Abstract:
Numerous rice blast resistance (R) genes have been identified, and a comprehensive
understanding of their underlying mechanisms was deemed essential. Therefore, three major genes (Pb1,
Pi21, and Pita) associated with rice blast (BL) were studied using genome sequences of 32 Sri Lankan
rice varieties. The domain structure of each gene, Pb1, Pi21, and Pita of each variety was
comprehensively analyzed in comparison to the three resistant varieties, Modan, Owarihatamochi, and
Tetep. Results revealed that Alagusamba and Mudaligawee could be possessed relatively a stronger
resistance compared to other varieties, due to the presence of complete pathogen recognition LRR domain
which is necessary for triggering innate immunity. The resistant allele of the Pb1 gene is reported to
contain two deletions with 21 bp and 48 bp giving rise to a low amount of proline amino acids, but such
lengthy deletions could not be found in any of the Sri Lankan varieties. Few Sri Lankan varieties
contained alanine at the 918th amino acid position which is considered as a feature of a resistant allele of
the Pita gene. The results of the characterization of 32 Sri Lankan rice varieties regarding three blast-
resistant genes would be useful for breeding rice for blast resistance
