| dc.description.abstract | Rice is one of the principal foods to over 60% of the world inhabitants and is mostly produced under semi-aquatic conditions and its production is water intensive. In Kenya, the key abiotic stress affecting rice production is drought stress which is experienced mainly during reproductive phase of the crop. This study evaluated the performance of advanced lines and segregating populations under well-watered and drought stressed environment with the aim of identifying the phenotypic traits that confer drought tolerance in rice.
19 crosses, 6 parents and 5 checks rice (Oryza sativa L.) lines were evaluated for response to drought under two environments: drought stressed and well-watered environment over two seasons in the year 2016/2017 at Kenya Agricultural Livestock Research Organization (KALRO) -Mwea Centre. The experiment was laid down in an alpha lattice design with three replications. Drought stress was imposed at panicle initiation in the drought stressed environment by withholding irrigation whereas in the well-watered environment irrigation was applied throughout from planting to physiological maturity. There were significant variations among genotypes, between seasons and conditions (well-watered and drought stressed), and interaction of season x condition x genotype for agronomic, yield and yield related parameters at p<0.05. A mean of 90.6cm of plant height was recorded by genotypes in the well-watered environment while those under drought stress recorded a mean of 88.8cm in plant height. Traits such as number of tillers (15.8), days to flowering (102.5 days), panicle length (20.00cm), flag leaf length (26.1cm), number of panicles per plant (16.3), biomass(42.3g), percentage spikelet fertility (78.1%), 1000-grain weight (27.6 grams) and grain yield (5.4t/ha) were significantly decreased under drought stress to 9.9,100.2 days, 18.8cm, 21.4cm, 12.4, 23.8 grams, 51.9%, 22.2 g and 1.6 t/ha respectively.
Phenotypic correlation coefficient results show that under drought stress, there was a significant negative correlation between plant height and number of tillers (r= -0.607), days
to flowering (r=-0.678), number of panicles (r=-0.234) and biomass (r= -0.274) but a positive correlation was observed between plant height and panicle length (r= 0.244), flag leaf length (r=0.264) and grain yield (r = 0.220).
Under well-watered conditions, there was a negative correlation between plant height and number of tillers (r=-0.129), days to flowering (r=-0.177) and number of panicles per plant (r=-0.030). Plant height was positively correlated though not significantly with panicle length and grain yield with r= 0.022 and r=0.032 respectively under well-watered environment.
Additive Main Effects and Multiplicative Interaction (AMMI) analysis of variance for grain yield showed that generation of crosses SARO5 x NERICA11, NERICA 2 x SARO5 and NERICA 15 x SARO5 expressed higher grain yield than genotypes NERICA 2, Komboka x Ner15 and NERICA 2 x NERICA 1. AMMI Stability Variance (ASV) showed that genotypes NERICA 15, Dorado Precoce, NERICA 11 x NERICA 2, SARO5 x Komboka and NERICA 2 x NERICA 11 were the most stable.
Genotype and Genotype Environment (GGE) showed that Principal Components (PC1) and PC2 accounted for 96.46% and 3.54% respectively. From the biplots, drought stressed environment and well-watered environment were positively correlated, meaning that these two environments had an impact on grain yield. GGE biplots ranked the19 crosses, 6 parents and 5 checks rice lines as follows: those above average in performance, the stable ones, unstable and those below average in performance. SARO5XNERICA11 is worth for selection due to its high mean value and is stable across the mega-environments.
GGE biplots analysis gives a graphical biplot analysis which makes genotype by environment interaction study easy and is recommended as one of the most appropriate analysis to evaluate genotypes under different target environment (Maqbool et al., 2015).
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The results in this study showed that genotypes from generation of crosses of NERICA 1 x SARO5, SARO5 x NERICA 11, NERICA 15 x SARO5 and Komboka x NERICA 15 had superior traits such as high yields in tonnes per hectare and also exhibited superiority in traits such as panicle length, plant height, flag leaf length and 1000-grainweight under drought stress. | en_US |
