Cob color, an indicator of grain dehydration and agronomic traits in maize hybrids

Screening for agronomic traits associated with grain moisture is important for mechanical grainharvesting of maize. Cob color as a visual indicator has received limited attention, though it has been subjected to artificial selection, and may have some association with threshability. To investigate the relationships between cob color and grain moisture and other agronomic traits, field experiments were conducted during 2016–2017 using 23 commercial hybrids with red or white cobs. Kernels of red-cob hybrids dehydrated faster, showing lower moisture content at harvest than white-cob hybrids. A cob color index(CCI) was established as a quantitative measure of cob color in the hybrid panel. Ranging from0(whitest) to 17.98(reddest), CCI correlated well with grain dehydration and other agronomic traits associated with growth ontogeny, plant morphology, and plant N content. Strong selection of red cob for recently released hybrids suitable for mechanical grain-harvesting indirectly validated the observed link between cob color and grain dehydration. We propose that cob color and CCI could be used in future selection of maize cultivars bred for mechanical grain-harvesting.

Grain dehydration rate is related to post-silking thermal time and ear characters in different maize hybrids

Mechanized grain harvest of maize becomes increasingly important with growing land plot size in Northeast China. Grain moisture is an important factor affecting the performance of mechanized grain harvest. However, it remains unclear what influences grain dehydration rate. In this study, maize grain dehydrating process was investigated in a two-year field experiment with five hybrids under two planting densities in 2017 and 2018. It was found that damaged-grain ratio was the main factor affecting mechanized harvest quality, and this ratio was positively correlated with grain moisture content at harvest(R^(2)=0.6372, P<0.01). To fulfill the national standard of <5% damaged-grain ratio for mechanized grain harvest, the optimal maize grain moisture content was 22.3%. From silking to physiological maturity, grain dehydrating process was mostly dependent on the thermal time(growing degree days, GDDs)(r=-0.9412, P<0.01). The average grain moisture content at physiological maturity was 29.4%. Thereafter, the linear relationship between GDDs and grain moisture still existed, but the correlation coefficient became smaller(r=-0.8267, P<0.01). At this stage, grain dehydrating process was greatly affected by genotypes. Grain dehydrated faster when a hybrid has a smaller husk area(r=0.6591, P<0.05), larger ear angle(r=-0.7582, P<0.05), longer ear peduncle(r=-0.9356, P<0.01) and finer ear(r=0.9369, P<0.01). These parameters can be used for breeders and farmers to select hybrids suitable for mechanized grain harvest.