Effects of entomopathogenic nematodes Steinernema carpocapsae and Heterorhabditis bacteriophora on the fitness of a Vip3A resistant subpopulation of Heliothis virescens (Noctuidae: Lepidoptera)

ABSTRACT The widespread use of transgenic plants imposes selection pressure on insect pest populations to develop insecticide resistance. Evaluation of effectiveness of resistance management strategies is very important in resistance management programs. Resistance management to insecticides is widely believed to depend in part on associated fitness costs. Fitness costs can delay the development of resistance. In the present study, the effects of two entomopathogenic nematode species, Steinernema carpocapsae and Heterorhabditis bacteriophora were studied on the fitness of first insect population of Heliothis virescens selected with Vip3A in the laboratory. It was found that both nematodes species increased the fitness cost of Vip3A selected insects. The mortality of the Unsel subpopulation after exposure to either nematode species was significantly lower than that of the Vip3A-Sel subpopulation. Likewise, the reproduction of both nematode species was significantly greater in cadavers of the Unsel compared with the Vip3A-Sel subpopulation of H. virescens. There was positive correlation between nematode reproduction and the larval instar infected with nematodes. The penetration of infective nematode juveniles (IJ) was greater in the Vip3A-Sel subpopulation than in the Unsel subpopulation of H. virescens. It is concluded that entomopathogenic nematodes could increase the fitness costs and subsequently delay the resistance.

摘要：转基因植物的广泛应用对害虫种群施加了选择压力，促使其演化出杀虫剂抗药性。在抗药性治理项目中，抗性治理策略的有效性评估极为关键。学界普遍认为，杀虫剂抗性治理在一定程度上依赖于相关适合度代价，而适合度代价可延缓抗药性的演化。本研究以实验室中经Vip3A筛选的烟芽夜蛾（Heliothis virescens）初代种群为对象，探究了两种昆虫病原线虫——斯氏线虫（Steinernema carpocapsae）与异小杆线虫（Heterorhabditis bacteriophora）对其适合度的影响。研究结果表明，两种线虫均可提升经Vip3A筛选种群的适合度代价。经任意一种线虫侵染后，未选择亚群的死亡率均显著低于Vip3A选择亚群。同样，相较于Vip3A选择亚群的烟芽夜蛾虫尸，未选择亚群虫尸内两种线虫的繁殖量均显著更高。线虫繁殖量与被侵染幼虫的龄期呈正相关。侵染期线虫幼虫（IJ）在Vip3A选择亚群中的侵入能力强于未选择亚群。综上，昆虫病原线虫可提升害虫的适合度代价，进而延缓抗药性的演化。