Evaluation and selection of inbred maize lines with high overall combining ability according to grain productivity based on the three-year test-cross analysis results

The purpose of the current study was to identify inbred maize lines with high general combining ability (GCA) according to the trait «grain productivity» and to clarify the role of specific combining ability (SCA) in the formation of superadditive combinations in test-cross analysis. There have been studied fifty-six lines in crosses with three testers (a total of 168 lines×tester) in 2022–2024 using a randomized block design with three replications. There has been performed a pooled ANOVA with such factors as «line», «tester», «year/environment», and correlations, and estimated GCA/SCA effects using the classical «line×tester» approach. There has been established that yield variance is statistically significantly determined by the additive component. The GCA of lines and testers makes the main contribution, while the SCA is present but selective in nature. There have been identified donor lines with consistently positive GCA effects (the top group demonstrates increases of +3.8 to +4.9 t/ha relative to the average additive expectation), suitable for a wide combination. There has been found that the use of a «diagnostic» tester with a negative GCA allows displaying large positive SCA in several pairs, and the maximum SCA effects in the best combinations have reached ≈+7.35 t/ha, indicating strong complementarity of the parental alleles. There have been given characteristics to the following regularities: (i) primary selection by GCA ensures a reproducible productivity increase in different environments, (ii) subsequent optimization by SCA is necessary to identify peak hybrids and exclude incompatible pairs.

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