTANCe geNeS
S. de Groot 2. and W.C. Botes 1
1 Stellenbosch University Plant Breeding Laboratory, Department of Genetics, Faculty
of Agrosciences, Private Bag X1, Matieland 7602
2 Sensako, Pty. Ltd., P.O. Box 556, Bethlehem 9700
E-mail Address of presenting author: wcb@sun.ac.za
In South Africa wheat rust plays an important role when it comes to wheat yield stability and overall
profitability. Wheat rust is thus considered an economically important wheat disease in South
Africa. Three wheat rust pathogens are of importance in South Africa, namely stem rust (Puccinia
graminis f. sp. tritici), leaf rust (Puccinia triticina) and stripe rust (Puccinia striiformis f. sp. tritici).
These Puccinia species can rapidly adapt to a single resistance source in wheat when a specific cultivar
is planted over a wide area and only relies on a single major gene for resistance. Unfortunately
this is very much the current situation over large parts of the South African wheat production
areas. Breeding for durable rust resistance, by incorporating more than one gene of resistance in
a single genotype, has become an increasingly important strategy to assist securing a sustainable
wheat industry. This enables a buffering effect which gives the genotype a more durable defense
against an adapting pathogen. The objective of this study is to establish a set of line with an array of
effective resistance genes for all three rust pathogens plaguing the winter rainfall region of South
Africa. These lines will be included in the annual wheat rust nursery distributed by the Stellenbosch
University’s Plant Breeding Laboratory (SU-PBL), and will be used by South African wheat
breeding programmes (both public and private) as resistance sources in their crossing blocks. In
order to develop these multi-gene resistant genotypes, a breeding strategy based on male sterility
(Ms3) mediated marker assisted recurrent selection (MS-MARS) are being followed. Starting material
was taken from an existing MS-MARS population from the SU-PBL. Genotypes in this MS-
MARS population contained the Ms3 gene (conferring dominant male sterility) and multi-gene
complexes Sr31/Lr26/Yr9, Lr24/Sr24, Lr37/Sr38/Yr17 and Lr19. Selected genotypes from the MS-
MARS population were crossed with each other to form a base population. This base population
segregated for multi-gene resistance, as well as, the male sterility gene Ms3. From this base population,
female (male-sterile) and male (male-fertile) parents were selected and inter-crossed with
each other. Progeny obtained from these crosses were planted out and screened by means of molecular
markers for the four rust resistance gene complexes Sr31/Lr26/Yr9, Lr24/Sr24, Lr37/Sr38/
Yr17 and Lr19. This was continued for three cycles. From the F1 population (at the end of cycle 3),
11 genotypes were identified by means of MAS to carry all the resistance gene complexes selected
for. These genotypes were incorporated into a doubled haploid program to fast track them. MAS
was again applied on the haploid plants before chromosome doubling to insure that the resistant
gene complexes were present. The doubled haploid (DH) population will be planted during the
winter of 2010 to evaluate their field resistance, and also to annotate their agronomical properties.
Selected lines will then go through a quality screening to evaluate their baking quality, and a final
selection made. Selected lines shall be included in the 2011 annual SU-PBL wheat rust nursery.
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