REPEAT SEQUENCE PRIMER‐PCR STUDY ON DNA POLYMORPHISM OF GEOGRAPHIC POPULATIONS OF COTTON APHID,APHIS GOSSYPII,IN CHINA*

Abstract The repeat sequence primer‐PCR technique was used to determine DNA polymorphism of the aphid Aphis gossypii (Glover) collected from 8 different localites in China. Three primers were selected and used for similarity index (SI) and cluster analysis based on the data of Nei's genetic distance (D). We found that the populations in the north and northwest of China was linked before they were joined by those in southern China. A proposed explanation emphasizes the populations in the north and northwest of China were located near — 4 °C isotherm or lower in January with less than 200 frost‐free days per year, whereas populations in southern China were located near 0 °C isotherm or higher with more than 300 frost ‐ free days per year. So it may be the over‐winter host plants instead of the geographic distance or gene flow, exert pronounced influence on the geographic population differentiation of A. gossypii. Species on different over‐winter host plants may directly lead to the genetic differentiation of their summer offsprings.