Dynamic changes of seed development, oil accumulation and fatty acid composition in peanut under soil water deficit

Soil water deficit is a key environmental factor limiting peanut yield and quality, which can occur at any growth stage of peanut. But the exact mechanism of soil water deficit affecting the formation of peanut yield and quality remains unclear. In this study, the seed development, yield components, oil accumulation and fatty acid composition of common (HY25; FH18) and high oleic acid varieties (KN71; HY52) under soil water deficit throughout the growth period were investigated. It was found that the decrease of pod number and 100-pod weight per plant was the main factor leading to the reduction in peanut yield under soil water deficit. The number of oil bodies, maximum oil accumulation rate and oil content were significantly reduced, especially in drought-sensitive peanut varieties. The down-regulation of enzyme activities on the Kennedy pathway was the main factor hindering oil synthesis. Peanut varieties with lower levels of FAD2 transcripts might more sensitive to drought stress in terms of fatty acid metabolism. Under soil water deficiency, high oleic acid peanut oleate synthase activity was reduced, oleic acid metabolizing enzyme activity was elevated, which lead to decreased oleic acid content and the ratio of oleic acid to linoleic acid (O/L), and impaired lipid quality. Among them, the lipid quality of HY52 was most severely compromised. In contrast, the common varieties exhibited opposite enzyme activity patterns, with increases in oleic acid content and O/L, and improved lipid quality. This study elucidated the response mechanism of peanut grain development and oil metabolism to soil water deficit, which can provide theoretical basis and technical support for realizing high quality and stable yield of peanut under adversity.