Background: Although the genetic structure of rice germplasm has been characterized worldwide, few studies
investigated germplasm from Thailand, the world’s largest exporter of rice. Thailand and the International Rice
Research Institute (IRRI) have diverse collections of rice germplasm, which could be used to develop breeding lines
with desirable traits. This study aimed to investigate the level of genetic diversity and structures of Thai and
selected IRRI germplasm. Understanding the genetic structure and relationships among these germplasm will be
useful for parent selection used in rice breeding programs.