Heritability and development of the free fatty acids and acylglycerideconstituent fatty acids in Vernonia galamensis oil

Abstract

Since the mid-1970's, there has been active research on the development of Vernonia galamensis (Cass.) Less. as a potential new oilseed crop. Vernolic acid (cis-12:13-epoxy-cis-9-octadecenoic acid) comprises 70--75% of vernonia oil and is chemically reactive, affording it a variety of industrial applications. A concern in the domestication of an oilseed crop is to establish a breeding program to improve oil quality traits. The objectives of this research were to (1) develop a rapid procedure for seed analyses; (2) determine the development of vernonia oil; and (3) estimate the narrow-sense heritability (h 2) of oil quality traits. Successful separation of free fatty acids (FFA) and acylglycerides from small vernonia seed samples was achieved using aminopropyl solid phase extraction columns. Acylglycerides were eluted with a mixture of chloroform and isopropanol, while FFA were eluted with a mixture of acetone and trifluoroacetic acid. Four breeding lines from a collection of Vernonia galamensis held at the US Water Conservation Laboratory in Phoenix, AZ were used for the oil development study and grown in field trails in Phoenix and Tucson, Arizona. Seeds were collected on nine different days after flowering over the course of seed maturation. Seed samples were analyzed for FFA, acylglyceride constituent fatty acids, total acylglycerides, and total oil. In each breeding line, FFA content changed significantly throughout the course of the measurement period, and synthesis of acylglycerides constituent fatty acids followed a previously described pathway proceeding from C16:0 to C18:0 to C18:1 to C18:2 to C18:1 epoxy. Vernolic acid increased late in the measurement period, while total acylglycerides and total oil increased steadily over the period. Mature vernonia seed exhibited substantial variation in the amount of FFA, acylglyceride constituent fatty acids, total acylglycerides, and total oil. Sixty-nine half-sib families were created to study the heritability of FFA, vernolic acid, acylglycerides, and total oil production. Mature capitula were collected and analyzed individually for oil constituents. Narrow sense heritability estimates for these four oil quality traits were: FFA = 33%, vernolic acid = 65%, acylglycerides = 47%, and total oil = 50%. The results indicate potential for progress in selection for these traits.