Effect of thermal shock on cotton seeds for identifying heat-resistant cultivars

Abstract A severe consequence of climate change is global warming, with heatwaves occurring worldwide, including in many important agricultural production areas, leading to a significant decline in crop yields. Identifying genotypes capable of thriving under relatively high-temperature conditions is of fundamental importance for addressing climate change. The cotton crop Gossypium hirsutum L. is one of the most popular natural fibers in the world and is considered a highly economically significant crop for the textile industry. Our research aimed to evaluate the physiological quality of seeds and the photosynthetic metabolism of cotton cultivars subjected to thermal shock to identify heat-resistant genotypes. The seeds of the cultivars BRS RUBI and BRS JADE were distributed in a gerbox, kept in a water bath for 24 hours at 25, 30, 35, 40, and 45 °C, and then subjected to seed and seedling evaluations. The seeds of the cotton cultivars BRS JADE and BRS RUBI have different physiological responses to thermal shock. BRS JADE demonstrated greater vigor than BRS RUBI, resulting in an increase in germination percentage of emergence and speed of seedling emergence. In contrast, cv. BRS RUBI, despite having decreased vigor than BRS JADE, presented an increase in root length. Chlorophyll a content varied with temperature, showing different peaks for each cultivar. Chlorophyll b decreased as temperature increased, while carotenoids rose up to 35 °C. Temperatures above 34 °C caused significant leaf damage in both cultivars. Seeds of cultivars BRS JADE and BRS RUBI were tolerant of the thermal shock imposed on them.