Effectiveness of the influence of Sr and Lr genes on the field resistance of wheat to stem and leaf rust

Stem and leaf rust have a tremendous impact on wheat yields. The spread of these diseases can compromise any country’s food security. The Sr and Lr resistance genes, comprising 60 and 80 genes, respectively, are gradually losing their effectiveness due to the emergence of virulent populations of rust pathogens. The paper reports the results of field and molecular studies of resistance to the two types of rust in several varieties and lines of spring soft wheat. It is discovered that the Sr2, Sr21, Sr32, and Sr35 genes have virtually no effect on resistance to stem rust, as with an average plant disease severity of 42.2% the four genes prove ineffective. However, the area under the disease progress curve in the presence of Sr2 is reliably lower by 3.2% (p≤0.01). Regarding the coefficient of infection, susceptibility in the presence of Sr21 or Sr35 is reliably lower by 3.5%. The Lr19, Lr24, Lr27, and Lr39 leaf rust genes retain their positive effect on wheat resistance to the disease. The Lr19 and Lr39 genotypes show moderate resistance in 100% of the cases. The average coefficient of infection in the presence of both genes amounts to 6.5 units, with average plant disease severity equal to 16.3%. The Lr39 gene reliably reduces the area under the disease progress curve by 4.5 units. The obtained findings indicate the need to identify donors of Sr resistance genes for their use in selection. There is also a need to study the influence and prevalence of the Lr24 and Lr27 genes in different varieties and lines of spring soft wheat.