回交对小菜蛾近交种群适合度衰退的清除效应

Purging effects of backcross on the population fitness depression of the inbred Plutella xylostella line

研究近交种群的清除效应对深入探索昆虫近交衰退的遗传机理具有重要作用。本文在连续近交10代的基础上,采用年龄-龄期、两性生命表方法分析回交对小菜蛾近交衰退的清除效应,结果显示,回交1代即可显著提升近交小菜蛾卵的孵化率、成虫前期存活率与繁殖力,雌、雄成虫寿命也显著延长,回交小菜蛾的种群适合度达到杂交种群的水平。其中,回交小菜蛾的单雌产卵量甚至显著高于杂交种群。回交小菜蛾种群的内禀增长率、周限增长率、净增殖率也显著提高,与杂交种群相比无明显差异。同时,对种群数量的模拟发现,回交与杂交小菜蛾的种群数量变化趋势均较一致,60 d时回交与杂交各代种群数量均达到108以上。该结果为进一步研究揭示小菜蛾近交衰退的遗传机理奠定基础。

Studies on the effects of backcross on inbred populations is helpful for elaborating molecular and genetic mechanisms of inbreeding depression in insects.The present paper deals with the purging effects of backcross on the population fitness of an inbred F10 of Plutella xylostella,based on the agestage-specific life tables.The results showed that the egg hatching rate,survival and fecundity of the inbred F10 of P.xylostella could be immediately increased,and the longevity of female and male adults be prolonged in the backcrossed F1.The population fitness of P.xylostella in the backcrossed line was found to be consistent or even higher as compared to the outbred line.The backcrossed P.xylostella line showed a significantly higher intrinsic rate of increase（r）,net reproduction rate（R0）,and finite increase rate（λ）,and increasing generation time（T）,with no significant difference compared to the outbred line.Additionally,the population size of P.xylostella tended to be no significant differencebetween the backcrossed and outbred lines,with the population size increased from an initial 10 eggs to over 108 individuals after 60 d in both lines.Our work provides a foundation for further studies on molecular and genetic bases of the inbreeding depression for P.xylostella.