二化螟水稻种群与茭白种群光周期反应的比较

Comparison of photoperiodic response between rice-and water-oat-populations of Chilo suppressalis (Walker)

本文报道了用水稻和茭白分别饲养二化螟水稻种群和茭白种群的光周期反应.光周期反应曲线显示,用水稻饲养茭白种群或用茭白饲养水稻种群,无论是在短光照还是在长光照条件下,绝大多数幼虫被诱导进入滞育,丧失了各自原有的光周期反应特性,表明这两个种群已分化到仅适应其本身寄主的程度.用水稻饲养的茭白种群仅有5%～6%的个体化蛹,且其幼虫期较用茭白饲养的延长了15～18天;而用茭白饲养的水稻种群有30%～40%的个体化蛹,其幼虫期与水稻饲养的仅相差3～8天.茭白种群用水稻饲养时32日龄幼虫体重仅为茭白饲养的53.1%,而水稻种群用水稻饲养时32日龄幼虫体重为茭白饲养的79.5%.这些结果表明,茭白种群不适应取食水稻,而水稻种群对取食茭白则有一定的适应能力.根据这些结果,我们认为:(1)这两个种群已出现种下分化的迹象;(2)茭白种植不会对水稻田二化螟的发生产生大的影响.

Photoperiodic responses of diapause induction in the striped stem borers, Chilo suppressalis, collected from both rice field （rice-population） and water-oat field （water-oat-population） were investigated, with the two populations fed on rice and water-oat, respectively. The photoperiodic response curves showed that most of larvae entered diapause regardless of photoperiod length when the rice-population was fed on water-oat or the water-oat-population was fed on rice. This indicated that the two populations have evolved to adapt to their corresponding hosts. Only 5%-6% water-oat-population pupated when larvae fed on rice and larval duration was 15-18 days longer than that fed on water-oat; whereas 30%-40% rice-population fed on water-oat pupated and the larval duration was only 3-8 days shorter than that fed on rice. When the water-oat-population was fed on rice and water-oat, respectively, the weight of larvae （32 days old） fed on rice was equal to 53.1% of the larvae fed on water-oat; whereas when the rice-population was fed on rice and water-oat, respectively, the weight of larvae fed on rice was equal to 79.5% of the larvae fed on water-oat. These results indicated that water-oat-population had little adaptability to rice, whereas the rice-population had some adaptability to water-oat. This suggests that the intra-species differentiation has appeared between the two populations and planting of water-oat should be no significant influence on the incidence of striped stem borers in rice field.