Resistance factors of pecky rice incidence caused by the rice stink bugs (Leptocorisa chinensis, Nezara viridula) in rice line CRR-99-95W

Pecky rice incidence caused by rice stink bugs greatly decreases the quality of rice grain and has come a big problem not only in Japan but also many other rice producing countries recently. In this study, antixenosis and tolerance were examined as the factors of resistance to rice stink bugs attack of rice line CRR-99-95 W. Two experiments were conducted to determine a possibility of antixenosis involvement as a factor of the resistance in CRR-99-95 W. The results showed no correlation between the number of Leptocorisa chinensis parasites and pecky rice incidence. Furthermore, no significant difference was found between the sucking frequency of Nezara viridula on mature husks of CRR-99-95 W and that on the check genotypes. These results suggest that CRR-99-95 W does not exhibit antixenosis effect against rice stink bugs. Then, to examine the tolerance factor involved in the resistance mechanism, the husks structures were analyzed. The results showed that the packing ratio of cell wall of the sclerenchyma fibers in the palea tended to be higher in CRR-99-95-W compared to the check genotype. In addition, the width of the hook openness of the palea of CRR-99-95 W was narrower than that of the check genotype. Such morphological characteristic of CRR-99-95 W may play an important role in its resistance against stink bug attack.