Studies On The Expression And Inheritance Of Bt+CpTI Gene Resistance To Helicoverpa Armigera In Transgenic Bt+CpTI Upland Cotton

Using transgenic Bt cotton line (Zhongxin 94) and commercial variety, Sumian 12 as controls, a series of researches on the expression and inheritance of Bt and CpTI genes resistant to Helicoverpa arm igera in transgenic Bt fCpTI upland cotton lines (named Shuangkang I and Shuangkang 2) were conducted. Laboratory bioassay indicated that the transgenic cotton lines showed good efficacy against Helicoverpa armigera. No 3rd instar bollworm larvae survived 5 days after being fed with the leaves on the 4th to 21st main-stem nodes on plants of double-copy transgenic cotton lines and single-copy Zhongxin 94, whereas more than 40% 3rd bollworm larvae survived in Sumian 12, the CK variety. However, there was a decline of resistance as plants grew since the mortality (%) of H. armigera decreased gradually. The temporal fluctuation of resistance in these transgenic cotton lines was also demonstrated in laboratory bioassay of leaves simultaneously collected from transgenic plants sown at different times from March 1 to September 19, 1999. The resistant tendency of double-copy transgenic cotton lines were consistent with that of the resistance tested with main stem leaves. The resistance of leaves of Shuangkang I at different sites on the plant showed a similar mode of change that resistance was higher at earlier 3 I 1ki~~ developmental stage while declined at later stage, however, their leaves showed resistance to cotton bollworm continuously just contrasting with those of Sumian 12 (CK). The 1st, 2nd and 3rd instar larvae all developed slowly, could not pupate and emerge then died finally while fed with the leaves of Shuangkang 1 during later developmental stage whereas they could normally pupate and emerge while fed with the leaves of Sumian 12. The buds, flowers and boils of Shuangkang I during later developmental stage were not damaged in the experimental field and presented significant resistance to bollworrns. The Shuangkang I during seedling, squaring, flowering and boll setting periods presented the resistance at same level among four generations, which indicated that the resistance of the cotton line is genetically stable. The inheritant pattern of the two double-copy transgenic cotton lines developed by pollen tube mediated transformation was presented in the paper. The F1 hybrids crossed between double-copy transgenic cotton lines and several rIon-transgenic cotton varieties showed significant resistance to bollworm. The segregation of the resistance and susceptible plants in F2 and BC1 populations fit 3:1 and 1:1 ratio, which demonstrated that the resistance of Shuangkang I and Shuangkang 2 to boliworm were controlled by one pair of dominant gene. The double-gene of Shuangkang I and Shuangkang 2 inherits independently with eleven morphological marker genes in 1586 and 1582 and is also non-allelic to the fit genes of Shanxi 94-24 and R19. but the double-gene of Shuangkang I might be inserted in the same chromosomes with Zhongxin-94.