Peanut varieties with high oleic/linoleic acid ratios have become preferred by the peanut industry due to their increased shelf life and improved health benefits. Many peanut breeding programs are trying to incorporate the high oleic trait into new and improved varieties and are in need of diagnostic tools to track its inheritance early in development and at the single seed level. Traditionally, gas chromatography has been used to accurately determine the properties of peanut oil. Recently a method was developed to carry out this analysis by capillary elecrophoresis providing researchers with an alternative analytical platform. In this study, the use of capillary electrophoresis and gas chromatography for analysis of oleic/linoleic acid ratios are compared. Oil was extracted from approximately 0.10 g of peanut seed tissue taken from the distal end, leaving the embryonic end of the seed intact for subsequent germination. Over 100 samples inclusive of runner, Spanish and Virginia market types were processed. Oil extracts were analyzed for oleic/linoleic acid ratio using (1) capillary electrophoresis (CE) and (2) gas chromatography (GC). Results showed that the two methods are 100% in agreement in determining whether a peanut seed is “high-oleic” or “normal oleic” in oil content. Furthermore, the two methods are highly correlated (r = 0.96; p < 0.0001) with respect to determining the exact oleic/linoleic acid ratio from each sample. Results from this study validate the use of CE as a diagnostic tool for breeding programs to identify individual high oleic peanut seed for further testing and development.

Peanut (Arachis hypogaea L.) is an important food crop for the U.S. and the world. The Virginia-Carolina (VC) region (Virginia, North Carolina, and South Carolina) is an important peanut-growing region of the U.S and is affected by numerous biotic and abiotic stresses. Identification of stress-resistant germplasm, along with improved phenotyping methods, are important steps toward developing improved cultivars. Our objective in 2017 and 2018 was to assess the U.S. mini-core collection for desirable traits, a valuable source for resistant germplasm under limited water conditions. Accessions were evaluated using traditional and high-throughput phenotyping (HTP) techniques, and the suitability of HTP methods as indirect selection tools was assessed. Traditional phenotyping methods included stand count, plant height, lateral branch growth, normalized difference vegetation index (NDVI), canopy temperature depression (CTD), leaf wilting, fungal and viral disease, thrips rating, post-digging in-shell sprouting, and pod yield. The HTP method included 48 aerial vegetation indices (VIs), which were derived using red, blue, green, and near-infrared reflectance; color space indices were collected using an octocopter drone at the same time, with traditional phenotyping. Both phenotypings were done 10 times between 4 and 16 weeks after planting. Accessions had yields comparable to high yielding checks. Correlation coefficients up to 0.8 were identified for several Vis, with yield indicating their suitability for indirect phenotyping. Broad-sense heritability (H²) was further calculated to assess the suitability of particular VIs to enable genetic gains. VIs could be used successfully as surrogates for the physiological and agronomic trait selection in peanuts. Further, this study indicates that UAV-based sensors have potential for measuring physiologic and agronomic characteristics measured for peanut breeding, variable rate input application, real time decision making, and precision agriculture applications.

Athelia rolfsii (=Sclerotium rolfsii) is a soilborne fungus that causes the disease commonly known as southern blight, southern stem rot, stem rot, and white mold. Despite the fact that A. rolfsii is one of the most destructive pathogens of peanut, the U.S. germplasm collection has not been evaluated for resistance to this pathogen. Therefore, 71 of the 112 accessions comprising the U.S. peanut mini-core collection were evaluated in the field for resistance to southern blight in 2016 to 2018 in Oklahoma. Moderate to low levels of southern blight were observed, but four accessionsCC125, CC208, CC559, and CC650had low levels of disease in 2017 and 2018, the most favourable years for A. rolfsii. Ratings for web blotch, a yield-limiting foliar disease in some production areas caused by Didymella arachidicola, were also taken in 2017 and 2018, when outbreaks occurred. Five entriesCC287, CC155, CC149, CC812, and CC559had between 10% and 20% disease in 2018, a year when over half of the mini-core accessions exhibited between 50% and 93% disease. Because cultivated peanut in the U.S. has a narrow genetic base, these results will be useful to breeders seeking additional sources of resistance to A. rolfsii and web blotch.