Recombinant inbred lines (RILs) developed from a cross between rust resistant (FLIP‐2004‐7L) and susceptible (L‐9–12) genotypes were phenotyped against lentil rust at two hot‐spot locations for two consecutive years (2017–2018 and 2018–2019) and analysed genetically for molecular map construction. Based on the mean score of both the locations, the RILs were classified into resistant and susceptible classes. The frequency distribution of disease severity in the RILs did not show a continuous variation, which strongly indicate the role of a major gene controlling the rust resistance. Resistant and susceptible bulks were constituted based on phenotypic data of RILs. Of 389 SSR markers, eight were found polymorphic between bulks. Genotyping of RILs with these eight markers revealed two markers, namely LcSSR440 and LcSSR606, showing co‐segregation with rust resistance, which flanked the gene at 8.3 and 8.1cM, respectively. The applicability of these markers for marker‐assisted breeding was further evaluated on a set of rust resistant and susceptible genotypes of lentil.
The periodic breakdowns of stripe rust resistance due to emergence of new virulent and more aggressive pathotypes of Puccinia striiformis f. sp. tritici have resulted in severe epidemics in India. This necessitates the search for new and more durable resistance sources against stripe rust. The three bread wheat cultivars PBW 343 (carries Yr9 and Yr27), PBW 621 (carries Yr17) and HD 2967 (gene not known) were highly popular among the farmers after their release in 2011. But presently all three cultivars are highly susceptible to stripe rust at seedling as well as at adult plant stages as their resistance has been broken down due to emergence of new pathotypes of the pathogen (110S119, 238S119). In previous study, the crosses of PBW 621 with PBW 343 and HD 2967 and evaluation of further generations (up to F4) against pathotype 78S84 resulted in resistant segregants. In the present study, the F5 and F6 RIL populations have been evaluated against new pathotypes of Pst. The RILs categorized based on the disease severity on the P (Penultimate leaf) and F (flag) leaf into three categories i.e., high, moderate and low level of APR (adult plant resistance) having 1–200, 201–400 and >400 values of AUDPC, respectively, upon infection with stripe rust. The various APR components (latent period, lesion growth rate, spore production and uredial density) were studied on each category, i.e., resistant, moderately resistant and susceptible. The values of APR parameters decreased as the level of resistance increased. Based on molecular analysis, the lines (representing different categories of cross PBW 621 X PBW 343) containing the genes Yr9 and Yr17 due to their interactive effect provide resistance. Based on BSA using 35k SNPs and KASP markers association with phenotypic data of the RIL population (PBW 621 X HD 2967) showed the presence of two QTLs (Q.Pst.pau-6B, Q.Pst.pau-5B) responsible for the residual resistance and two SNPs AX-94891670 and AX-94454107 were found to be associated with the trait of interest on chromosome 6B and 5B respectively. The present study concludes that in the population of both the crosses (PBW 621 X PBW 343 and PBW 621 X HD 2967) major defeated gene contributed towards residual resistance by interacting with minor gene/QTLs.
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