Analysis of variations in several grain and ecological characteristics among cultivated rice [Oryza sativa] varieties in northern Laos

Lao P.D.R. (hereinafter referred to as Laos), the only landlocked country in Southeast Asia, is a multi-ethnic country divided into altitudinal zones inhabited by Tai Group, the rice grower in the lowlands, and non-Tai Groups comprised of farmers engaged in slash-and-burn agriculture. These groups contribute to the formation of a unique composite society from cultural and agricultural aspects, through exchanges of material and culture, with the preservation of the respective production systems. This study aimed at elucidating the characteristics of rice cultivation in Luang Phabang, northern Laos, by analyzing grain and ecological characteristics of cultivated rice varieties. The predominant grain type of the rice varieties grown in the study area was the b-type, according to Matsuo's classification. Differentiation between glutinous and non-glutinous varieties by farmers corresponded to the results of iodine tests, and the glutinous varieties were predominant in the study area- Non-glutinous varieties tended to belong to the c-type. Phenol test showed the coexistence of positive (+) and negative (-) reactions, and the positive reaction (+) predominated in the lowland varieties. On the other hand, in the glutinous upland varieties of the b-type, the phenol reaction was negative, suggesting that the varieties belonged to the tropical japonica group. Based on cluster analysis of several grain and ecological characteristics, cultivated rice varieties in this area may be classified into clusters A and B. All the b-type varieties in cluster A were glutinous, and grouped into 3 sub-clusters. In the study area, while some ethnic groups preferred to cultivate non-glutinous upland rice varieties, most of the inhabitants planted glutinous upland varieties belonging to Cluster A-2. Tai Group also tended to cultivate lowland varieties belonging to Clusters A-1 and B, which may have the genetic background of the indica type. It will be necessary, in future, to investigate the characteristics of the varieties that on grown under both upland and lowland conditions.