Multiple functional polymorphisms in a single disease resistance gene in rice enhance durable resistance to blast

Abstract

The improvement of resistance to blast, a devastating fungal disease of rice, would support the sustainable production of one of the world's staple foods, yet the identification of genes for durable resistance in rice is a challenge owing to their complicated genetic control. Here we show that map-based cloning of Pi35 identifies multiple functional polymorphisms that allow effective control of the disease, and that Pi35 is allelic to Pish, which mediates race-specific resistance to blast and encodes a protein containing a nucleotide-binding site (NBS) and leucine-rich repeats (LRRs). Analysis using Pish-Pi35 chimeric genes demonstrated that multiple functional polymorphisms cumulatively enhance resistance, and that an amino acid residue in a LRR of Pi35 is strongly associated with the gene's mediation of quantitative but consistent resistance to pathogen isolates in Japan, in contrast to Pish, which mediates resistance to only a single isolate. Our results reinforce the substantial importance of mining allelic variation for crop breeding.