Post-flowering high night-time temperature stress impacts physiology and starch metabolism in field-grown maize

The global average daily minimum temperatures are increasing at a quicker pace than the average daily maximum temperatures, which are predicted to increase in severity impacting global food production. This study focuses on elucidating the physiological and transcriptional response to high night-time temperature (HNT) stress in 12 US commercial maize (Zea mays) hybrids using unique field-based infrastructure. Our experimental objectives were to (i) impose an accurate and uniformly distributed post-flowering HNT stress of +4.0°C until physiological maturity, (ii) quantify the impact of HNT stress on physiological and yield-related traits, (iii) establish the impact on end-use quality of maize kernels formed under HNT stress, and (iv) analyze the differential expression of genes involved in grain starch metabolism. Accurate and uniformly distributed HNT stress of 3.8°C higher than the ambient night-time temperature throughout the grain-filling period reduced yield (−14%), kernel weight (−8%), and significantly reduced kernel nutrient content, specifically magnesium in the susceptible hybrids. HNT significantly increased the expression of key genes involved in starch metabolism in the tolerant hybrid. Although HNT stress had a negative impact on yield and quality in field grown maize, two hybrids had physiological and transcriptional regulation that favored higher level of resilience which lays the platform for developing climate smart maize hybrids.