5 Conclusion
Te, Tr, and TeTr maize inbred lines respond differently to high temperature around flowering and KDD during the entire growth season, with Tr lines on average having a higher heat tolerance than Te lines. However, three inbred line groups all have large variations in kernel number under high temperature during flowering, suggesting each of Te, Tr, and TeTr lines has heat tolerant and susceptible germplasms. As compared with genetic background, flowering patterns can be regarded as more reliable indexes for evaluating and selecting heat tolerance of maize genotypes. Sowing date is proved a more feasible strategy for alleviating negative effects of high temperature than genotype, but these two strategies combined together are still limited when meeting frequent occurrence of extreme heat waves. Hence, more heat tolerant maize hybrids and proper sowing date should be combined with alternative strategies to cope with high temperature stress in the warming climate.