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General Combining Ability Effects and Heterotic Patterns in Early Maize (zea Mays L.) Synthetics

K. M. Kabir
Plant Breeding Division, BARI, Gazipur, Bangladesh

A. Momotaz
Plant Breeding Division, BARI, Gazipur, Bangladesh

H. Z. Cross
Department of Agronomy North Dakota State University Fargo, ND 58105, USA

Abstract/ Executive Summary:

The study was undertaken to determine the General Combining Ability (GCA) effects and heterotic patterns from ear moisture selection of two early maize synthetics for yield and its components. Selection for high (HM) or low (LM) ear moisture did not alter grain yield for their combining abilities in hybrids. Selection for LM significantly increased test weight GCA effects while they were one the average and unchanged for HM selection. Group heterosis indicated highly significant heterotic effects for grain yield, 1000-kernel weight. and root lodging. Phenotypic correlations indicated that grain yield was significantly and positively correlated with plant and ear height and significantly and negatively associated with ear moisture and 1000-kernel weight. Selection for LM increased the test weight GCA effects, which may be promising. This study also suggests that proper emphasis be given to the heterotic patterns of yield and its components for LM selection at harvest by considering genetically diverse parental synthetics in different cross combinations. Better evaluation of the combining abilities of early maize strains selected for yield and its components should be made before any judgments are made.

Keywords: Heterosis, GCA, and Maize

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End Date:

Program Area: Variety and Species

Commodity: Maize

Objectives:

Thus, the present investigation was undertaken to study the general combining ability effects of yield and its components in two early maize synthetics having high and low ear moisture content.

Methodology:

Two early yellow dent maize synthetics. NDSC and NDSAB with good agronomic traits and high yield potential were used in the experiment. Four cycles of divergent mass selection for ear moisture content at approximate physiological maturity produced eight strains (four with high and four with low moisture) within each synthetic giving a total of 16 parental strains. The parental strains were crossed in various combinations to produce strain hybrids that will he referred to as crosses in this paper. Sub-strains of both synthetics were crossed together to produce 64 crosses and 64 reciprocal crosses for a total of 128 strain hyhrids. The total number of genotypes in the experiment including the 16 parental strains was 144. Field trial were conducted in 1986 at Fargo, Casselton, and Larimore. North Dakota. USA. The experiments was arranged at each location as a 12 x 12 lattice design with two replications randomized differently at each location. Single row plots were (6 m long with 76 cm between plots. All plots were over seeded and thinned to 47000 plants per hectare. All ears were hand harvested from each row, weighed, dried for a week at 45"C in a forced air dryer, reweighed, and shelled. Phenotypic correlation coefficients were computed between grain yield with ears per plant, plant and car height. kernel rows. test weight. 1000-kernel weight. and root lodging using means over locations

Source of Information: Bangladesh J. Plant Breed. Genet., 6( I): 35-43. 1993

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Achievement/Findings:

An independent estimate of heterosis was also computed for grain yield and root lodging. Grain yield had an average heterosis of 4.6 per cent compared to the group heterosis estimate of 14.1 per cent. It is difficult to determine if this discrepancy is due to real differences or due to problem of estimation. Negative average heterosis of -31.71 per cent versus the estimate of -30.74 per cent for group heterosis was obtained for root lodging. Both estimates of heterosis for root lodging were more similar than those for grain yield. Grain yield, plant height, and test weight had significant average heterosis indicating that the average performance of these traits were significantly different from the average performance of the parents. Group heterosis had significant difference for grain yield indicating a yield advantage of interstrain hybrids over intrastrain hybrids, Thousand-kernel weight and root lodging also had significant group heterosis. Proper emphasis should thus he given to the heterotic patterns of yield and its components when selection is for low ear moisture content at harvest by considering genetically diverse parental synthetic in different cross combinations.

Knowledge Management: Journal