Combining abilities for maize stem antibiosis, yield loss, and yield underinfestation and non infestation with pink stem borer

The pink stem borer (Sesamia nonagrioides Lef.) is the main pest of maize ( Zea mays L.) in northwestern Spain. Little is known about combining ability for antibiosis and tolerance to this Rest. Therefore, the objectives of th is work were to estimate general combining ability (GCA), specific combinin g ability (SCA), and reciprocal effects for stem damage traits, yield, and yield loss by a complete diallel of 10 inbreds and to determine the most us eful trait for evaluating the level of defense to pink stem borer. The dial lel design was evaluated for 2 yr for stem damage traits, yield loss, and f or yield under two conditions, infestation with Sesamia nonagrioides and no n infestation. For all stem damage traits, GCA was significant, while SCA, and reciprocal effects were not significant. This indicated that, for this set of inbreds, only additive effects were important for stem antibiosis. G CA and SCA effects were significant, in at least one trial, for yield under both infestation conditions and for yield loss. Reciprocal effects were si gnificant for yield of infested and non infested plants in 1995. The lack o f concordance among lines that exhibited the most favorable GCA effects for stem antibiosis, yield loss, and yield under infested conditions and the l ow correlation coefficient between SCA effects for yield under infested and non infested conditions showed that yield under infested conditions is the best trait for evaluating the level of defense against pink stem borer att ack.