| Asian corn borer, Ostrinia furnacalis Guenee, (ACB), is the primary insect pest targeted by transgenic Bt com in China. Bt corn can provide season long protection from this insect, but its success will be short-lived if ACB adapt to Bt corn. The primary strategy for delaying ACB resistance to Bt com is to provide refuges of non Bt corn and other host plants. However, the feasibility of refuge strategy depends on the biology of resistant colony and inheritance of resistance. We investigated the biology of a laboratory-selected CrylAb resistant colony of ACB and inheritance of resistance, which included the survival of resistant colony fed on diet incorporated with CrylAb protein and transgenic Bt corn event MON810, mating attractiveness between resistant and susceptible colonies, cold tolerance among resistant, susceptible and their hybrid progeny F1 colonies, resistant gene dominant level, mater effect, stability, and the cross resistance between CrylAb and Cryl Ac.There were 70% survival of larvae and 60% pupation rate when resistant colony fed on the diet incorporated with 100ng/g CryAb. The larval developmental time of resistant colony was significantly longer (5 days) than susceptible. The average pupal weight of resistant colony was 42.0% less than susceptible. When the resistant colony was exposed to the high dosage of CrylAb protein diet, the survival and the pupation decreased in a few generations and then increased. This indicated that ACB would evolve resistant to CrylAb when it was selected by the CrylAb protein.Bioassays with neonate of resistant and susceptible colonies infested on whorl leaves, fresh husks and silks of Bt corn Event MON810 for 4 generations, showed that the resistant colony could not survive more than 7 days on the whorl leaves and husks of Bt corn, but it could complete the development of larva and average pupation rate was 14.5%. This was the first report that laboratory-selected Bt resistant colony could complete the development of larva on fresh silk of Bt maize. The expression of CrylAb protein in the silk of Event MON810 was 585.46ng/g (fresh weight) according to enzyme-linked immunosorbent assays.Among four type of mating combinations (RR SS/RR, SS SS/RR, SS/RR SS, SS/RR RR), the inter-population mating was 43-62.5% in the combinations of RR SS/RR, SS SS/RR, and SS/RR SS, no significantly was observed between the inter-population and intro-population mating, i.e. the mating between resistant and susceptible moths was random. However, the inter-population mating was only 28.0% in the combinations of SS/RR RR, which was significantly lower than intro-population mating. This indicated that the resistant males were more attracted to the resistant females, i.e. the mating between the inter- and intro-population. In this case, when the population density of resistant males was higher, the mating within resistant population could be higher, and the resistant homozygous of offspring were increase. Both resistant and susceptible moths had the same daily mating activity rhythm. This indicates that if resistant and susceptible moths emerge synchronizing well, the daily mating activity rhythm would not affect the random mating between resistant and susceptible colonies.The suppercooling points were tested for diapaused and non-diapaused larvae of resistant and susceptible colonies and their F1 progeny. There was no significant difference in suppercooling points and freezing points between resistant (-11.5 C) and susceptible (-11.4 C) colonies of non-diapausedlarvae. The suppercooling point of diapause larvae from resistant colony was significant higher than those from susceptible and FI progeny of resistant and susceptible colonies. There were no significant different among susceptible and F1 progeny of resistant and susceptible colonies. Although the suppercooling point was only 1.5 C higher for resistant colony than susceptible, this could not impact the overwintering of resistant larvae.Susceptibility to the CrylAb protein was determined by dose mortality response for resi... |
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