Yongmo Wang1, Chen Huang1, Bing Hu1, Yue Liu1, Gimme H Walter2, James P Hereward2. 1. Hubei Insect Resources Utilization and Sustainable Pest Management Key Laboratory, College of Plant Science & Technology, Huazhong Agricultural University, Wuhan, People's Republic of China. 2. School of Biological Sciences, The University of Queensland, Brisbane, Australia.
Abstract
BACKGROUND: The rice stem borer, Chilo suppressalis, is a serious pest of rice, but also damages an aquatic vegetable, water oats (Zizania latifolia Turcz.). The time at which mating occurs is different between populations of rice stem borer associated with rice and those associated with water-oats, which suggests that undetected cryptic species may be associated with these plant hosts. If true, this would have significant management implications. This study is the first empirical test of this idea, using population genetic tools from two sampling cohorts. We genotyped 320 rice stem borer individuals from 2014, collected from rice and water-oats across five locations (where they exist in sympatry), using seven microsatellite loci. RESULTS: We found no genetic structuring associated with host plant species. On water oats, some rice stem borers were found that had a similar mating time to the rice population, so in 2016, a second cohort of samples was screened by their timing of mating to get 'pure rice feeders' and 'pure water oats feeders'. These samples were genotyped with microsatellites, mitochondrial DNA (mtDNA) (COI and COII), and a nuclear gene (EF1-α). Our mtDNA data suggest a relatively low amount of population subdivision associated with plant host, but the microsatellite data revealed no such genetic structure, and we were only able to identify one haplotype of EF1-α. CONCLUSIONS: Our results indicate gene flow between rice and water oats populations of rice stem borer, indicating that water oats will likely provide a refuge for resistance management of Bt rice.
BACKGROUND: The rice stem borer, Chilo suppressalis, is a serious pest of rice, but also damages an aquatic vegetable, wateroats (Zizania latifolia Turcz.). The time at which mating occurs is different between populations of rice stem borer associated with rice and those associated with water-oats, which suggests that undetected cryptic species may be associated with these plant hosts. If true, this would have significant management implications. This study is the first empirical test of this idea, using population genetic tools from two sampling cohorts. We genotyped 320 rice stem borer individuals from 2014, collected from rice and water-oats across five locations (where they exist in sympatry), using seven microsatellite loci. RESULTS: We found no genetic structuring associated with host plant species. On wateroats, some rice stem borers were found that had a similar mating time to the rice population, so in 2016, a second cohort of samples was screened by their timing of mating to get 'pure rice feeders' and 'pure wateroats feeders'. These samples were genotyped with microsatellites, mitochondrial DNA (mtDNA) (COI and COII), and a nuclear gene (EF1-α). Our mtDNA data suggest a relatively low amount of population subdivision associated with plant host, but the microsatellite data revealed no such genetic structure, and we were only able to identify one haplotype of EF1-α. CONCLUSIONS: Our results indicate gene flow between rice and wateroats populations of rice stem borer, indicating that wateroats will likely provide a refuge for resistance management of Bt rice.