Seed quality issues associated with high-oleate peanut (Arachis hypogaea L.)

by Sun, Minghui

ABSTRACT SUN, MINGHUI Seed quality issues associated with high-oleate peanut (Arachis hypogaea L.) (Under the direction of Dr. JANET SPEARS) The high-oleate trait of peanut is of great interest to the peanut processing industry because it produces greater oxidative stability of the oil without adversely affecting flavor. Most US peanut breeding programs have incorporation of the high-oleate trait into existing cultivars and future releases as an objective. While much of the peanut industry is concerned about peanut dietary oil quality, seed technologists are concern that altering peanut seed fatty acid or total lipid composition could influence germination rate, seed and seeding vigor, and seedling survival, especially if the seed are planted in stressful soil conditions. An experiment was designed to evaluate temperature effect on seed oil quality of high-oleate and normal peanut cultivars in controlled greenhouse environment. Two cultivars, NC-V 11 and Gregory, along with their paired backcross-derived high-oleate lines were planted in greenhouses maintained at 22/18oC, 26/22oC and 30/26oC day/night temperature. A split-plot experimental design with two replications was used. Peanut kernels were analyzed for fatty acid composition of the whole seed and axis lipids. The whole seed oleic to linoleic acid (O/L) ratio of normal peanuts grown in 30/26oC, 26/22oC, and 22/18oC, measured 1.9, 1.5, and 1.3, respectively. The O/L for their high-oleate pairs decreased from 24.7 when grown in 30/26oC to 15.9 in 26/22oC and to 13.7 in 22/18oC. Temperature did not affect the fatty acid composition of axis total lipid or phospholipid fractions. The high-oleate trait was however, expressed in the axis lipids. The average O/L of axis from normal peanut was 1.1 while that of high-oleate lines was 4.6. Likewise, axis phospholipids for normal and high-oleate lines were 1.0 and 5.9. Decreased production environment temperature in this study decreased the O/L ratio of seed oil of high-oleic peanut lines, and the high-oleate trait expressed in peanut seed storage lipids is also expressed in axis membrane lipids to a lesser degree. The second experiment was designed to determine if the production methods applicable to traditional peanuts will hold for high-oleate cultivars. Six Virginia-type peanut cultivars and their paired backcross-derived high-oleate lines were grown at the Peanut Belt Research Station near Lewiston, NC in 2003 and 2004. A split-plot experimental design was used with 2 × 2 factorial combinations of planting and harvest date as whole plot treatments, and 2 × 6 factorial combinations oleic acid and cultivars as subplot treatments. Seed quality evaluation included standard germination (SG), cool germination (CG), and electrical conductivity (EC). Oleic acid level had no influence on SG but did significantly alter CG and EC of high-oleate lines. Averaged across background genotypes, high-oleate lines had lower seed vigor than their paired lines with normal oleic content. The high-oleate lines of three of the six pairs had significantly lower CG and higher EC. Planting and harvest date affected all the seed quality traits measured. SG of both normal and high-oleate lines was reduced in 2004 when harvest was delayed, but was not affected in 2003. In 2003, CG of the high-oleate lines was significantly lower than that of normal lines in three of the four production environments; EC was significantly higher in the high-oleate lines in all planting date and harvest date combinations. In 2004, there was no statistical difference between the CG of normal and high-oleate lines, but EC was significantly higher in the high-oleate lines for three of the four environments.