High resolution mapping of chromosome elimination approach mediated rye Secale cereale chromatin introgressed bread wheat Triticum aestivum recombinants for drought tolerance and rust resistance through molecular cytogenetic techniques

Abstract

The present investigation was undertaken to accelerate the wheat improvement programme with enhanced precision in respect of transferring the rye chromatin (Secale cereale) into wheat (Triticum aestivum) through triticale (x Triticosecale) as a bridging species. Five triticales and 16 wheat genotypes along with Himalayan rye were utilized as the parents in the wide hybridization programme. Analysis of variance revealed significant high seed setting in dry temperate zone, Kukumseri (long photoperiods) (26.50%) than that of sub-humid mid hills, Palampur (short photoperiods) (22.46%), which indicated the influence of environment on the seed set in wide hybridization. Moreover, indigenous triticales (Tyari 1 x Rye and Tyari 2 x Rye) have been synthesized utilizing Himalayan wheat landraces and rye. The triticale x wheat recombinants were further subjected to Imperata cylindrica mediated chromosome elimination approach of doubled haploids production. The variability in the haploid induction parameters was observed to be under genetic control for embryo formation and regeneration, while pseudoseed formation was only affected by auxin treatment. The detection of new recombinants for introgression of rye chromatin through molecular cytogenetic analysis revealed that 67 lines were carrying 1RS.1BL translocation, 21 lines with five or more pair rye chromosomes substitution, 16 lines carrying translocation along with the substitution and 12 lines with 1R(1D) substitution, while only three lines carrying rye addition and two lines carrying rye addition along with translocation. There were 18 lines detected through GISH which had no rye chromatin. In the line F7 DT 126 x VL 829, two translocation (1RS.1BL and 6BS.6RL) along with 2R(2D) substitution have been detected. The GISH revealed genetic stability and hexalpoid level instead of octoploid in new indigenous triticales. There was complete loss of D genome which was substituted by R genome. Moreover, Tyari 2 x Rye has also carried 1RS.1BL translocation along with R genome. To validate molecular cytogenetic results, all 139 genotypes were subjected to field evaluation. Analysis of variance revealed significant variation among genotypes for all the yield traits. The introgression of rye has directly influenced grain yield, tillers number, spikes number and harvest index. The screening for yellow rust resistance revealed differential disease reaction, where 117 recombinants were observed from immune to resistant. The screening for drought tolerance under in vitro conditions revealed that rye introgressions have no significant effect on germination percentage. Translocations have significant influence on most of the drought parameters. Root shoot length ratio increased significantly with substitution of more than five pair of rye chromosomes, while root shoot weight ratio increased with increase in stress level in all types of introgressions. Similarly, among all the introgressions, tolerance index decreased by 50% as the moisture stress level doubled. The lines exhibiting positive significance for the traits can be used as a parental source in wheat improvement endeavours. newline