PARTIAL AND SPECIFIC RESISTANCE TO STEM RUST IN THE ADVANCED BREAD WHEAT LINE ‘KIJIL’

Abstract

The fungus Puccina graminis f. sp. tritici is the causal agent of wheat (Triticum aestivum) stem rust, it can cause yield losses of up to 40 % in susceptible varieties; it can also mutate and overcome resistance genes, so it is necessary to identify new sources of resistance to fight the virulent races of this pathogen. Bread wheat advanced line Kijil has shown high levels of resistance to stem rust in the stages of seedling and adult plant, but the number of genes that confer such resistance is unknown. The genetics of stem rust resistance was investigated in an F₆ population consisting of 99 families derived from the Apav #1 × Kijil cross. Greenhouse and field trials were carried out in El Batán, Texcoco and Ciudad Obregón, Sonora, Mexico, respectively, during 2016 and 2017. Genetic analysis indicated that there are four race-specific genes that confer resistance in seedling stage. The first gene was identified as Sr38 and the other three were temporarily designated as SrKj;1, SrKj22+ and SrKjX-, according to the infection types recorded. In adult plant stage, the families positive to Sr38, showed severities of 0 to 20 %, while families carrying SrKj;1, SrKj22+ and SrKjX- genes presented severities from 1 to 30 %, 30 to 60 % and 1 to 30 %, respectively. Additionally, it was determined that there are three genes that confer resistance only in adult plant stage, including Sr2 and Sr58. Families positive to Sr58 displayed severities from 30 to 90 % and only one family presented 5 %; those families positive to Sr2 + Sr58 presented 60 to 100 % severity. According to the results, Kijil is a potential source of resistance to stem rust by conferring high levels of resistance in seedling and adult plant stages.