Early Tuberization: A Heat Stress Escape Strategy in the Fresh Market Potato Variety Vanguard Russet

Vanguard Russet, a fresh market potato developed by the Texas A&M Breeding Program, has been reported to be heat tolerant based on previous greenhouse and field studies. Until now, no studies have been conducted to understand the mechanisms involved in its heat tolerance. We compared Vanguard Russet and the heat-sensitive potato variety Russet Burbank using contrasting conditions in growth chambers (normal, 25/15⁰C day/night vs. high-temperature, 25/15⁰C day/night for four weeks, followed by 35/25⁰C day/night). Differences in tuber initiation time, bulking, tuber number, plant height, leaf area, stem thickness, leaf angle, plant biomass, and photosynthetic parameters were sequentially documented at five-time points: 30, 45, 60, 75, and 100 days after planting. Although having slower above-ground plant growth under both conditions, Vanguard Russet initiated tuber formation significantly earlier (< 30 days) than Russet Burbank (30–45 days). This indicates its ability to quickly channel photoassimilates toward tubers, employing early tuberization as a possible heat escape strategy. Screening for early tuberization could be considered as an initial approach to identify varieties able to escape heat stress. In addition to early tuberization, heat-tolerant varieties must produce a high yield of marketable tubers with few internal and external defects.