Morphometric variation within apterous females of Schizaphis graminum biotypes

Abstract

SummaryThe occurrence of greenbug, Schizaphis graminum (Rondani), biotypes is a constant threat to the development and stability of pest‐resistant cereal crop varieties. Of the five biotypes (A, B, C, D, E) reported, only biotype B can be differentiated in life from the others by the physical characteristics of color. The other biotypes are differentiated on the basis of their ability to kill certain hosts or to withstand selected insecticides. The purpose of this research was to differentiate biotypes of apterous viviparous female greenbugs by multivariate techniques.Appendages from individuals of biotypes B, C, and E were measured. Some of the characters including the length of first and fourth flagellar segments, profemur, mesofemur, mesotibia, metafemur and metatibia differentiated the biotypes in multiple comparisons in univariate analyses. Using discriminant functions based on within‐group covariance matrices, all greenbugs were classified into their correct group. The shortest Mahalanobis distance was between biotypes B and C. This suggests that biotype B is more closely related to biotype C than it is to biotype E. The coefficients of variation in the body measurements of biotype E were higher as compared to those of the other biotypes, indicating that a new biotype may evolve from biotype E in the future.