Browsing by Author "De Groot, Stephan"
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- ItemInitiation of a pre-breeding programme for enhancing genetic resistance against wheat rust(Stellenbosch : Stellenbosch University, 2012-12) De Groot, Stephan; Botes, Willem; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.ENGLISH ABSTRACT: Plant diseases are among the major causes of food insecurity. In South Africa the wheat fungal diseases including stem rust caused by Puccinia graminis f. sp. tritici, leaf rust caused by P. triticina and stripe rust caused by P. striiformis f. sp. tritici are the most important. Genetic resistance is a viable way of protecting wheat crops against the wheat rusts, especially cultivars carrying multiple genes that confer durable resistance. In order to breed for multi-gene resistance an effective breeding strategy that allows for selecting multiple resistance genes and other desirable traits needs to be devised. The aim of this study was to identify a number of genotypes with combinations of different rust resistance genes, good grain yield and end-use quality out of an existing pre-breeding population and thereby identify superior parents. In order to achieve the stated aim the following objectives have been identified: identify wheat lines through marker-assisted selection (MAS) carrying the gene complexes, Sr31/Lr26/Yr9, Lr24/Sr24, Lr37/Sr38/Yr17, Lr34/Yr18 and Sr2; to develop inbred lines to evaluate selected lines under field trials. From the initial subset of 64 lines, 60 were chosen and advanced to the doubled haploid (DH) phase and seed multiplication. The 60 lines either carried one or more of the three rust resistance gene complexes. The genes that were the most prominent were Sr31/Lr26/Yr9 and Lr24/Sr24. The selected lines were incorporated into a DH seed multiplication phase. After 4 cycles of seed increases and preliminary field evaluation during multiplication, 15 lines were chosen and subjected to multi-location field trails. The extensive multi-location field trails carried out in this study aided in identifying genotypes from the 15 MS-MARS lines with good adaptability and stability in regards to yield and baking quality. An important observation was that the molecular markers employed to indentify quality loci correlated well with the genes encoding the HMW-GS 5, 10 and 12 as observed with the Agilent© 2100 Bioanalyzer. In future studies the lines which performed the best could be re-introduced into the existing MSMARS pre-breeding programme of the Stellenbosch University’s Plant Breeding Laboratory (SUPBL). The frequencies of desired alleles could be increased in this manner. Since the majority of these characteristics are influenced by quantitatively inherited alleles, using these lines as recurrent parents will increase the frequencies of these alleles in the existing SU-PBL pre-breeding population.