Prospects for Breeding Winter Common Wheat for Resistance to Leaf Rust Using Molecular Markers

Abstract

Wheat leaf rust is a harmful disease whose epiphytotics lead to serious grain yield losses. Severe epiphytoties of leaf rust are observed once every 3-4 years in the Volga Region. Despite numerous breeding achievements, many modern wheat varieties in the Russian Federation are not resistant to leaf rust. Studies of the newest assortment of soft wheat, carried out by Russian researchers, show that the genotypes of 93% of the studied varieties contained Lr genes individually or in various combinations; the Lr34 gene is widely represented in combinations with the ineffective juvenile genes Lr3, Lr10 and Lr26, which provides an acceptable level of field resistance to leaf rust. Selection for resistance is hampered by the constant change in the race composition of the pathogen, which goes hand in hand with the introduction of highly expressed genes of vertical resistance into the wheat genotype by breeders. The priority in breeding is the use of "field" or long-term resistance. There are suggestions that this type of resistance is due to the additive effects of several genes that cause the effects of age resistance and "slow rusting”. Development of cultivars possessing "pyramids" of genes will produce a long-term effect of resistance. However, the use of classical methods of hybridological analysis and phytopathological tests for gene pyramiding is time-consuming and labor-intensive and not always effective. Marker-assisted selection makes it easy to identify the right alleles in both starting material and breeding lines, making it an indispensable tool in immunity breeding. The use of molecular markers makes it possible to quickly and successfully create varieties with multiple resistance genes if donors of resistance genes and specific molecular markers of these genes are available. The breeding program for winter soft wheat at the Samara Research Institute of Agriculture uses donors of genes Lr3, Lr9, Lr10, Lr26, Lr34, Lr39(41) and others, as well as a replaced chromosome 6Agi2 of wheatgrass intermediate, whose direct donors are spring soft wheat varieties ‘Tulaikovskaya 10’ and ‘Tulaikovskaya Zolotistaya’. As a result of hybridization and subsequent individual selection, promising breeding material of winter soft wheat was created in Samara Research Institute of Agriculture for further identification of valuable genotypes that contain genes of resistance to leaf rust and chromosome 6Agi2, using molecular markers.