Impact of High Temperatures, Considerations and Possible Solutions for Sustainable Lettuce Production

High temperature is a major environmental stress factor that affects lettuce (Lactuca sativa L.) growth, development, and productivity. As global temperatures continue to rise, understanding the impact of heat stress on lettuce production is crucial for maintaining crop yields and quality. In fields and in controlled environment agriculture, these elevated temperatures lead to poor seed germination due to thermoinhibition, earlier bolting due to faster crop development, and reduced marketable yields and an increased likelihood of heat-related disorders such as tipburn. Achieving heat tolerance in controlled environment agriculture is paramount as this industry struggles with higher production costs from the excessive use of cooling systems to acclimate greenhouses to temperatures ideal for lettuce production whereas field-grown lettuce must withstand highly variable and extreme thermal conditions, making heat stress a major constraint in both systems. This review comprehensively summarizes the current literature on the impact of heat stress on lettuce and highlights the influence of heat stress at the physiological, biochemical, and molecular level. In addition, we highlight management practices on lettuce production and sustainability as well as the breeding potential for heat tolerance. We synthesized these findings into a proposed conceptual framework for selecting and identifying genomic targets to advance the improvement of heat resilience in lettuce.