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Heterosis, Combining Ability, and Yield Prediction in Hybrids from Local Maize Inbred Line
Dissertation Abstract:
Studies were conducted to identify and select superior maize inbred lines based on their performace, and to evaluate their performance and combining ability in all possible crosses.
Performance and heterosis of the single crosses were evaluated at two locations in Universiti Pertanian Malaysia, Serdang. Some promising double-cross hybrids developed from the potential single crosses were also evaluated for performance and for comparison with the predicted outcome.
In general, most of the inbred lines exhibited poor performance due to inbreeding effects after successive generations of selfing, but some had high potential for use in hybrid production. Hy-58, Hy-59, and Hy-60 were identified as the best performing F1 single-cross hybrids in both locations, with grain yields of 3,703.7 kg/ha, 3,940.7, and 3,451.9 kg/ha, respectively, in Field 2; 5,659.3 kg/ha, 5,725.9 kg/ha, and 5,948.1 kg/ha, respectively, in Share Farm; and 4,681.5 kg/ha, 4,833.3 kg/ha, and 4,700.0 kg/ha, respectively, in the combined locations. In general, hybrids that produced high yields were those formed between high yielding inbred parents and from genetically diverse population sources.
High heterosis was shown by grain yield, ear weight, and grain weight per ear, while moderate heterosis by number of kernels per row, ear height, plant height, and ear length. Low heterosis was shown by ear diameter, number of kernel rows per ear, 100-grain weight, and shelling percentage. Maturity characters showed negative heteros is, indicating earliness ofthe hybrids.
Results of combining ability analyses showed significant general combining ability (GCA) and specific combining ability (SCA) effects of all characters studied, except for shelling percentage. This indicated the importance of both additive and non-additive gene actions in the control of these characters. However, the SCA variances for most characters were much higher than their respective GCA variances in both locations.
The varied estimates of broad-sense heritability between the two locations for all characters were due to the presence of genotype x location interactions. Estimates of broad-sense heritability were high for 100-grain weight, plant height, days to tasseling, and days to silking in Field 2; for grain yield, ear weight, ear length, number of kernels per row, 100-grain weight, days to tasseling, and days to maturity in Share Farm; and for 100-grain weight, days to tasseling, days to silking, and days to maturity in the combined analysis.
Narrow-sense heritability estimates obtained from the variance components were generally in agreement with those from the parent offspring regression. However, those obtained from the regression were slightly higher. The variance-covariance (Wr-Vr) analysis indicated that the gene actions involved in the control of ear diameter and days to tasseIing were generally over dominance, whiIe that for number of kernel rows per ear was between partial dominance and complete dominance, and that for plant height was between complete dominance and over dominance.
Grain yield for the single-cross hybrids was highly significantly correlated with most of the other characters studied. With some exceptions, correlations among the yield components were generally positive and significant. Maturity characters were negatively correlated with most other characters. The best performing double-cross hybrids, DC-26 and DC-34, were found to have high yield potentials. From the correlation analysis, the actual and the predicted performances of the double-cross hybrids were found to have a generally good agreement in both locations, and location combined.