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INHERITANCE OF Bt TRANSGENE CONTROLLING THE LEGUME POD BORER (Maruca vitrata [Geyer] ) IN COWPEA(Vigna unguiculata L. Walp)
Abstract:
The inheritance of Bt transgene controlling the legume pod borer [Maruca vitrata (Geyer)] in cowpea (Vigna unguiculata L. Walp.) was studied using two transgenic lines namely; 709 and 711. These were crossed to three non-transgenic lines viz; IT97K-499-35, IT93K- 693-2 and IT86D-1010 to produce six hybrids. Field trial was conducted at confined field trial site (CFT), Samaru, involving F1, F2, backcross populations and the five parental materials. The study was undertaken to understand the mode of inheritance, segregation and stability of Cry1Ab gene in different cowpea genetic backgrounds. The results showed 3:1 and 1:1 segregation for F2 and first backcross generations respectively. These demonstrated the existence of Mendelian inheritance of Cry1Ab gene in cowpea genome. Cry1Ab gene was inherited as a single dominant gene and segregates in the Mendelian fashion. Therefore, classical cross and backcross can introgress the Cry1Ab Maruca resistant gene from the transgenics into conventional cowpea varieties. Quantitative analysis for Cry1Ab gene resistance with the use of artificial infestation showed that the inheritance of Cry1Ab gene was governed by a dominant gene action. The performance of the transgenic lines and their hybrids in comparison with the non-transgenic parents regarding some key paramters were conducted. The transgenics and the hybrids did not sustain pod damage due to Maruca feeding while the non-transgenic genotypes sustained various degrees of pod damage as a result of feeding activities by the Maruca. In addition, the impact of genetic transformation of cowpea on the expression of some morphological traits of the transgenic lines were investigated. In the present study, comparison made between the cowpea transgenic line 709 and original parental type (IT86D-1010) showed non-significant differences in all the parameters compared while, comparison made between cowpea transgenic line 711 showed highly significant differences for days to first flowering, days to first pod maturity and plant height. However, the phenotypic data showed no pattern of changes that would support the hypothesis that the introduction of Cry1Ab gene had any unintended impact on the productive performance of cowpea plants, besides conferring resistance to Maruca pest.
INHERITANCE OF Bt TRANSGENE CONTROLLING THE LEGUME POD BORER (Maruca vitrata [Geyer] ) IN COWPEA(Vigna unguiculata L. Walp)
