Breaking the association between gametocidal gene(s) and leaf rust resistance gene (LrS2427) in Triticum aestivum-Aegilops speltoides derivative by gamma irradiation

Abstract

Utilization of crop wild relatives of wheat can be very effective in building the genetic diversity to cater to the evolving strains of disease pathogens. Aegilops speltoides is a rich source of rust resistance genes however transferring those to wheat genome can be tedious due to co-transfer and preferential transmission of undesirable genes causing gametocidal activity. Such an unholy association was observed in Triticum aestivum-Ae. speltoides derivative line Sel. 2427 which possess the broad-spectrum leaf rust seedling resistance gene (LrS2427). In situ hybridization studies revealed the presence of S genome in Sel. 2427, showing translocations to six telomeric regions involving four chromosomes. This confirms the presence of genes associated with gametocidal activity along with the beneficial LrS2427. QTLs associated with the component traits of gametocidal activity have been localized to 2A, 2D, 3D chromosomes however candidate genes for fertility were identified only in 2A and 2D chromosomes. This is in accordance with the reports of gametocidal genes mapped to 2S chromosomes in Ae. speltoides. To break the inadvertent association, F₁(Agra Local X Sel. 2427) seeds were irradiated with gamma rays and leaf rust resistant mutants lacking gametocidal activity were developed. These mutants showed resistance to different races of leaf rust pathogen and showed superior agronomic performance as well. These mutants could be a great resource in wheat improvement for utilization of the leaf rust resistance gene LrS2427 without any yield penalty.