• Ashutosh Singh

      Articles written in Journal of Genetics

    • Assessment of genetic diversity in Indian rice germplasm (Oryza sativa L.): use of random versus trait-linked microsatellite markers

      Sheel Yadav Ashutosh Singh M. R. Singh Nitika Goel K. K. Vinod T. Mohapatra A. K. Singh

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      Assessment of genetic diversity in a crop germplasm is a vital part of plant breeding. DNA markers such as microsatellite or simple sequence repeat markers have been widely used to estimate the genetic diversity in rice. The present study was carried out to decipher the pattern of genetic diversity in terms of both phenotypic and genotypic variability, and to assess the efficiency of random vis-à-vis QTL linked/gene based simple sequence repeat markers in diversity estimation. A set of 88 rice accessions that included landraces, farmer’s varieties and popular Basmati lines were evaluated for agronomic traits and molecular diversity. The random set of SSR markers included 50 diversity panel markers developed under IRRI’s Generation Challenge Programme (GCP) and the trait-linked/gene based markers comprised of 50 SSR markers reportedly linked to yield and related components. For agronomic traits, significant variability was observed, ranging between the maximum for grains/panicle and the minimum for panicle length. The molecular diversity based grouping indicated that varieties from a common centre were genetically similar, with few exceptions. The trait-linked markers gave an average genetic dissimilarity of 0.45 as against that of 0.37 by random markers, along with an average polymorphic information constant value of 0.48 and 0.41 respectively. The correlation between the kinship matrix generated by trait-linked markers and the phenotype based distance matrix (0.29) was higher than that of random markers (0.19). This establishes the robustness of trait-linked markers over random markers in estimating genetic diversity of rice germplasm.

    • 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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