Development and characterisation of leaf rust resistant Triticum timopheevii derived introgression lines in hexaploid wheat

Tetraploid wheat, Triticum timopheevii (Zhuk.) (AtAtGG, 2n = 4x = 28) is a well-known source of resistance against many pests and diseases. It has been practically utilized in various breeding programmes against leaf rust disease. The present study developed a set of 41 introgression lines (ILs) by crossing two T. timopheevii accessions viz., T. timopheevii-191 and T. timopheevii-235 with bread wheat genotype Chinese Spring. The F1s were backcrossed thrice to susceptible cultivars, Agra Local and Kharchia Local, followed by selfing for five generations. All the ILs were screened for leaf rust resistance using leaf rust pathotype 77-5 at seedling stage in a glass house. Out of 41 ILs, 33 showed resistant reactions to leaf rust ('0;' to '13'). Two ILs, TTm Derivative-638 and TTm Derivative-793, showing high degree of resistance, were further tested against 19 different leaf rust pathotypes, produced "0;" to ";" type of infection type (IT). To characterize the genomic constitution of these two ILs and to detect the presence of introgression segment(s) of two wild Triticum timopheevii wheats, 35K Affymetrix Wheat Breeders'Axiom & REG; array was used. SNP (Single nucleotide polymorphism) analysis confirmed T. timopheevii introgressions in two ILs and was used for graphical representation using software GTM v1.0. Genomic characterization revealed 30.59 and 20.30% of introgression from wild accessions, T. timopheevi-191 and T. timopheevi-235 into ILs TTm Derivative-638 and TTm Derivative-793, respectively. Genomewise analysis in ILs TTm Derivative-638 and TTm Derivative-793 revealed maximum introgression in B genome (32.18) and A genome (22.75%), respectively. These ILs will help in widening the genetic base for leaf rust resistance in wheat.