PHD theses : Science
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Item ESTIMATION OF GENETIC VARIABILITY AND HETEROSIS FOR YIELD AND RELATED TRAITS IN SEED AND RATOON CROPS OF FORAGE SORGHUM(Alneelain University, 2012) Alaaeldin Ibrahim TageldinABSTRACT Twenty five forage sorghum genotypes, comprising eleven F1 hybrids together with their twelve parents and two standard cultivars, were included in this study. These genotypes were grown at the University of Khartoum Farm, Shambat, during the seasons of 2007/08 and 2008/09 using a triple lattice design with three replications. All the genotypes in this study were evaluated in the seed and ratoon crop for growth, forage yield and their components. Estimates of variability, such as genetic coefficient of variation, heritability and genetic advance, the phenotypic and genotypic correlation coefficients as well as the expression of heterosis for the different characters studied in the seed and ratoon crops have been investigated. The genotypes showed high genetic variability for many characters in the seed crop, while most of the characters in ratoon crop were highly affected by the environment. However, the highest values of genotypic variance, genetic coefficient of variation and expected genetic advance in the seed and ratoon crops in both years were recorded for green forage yield, dry matter yield and number of tillers per plant together with leaf area per plant and leaf area index in the seed crop. High heritability estimates coupled with high genetic advance were recorded, also, for these traits. ' . The correlation studies at both stages of crop growth revealed that the characters with high heritability values and strongly associated with green forage and dry matter yield. This could be used as effective criteria for forage yield improvement. These characters were leaf area per plant and leaf area index at both stages of crop growth, plant height and stem diameter in the seed crop as well as number of tillers per plant in ratoon crop. Highly significant positive better-parent heterosis was expressed in the seed crop by most of F1 hybrids in both years for green forage yield, dry matter yield, plant height, stem diameter, leaf area per plant and leaf area index. Similarly in ratoon crop this was recorded for green forage yield, dry matter yield and tiller number. The increase in forage yield of F1 hybrids in the seed crop was due mainly to increases in plant height, stem diameter and leaf area, while in ratoon crop it might be related to increases in tiller number. In this study, exploitation ofheterosis at both stages of crop growth indicated four high yielding, multicut hybrids. These were, 366 x SSRZ, 366xSSR4, 366 X SSR6 and 366 x SSR7.