Abstract

Transgenic cowpeas are those genetically engineered with Cry1Ab gene for protection against the lepidopteran pest Maruca vitrata that could inflict upto 80% yield loss in severe infestation. Two transgenic events TCL-709 and TCL-711 were crossed to three non-transgenic lines IT97K-499-35, IT93K-693-2 and IT86D-1010 to generate six set of F₁ hybrids. The study was designed and conducted to evaluate the performance of transgenic cowpeas and hybrids derived from them under natural field conditions. The transgenics, non-transgenics and the hybrids were planted with intra and inter-row spacing of 30 and 75 cm respectively in a completely Randomized Block Design during the 2012 cowpea growing season at Confined Field Trial site of Institute for Agricultural Research of Ahmadu Bello University Samaru-Zaria. The plot sizes consisted of 2 rows of 5 m long. The trial was kept weed-free by constant manual weeding. The various generations of  IT97K-499-35 x TCL-709 were infested six times with first instar Maruca larvae at four day interval at flower initiation stage while the remaining crosses were exposed to natural infestation of Maruca. The data were recoreded on various characters and the results revealed that the cowpea lines containing the cry1Ab gene produced enough toxin to kill and inhibit the feeding of Maruca on cowpea plants. The result on infestation of Maruca larvae scored as number of damaged pods per plant gave a clear proof of the achievement of the goal of the genetic transformation of cowpea lines with Cry1Ab gene. As the Cry1Ab gene conferred a high degree of resistance to cowpea pod borer, the transgenic cowpea lines should be used as a precious insect-resistant line to be employed in traditional breeding programs to develop Maruca resistant cowpea varieties.

Key words: Bacillus thuriengiensis, confined field trial, Cry1Ab gene, transgenic cowpea, Maruca vitrata.