Physiological Parameters as Selection Tools for Identifying Heat-Tolerant Potato Genotypes

Abstract As a crop naturally adapted to high-altitude and cool climates, potato experiences significant yield losses when cultivated in tropical regions exposed to elevated temperatures. Developing heat-tolerant genotypes is therefore essential to mitigate these adverse effects. This study aimed to evaluate the heat stress tolerance of elite clones and cultivars from Embrapa’s breeding program and to identify physiological patterns, based on the stability of photosynthetic parameters and photoprotective mechanisms, that could facilitate accelerated selection of heat-tolerant genotypes. The experiment was conducted in growth chambers using a randomised block design with three replicates. After planting, tubers were maintained under control conditions (14–24 °C) until the onset of tuberization. At this stage, a subset of plants was exposed to 14 days of heat stress (24–34 °C). Physiological measurements were taken on the final day of stress. Plants were then returned to control conditions and grown until harvest, 75 days after planting, when biometric and yield-related traits were assessed. Heat stress reduced photosynthetic activity and yield, underscoring the multifactorial nature of heat tolerance in potato. The cultivar Granola exhibited photosynthetic stability and effective photoprotection, representing true physiological tolerance, whereas BRS F63 showed an escape strategy characterised by a shorter growth cycle. Our results identified net CO₂ assimilation ( A ), maximum quantum yield of PSII (F V /F M ), and non-photochemical quenching (NPQ) as reliable physiological markers for selecting heat-tolerant potato genotypes in breeding programs.