Abstract
Rice stink bugs are one of the most important rice pests, which cause pecky rice. Effective bioassay methods have been developed to assess the resistance of newly bred rice to these pests. The most suitable time for release and the release period of rice stink bugs were examined. Adults of the rice bug Leptocorisa chinensis were released on four rice cultivars. By releasing the rice bug at 15 and 20 d after heading, differences in the resistance between cultivars became quantitatively evident. At 20 d after heading, we released the rice bugs on each cultivar for various periods. As the release period was lengthened, the rate of the incidence of pecky rice increased and differences in the resistance among the cultivars became evident 4 d after the release. On the other hand, a simple bioassay using cut panicles was performed. The panicles cut at the third internode below the node of the second leaf from the flag leaf at 20 d after heading were grown with the cut end in water. Exposed to L. chinensis for 7 d, and pecky rice incidence was investigated. Differences in the resistance to the rice sting bugs between the two methods were evident. Thus, the simple cut panicle bioassay method was effective for the selection of resistant cultivars and reduced the labor for breeding.
