Growth and development of nerica rained rice (Oryza Satiya)under water deficit conditions

Abstract

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. Water deficit is a major problem 'in rice grown under rainfed conditions in Kenya. It affects plant growth and development and ultimately leads to a considerable yield reduction or crop failure. NERICA (New Rice for Africa) are high yielding rainfed rice varieties with early maturity and have shown high potential to revolutionize rice farming even in Africa's stress afflicted ecology. However, the effect of drought in NERICA rice varies with the variety and its coincidence with different growth stages. It is therefore necessary to establish the effect of water deficit at different stages of crop growth in order to develop crop management strategies to minimise risk in rice production. The objective of this research was to investigate the effects of water deficit on growth and development of NERICA rainfed rice with a view of identifying the most drought tolerant variety that may be grown under rainfed conditions in Kenya. This study was carried out in the University botanic garden, Maseno during 2008-2010. Plants were subjected to water deficit treatments in the green house and in the field. The experiment layout was factorial 2 in a Randomized Complete Block Design (RCBD) with three replicates. The seeds were sown in 20 litres Polyvinyl chloride pots (PYC pots) in the green house and in 2 m x 2 m plots with a spacing of 0.5 m between the plots in the field. The treatment combinations in the greenhouse consisted of three levels of water deficit, viz T1-well watered throughout the lifecycle; T2-water deficit at vegetative stage; T3-water deficit at reproductive stage; and five varieties of NERICA rice. The field experiment was based on rainfall precipitation with supplemental irrigation during long drought durations. The parameters measured included soil moisture content, physiological parameters which included germination rate, transpiration rate, stomatal conductance, net photosynthesis, chloronhvll fluorescence, electron transport rate and leaf relative water content. Biochemical parameters included chlorophyll and protein content. Morphological parameters included plant biomass, plant height and root length. Yield and yield component parameters included tiller number, panicle length, days to heading, harvesting and maturity, field grain ratio and yield. The collected data was subjected to analysis of variance (ANOY A) and means separated using least significance difference (LSD). Correlation analysis was used to examine the nature and strength of the relationship among parameters. The parameters recorded a similar trend in the green house and in the field. Soil water content, physiological, biochemical and yield parameters of the five NERICA rice varieties were affected more by reproductive stage water deficit as compared to vegetative stage water deficit while the morphological parameters were more sensitive to water deficit occurring at vegetative compared to water deficit at reproductive stage. The most sensitive growth stage to water deficit was the reproductive stage with yield reduction from 44% to 58% depending on variety. The overall results indicate that there is genetic variability in the NERICA rice varieties studied and NERICA 2 and 4 were tolerant to water deficit occurring at vegetative or reproductive stage as compared to NERICA 1, 3 and 5 because their physiological, biochemical and yield parameters were less affected by water deficit. NERICA 2 and 4 could play an important role in improving rice production in Kenya and therefore their production in various agroecological areas under rainfed condition should be cncDUl-c.;;?j ~;-~~ thf3)' qr~ W?t~,. rl~f;,:it toleraT't Tl-.prp is MPPrl t(\ rlptf",..,..,i1"~ I"rm<:llmntivp, moisture level for the NERICA varieties that will not affect the yield severely hence denying a farmer chances of breaking even in their production. Two peer reviewed publications have been published from the results of this work and are attached at appendix 2,