Refractive Index as a Basis for Assessing Fatty Acid Composition in Segregating Populations Derived from Infraspecific Crosses of Cultivated Peanuts1

Abstract
Refractive indexes of oil were converted to calculated iodine values (C.I.V.'s) and used to assess the fatty acid composition of hybrid and segregating populations of six crosses of cultivated peanuts (Arachis hypogaea L.). Two subspecies (hypogaea and fastigiata), three botanical types (Virginia, Spanish, and Valencia), and four market types (Virginia, Southeastern Runner, Spanish, and Valencia) were represented in the four parents.Highly significant statistical effects of locations and genotypes on mean C.I.V.'s were noted. Parent by location interactions were statistically significant, but hybrid by location interactions were nonsignificant.The use of a refractometer as a practical, rapid, inexpensive, and objective means of assessing the fatty acid composition of peanut oil was demonstrated. Significant positive correlation coefficients between C.I.V.'s and the actual linoleic acid compositions of oils from 40 F2 plants supported the use of the refractometer method.The wide range of genetic variability for C.I.V.'s in F2 populations of infraspecific crosses indicated selection potential for the improvement of quality and stability of seed oil within specific botanical plant types.C.I.V. appears to be highly heritable, and its expression is controlled by a few additive genes.

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