Submitted to: Journal of Economic Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/8/2007
Publication Date: 5/1/2007
Citation: Daves, C.A., Williams, W.P., Davis, F.M., Baker, G.T., Ma, P.W.K., Monroe, W.A., Mohan, S. 2007. Plant resistance and its effect on the peritrophic membrane of southwestern corn borer (Lepidoptera: Crambidae) larvae. Journal of Economic Entomology. 100:976-983. Interpretive Summary: The southwestern corn borer is a serious pest of corn in the southeastern United States. Larvae attack the corn plants in the whorl and tassel stages of growth. Damage inflicted to plants at various stages of growth can result in substantial yield losses. Inbred lines with leaf-feeding resistance to this and other lepidopteran pests such as the fall armyworm have been released by USDA-ARS scientists. Previous studies with the fall armyworm indicated that larvae feeding on the resistant corn plants exhibited reduced weight and damage to the peritrophic membrane, the lining of the midgut. The objective of this study was to examine the effects of plant resistance on the peritrophic membrane of southwestern corn borer larvae feeding under field and laboratory conditions. Three microscopy techniques were used to examine the peritrophic membrane (transmission, light and electron microscopy). Electron microscopy proved to be the most effective method for evaluating peritrophic membrane damage or disruptions. Extensively damaged areas of the peritrophic membrane were observed in larvae feeding on both resistant and susceptible plants. Plant resistance reduced the amounts of damage to the plants and adversely affected southwestern corn borer larvae in terms of reduced larval weight, slower growth and longer developmental times. Differences in degree of damage to peritrophic membrane were not detected between larvae fed on resistant and susceptible plants. Further investigations may lead to a better understanding of how plant resistance affects the peritrophic membrane of this pest.
Technical Abstract: The southwestern corn borer (Diatraea grandiosella Dyar) is a serious pest of corn (Zea mays L.) in the southern United States. Corn germplasm lines with conventional genetic leaf-feeding resistance to this pest, the fall armyworm (Spodoptera frugiperda), and other lepidopterans have been released to the public by USDA-ARS scientists located in Mississippi. The objectives of this study were to investigate any morphological differences in the structure of the peritrophic membrane of southwestern corn borer larvae feeding on resistant and susceptible corn hybrids and to quantify the damage. Larvae were reared under field and laboratory conditions on three corn hybrids (two resistant and one susceptible). Scanning electron microscopy was used to examine the peritrophic membrane for abnormalities such as holes or tears and to count the holes/tears in the membrane. Differences in the degree of damage to peritrophic membrane of larvae fed on resistant and susceptible plants were not detected. Up to five distinct layers of the membrane were observed in each larva. Variation in the amounts of damage to the peritrophic membrane observed from larvae feeding on all plant material was high. Plant resistance adversely affects growth and development of southwestern corn borer larvae and further investigations are needed to explain the role of plant resistance and its relation to peritrophic membrane in southwestern corn borer larvae.