RELATIVE ADVANTAGE OF HIGH YIELD POTENTIAL AT LOW-YIELDING ENVIRONMENTS FOR COMMERCIAL MAIZE HYBRIDS CROPPED IN ARGENTINA

摘要

An extended assumption in maize breeding is that potential yield (Upsilon(max)) predicts yield (Upsilon) under stress conditions (here, Upsilon(min)) justifying genotypic selection under moderately high-yielding environments. Moreover, it has been postulated that Upsilon tolerance to stress is relatively independent on the main stress factor involved in Upsilon reduction (cross-tolerance). We carried out an analysis of four datasets from Argentine Federated Farmers network (2010/11, 2011/12 and 2012/13, 11 locations and >20 hybrids) and the National Institute of Agricultural Technology (INTA) (12 locations, 13 hybrids). No consistent relation was detected between Upsilon(max) and Upsilon(min) (r(2) 0.14) in each dataset. Upsilon stability assessed by the coefficient of variation positively related to Upsilon (r(2) > 0.68 across datasets) but not to Upsilon(max). Depending on the dataset, 40-70% of the hybrids had a varying Upsilon performance (from worse to better) compared with the average of all hybrids, with no consistent advantage of hybrids with high Upsilon(max) within the environmental range explored in the dataset. In order to assess the existence of cross-tolerance, INTA environments were divided into two groups: water-limited environments and environments exposed to other(s) type(s) of stress. While a relation was found between average yields (r(2) = 0.64) of each hybrid in both environments, there was no relation for ratability (r(2) = 0.07). Taken together, our results suggest that: (i) a high Upsilon(max) is not a good indicator of high Upsilon tolerance under stressful conditions; (ii) Upsilon tolerance is related to high rstability, which may or may not involve a Upsilon penalty under high-yielding environments; (iii) around 50% of the genotypes have Upsilon performance that is not consistently worse or better than the average throughout the range of environments explored and (iv) cross-tolerance to stress is a peculiar trait of some hybrids, but most of the hybrids analysed here do not show cross-tolerance.