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 ' cycle ~' 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.

Characterization of correlation between grain moisture and ear rot resistance in maize by QTL meta-analysis

“…Ear moisture differences at physiological maturity were deemed important (Cross 1985). Selection inbred lines based on low ear moisture at 45 day post-pollination could effectively reduce ear moisture at harvest (Cross et al 1987;Cross and Kabir 1989). Besides measuring with machine directly, husk senescence has been often proposed as an indirect inbred selection criterion to reduce gain moisture (Sweeney et al 1994).…”

QTL Detection for Grain Water Relations and Genetic Correlations with Grain Matter Accumulation at Four Stages after Pollination in Maize

“…A negative correlation between late-season drying rate and grain moisture at harvest was reported by Kang and Zuber [56]. Selection of inbred lines based on low GWC at early stages has been proved effective in reducing GWC at harvest [37][38][39].…”

“…For GDR during the latest period (34 DAP), insignificant correlations with GWC at 10 DAP and 20 DAP, and positive correlation with GWC at 30 DAP were obtained. Therefore, GWC at late stage could be predicted according to data at any early stages, which had been proved through selection of inbred lines and their crosses [37][38][39]. But GDR at late period could only be predicted according to periods with overlapping stages.…”

“…Obviously, direct selection for low GWC and high GDR at late stage/ period would result in decrease in grain weight at final stage, although this was favorable for maize production in temperate regions [28,[33][34][35][36][37][38]. To obtain hybrids with low GWC and high GDR at harvest in such areas, increase in grain weight might be limited.…”

“…Besides, low GWC and high Grain Dehydration Rate (GDR) at harvest were very important for maize production in temperate regions (midto short-season areas, such as Huanghuihai maize belt in China), which could facilitate machinery harvest, shelling efficiency, grain quality and reduce additional drying cost and shrinkage penalties [28,[33][34][35][36]. Previous research has shown that selection of inbred lines based on low ear-moisture content at a given date after pollination was an effective way to result in low grain moisture content at harvest for inbred lines and associated hybrids [37][38][39]. However, QTL mapping for grain water relations had been reported mostly for Grain Water Content at harvest [21,36,[40][41][42].…”