Rice (Oryza sativa L.) is the main food for people in Laos, where it has been grown and eaten since prehistory. Diverse landraces are grown in Laos. ‘Khao Kai Noi’, a landrace favored for its eating quality, is held in the nationwide collection of traditional landraces in the Lao national genebank. Genetic diversity is crucial for sustainable use of genetic resources and conservation. To investigate the genetic diversity of ‘Khao Kai Noi’ for conservation, we genotyped 70 accessions by using 23 polymorphic simple sequence repeat markers. The markers generated 2 to 17 alleles (132 in total), with an average of 5.7 per locus. The total expected heterozygosity over all ‘Khao Kai Noi’ accessions was 0.271. Genetic variation was largest among accessions and smallest within accessions. Khao Kai Noi accessions were classified into three different genetic backgrounds, but there was unclear association between the three inferred population and name subgroups and geographical distribution. Most of the accessions were clustered with temperate japonica and showed genetic relatedness to rice from neighboring provinces of Vietnam, suggesting a Vietnamese origin. The results of this study will contribute to the conservation, core collection and future breeding of the Khao Kai Noi population.

Khao Kai Noi rice is considered as an elite quality landrace in Laos, which has led to its germplasm conservation in the Laos National Genebank. As happens with other germplasm collections, a manageable yet representative sub collection has become an essential element for researchers and breeders to simplify many activities, including those related to crop improvement, phenotype-genotype correlation and determination of diversity hotspots. In this study, 109 accessions were used as a test collection for core collection development to determine the feasibility of collection reduction in a closely related rice group. Three core collections were developed by two established methodologies and evaluated by diversity indexes, allele retention, phylogenetic distribution and geographical location. Based on SSR molecular markers and PowerCore, a reduction to 24 accessions was achieved with the conservation of complete genetic diversity. A K-means based on reduction to 24 accessions rendered slightly lesser results while based on 12 accessions resulted in a 17% diversity loss. These core collections may be useful for genebank management, research and breeding activities in the future. Also, they may as well serve to estimate core collection development behavior in other landraces and cultivars, which is fundamental in genetic resources management and utilization.