• R. L. Ravikumar

      Articles written in Journal of Genetics

    • Development of molecular map and identification of QTLs linked to Fusarium wilt resistance in chickpea

      Pavankumar Jingade R. L. Ravikumar

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      A number of genetic maps for Fusarium wilt resistance in chickpea have been reported in earlier studies, however QTLs identified for Fusarium wilt resistance were unstable. Hence, the present study aims to map novel molecular markers and to identify QTLs for Fusarium wilt resistance in chickpea. An intraspecific linkage map of chickpea (Cicer arietinum L.) was constructed using F10–F11 recombinant inbred lines (RILs) derived from a cross between K850 and WR315 segregating for H2 locus. A set of 31 polymorphic simple sequence repeat (SSR) markers obtained by screening 300 SSRs and were used for genotyping. The linkage map had four linkage groups and coverage of 690 cM with a marker density of 5.72 cM. The RILs were screened for their wilt reaction across two seasons in wilt sick plot at International Crop Research Institute for Semi-Arid Tropics (ICRISAT), Hyderabad, India. Five major quantitative trait loci (QTLs) were detected in both seasons for late wilting (60 days after sowing). A stable QTL (GSSR 18-TC14801) for wilt resistance was identified in both the seasons, and the QTL explained a variance of 69.80 and 60.80% in 2007 and 2008 rabi respectively.

    • Consequence of cyclic pollen selection for heat tolerance on the performance of different generations in maize (Zea mays L.)


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      The reproductive stage in many crops, including maize, is very sensitive to heat stress and the genetic overlap between gametophytic and sporophytic phase gives an opportunity to select superior stress tolerant genotype at gametophytic stage. An attempt was made to evaluate the response of cyclic pollen selection in the F1 and F2 generations on the performance of F3 generation progenies for seed yield and yield contributing traits under natural heat stress conditions. In this direction three groups of F3 progenies, namely (i) pollen selection in F1 and F2 generations (GG), (ii) pollen selection only in F2 generation (CG), (iii) no pollen selection in F1 and F2 generations (CC) were screened for heat stress at Agricultural Research Station (ARS), Bheemarayanagudi. The GG progenies recorded significantly higher chlorophyll content, more number of pollen grains per anther and less pollen sterility compared to CG and CC group of progeniesunder heat stress. Further, the F4 progenies obtained through cyclic pollen selection (in F1, F2 and F3) were also tested for heat stress tolerance at seedling stage. The significant improvement for heat stress tolerance was recorded in F4 progenies derived through cyclic pollen selection as compared to control (no pollen selection for heat tolerance in any generation) F4 progenies. The results indicated that cyclic pollen selection in F1, F2 and F3 generations improved the heat stress tolerance of the progenies in the succeeding generations. To provide genetic evidence for the effect of pollen selection for heat tolerance, the control F2 (C) and selected F2 (G) populations were compared for the segregation of SSR markers. The selected F2 (G) population showed significant deviation from normal Mendelian ratio of 1:2:1 and showed skewness towards the alleles selected from male parent. The results provide strong evidence for an increase in the frequency of parental alleles in the progenies that impart heat stress tolerance.

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