Seeds kept in long-term storage are essential for maintaining genetic resources of crops and other plant materials in seed banks and national germplasm systems. But seeds undergo chemical changes over time as part of the ageing process that result in reduced germination rates and seedling normalcy. For example, oilseed crops such as peanuts are particularly vulnerable to oxidation and rancidification due to their high oil content. To test the effect of storage time on seed oil in peanuts, we grew different accessions and harvested fresh seeds to compare the oil composition of new seeds with seeds aged in storage for varying lengths of time. Out of the nine fatty acids detected and measured by gas chromatography, five including oleic, gadoleic, behenic, lignoceric and cerotic acids differed significantly between new and old seeds. Additionally, old seeds accumulated up to four oxidation products together averaging about 1% of the total oil composition. The concentration of these oxidation products was positively correlated with the age of the seeds, increasing linearly up to more than 6% of the total in the oldest seeds. The presence and concentration of oxidation products measured using simple chromatography techniques can be used as an initial indication of quality and viability in older seed inventories stored in germplasm repositories.

Wild peanut species are useful genetic resources for improving the levels of disease/pest resistance and for enhancing the quality of seed composition by interspecific hybridization. The variation in oil content and fatty acid composition of wild peanut species in the United States Department of Agriculture germplasm collection is unknown. Seeds available from 39 wild species (plus a cultivated peanut) were requested from the U.S. peanut germplasm collection. Oil content was measured using nuclear magnetic resonance, fatty acid composition was analysed using gas chromatography, and the D150N functional mutation of the FAD2A gene was screened by real-time PCR. Significant variability in oil content (41.7–61.3%) was identified among the wild peanut species. Arachis magna contained significantly more oil (61%) than cultivated peanut (56%). There was no functional mutation identified within the FAD2A gene target, and no wild species were identified with a high ratio of oleic acid to linoleic acid. The results from gas chromatography and real-time PCR analyses were consistent. However, Arachis sylvestris contained a significantly higher amount (22%) of long-chain fatty acid (LCFA) than the cultivated peanut (4%). Thus, A.magna and A. sylvestris may be good breeding materials to use for increasing oil content or LCFA composition of cultivated peanuts in breeding programs.

Within the cultivated peanut species (Arachis hypogaea L.), there are two subspecies comprising six botanical varieties, and the effect of botanical taxon on oil content and fatty acid composition variability is unclear. To gauge the variability, 83 peanut accessions were analyzed for oil content (expressed at 0% moisture) and fatty acid composition. We found that within the subsp. hypogaea, var. hypogaea contained a much higher amount of oil in seeds than did the var. hirsuta Köhler (520 vs. 473 g/kg, P < 0.05); within the subsp. fastigiata Waldron, the vars. aequatoriana Krapov. & W.C. Gregory and vulgaris Harz contained a similar amount of oil in seeds (491 g/kg), not significantly different from other botanical varieties, but var. fastigiata contained a higher amount of oil (500 g/kg) than the var. peruviana Krapov. & W.C. Gregory (483 g/kg). In terms of the fatty acid composition, oil from seeds of var. hypogaea contained much more oleic acid than did var. hirsuta (491 vs. 377 g/kg, P < 0.05), but much less palmitic acid (97 vs. 138 g/kg, P < 0.05%) and linoleic acid (308 vs. 402 g/kg, P < 0.05). Oil from seeds of var. vulgaris contained much more oleic acid than did var. aequatoriana (437 vs. 402 g/kg, P < 0.05), but much less linoleic acid (346 vs. 380 g/kg, P < 0.05). Significant negative correlations of oleic with palmitic and linoleic acids were detected. The information on the oil content and fatty acid composition variability among botanical varieties would be useful for peanut breeders seeking germplasm containing both high oil content and proper fatty acid composition.