Diversity assessment and evaluation of Nepalese rice landraces for agronomic traits in Chitwan, Nepal

Nepal has a diversity among rice landraces whose exploration aids as a valuable source of traits for breeding programs. However, their cultivation is declining, leading to a shrinking genetic base for rice. Classifying landraces helps identify desirable traits and understand genetic diversity. This study evaluated 46 Nepalese rice landraces from different regions of Nepal along with three released varieties used as checks. A field experiment was conducted in the Plant Breeding Block of Agriculture and Forestry University, Rampur, Chitwan, using alpha-lattice design with three replicates and seven blocks with seven plots per replication, and they were evaluated to assess the diversity. Observations were taken for twenty- nine different qualitative traits and twenty-two quantitative traits. Shannon Weiner index, Simpson index, and evenness were calculated to assess the diversity in the accessions. Evaluation of variability, genetic parameters, correlation, cluster analysis and principal component analysis (PCA) based on different agronomic traits was performed in this study. All the qualitative traits under the study showed polymorphism, except for the shape of ligule, and all the quantitative traits showed significant differences. Higher estimates of phenotypic and genotypic coefficients of variability were observed for ligule length, grain width, total number of grains per panicle, thousand-grain weight, straw yield, grain yield, and harvest index. Grain yield showed a high positive association with leaf width, number of effective tillers per plant, grain length, grain width, and thousand- grain weight, which can be selection indices for the improvement of grain yield. The landraces were classified into eight different clusters. PCA revealed that seven components were significant and contributed to 77.68% of the variance. The observed genetic diversity among landraces for various qualitative and quantitative traits could be pivotal information for further study of genetic variation of rice germplasm and can be effectively used in future rice improvement programs.