Land race as a source for improving photosynthetic rate and productivity in cowpea (Vigna unguiculata W.)

Cowpea is an important grain legume of arid and semiarid regions of Asia and Africa. Productivity of cowpea is low and stagnant. Conventional breeding approaches aimed at improvement of yield per se have not been successful so far in breaking the yield barrier. Manipulation of physiological processes such as photosynthesis is expected to yield positive results. A land race ‘Goa local’ with a very high photosynthetic rate was used to improve this trait in selected cultivars, C-152, KM-1 and V-118 with different growth habits. KM-1 x Goa local and C-152 x Goa local Fi hybrids yielded better than the best parent, a land race itself. This improved productivity was mainly associated with the increase in number of pods per plant and seeds per pod as well as test weight. Physiologically, the improved productivity of hybrids could be associated with higher chlorophyll content, photosynthetic rate as well as conductance. Association analysis among biophysical traits and productivity traits indicated significant positive association of photosynthetic rate and chlorophyll content with seed yield per plant. Interestingly, the four biophysical traits showed significant and positive correlation with seeds per pod and hundred seed weight as well as with pod length (except transpiration rate) but, failed to show any association with number of pods per plant. The results indicated the scope of using a land race in improving the productivity in cowpea through manipulation of biophysical traits like chlorophyll content and photosynthesis.