Drought alters the physiological quality of runner-type peanut seeds during seed formation

Sub-optimal water supply during crop development, especially during peak flowering and pod filling, affects the quality of the produced seeds, generally resulting in poor seed quality. The goals of this study were to identify the acquisition pattern of physiological components in peanut seeds as well as to assess the impact of drought during peanut seed development on its physiological quality. The research was conducted at the USDA-ARS National Peanut Research Laboratory in Dawson, GA for three consecutive years (2019, 2020, and 2021) using field conditions under two water regimes, well-watered control and drought stress. Rainout shelters were used to prevent rain in the drought-stressed block for 30 d, starting 80 d after planting. The well-watered block received supplemental irrigation when soil water potential reached −40 kPa. Peanut pods from the cultivar Georgia-06G were harvested at 2500 growing degree days, and the peanut maturity profile board was used to classify the pods into different maturity classes. Germination, vigor, desiccation tolerance (DT), and longevity tests were performed on seeds from each maturity class and both water regimes. The acquisition pattern for the physiological components of seed quality was developed for seeds grown under well-watered and drought conditions. Maximum germination occurred in 'brown 1' and 'brown 2' under drought and well-watered conditions, respectively. Both water regimes reached maximum vigor in the 'brown 1'; however, under well-watered conditions, vigor had a rapid decline after 'brown 1' while under drought stress, the decline in vigor was slower. Maximum DT was achieved between ‘orange’ and 'brown 1' under drought conditions, whereas under well-watered conditions, maximum DT was achieved between 'brown 2' and 'black 1'. Seeds from immature classes had lower capacity to be stored compared with mature seeds. Overall, drought stress promoted greater physiological quality in the peanut seeds than the well-watered treatment. Maximum physiological quality was achieved in the transition from ‘orange’ into 'brown 1' under drought conditions, and in the transition from 'brown 2' to 'black 1' class under well-watered conditions. Also, drought stress preserved seed quality for a longer period.