Isolation and characterization of rice lesion-mimic mutants with enhanced resistance to rice blast and bacterial blight

Abstract

We isolated five lesion-mimic mutants that showed reduced symptoms after infection with the rice blast fungus Magnaporthe grisea from 13 000 M 2 lines of rice ( Oryza sativa L.). Genetic analysis showed that one mutant was allelic to spl5 and this was named spl5-2; the other four were derived from new loci and named Spl12, spl13, spl14, and Spl15. Spl12 and Spl15 were dominant mutations, while the others were recessive. Lesions were visible in the dominant mutants ( Spl12 and Spl15) from an early developmental stage, while lesions were visible in the recessive mutations ( spl5-2, spl13, and spl14) from 8–10 weeks after sowing. We analyzed the resistance to rice blast and bacterial blight using spl mutants derived from 14 loci. Resistance to two virulent strains of M. grisea was induced in spl4, spl5-1, spl5-2, spl7, spl10, Spl12, spl13, spl14, and Spl15 plants. Moreover, growth of the bacterial blight pathogen Xanthomonas campestris pv. oryzae was also suppressed in these nine mutants. These results demonstrate that many of the SPL genes enhance general disease resistance.