The genetic structure of Aphis gossypii populations in Japanese fruit orchards

Abstract

The genetic structure of Aphis gossypii Glover (Hemiptera: Aphididae) populations was characterized using microsatellite analysis of insects sampled from pear and citrus orchards at three locations in the summer seasons of 2001 and 2003. These data will enable more precise forecasting of infestation and will be of value to the development of better control methods. In total, 89 genotypes were found in 500 aphid samples. The diversity indices in aphid populations on pear trees fluctuated but showed a decrease with time in citrus orchards. Japanese aphid populations have greater variation in their microsatellite loci than African, European, or Southeast Asian populations. Approximately half of the genotypes were found in only one colony, whereas the remainder were identified in two or more colonies. Fifteen genotypes appeared in different years, in samples from different areas, or on different host plants. Our data suggest the existence of aphid populations with pear-adapted genotypes and with a permanent parthenogenetic life cycle. Some of the genotypes included genes conferring resistance to pirimicarb and pyrethroid insecticides. Japanese A. gossypii populations may maintain their large genetic variation through differences in their life cycles.