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Title: Genetic differentiation among Maruca vitrata F. (Lepidoptera: Crambidae) populations on cultivated cowpea and wild host plants: implications for insect resistance management and biological control strategies

item AGUNBIADE, TOLULOPE - University Of Illinois
item Coates, Brad
item DATINON, BENJAMIN - International Institute For Tropical Agriculture
item DJOUAKA, ROUSSEAU - International Institute For Tropical Agriculture
item SUN, WEILIN - University Of Illinois
item TAMO, MANUELE - International Institute For Tropical Agriculture
item PITTENDRIGH, BARRY - University Of Illinois

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2014
Publication Date: 3/19/2014
Citation: Agunbiade, T.A., Coates, B.S., Datinon, B., Djouaka, R., Sun, W., Tamo, M., Pittendrigh, B.R. 2014. Genetic differentiation among Maruca vitrata F. (Lepidoptera: Crambidae) populations on cultivated cowpea and wild host plants: implications for insect resistance management and biological control strategies. PLoS One. 9(3):e92072.

Interpretive Summary: Insect pests of cultivated crops threaten producer viability and contribute to human food shortages worldwide. Insect resistance management strategies that are aimed to prevent or delay the onset of resistance to transgenic crops make assumptions regarding gene flow and application of non-transgenic refuges. In this research, the feasibility of using alternate wild host plants as a natural refuge was investigated in West Africa prior to the release on cowpea varieties that express the Bacillus thuriengsis toxin Cry1Ab. Genetic markers were used to genotype larval legume pod borers (Maruca vitrata) collected from four different host plant species in the West African country of Benin. Pairwise comparisons showed that significant levels of genetic differences were present among larvae collected from the different host plants, but these differences were not consistent among all geographic locations that were tested. These results show that complex and potentially location specific plant-insect interactions may influence variation in insect populations. These results will be useful to all scientists, particularly scientists whom are developing and modeling insect resistance management strategies.

Technical Abstract: Maruca vitrata is a polyphagous insect pest on a wide variety of leguminous plants in the tropics and subtropics. The contribution of host-associated genetic variation on population structure was investigated using analysis mitochondrial cox1 sequence and microsatellite marker data from M. vitrata collected from cultivated cowpea (Vigna unguiculata), and alternative host plants Pueraria phaseoloides, Loncocarpus sericeus, and Tephrosia candida from three different geographic locations. Analyses of both datasets revealed a significant global FST estimate of 0.05 (P = 0.001). The program STRUCTURE estimated 2 genotypic clusters (co-ancestries) on the four host plants across three geographic locations, but little genetic variation was predicted among genotypes from different geographic locations using analysis of molecular variance (AMOVA; among group variation -0.68%) or F-statistics (FST = -0.0068; P = 0.6187). These results was corroborated by mitochondrial haplotype data (Phi ST = 0.0533; P = 0.9149). In contrast, genotypes obtained from different host plants showed low but significant levels of genetic variation (FST = 0.0407; P =0.008) which accounted for 4.08% of the total genetic variation, but did not agree with mitochondrial haplotype analyses (Phi ST = 0.05849; P = 0.2659). Variation among host plant at a location and host plant among locations showed no distinct consistent evidence of M. vitrata population subdivision. These results suggest that host plants do not significantly influenced the genetic structure of, and have implications for biocontrol agent releases as well as insecticide resistance management (IRM) for M. vitrata in West Africa.