Determination of tester lines with higher combining ability in hybrid corn breeding program

The general and specific combination abilities and hybrid vigor of corn lines developed from the May Tohum corn breeding program involving hybridizations conducted between 16 self-pollinated pure lines and 5 pure tester lines in Adana province during 2020 were analyzed using the multi-series (Line x Tester) analysis method. The 40 hybrid combinations obtained from these hybridizations were divided into two different test groups based on the heterotic group of tester lines and grown in the 2021 production year along with 3 control varieties in a randomized block design with 2 replications. The hybrid combinations were analyzed for traits such as plant height, ear height, ear length, ear diameter, number of rows around the ear, cob diameter, 1000-kernel weight, hectoliter weight, moisture content, and grain yield. The variances and effects of the general combining ability and specific combining ability of the parents were calculated. In order to determine the genomic similarities of the parental lines used in the study, a genetic diversity analysis was conducted using SNP-based molecular markers, and a phylogenetic tree of these lines was constructed. The results indicate that the MT01 tester line, originating from the Lancaster heterotic group, exhibits the highest general combining ability (GCA). In breeding programs, tester lines has a crucial role in developing the most efficient and suitable pure lines from newly developed populations. A tester line with high general combining ability will allow for the development of lines with superior characteristics from the breeding program thus enabling the development of new varieties that are more efficient and resilient against biotic and abiotic stress conditions at every stage. To meet the demands of farmers for higher-yielding new grain and silage hybrid varieties that have greater tolerance to diseases and pests, and are resistant to lodging, researchers need to develop new tester lines in response to changing environmental and climatic conditions. Tester lines with high specific combining ability enable the development of a limited number of commercial hybrid varieties within the breeding program, while each new tester line with high general combining ability facilitates the development of more commercial hybrids. The development of competitive domestic hybrid varieties contributes significantly to the national economy by creating substantial sales potential in both domestic and international markets. Keywords: Corn, Line x Tester analysis, Yield and Yield Components, Combining Abilities, General Combining Ability, Specific Combining Ability