| Asiatic corn borer Ostrinia furnacalis(Guenée)(corn borer for short),is the largest pest on corn in my country.It seriously affects the yield and quality of corn in China,causing huge economic losses(only in outbreak year Jilin Province,the occurrence area of corn borer was as high as 1.667 million hm~2,the loss of corn can reach 1.5 billion kg,worth 1.5 billion yuan).In the past two decades,more than 20countries including North America,Western Europe,South America,and the Philippines have commercially grown Bt(Bacillus thuringiensis)insecticidal toxin transgenic Bt corn(Bt corn for short)on a large area(reached 58.9 million hm~2 as of2018),which is used to prevent and control European corn borer,etc lepidopteran pests.In China,the commercial planting of transgenic Bt insect-resistant corn has not yet been approved.The domestic and foreign research and development mentioned that they have prepared new technologies for the efficient control of Cry1Ab,Cry1Ac,Cry1Ie,Cry1Ah,Cry1F and other Bt corn to corn borer.Practice in more than 20countries including North America has proved that Bt corn stress target pests have genetic differentiation,leading to new resistant populations of pests.In order to delay the development of resistance of corn borer to Bt corn and extend the application time of Bt corn in China in the future,it is necessary to understand the principle of resistance formation of pest populations to transgenic Bt corn.There are few reports on the prevention and delay of pest resistance to Bt corn in China,and on measures to delay pest resistance such as shelters as well.In this study,we mainly study the reproductive characteristics and mating behavior changes of corn borer successively feed by semi-artificial feed under low selection rate(10.57%-52.88%),which provides a preliminary basic theory for delaying the formation of resistance of corn borer to Bt corn.The test results show that:1.Regarding the reproductive resistance of corn borer to Bt corn:after continuous feeding of semi-artificial Bt corn feed,resistance was formed on the 5th to 10th generation corn borer larvae,and the corrected mortality of corn borer larvae gradually decreased(10.57%),the female larval growth cycle(larval stage)is shortened(22.4±2.79d).As the number of eliminated-selected generations increases,the growth development and survival rate of the population increases,a low-level resistant population comes out.2.For the mating behavior resistance of the corn borer to Bt corn:the female corn borer can mate for many times,and life span of the female moth is negatively correlated with the number of mating.For the mating frequency,the corn borer(female moth 4.06 times,male moth 1.72 times)that fed on Bt corn was lower than wild corn borer(female moth 4.25 times,male moth 1.91 times).The eliminated-selected form of transgenic Bt corn will change the fitness of the species,and the development of resistance will reduce the fitness disadvantage,which is manifested in the decrease in the number of matings,but the mating rate increases.3.In terms of using other host fields as natural refuges for corn borer populations:corn borer male moths have two peak periods in different host fields,and the first peak outbreak period of male moths(rice field June 12;Bt corn field 6 June 16;sorghum field on June 25;soybean field on June 25)and the second outbreak of male moth(Bt corn field on August 12;paddy field on August 12;sorghum field on August12;soybean field August 12;weeds September 5).The results showed that there are the overlapped synchronized period for the adult occurrence in different host fields overlapped,and the adult could achieve random mating and mature shelters were provided accordingly. |
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