Song Beng Kah has completed his PhD in Universiti Kebangsaan Malaysia and joined Monash University Malaysia as a Lecturer in Genetics. He was an Honorary Research Scientist at the Washington University in St. Louis, USA, researching population genetics and evolution of rice (2011-2013, 2016). In 2014, he was promoted to Senior Lecturer. He has teaching and research responsibilities in genomics and molecular genetics. His research has won a Gold Medal at the University Malaysia Sabah Research Competition, 2013. His current research investigates the development of genome-wide SNPs for assessment of genetic structure and evolutionary history of Malaysian and Southeast Asian weedy rice. He serves a number of societies including the Genetics Society of Malaysia and the Malaysian Society for Biochemistry and Molecular Biology.
Statement of the Problem: Weedy rice is a conspecific form of cultivated rice (Oryza sativa) that infests the rice fields and causes severe production loss worldwide. There has been on-going study of weedy rice in the western hemisphere and East Asia, but less in the Southeast Asian regions.
Methodology & Theoretical Orientation: Using a combined analysis of 24 neutral Simple Sequence Repeat (SSR) loci, four domestication genes (sh4, Bh4, Rc, and An-1 controlling seed shattering, hull color, pericarp color and awn development, respectively), 45,000 genotyping-by-sequencing-derived SNPs and whole genome sequences, we examined the complex evolutionary dynamics and origins of weedy rice in Southeast Asia.
Results & Conclusion: Comparative analysis between these genotypic datasets from weedy rice collected from Southeast Asian (SEA) countries and regions where no reproductively compatible wild Oryza species occur (US and South Korea) revealed independent evolutionary origins for SEA weeds and US-Korean strains. Wild-to-weed gene flow was observed in SEA weed populations, including adaptive introgression of domestication alleles, whereas de-domestication of cultivated rice is the major cause of weedy rice emergence in regions without wild rice. In Malaysia, modern cultivars played a prominent role in the origin and recent proliferation of weedy rice, with wild rice introgression, although less predominant than in other SEA countries, nonetheless contributing to the weed origin. Genome-wide assessment of nucleotide diversity further demonstrated that Thai and Malaysian weedy strains harbored very few of genomic regions that were supposed to undergo selection and overlapped among these weedy rice strains. Our study provides a genome-wide view of origin and adaptive evolution of weedy rice strains which could shed light on further molecular breeding of cultivated rice. It is also be useful for advising farmers appropriately in strategies for controlling the spread of weedy rice.