Physiological and biochemical responses of five nerica rice varieties (Oryza sativa L.) to water deficit at vegetative and reproductive stage

Food shortage is a major problem in sub Saharan Africa as population increases. Over 89% of Kenyans are food poor and are malnourished especially in rural areas. NERICA (New Rice for Africa) are high yielding rainfed rice varieties with early maturity and has shown high potential to revolutionize rice farming even in Africa’s stress afflicted ecologies. However, NERICA varieties vary in their response to water deficit. A pot experiment was conducted in 2009 at the Maseno University Botanic garden, to evaluate the responses of five NERICA varieties (NERICA1, NERICA 2, NERICA 3, NERICA 4 and NERICA 5) to water deficit during their vegetative or reproductive stage of their development. The response pattern of physiological and biochemical parameters to water deficit imposed at different growth stages might provide basis for selecting the most tolerant variety to water deficit in order to stabilize yield and solve food crisis. The treatments were; T1-irrigating the pots with a litre of water after every two days (Control), T2-water deficit at vegetative stage in which water was withheld by irrigating the plants using one litre of water after every six days from 30-50 days after planting; T3-water deficit at reproductive stage in which water was withheld by irrigating the plants using one litre of water after every six days from 51-71 days after planting. Water deficit caused a significant reduction in physiological parameters i.e. growth, chlorophyll fluorescence and biochemical parameters i.e. chlorophyll and protein content both at vegetative stage and at reproductive stage. However, Growth parameters i.e. plant height, root length and plant dry weight were affected more by water deficit imposed at the vegetative stage as compared to water deficit imposed at the reproductive stage while chlorophyll fluorescence, chlorophyll content and protein content were affected more by water deficit imposed at reproductive stage as compared to water deficit at reproductive stage. The results indicate that NERICA 2 and 4 were tolerant as compared to NERICA 1, 3 and 5 to water deficit occurring at vegetative stage or reproductive stage because their growth, chlorophyll fluorescence and biochemical parameters were least affected.