RESOURCE ALLOCATION IN A MAIZE BREEDING PROGRAM FOR NATIVE RESISTANCE TO WESTERN CORN ROOTWORM

The objective of this study was to determine the optimum allocation of the number of plants sampled per plot and number of locations and years required for screening maize genotypes for reduced root damage caused by western corn rootworm (WCR) larvae, major pest of maize in Croatia, Europe and in the USA. Field trials were conducted on two locations Eastern Croatia, a major maize production area with natural WCR occurrence under continuous maize growing conditions. The trials were set as an incomplete lattice block design in two replications in 2007, 2008 and 2009 including 128 genotypes from various maize gene-pools. Our results suggest that the effect of year and respective interactions including year were the most important factors in maize breeding programs for native resistance to WCR. Thus, screening germplasm for WCR resistance should be made in a multi-year experiment, but not necessarily as a multi-location experiment. Resource optimization should be done by reducing number of roots per plot to minimum 4 sampled plants due to small within-plot environmental variance.