الفهرس 
MATERIALS AND METHODSOnly 14 pages are availabe for public view
 |  | from | 149 |  |  |
| | | from | 149 | | |
Abstract
Essam Ahmed Mohamed Amer: Selection of Some Clones in Certain Sugarcane Populations. Unpublished Ph.D. Thesis, Department of Agronomy, Faculty of Agriculture, Ain Shams University, 2011. br Twenty nine sugarcane clones and the check cultivar G.T.54-9 were evaluated at two locations, i.e. Mallawi Agric. Res. Stn., El-Menya Governorate and El-Mataana Agric. Res. Stn., Quena Governorate during two successive growing seasons of 2008/09 and 2009/10 to assess genetic parameters for sugar yield and its components in plant and first ratoon crops. Analysis of variance revealed highly significant differences between sugarcane clones for all the studied traits. br Genotypic variance was higher than environmental one for stalk weight, cane yield/plot and sugar yield/plot in plant cane crop. Meantime, in first ratoon crop genotypic variance was higher than environmental one for millable stalks number, stalk height, stalk weight, cane yield/plot, sucrose percentage, sugar recovery and sugar yield/plot. br Sugar yield/plot, cane yield/plot and stalk height had high phenotypic and genotypic coefficients of variation in plant cane crop, while sugar yield/plot, cane yield /plot and stalk diameter had high phenotypic and genotypic coefficients of variation in first ratoon crop. Moreover, high heritability estimates were obtained for all studied traits except stalk weight which had moderate value in plant crop, while the heritability percentage was high for stalk weight followed by sugar yield/plot and cane yield/plot. Maximum genetic gain as percent of mean was observed for sugar yield/plot, cane yield/plot, stalk weight and stalk height in both crop stages. The phenotypic correlations between all pairs of the studied characters were calculated at the phenotypic level. There were significant correlations between cane yield and all studied traits except Brix reading which was insignificantly correlated in plant cane crop, the correlation between sugar yield and all studied traits was significantly high except the Brix reading. br In the first ratoon crop, the correlation coefficient between cane yield and each of number of millable stalks, stalk height, number of internodes/stalk, stalk diameter, stalk weight, Brix reading and sugar yield was highly significant, the correlation between sugar yield and all studied traits was highly significant except the purity percentage which was insignificant. br The results of path coefficient analysis indicate that number of millable stalks had the most important variable contributing to sugar yield variation, since its direct, indirect and total effects represented the first rank in the degree of importance. It is noteworthy that direct, indirect and total effects for sucrose percentage on sugar yield variation came in the second rank in the degree of importance, and its correlated significantly with sugar yield in both plant cane and first ratoon crops. Therefore, direct or indirect selection for number of stalks/m2 and sucrose percentage would be effective for sugar yield. Concerning repeatability estimates, it can be concluded that the performance of the selected clones under study was nearly the same for most traits during the plant cane cycle along the two growing seasons of 2008 and 2009, -#119;-#104;-#101;-#114;-#101; repeatability percentages were highly significant for all traits and ranged -#102;-#114;-#111;-#109; 76 to 96%. On the other side, the performance of these clones differed -#102;-#114;-#111;-#109; the plant cane crop to the first ratoon crop either in 2009 season or in the two seasons of 2008 and 2009, -#119;-#104;-#101;-#114;-#101; repeatability percentages for most traits were low and insignificant, indicating that the behavior of the clones widely differed between the two crop cycles (plant cane and its ratoon). Therefore, selection for improving most traits should be done in plant cane crops as well as in the first ratoon crop regardless the growing season. br Key Words: Sugarcane, populations, Phenotypic Coefficient of Variation (PCV), Genotypic Coefficient of Variation (GCV), Heritability, Expected Genetic Advance (GA), Phenotypic Correlation, Path Coefficient Analysis, Repeatability.