MAIZE PHYSIOLOGICAL TRAITS RELATED TO GRAIN-YIELD AND HARVEST MOISTURE IN MID-SEASON TO SHORT-SEASON ENVIRONMENTS

Identification of easily measured physiological traits contributing to yield under specified environmental conditions would benefit genotypi c selection for maize (Zea mays L.). A field experiment was conducted to determine relationships between grain yield, harvest moisture, the ratio yield/moisture (Y/M), and 10 maize physiological traits related to development time, vegetative growth, and partitioning to the grain. Nine commercial hybrids, representing three maturity classes from 75 to 95 d, were planted at three sites with zonations, based on corn hea t units (CHU), corresponding to the three maturity classes within 100 km of Ottawa, Canada (45 degrees 22' N, 75 degrees 43' W), in 1988, 19 89, and 1990. Grain yield and harvest moisture were related to hybrid maturity; i.e., late maturity hybrids produced high yields with high g rain moisture, but traits related to development time alone did not pr edict yield and moisture. Traits most highly correlated with grain yie ld and Y/M for the three maturity classes at the three sites were harv est index, vegetative dry matter (at tasselling), time to develop betw een silking and maturity (TFILL), and time to develop to silking (TSIL K). Traits most highly correlated with harvest moisture were time to d evelop to maturity, TSILK, and TFILL. Models to estimate grain yield h ad higher coefficients of determination than those for harvest moistur e and models for Y/M had intermediate coefficients. Results suggest th at selection for high yielding low moisture hybrids in mid- to short-s eason production areas should aim to increase (i) the grainfilling per iod (TFILL); (ii) vegetative dry matter; and (iii) harvest index.