What Was the Reason for the Durable Effect of Sr31 against Wheat Stem Rust?

Abstract

Common wheat cultivars have been protected from stem rust for several decades worldwide by the Sr31 resistance gene transferred from Secale cereale L. (cv. Petkus). In 1998, Sr31 was overcome in Uganda by the Ug99 race of Puccinia graminis f. sp. tritici Eriks. & Henn. (Pgt). The Ug99 race and its derivatives have spread widely in Africa, neighboring regions and Europe. However, Sr31 remains effective in other areas of the world, including Russia. To breed wheat with durable resistance, it is promising to research the resistance mechanisms of nonhost species and introgressive cultivars. The aim of the research was to estimate the resistance of S. cereale and Triticum aestivum cultivars with Sr31 to stem rust and to study the mechanisms of incompatibility of Pgt with plants at the cellular level. The research was carried out in Western Siberia (Russia, Omsk region) in 2018–2022. Rye and wheat with Sr31 (cvs. Kavkaz, Seri 82, Bacanora (=Kauz’s’), NIL Thatcher TcLr26/Sr31) were resistant at the stages of seedling and adult plant, and cv. PWB343 was more susceptible to disease. Cytological studies have shown that Pgt died on the rye plants on the surface, and cv. Petkus intensively suppressed the development of the appressoria necessary to penetrate into tissues. Wheat cultivars inhibited the Pgt development mainly on the surface and while it attempted to penetrate into the stomata (pre-haustorial resistance). It has been demonstrated that Pgt has to adapt step-by-step to the surface and tissue properties for compatible interaction, which may be the reason for the durable effectiveness of Sr31.

Permanent Spreading of 1RS.1AL and 1RS.1BL Translocations in Modern Wheat Breeding

“…Thus, it can be concluded that translocation 1RS.1BL is one of the most important components of the genotypic landscape for breeding high-yielding and highly adaptive winter bread wheat. Despite reports of overcoming resistance conferred by the genes located on 1RS [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ], in general, the adaptability provided by this translocation into the wheat genome is still a highly demanded factor in the breeding of bread wheat. The presence of the 1RS.1BL was shown in cultivar Viza, which, according to the results of multi-year trials, showed high resistance to yellow stem rust and was classified as highly resistant, along with other carriers of the 1RS.1BL translocation Alekseich, Ayvina and Urup [ 47 ].…”

“…Genes for resistance to leaf rust ( Lr26 ), stem rust ( Sr31 ), powdery mildew ( Pm8 ), yellow rust ( Yr9 ), wheat streak mosaic virus ( Wsm ), aphids ( Gb2 and Gb6 ), wheat curl mite ( Cmc3 ) and others are localized to the short arm of 1R [ 16 ]. However, according to some reports, to date the resistance determined by these genes has lost its effectiveness as new virulent pathogenic biotypes that can infect wheat plants with the Lr26 , Pm8 , Sr31 and Yr9 have appeared in Europe, Asia and Africa [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ]. Besides the partially overcome resistance to biotic factors, the presence of a short arm of chromosome 1R in the wheat genome results in better water supply, increased zinc efficiency, stronger root development and higher yields under water-stress environments compared to parental lines [ 26 , 27 , 28 , 29 , 30 , 31 ].…”