The European corn borer (Ostrinia nubilalis Hbn) is an important insect pest of maize (Zea mays L.) in Europe. However, the larvae of pink stem borer (Sesamia nonagrioides Lef.) produce important damage to the stems, especially in Southern Europe. The first step in an insect-resistance breeding program is to identify sources of resistance. The objective of this work was to study the resistance/tolerance of several populations of maize to attack by corn borers in general, and of Sesamia nonagrioides in particular. Twenty landraces of maize were evaluated for two years at two locations under natural infestation. In one location most of the larvae that were found belonged to Sesamia while in the other location the larvae of Ostrinia were more abundant. Agronomic and resistant traits were analyzed in all trials and the best varieties for resistance. along with new material, were evaluated further under artificial infestation conditions with Sesamia nonagrioides. The extraearly and early material suffered less borer damage than the late and midseason material, because the early populations probably escaped the second brood of borers. Moreover, the varieties with small proportion of damaged stems come from the Ebro valley. The germplasm of this area. then, could be a good source of resistance or tolerance to the borers. However, it showed a low yield. The EPS7(S)C2 synthetic also had good resistance under artificial infestations with Sesamia nonagrioides. Further, it showed better yield than the landraces because two cycles of S1 recurrent selection for yield have been carried out in this synthetic. Therefore EPS7(S)C2 could be the base material in a breeding program to obtain resistant varieties to the pink stem borer.

This workk was supportcd by the Commitee for Science and Technology (Comisión Inteministerial de Ciencia y Tecnología) of Spain (projecl AGR89-0537) and the Department of Education of the Autonomous Government of Galicia (project XU-GA40301A90).

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Peer reviewed