| Popis: |
This study covered three aspects, namely; assessment of genetic diversity for rust resistance genes among released cultivars, inheritance of adult plant resistance (APR) in two North American wheat cultivars and genetic association between the stern rust resistance gene Sr3 9 and the stripe rust resistance gene YrSp. Queensland and northern New South Wales cultivars carried more diverse gene combinations in comparison to rest of the nation. Genetic diversity for all three rust diseases is a concern in Victoria and South Australia. There is need to release cultivars carrying combinations of resistance genes against three rust diseases. This will ensure environmentally safe control of rust diseases. Cultivars Jagger carried three genes for APR to stripe rust. Combinations of these genes provide high levels of resistance. Isolation of these genes individually was initiated and molecular mapping will determine identities of these genes. American workers detected the presence of Yr] 7 in at least one source of Jagger. Based on marker genotyping, the Jagger source used in this study did not carry Yr] 7. Cultivar Katepwa carried a single APR gene for stripe rust resistance. It is likely to be located on chromosome 2D. Repulsion linkage between the Triticum speltoides-derived stem rust and leaf rust genes Sr39/Lr35 and the stripe rust resistance gene YrSp was demonstrated. A recombination faction of 7.7:tl.5 cM between these genes was computed. These results refuted the previous location of YrSp in the short arm of chromosome 2B. Comparative results from other sources suggested the location of YrSp in the long arm of chromosome 2B. Progenies from three recombinant genotypes (Sr39Sr39YrSpyrSp) would enable the isolation of Sr39, Lr35 and YrSp in a single genotype. Such triple rust resistant genotype will be useful in improving rust resistance in future wheat cultivars. |
