Resistance of Rice Genotype CRR-99-95W to the Sorghum Plant Bug, Stenotus rubrovittatus and the Suitable Period for Screening

The resistance of rice genotype CRR-99-95W to the sorghum plant bug Stenotus rubrovittatus was investigated. In CRR-99-95W, the incidence of pecky rice caused by S. rubrovittatus decreased with the progress of ripening, as did that of the genotype, Aichinokaori SBL examined for comparison. At seven and 14 days after heading, the incidence of pecky rice was significantly lower in CRR-99-95W than in Aichinokaori SBL. At seven days after heading, the incidence of sterile grains was significantly lower in CRR-99-95W. These results indicated that in CRR-99-95W the incidence of pecky rice was suppressed in the early-middle stage of ripening and the incidence of sterile grains was suppressed in the early stage of ripening. Therefore, releasing the bugs to rice spikes at 14 days after heading, when pecky rice incidence is significantly high, is considered suitable for screening the resistance to S. rubrovittatus. We further examined the number of hill-cracked rice, which is highly susceptible to S. rubrovittatus. In CRR-99-95W, the number of hill-cracked rice increased under low temperature and low light conditions before heading, as in the genotypes examined for comparison. Since the number of hill-cracked rice in CRR-99-95W was the same as that in the genotypes examined for comparison, it can be inferred that the higher resistance of the former was not due to the presence of hill-cracked rice.