Estimating Genetic Variability and Diversity for Vein Density, Photosynthesis and Yield in Rice Genotypes

Understanding the physiological and leaf anatomical traits having positive association with higher yields is critical to utilize these traits effectively in breeding programs for yield improvements in stable food crops. In rice, this would help in improving the productivity to feed the ever growing population. Therefore, the experiment was conducted to evaluate the variability and diversity of ninety-nine rice genotypes for photosynthesis, vein-related characters, and yield. The field trial was carried out in a wetland in Tamil Nadu Agricultural University, Coimbatore during Rabi, 2020. To investigate the genetic variability, efforts were made to estimate the percent of genotypic and phenotypic variation, heritability, and genetic advance likewise genetic diversity was estimated for twelve traits using Mahalanobis (D2) statistics. Analysis variance elucidates the existence of significant variation among the genotypes for all the twelve characters studied. The difference between GCV and PCV was narrow for all the characters studied which shows these characters are less influenced by environmental factors. The highest GVC and PCV was observed in yield and biomass simultaneously the high heritability in broad sense along with high genetic advance as percent mean was estimated in biomass, photosynthetic rate, yield, interveinal distance between major vein, leaf width, total number of veins, and total number of minor veins. These characters are considered to be inherent in nature and selection for improving these traits may be effective in the genetic improvement program. Based on the D2 value ninety-nine genotypes were diversified into five clusters in which Cluster II is the largest containing 37 genotypes followed by cluster I. The highest inter-cluster distance was estimated between cluster II and cluster IV whereas the highest intracluster distance was observed in cluster V indicating that genotypes in this cluster are highly diversified. Subsequently, the higher cluster means of most of the characters including vein characters, leaf width, and photosynthetic rate along with optimum yield and biomass fell in cluster II. Whereas in cluster IV the highest cluster means for biomass and yield was recorded. The traits biomass, yield, photosynthetic rate, interveinal distance between major veins, the total number of minor vein is the major contributors of total divergence in this population. Based on the trait contribution percentage for genetic diversity and genetic distance this study suggests that the genotypes from cluster II and cluster IV can be selected as parents for genetic improvement programs. Hence, information on the nature and degree of divergence in this population would help the plant breeder in the selection and hybridization procedure for choosing the right type of parents to improve vein characters, photosynthetic rate, yield, and biomass.