Identification of Heat-Tolerant Impatiens platypetala Genotypes: Morphological Responses and Stress Tolerance Indices Under Elevated Temperatures

Abstract

This study aimed to identify I. platypetala (balsam plant) genotypes with superior heat tolerance traits and to explore how temperature affects plant morphology. The research compared ten I. platypetala genotypes under heat stress and normal conditions. Measurements were taken during the vegetative and generative stages and at the end of the observation period. Results revealed significant genotype-specific responses to temperature, with genotype-by-temperature interactions. Some genotypes exhibited superior plant height, leaf number, and flower production traits. However, under heat stress, many traits generally declined, including plant height (by 24–38%) and flower number (by 31–45%), while others, such as leaf length and width, increased slightly (by 8–15%). We found the darker colors in leaves, stems, and flowers under heat stress compared to control conditions. We also calculated heat tolerance indices. The correlation and biplot analyses found that heat tolerance (TOL) often indicates susceptibility, while the stress tolerance index (STI), mean productivity (MP), and the geometric mean of productivity (GMP) reflect stress tolerance and yield performance under stress. STI, MP, and GMP showed strong positive correlations with both yield potential and yield under stress (r = 0.76–0.91) and were the most effective tools for selecting heat-stress-tolerant plants among our I. platypetala genotypes. The identified specific genotypes with high STI (0.82–0.89), MP (0.75–0.83), and GMP (0.77–0.85), along with low TOL value, such as 22.04.16 and 22.04.08, exhibit resilience and robust performance under heat stress.