COMBINING ABILITY OF TESTERS WITH INBRED LINES OF MAIZE DERIVED THROUGH CONVERGENT BREEDING

Abstract

The development of maize hibrids involves identifying combinations that express high combining ability for grain yield and agronomic characteristics. Combining ability is an important attribute that allows plant breeders to increase productivity by selecting progenitors that express the best combinations. A scheme for convergent breeding of maize lines was initiated in 2015, which focused on incorporating desirable genes through backcrossing from donor to recurrent parents. The lines used in this trial had more than 96.9 % inbreeding, resulting from three backcrosses and two selfings. With this background, the objectives of the present study were 1) to evaluate testcrosses for grain yield and other agronomic traits in a set of maize lines obtained by convergent breeding, 2) to identify the best combinations in grain yield and agronomic characteristics, and 3) to select the best tester. Thirteen maize lines obtained by convergent improvement and two original elite lines, which were crossed with two testers (inbred lines) were evaluated using a randomized complete block experimental design, in two localities of the state of Guerrero, Mexico, established in the Spring-Summer 2021 and Fall-Winter 2022/2023 agricultural seasons. Significant differences were detected for all traits recorded between the sources of variation localities, testers, recovered lines and their interaction with testers, finding that the recovered lines exhibited wide genetic variation with the testers. It was determined that crosses L1×P1, L1×P2, L2×P1, L2×P2, L12×P1, L12×P2, L13×P1 and L13×P2 expressed excellent grain yields, as well as good expression in yield components. It was observed that grain yield had a close relationship with agronomic traits of plant and ear: ear length, kernel length, width and thickness. The two testers exhibited a different combining ability to discriminate between the test lines, with P2 (LT156) tester producing the highest genetic variability and crosses with higher grain yield.