Abstract: Virulence variation in three host related popula ti ons of brown planthopper (BPH), which differed in virulence and had been reared on rice variety TN1, Mudgo and ASD7 for 82 generations respectively, was studied with honeydew excretion of female adult in 48 h. Honeydew excreted by avirulent BPH population (TN1 population, most individuals are avirulent, called T population), or virulent BPH populations (Mudgo or ASD7 populations, most individuals are virulent, called M or A), on susceptible and resistant varieties were weighed, and the resulsts showed that the susceptibility and resistance of host pl ants interacted with the virulence of BPH. BPH with different virulence should be reared on resistant varieties to observe evident difference, so virulence of BPH under different treatments to resistant varieties was tested to study virulence variance. Mean virulence in F₁ populations was an intermediate value and near to that of virulent parent, and the variance of honeydew distribution in F₁ populations was obviously bigger than that of avirulent parent and near to that of virulent parent. It seemed that virulence was dominant to avirulence. When compared with those in F₁ populations, the mean virulence in F₂ populations performed few changes in the treatment T _♀×M _♂ , and was significantly bigger than that in the treatment A _♀×T _♂. The variance in F₂ populations was obviously smaller or bigger but not significantly than that in F₁ populations. Based on the above results, it is concluded that there were no new genetic segregations in F₂ populations compared with F₁ populations.

Key words: Nilaparvata lugens, virulence, virulence variation, laboratory population

摘要： 以蜜露排泄量为稻褐飞虱致害性指标对稻褐飞虱实验种群的致害性变异进行了研究。首先测定了褐飞虱3个实验种群(TN1种群、Mudgo种群和ASD7种群)[分别用水稻品种TN1、Mudgo和ASD7强迫饲养82代，其中TN1种群(T)为弱致害力种群，Mudgo种群(M)和ASD7种群(A)为强致害力种群]分别在感虫和抗虫品种上的蜜露排泄量。结果表明，寄主表现感虫还是抗虫，与褐飞虱致害力之间存在交互作用。将不同致害力的褐飞虱种群接在抗虫品种上，才可能观察到较大的致害性差异，据此比较了杂交F1代与亲本种群个体、自交F2代与杂交F1代种群个体在抗虫品种上的致害性差异，以分析褐飞虱致害性变异规律。杂交F1代（包括T♀×M♂，A♀×T♂两种处理）雌成虫的平均致害力均介于两个亲本之间，其值与强致害力亲本的更为接近；杂交F1代雌成虫致害力的变异程度均显著地大于弱致害亲本，而与强致害性的亲本相比几乎无明显的差异；表明相对于弱致害性，褐飞虱的强致害性可能为一显性性状。与杂交F1代相比，T♀×M♂处理中自交F2代雌成虫的致害力无显著变化，而A♀×T♂处理中自交F2代雌成虫的致害力显著大于杂交F1代；两种处理中，自交F2代的方差或显著小于杂交F1代，或稍大于杂交F1代，表明自交F2代种群个体未增加新的遗传分离。

关键词: 稻褐飞虱, 致害性, 致害性变异