Pattern of genetic diversity in indigenous Ahu rice germplasm of Assam

The north-eastern part of India including Assam is one of the key centres of diversity of cultivated rice. Among the diverse varietal types, Ahu group of varieties with their evolutionary significance being intermediate between indica and japonica deserves attention for their detailed evaluation and utilisation in crop improvement programme. This work was attempted to elucidate the pattern of genetic variation and genetic diversity in a set of 147 indigenous Ahu rice genotypes of Assam grown under rainfed upland direct seeded condition. Among the 13 traits under study, the highest genotypic coefficient of variation was exhibited by primary branches per plant followed by secondary branches per plant and grain yield. Heritability in broad sense was the highest for grain L: B ratio followed by grain width and grain length. More than 90% heritability in broad sense was, observed for all the traits except effective tillers per plant, panicle length and grain yield. The highest genetic advance as per cent of mean was observed for primary branches per plant followed by secondary branches per plant and grain yield. Hence, selection for these traits would be most effective for further genetic improvement. At the intermediate linkage distance, four main and nine sub clusters were obtained by Euclidean cluster analysis. Cluster III b was the largest containing 35 entries, which was followed by cluster I c containing 32 entries. The variety Chidon Ahu remained distinct from all other entries and belonged to cluster I b. Based on per se performances of the genotypes and their inter se distance, promising genotypes were suggested for hybridization in order to obtain desirable segregants for further genetic improvement of Ahu rices.