Genetic differentiation in Oryza meridionalis Ng based on molecular and crossability analyses

Molecular and hybridization studies were carried out to detect variation patterns in O. meridionalis. A total of 119 polymorphic RAPD markers were produced from 12 10-mer operon primers while 67 alleles were detected using 11 SSR primers. Cluster analysis based on RAPD and SSR markers identified distinct clusters for accessions coming from Irian Jaya (Indonesia) and Queensland, the Northern Territory, and Western Australia. Intraspecific hybrids showed pollen stainability and panicle fertility ranging from 0 to almost 97%. Fertile hybrids were obtained from crosses between accessions of the same geographic origin, specifically those involving the Irian Jaya accessions that showed greater than 70% pollen stainability and panicle fertility. In crosses involving accessions with different origins, partially fertile to sterile hybrids were obtained between accessions coming from Irian Jaya and Queensland. In contrast, most crosses between the Northern Territory and Irian Jaya accessions and Northern Territory and Queensland accessions produced sterile hybrids. The study proves that O. meridionalis is a good taxonomic species undergoing gradual speciation corresponding to its geographic distribution in northern Australia and Irian Jaya.