检查语法：Here we discussed the trend of maize yield together with planting density in major maize countries the optimal planting density OPD with different methodologies and the realization for OPD via ge

Here, we discussed the trend of maize yield together with planting density in major maize countries, the optimal planting density (OPD) with different methodologies, and the realization of OPD via genetics × environment × management interactions.