Breeding for Complete Resistance in Bread Wheat to Puccinia Striiformis in Kenya: A Case Study
1994
Danial, D.L. | Kirigwi, F.M. (N.P.B.R.C., Njoro (Kenya))
In Kenya, multi-location testing was carried out from 1984 to 1987 to evaluate over 11,000 wheat genotypes for resistance to yellow, stem and leaf rust. Across seven locations, a total of 35 genotypes were identified as carrying high levels of resistance to the three rust species at the adult plant stage. In a controlled environment, the yellow rust reaction of the 35 genotypes was studied in the seedling stage with six yellow rust races differing in their virulence to 20 differential cultivars. Fifteen genotypes showed a complete to intermediate resistance to all six races, indicating the presence of at least one unidentified seedling resistance gene. The remaining genotypes appeared to differentiate the test races, and varied in reaction from susceptible to resistant. In 1987, crosses were made between six Kenyan wheat cultivars and the 15 genotypes identified as having seedling and possibly adult resistance. F2 selections were advanced to the F7 generation using conventional breeding procedure, selecting the most resistant plants having good agronomic characteristics. In 1992, F7 progenies and their parents were evaluated for agronomic performance and resistance to yellow rust in 53 percent of the parents and in a considerable number of the F7 lines, indicating that a build up of more complex yellow rust races is inevitable for the wheat-yellow rust pathosystem when resistant parents are selected and tested carefully.
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