Analysis of divergence in some cold-tolerant rices

Genetic divergence of ninety-four rice genotypes, comprising 74 F₁s and 20 parents, grown over three cold stress environments, was assessed based on five reproductive stage cold tolerance and adaptability related characters. Using D² statistic and canonical analyses, the genotypes were grouped into 18 clusters. The clustering pattern suggested that genetic and geographic diversity were not necessarily related. Plant height, days to flowering, fertile spikelets/panicle and percent fertility were indicated as important contributors to genetic divergence in cold tolerant rices. Traditional japonica varieties and their japonica x indica hybrids were distinctly apart from the indica varieties and indica X indica hybrids in the analyses. The divergence of japonica cultivars K332 and Sarkat, and the indica X indica hybrids of Silewah was substantial from both the indica and japonica stocks, suggesting their use in breeding.