The effectiveness of a hybrid breeding program depends on the heterotic patterns that can be used to utilize grain-yield heterosis. This study was carried out to (a) categorize inbred lines into heterotic groups using three different methods and (b) determine the most effective heterotic grouping method for categorizing set of inbred lines. A total of 96 hybrids generated from thirty-two set of inbred lines crossed to three elite testers (87036, 1368 and 9071) using the line × tester design were evaluated together with three checks under low N (30 kg ha-1) and high N (90 kg ha-1 N) environments at three locations in Ghana. Classification of inbred lines were based on three different methods: Heterotic group's specific and general combining ability (HSGCA), specific combining ability (SCA), and general combining ability effects of multiple traits (HGCAMT). The SCA approach, which had the highest breeding efficiency across all test environments, was ultimately determined to be the most effective way for classification. The inbred in each heterotic group may be recombined to form populations which could be improved through recurrent selection. The various heterotic groups can be useful in designing hybridization strategies to create maize hybrids that are both high-yielding and tolerant to low levels of nitrogen in stressful environments.
Key words: Inbreds, nitrogen, heterotic, grouping, efficiencies, hybrids, maize.
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