Effects of selection for maize resistance to Sesamia nonagrioides on the additive and dominant components of genetic variance

Sesamia nonagrioides causes high yield losses in maize in northwestern Spain. Therefore, a recurrent selection programme to improve resistance against this pest has been carried out in a maize synthetic population. The main purposes of this investigation were to determine which are the main components of genetic variance for stem tunnelling and yield under infestation, to determine the variance remaining after selection, and, finally, to establish the genetic relationship between traits used as selection criteria and other ear resistance and agronomic traits. A North Carolina Design I mating system was used. Individual analyses by year were carried out and additive variance was identified as the only significant component of the genetic variance for stem tunnel length while a dominant variance was significant for yield. Those variances have decreased due to selection, but not significantly. Selection could continue for more cycles as there is enough variance. Additive genetic correlation coefficients between tunnel length and yield could not be determined. Thereafter, we propose three different methodologies of the selection to determine the relationship between resistance and yield under infestation.