COMBINING ABILITY AND GENETIC POTENTIAL OF TROPICAL MAIZE GERMPLASM

Abstract

The performance of 57 maize accessions was evaluated through testcross using two populations and two inbred lines as testers in order to identify their genetic potential. The evaluation was carried out in two environments, at Cotaxtla, Ver. under rainfed conditions (during the Spring-Summer season of 1997 cycle), and Tepalcingo, Mor. under irrigation (during the Fall-Winter season of 1998-99). Two experiments were established. Experiment I consisted of crosses between 42 accessions with POB21 (Tuxpeño) and POB32 (ETO). Experiment II included partial crosses between 31 accessions with the two inbred lines CML-247 and CML-254. The experiments were set up as an incomplete block design in lattice arrangements of 9x10 and 6x7 with two replications, respectively. The broad and narrow genetic base testers were efficient to identify the genetic potential and combining ability of the evaluated accessions. The best crosses were selected based on their performance per se and the additive and nonadditive genetic effects. Genetic analyses of Experiment I (landraces by populations) were useful to identify the accessions TAM131, CUBA137, JAL285 and SIN70, as the best general combining ability (GCA) effects. From the best-identified crosses of Experiment II, accessions PUERGP5A, CUBA134, CUBA28, CUBA72 and CUBA79 obtained the best GCA values. Crosses having the best values of specific combining ability (SCA) included: CHIS567xPOB21, PUERGP5AxPOB21, OAX220xPOB32 and CUBA79xCML254. In the identification of accessions to be used in a breeding program, besides the per se performance it is convenient to consider the genetic effects such as combining ability.