Abstract

Cowpeas (Vigna unguiculata) are important grain legumes grown by resource poor farmers across Sub-Saharan Africa. In Kenya, cowpeas continue to produce low yields due to erratic rainfall caused by the current climate change. This study sought to enhance drought tolerance in Kenyan cowpeas through transformation by Agrobacterium tumefaciens using L-Pyrroline-5-carboxylate synthase (P5CS) gene. Cowpea variety K80 was inoculated with Agrobacterium tumefaciens strains EHA105 and LBA4404 harbouring recombinant plasmids pCAMBIA1301:VuP5CS or pCIP100:VuP5CS through vacuum infiltration of pre-germinated seeds at 60 kpa for 25 min. The presence of the transgene in the transformed cowpea plants and its transfer to progeny was confirmed by PCR analysis of T0 and T1 plants. The highest transformation efficiency of 20.5% was achieved with strain EHA105 harbouring plasmid pCAMBIA1301:VuP5CS. A segregation analysis of the transgenes gave a 1:4 ratio for the VuP5CS transformed: non-transformed plants and did not follow the 3:1 Mendelian inheritance pattern for dominant genes. There was no difference in proline content in the transformed and non-transformed T1 plants. However, the roots of the transformed plants were significantly longer than those of the non-transformed plants. The numbers of harvested seeds were also significantly higher in the transformed plants with 10 to 11 seeds per pod in comparison to the non-transformed plants with an average of 5.58 seeds per pod, indicating drought tolerance potential of the transformed plants. The T2 and T3 plants need to be screened further to evaluate the stable integration of the transgene and physiological characterization under water stress.   

Key words: Vigna unguiculata, in planta transformation, Agrobacterium tumefaciens, VuP5CS (Vigna unguiculata pyrroline-5-carboxylate synthase).