Abstract
We investigated the diversification and diversity in waxy rice cultivars (Oryza sativa L.) in Laos, using three complementary DNA marker systems. We documented three variable DNA markers, including a SSR locus RM190 (number of CT-motif repeat), G-T substitution, and 23 bp duplication. These were analyzed in 389 strains that were collected from northern and central Laos. Variation in cpDNA, presence of absence of a 69 bp deletion at the ORF100, was used for a background classification of all strains as indica or japonica. The three nuclear polymorphisms was all variation within waxy locus. In the RM190 region, nine alleles with different numbers of CT repeats (n=10, 11, 12, 16, 17, 18, 19, 20 and 22) were detected in non-waxy (Wx) alleles, while seven of them (n=12, 16, 17, 18, 19, 20 and 22) were found in waxy (wx) alleles. Compared to previous studies, more allele types were found in northern and central Laos than in neighboring countries. It is considered that the genetic diversity of rice landraces is high in northern and central Laos, and it may be because the high cultural diversity and diverse agricultural systems that persist there. The distribution of landraces with each CT allele type showed neither ethnic bias nor geographical bias. This suggests that there has been frequent exchange of landraces beyond political-borders and between ethnic groups in northern Laos.
