Heat Stress Related Physiological and Metabolic Traits in Peanut Seedlings

ABSTRACT To maintain high yields under an increasingly hotter climate, high temperature resilient peanut cultivars would have to be developed. Therefore, the mechanisms of plant response to heat need to be understood. The objective of this study was to explore the physiological and metabolic mechanisms developed by virginia-type peanut at early growth stages in response to high temperature stress. Peanut seedlings were exposed to 40/35 C (heat) and 30/25 C (optimum temperature) in a growth chamber. Membrane injury (MI), the Fv/Fm ratio, and several metabolites were evaluated in eight genotypes at four time-points (day 1, 2, 4, and 7) after the heat stress treatment initiation. Even though we were able to highlight some metabolites, e.g., hydroxyproline, galactinol, and unsaturated fatty acid, explaining specific differential physiological (MI) responses in peanut seedlings, overall our data suggested general stress responses rather than adaptive mechanisms to heat. Rather than individual metabolites, a combination of several metabolites better explained (41 to 61%) the MI variation in heat stressed peanut seedlings. The genotype SPT 06-07 exhibited lower MI, increased galactinol, reduced hydroxyproline, and higher saturated vs. unsaturated fatty acid ratio under heat stress compared to other genotypes. SPT 06-07 was also separated from the other genotypes during hierarchical clustering and, based on this and previous fieldwork, SPT 06-07 is proposed as a potential source for heat tolerance improvement of virginia-type peanut.