Divergent Selecting for Ear Moisture in Early Maize1

Abstract

Two procedures to change ear drying rates were tested in five early maize (Zea mays L.) synthetics for their relative merits for breeding varieties adaptable to more timely harvest, which requires less grain drying and possession of acceptable agronomic characteristics. Objectives of this study were to assess the relative effectiveness of a laboratory and a field selection method for improving harvest moisture contents and to measure any correlated responses for other agronomic traits. Substrains in each synthetic, divergently selected for two or more cycles for relative rates of moisture loss from ears in the laboratory were evaluated in six environments along with substrains divergently selected for two cycles for ear moisture content at 45 days postpollination. Regression procedures were used to evaluate selection responses for ear moisture at harvest and correlated responses of other agronomic traits. Selection for slow relative moisture loss in the laboratory (SD) changed field harvest moisture by −6.73 g kg−1 cycle−1 and produced correlated reductions in ear length, kernels per ear, kernel rows per ear, ear weight, and root lodging. Selection for low ear moisture at 45 days postpollination (LM) changed harvest ear moisture in selected strains by −7.15 g kg−1 cycle−1. Correlated increases in test weight and decreases in stalk lodging also were observed. Selection for fast relative moisture loss in the laboratory (FD) or high moisture content at 45 days postpollination (HM) generally produced increased ear moisture at harvest in selected strains. Neither yield nor silking dates were changed by the selection methods. Harvest moisture responses from the SD method seemingly resulted from reduced moisture content at 45 days postpollination rather than changes in the rate of moisture loss from the ear. Whether selection has produced basic changes in endosperm composition remains to be determined. The LM method appears very feasible for practical breeding programs because of simplicity and effectiveness