Genetic diversity analysis of rice (Oryza sativa) genotypes for seedling characters under saline -alkaline condition

Rice is life for Asians as it provides 43 per cent calorie requirement for more than 70 per cent of the population. The production is often limited by salinity. Understanding of physiological and genetic mechanisms is necessary for a breeding programme to improve crop performance under environmental stresses. Thirty rice genotypes pre-germinated in saline-alkaline water (pH-9.60; EC-10.0; SAR-54.32; RSC-11.51) were placed in plastic cups filled with sterile soil and the stress was imposed upto 21 days. Genetic diversity was estimated based on the observations recorded on germination per centage, vigor index, shoot length, root length, seedling length, root/shoot ratio, seeding dry weight, Na⁺/K⁺ ratio. The genotypes were grouped in to five clusters based on the Euclidean coefficient which ranged between 2.09(CSR10 X CSR 13) and 76.29 (IWP X Chettiviruppu). Cluster II was largest (22 genotypes) followed by cluster I (4 genotypes). Genotypes grouped under cluster I showed low Na⁺/K⁺ ratio which is an important physiological trait for salinity tolerance. Cluster V (MI 48 & IWP) grouped the susceptible genotypes which had high Na⁺/K⁺ ratio. The hybrids thus developed from the genotypes of cluster I & V may express high magnitude of transgressive segregants.