Examination of methods for choosing locations for preliminary maize yield testing

Summary

The costs associated with yield testing cause maize (Zea mays L.) breeders to search for ways to maximize testing efficiency. The objective of this study was to select individual locations, or a group of locations as preliminary testing sites for yield evaluation of maize hybrids within FAO 600 maturity zone in Yugoslavia. Yield data for 12 locations obtained for the period 1975 to 1984 were used. The predictive potential of the site was judged by the correlations between location means and overall mean (r>0.95), linear regression of locations means on overall mean (b>1.0) and percentage of the 10% overall highest yielding hybrids selected by 10% selection intensity at each location, or at the group of locations (I_s>80%). Also factors as average location yield (x) and variation in individual location yield during the period of 10 years (CV) were related to the predictive potential of the site. Differences among locations in all criteria were found. Average yielding locations had higher values of estimators of predictive ability of overall performance than low yielding locations. None of individual locations satisfied all requested criteria. Five locations with highest values for each individual criterion were selected and all possible two, three, four and five-location combinations among them studied. Combinations of two locations could be used for very preliminary screening of hybrids by applying mild selection intensity. A more accurate prediction of overall one-year performance requires an evaluation of hybrids in a minimum of three, but frequently four, selected locations. However, for precise estimation of over-year hybrid performance, testing the hybrids at selected locations in more than one year is necessary.