A. BUTRÓN, P. SOENGAS, P. REVILLA, A. ORDÀS, AND R.A. MALVAR
Misiôn Biolôgica de Galicia (CSIQ, Apdo. 28, 36080 Pontevedra, Spain

The most important maize pest in northwestern Spain is the pink stem borer (Sesamia nonagrioides Lef). Evaluations under infestation conditions have revealed that some maize inbreds and populations could bring resistance genes to pink stem borer attack. More studies, however, should be addressed to look for new sources of resistance and to know how to manage those materials in a selection program to develop varieties resistant to Sesamia nonagrioides. The objective of this work was to know the genetic effects involved in the resistance to Sesamia nonagrioides in a diallel among diverse flint maize populations. That knowledge will allow us to design the most suitable selection program to develop resistant varieties. Ten flint maize populations, seven of them from diverse areas of Spain, two from Argentina and one from United States, were crossed following a diallel design. The diallel was analyzed following Gardner and Eberhart's design. The 45 crosses, plus ten populations, plus a check hybrid were evaluated under infestation with Sesamia nonagrioides at Pontevedra (northwestern Spain) in 1998 and 1999. Tunnel length and general appearance of the ear were recorded as estimates of damage produced by the pink stem borer larvae on stems and ears, respectively. There were significant differences among genotypes and non significant genotype x environment interactions for tunnel length and general appearance of the ear. Variety effects were the only significant effects for tunnel length. Variety and average heterosis effects were significant for general appearance of the ear. Therefore, the additive gene action was the most important in the inheritance of the resistance to Sesamia nonagrioides. The population Basto/Enano levantino (Ba/E1) showed the best variety effect for tunnel length and was among the populations with the most favorable variety effects for general appearance of the ear. Ba/El could be the base material in a recurrent selection program to develop flint maize resistant varieties.