Introgression and Exploitation of Biotic Stress Tolerance from Related Wild Species in Wheat Cultivars

Abstract

Bread wheat is one of the three most important cereal crops which has major role in feeding the population globally. Biotic stresses, mainly the fungal diseases, pose major constraint to wheat production. To combat against these diseases, continuous efforts have been made to mine genes from wide variety of sources including primary, secondary, and tertiary gene pools of cultivated wheat which are rich sources of genes against different biotic stresses. More than 100 resistance genes against leaf rust, stripe rust, stem rust, and powdery mildew have been identified from these gene pools and successfully transferred to cultivated wheat. The transfers from primary gene pool are achieved through homologous pairing while transfer from secondary and territory gene pool requires special chromosome engineering techniques for affecting transfers through induced homoeologous pairing or translocations. The introgressions have been reported as small cryptic alien segments or complete chromosome arms or chromosomes such as chromosome addition and substitution lines. Molecular cytogenetic techniques such as genomic in situ hybridization (GISH) have proved to be a highly efficient technique to directly and precisely detect the alien segments in wheat while molecular marker technologies now combined with next-generation sequencing techniques have facilitated the mapping as well as marker-based mobilization of alien genes to cultivated wheat background. Present review gives a brief description of the contributions of different gene pools of wheat toward the biotic stress resistance, methodologies of gene transfer, characterization of these transfers, and use of the molecular marker technologies for precisely mapping the alien genes for resistance to various biotic stresses in wheat.