Abstract
Rice blast is one of the most widespread and destructive diseases of rice. The panicle blast occurring after heading stage causes decreased yield and reduced quality of brown rice. Pb1 is a panicle-blast resistance gene, which was identified as a major quantitative gene. The blast resistance by Pb1 is effective during adult stages, and has not experienced breakdown for more than 20 years. We isolated Pb1 by map-based cloning to investigate the mechanisms underlying its characteristic traits of resistance. In 26kb of Pb1 region, five open reading frames were predicted but gene expression was detected for only P15 and P18. Complementation experiments showed that only P15 conferred blast resistance to rice. Pb1 encoded a protein of CC–NBS–LRR-family R protein of 1,296 amino acids. Expression analysis showed that the strength of blast resistance roughly paralleled with the expression levels of Pb1 at respective growth stages.
