Life cycle and population genetics of bird cherry-oat aphids Rhopalosiphum padi in China: an important pest on wheat crops

Rhopalosiphun padi is a pest that seriously devastates wheat crops. The life cycle, genetic diversity, and genetic structure of R. padi populations throughout China remain unclear. In the current study, we collected 17 R. padi populations throughout the wheat-growing region of China. Classical standard methods were used to determine the life cycles of 369 clones from the sampled populations. Five polymorphic microsatellite loci were used to genotype individuals from each clone. The results revealed that two populations from spring wheat-growing regions showed cyclical parthenogenesis, whereas 15 populations from winter wheat-growing regions showed obligate parthenogenesis. There was a significant genetic difference between populations with obligate parthenogenesis and populations with cyclical parthenogenesis. Populations with cyclical parthenogenesis did not show significant departures from Hardy-Weinberg equilibrium, whereas all populations with obligate parthenogenesis exhibited significant departures from Hardy-Weinberg equilibrium. Significant genetic structures were found in the populations. Two R. padi populations with cyclical parthenogenesis showed similar genetic structures, two populations from a subtropical plateau had similar genetic structures, and the populations sampled in the large winter wheat-growing regions in northern and central China showed similar genetic structures. There was a significant isolation-by-distance effect present among different populations. To the best of our knowledge, this is the first documentation of the life cycle and population genetic of R. padi in China. Our results are important for the design and optimization of sustainable pest management strategies.