Canopy structure, photosynthesis, grain filling, and dehydration characteristics of maize varieties suitable for grain mechanical harvesting

Abstract

<p id="C3">To provide technical support for the selection and popularization of corn varieties suitable for mechanized grain harvest, the canopy structure, photosynthetic characteristics, and mechanical harvesting characteristics of different types of maize varieties were compared with 24 maize varieties including Jingnongke 728 produced and widely promoted in China. The results showed that: (1) The average yield, moisture content, broken rate and impurity content at harvest of the tested varieties were 11,658.78 kg hm^-2, 24.66%, 3.90%, and 0.83%. The average yield of 18 suitable machine harvesting varieties such as Jingnongke 728 with Jing 2416 as male parent was 11,802.70 kg hm^-2, which was significantly higher by 7.69% and 4.45% than those of Zhengdan 958 and Xianyu 335, respectively. The grain moisture content at harvest was lower than 28% (average 24.61%); The average broken rate was less than 5% (average 3.42%), reaching the national standard of machine harvested grain. (2) 18 maize varieties suitable for grain mechanical harvesting such as Jingnongke 728 with Jing 2416 as male parent had small angle between stem and leaf, compact plant type, high average light transmittance and more reasonable light distribution. (3) The average net photosynthetic rate and chlorophyll content of the tested maize varieties were 34.10 μmol CO₂ m ^-2 s^-1 and 8.91 mg m². The average net photosynthetic rate of the 18 maize varieties suitable for machine harvesting with Jing 2416 as male parent was 35.21 μmol CO₂ m ^-2 s^-1, which was 19.60% and 6.73% higher than Zhengdan 958 and Xianyu 335. The average chlorophyll content was 9.87 mg m², which was 61.54% and 68.43% higher than Zhengdan 958 and Xianyu 335. (4) The average grain filling rate and dehydration rate after physiological maturity of 18 varieties with Jing 2416 as male parent were 0.83 g 100 grain^-1 d^-1 and 0.55% d^-1, respectively, which were significantly higher than those of Zhengdan 958 and Xianyu 335, showing a lower grain moisture content at harvest. (5) Correlation analysis revealed that the yield of the tested varieties was significantly positively correlated with net photosynthetic rate and grain filling rate. The net photosynthetic rate was negatively correlated with the angle between stem and leaf, and positively correlated with light transmittance and chlorophyll content. Grain moisture content at harvest was significantly positively correlated with breakage rate, impurity content and grain moisture content after physiological maturity, negatively correlated with dehydration rate after physiological maturity, and negatively correlated with grain filling rate. In conclusion, maize varieties suitable for mechanical harvesting under the condition of high planting density should have compact plant type, high canopy light transmittance, strong photosynthetic capacity, high grain filling, and dehydration rate, which could lead to achieve lower grain moisture content and higher yield.