A Comparison of Methods Used to Determine the Oleic/Linoleic Acid Ratio in Cultivated Peanut (Arachis hypogaea L.)

Cultivated peanut (Arachis hypogaea L.) is an important oil and food crop. It is also a cheap source of protein, a good source of essential vitamins and minerals, and a component of many food products. The fatty acid composition of peanuts has become increasingly important with the realization that oleic acid content significantly affects the development of rancidity. And oil content of peanuts significantly affects flavor and shelf-life. Early generation screening of breeding lines for high oleic acid content greatly increases the efficiency of developing new peanut varieties. The objective of this study was to compare the accuracy of methods used to classify individual peanut seed as high oleic or not high oleic.

Three hundred and seventy-four (374) seeds, spanning twenty-three (23) genotypes varying in oil composition (i.e. high oleic (H) or normal/not high oleic (NH) inclusive of all four peanut market-types (runner, Spanish, Valencia and Virginia), were individually tested by each method. Ten to twenty seed from each genotype were chosen randomly for the method comparisons. Samples were distributed in a blind manner. Individual seed were subjected to analysis in the following order: 1) near-infrared reflectance spectroscopy (NIRS) (1 and 2), 2) real-time polymerase chain reaction (RT-PCR), and 3) oil extraction. Oil extractions were then subjected first to capillary electrophoresis (CE) then to gas chromatography (GC). The proportion of similarity of responses for each sample was calculated for each pair of methods, both across all varieties and for each variety. Using GC as the reference standard, sensitivities (correctly identifying an H sample) and specificities (correctly identifying an NH sample) were computed for the other three methods. Percent accuracy levels for rating individual seed as high oleic (H) ranged from 97.4% (NIRS) to 99.5% (CE).

All of the methods examined in this study carry only a minor risk for miss-classification (loss of material) and are suitable for use by peanut breeding programs in early generation breeding line screening. And the results indicate that peanut breeding programs can confidently use any of the methods discussed in this study for screening early generation breeding lines for oleic acid content.

Article by Kelly D. Chamberlin, et al, from USA.

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