MOLECULAR PROFILING OF BLAST RESISTANCE GENES IN LOCAL MALAYSIAN RICE (Oryza sativa L.)

Paddy fields in Malaysia have been affected by rice blast disease since the early years of rice cultivation, and it continue to suffer from its devastating effects due to the rapid evolution of the causal pathogen Magnaporthe oryzae. Although Malaysia is home to various local indica rice, the potential for resistance among these resources remains limited. This study aims to investigate the distribution of blast resistance genes in Malaysian rice cultivars and to categorize them into clusters based on genetic similarities. We extracted DNA from 75 rice accessions and performed molecular genotyping for four blast resistance genes (denoted as Pi) using allele-specific functional markers: the major genes Pi33 (RM72) and Pi27(t) (RM259), as well as the minor genes pi21 (RM1359) and Pi26 (RM413). The results of this profiling analysis were used to construct a hierarchical dendrogram for cluster analysis. The findings revealed that Pi33 had the highest distribution frequency at 60.00%, followed by Pi27(t) at 49.33%, Pi26 at 34.67%, and pi21 at 21.33%. All rice accessions were grouped into eight clusters, with four accessions, viz., Malinja, Bahagia, Serendah, and Bario, classified together in Cluster 8 for harboring 100% of the Pi genes. Meanwhile, Cluster 1 included 17 candidates with the highest similarity to the widely used resistant variety IR64. In conclusion, this study provides a framework for marker-assisted breeding to develop blast-resistant rice cultivars with multigenic resistance, contributing to sustainable rice production in Malaysia.