Genetic diversity of morphological responses and the relationships among Asia aromatic rice (Oryza sativa L.) cultivars

Abstract

An investigation was conducted to determine the extent of diversity and relationships among 36 aromatic rice cultivars collected from Asia. Characterization for 22 morphological characters with 101 morphometric descriptors was carried out. High and comparative levels of phenotypic variation using phenotypic frequency distribution and Shannon-Weaver diversity index were found between countries of origin. Most traits were polymorphic except to ligule color. Grain size, grain shape, culm strength, plant height and secondar y branching contributed the highest mean diversity indices (H , = 0.91, 0.88, 0.87, 0.82 and 0.83, respectively). For trait groups, highest diversity was found in grain and culm traits (H , = 1.00 and 0.96, respectively). Populations from Vietnam were more diverse than others (H , = 0.92) whereas populations from India and Thailand displayed lower diversity indices (H , = 0.46 and 0.49, respectively). No clear association was detected between phenotypic diversity and countries of origin. Five clusters of 36 genotypes based on Euclidean distance were observed with 1 to 22 cultivars per group. The results of the character distribution and phenotypic diversity analysis permitted some broad generalization about collection and conser vation of aromatic rice cultivars. This also indicated the presence of important genes for future aromatic rice breeding purposes. Despite the limitation in estimating total genetic variation, the present study indicated that morphological traits were useful for preliminary evaluation and can be used as a general approach for assessing genetic diversity among morphologically distinguishable aromatic rice cultivars.