Differences in host preference, life cycle pattern, and insecticide susceptibility among Aphis gossypii clones and genetic relationships inferred from internal transcribed spacer 2 sequences of rDNA

Abstract

As part of an analysis of the genetic structure of Aphis gossypii Glover, one of the most polyphagous aphids and a pest of global agricultural importance, the ITS2 rDNA region was sequenced and compared among 38 Japanese aphid clones with different life cycles, host preferences, and insecticide susceptibilities. The preference of each clone for cucumber (Cucumis sativus L.), eggplant (Solanum melongena L.), citrus (Citnis unshiu Marcovitch), and pear (Pyrm pyrifolia Nakai) as a host was tested. About two thirds of the clones preferred cucumber or eggplant. No other particular combination of host plants was preferred. Five types of life cycle were found: holocyclic I, holocyclic II, intermediate, androcyclic, and anholocyclic. Each clone showed a different level of susceptibility to each of three insecticides. Apparent correlation between the various attributes was not found. Phylogenetic trees constructed from internal transcribed spacer 2 sequences showed ambiguous relationships between genetic differentiation and host preference. © 2008 Entomological Society of America.