Effects of thidiazuron and ethephon on the grain filling and dehydration characteristics of maize in Northeast China

A mixture of ethephon (ETH) and thidiazuron (TDZ) (called ETTD) has been proven to effectively reduce maize grain moisture content and improve yield and quality of mechanical grain harvesting, but the underlying mechanism is unclear. Field trials were conducted in 852 Farm, Heilongjiang Province, China, in 2017 and 2018, to study the effects of ETH, TDZ and ETTD sprayed on Xianyu335 at 25 days after flowering (appropriate time in the pre-experiment) on grain filling and dehydration characteristics. ETH, TDZ and ETTD significantly accelerated leaf senescence, increased grain, bract, and cob dehydration rates, and decreased grain filling duration and moisture content. TDZ and ETTD significantly increased grain filling rate and auxin (IAA), zeatin riboside (ZR), and abscisic acid (ABA) and decreased gibberellic acid (GA). ETH had no significant effect on ABA and GA, but significantly reduced IAA and ZR in the later period. The grain dehydration rate was significantly negatively correlated with grain filling duration and positively correlated with rates of grain filling and bract and cob dehydration. ETTD significantly decreased the rates of breakage, impurity, and increased mechanical grain harvesting yield. In conclusion, ETTD can be an effective measure to improve yield and quality of maize mechanical grain harvesting.