Browsing by Author "Mrimi,Geremiah A."

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A genetical analysis of yield and yield components in an s-parent diallel cross of spring barley
(Sokoine University of Agriculture, 1979) Mrimi,Geremiah A.
An 8 x 8 dlallel experiment involving parental and F2 progenies was conducted in the field at the Uyole Agricultural Centre, Mbeya, Tanzania In the 1977-78 growing season.The aim vias to obtain information on the magnitude and type of genetic variability for yield and its components, to estimate the magnitude of the various genetic components and to investigate the nature and magnitude of the correlations between yield and its components.Results indicate that additive and non«^dditive variation xvas present for all characters measured.The non-additive portion was greater than the additive portion for all characters except number of ears per plant. Dominance was found for all characters and it was the main source of non-additive variation. Average degree of dominance for the characters measured varied from partial dominance to overdominance•Epistasis was found to be small, and it was detected in the characters plant height, number of grain per ear, grain yield per plant and 1000 grain weight. Overall heterosis was found in the characters number of days to heading, plant height, ear length, grain yield per plant and 1000 grain weight. However,its magnitude and direction was4 specific to the cross.Heterosis for yield was generally associated with heterosis for the yield components, paarticularly number of ears per plantv number of grains per ear, earliness and plant height.Maternal effects were found for grain yield per plant and 1000 grain weight. Estimates of narrow sense heritability showed that aJ.l characters, except plstnt height, had values greater than 40?.'.Number of ears per plant showed the highest value (93»0fJ) while plant height had the lowest (24.3Q.High yield per plant and high 1000 grain weight were associated with dominance, while lateness and high number of grains per ear were associated with recessiveness.Correlation studies showed that the characters number of ears per plant, plant height, ear length, grain yield per plant and 1000 grain vzeight were positively intercorrelated• Number of grains per ear was negatively correlated with number of ears per plant and 1000 grain weight. Number of days to heading showed significant negative correlation with all characters except ear length and number of grains per ear.The implications of the results to barley improvement are discussed.