Characterization and mapping of a spotted-leaf genotype, spl Y181 that confers blast susceptibility in rice

A spotted-leaf mutant Y181, produced by 60Coγ-radiation treatment of Zixuan1, was identified in rice. The result of TEM demonstrated the number of starch grains decreased significantly, the distribution and volumes of osmiophilic granules and lipid balls were larger in the leaf cells around the lesion mimics, the chloroplasts in mesophyll cells disappeared and just leaving a few rupture thylakoid membranes in the cytoplasm and some transmutative starch granules in Y181. Compared with the wild type, the content of chlorophyll was decreased significantly, while the H2O2 content, and SOD, POD and CAT activity were obviously increased in mutant. DAB staining and H2O2 treatment further revealed oxidative burst in spotted leaves. Expression of lesion-related gene showed RuBisCo-L, RuBisCo-S, PDI and TPX was down-regulated, while PBZ1 was up-regulated in the leaf cell at the lesion mimics. Disease reaction to Magnaporthe grisea indicated that the resistance of Y181 was reduced. Genetic analysis showed that the mutant was controlled by a recessive nuclear gene, which was delimited to a 390 kb region between CH12-936 and RM7195.