Superiorty index combining yield and different stability parameters of some maize (zea mays l.) hybrids.

Includes references.

Seven new white promising maize hybrids,(five single crosses; i.e., Gm 2019, 2028, 2042, 2043, 2044, and two three-way crosses; i.e., Gm 3014, 3022). These hybrids and four white commercial hybrids (SC's Gz 10, 124 and TWC's Gz 321, 324) were evaluated at five locations in 2003 season. Data were recorded for grain yield (Mg ha-1), number of days to mid-silking (d) and plant height (cm). Data were analyzed for individual location and combined. The results showed the following: 1-The combined analysis of variance showed that the differences among hybrids were significant for the three characters under study. Also, the environments x hybrids interaction were significant, indicating that the ranking of hybrids was not consistent across the five environments. 2-Mean grain yield for the five environments ranged from 5.88 (Nubaria) to 9.59 Mg ha-1 (Gemmiza), while it ranged for hybrids from 4.77 for SC Gm 2042 (at Nubaria) to 11.02 Mg ha-1 for SC Gm 2028 at Gemmiza. For the combined analysis, SC Gm 2043 had the highest mean grain yield, followed by SC Gz 10 (8.66, 8.53 Mg ha-1, respectively). Also, days to mid-silking and plant height were affected by environments and hybrids. 3-The interactions between hybrids and environments were quantitatively expressed, using the model developed by Eberhart and Russell (1964). Out of this regression model, four stability parameters were estimated; i.e, regression coefficient (b), variance from regression (S2 y.x), variance of residual error (S2 y.x - S2 ē) and determination coefficient (r2). A fifth estimate was the C.V for hybrid mean across environments. 4-Rank correlation among the five estimates indicated that both b and S2 y.x were the least correlated among the five stability parameters. Mean yield was independent from the b values and was significantly correlated with S2 y.x and C.V values, but highly significant with r2. 5-In order to identify the most desirable hybrid, it should be high in yield and, at the same time, with a b value of 1.0 and S2 y.x equals to pooled error (S2 ē). Therefore, a superiority index was constructed, using the three parameters; mean grain yield, b (regression coefficient) and S2 y.x. A score was given for each of the three parameters and the total of the three score constitutes the superiority index. 6-The eleven hybrids, under study, were categorized in three groups. The super group, which was high in yield and stable, had a score ranging from 12 to 14 and included SC Gm 2043 and Gz 10. The intermediate group included SC Gz 124 and TWC Gz 321, Gz 324 and Gm 3019, with a score from 4 to 5. The poor group included TWC Gm 3022 and SC Gm 2019, 2028, 2042 and 2044, with a score ranging from 0 to -8. 7-This study indicated that a superiority index could be used in estimating the degree of desirability for the different hybrids.

Summary in Arabic.

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