INHERITANCE OF FATTY ACID COMPOSITION OF SEED OIL IN THE BUFFALO GOURD, CUCURBITA FOETIDISSIMA HBK.

Abstract

The buffalo gourd, Cucurbita foetidissima HBK, is a xerophytic perennial native to the southwestern United States and northern Mexico. A vigorous spreading vine, it produces edible oil and protein in the seeds, and edible starch in its fleshy storage root. This study concerns the inheritance of content of each fatty acid in the seed oil of the buffalo gourd, including heritability studies, physiological relationships between the fatty acids, and environmental influence on the oil composition. The mechanisms of fatty acid biosynthesis and desaturation and environmental effects on them are reviewed, as is the inheritance of fatty acid composition in commercial oilseed crops. In this study, crosses were made between plants selected for low or high linoleate content and the progeny analyzed by gas chromatography, using a non-destructive half-seed method. Analyzed seed of extremely high and low linoleate content were planted, and crosses made among the resulting plants. Their progeny were analyzed and half-seeds planted again, to be selfed or sib crossed. The fatty acid composition of buffalo gourd seed was found to be determined by the embryonic genotype. Linoleate and oleate content were negatively correlated, as has been previously shown in this and other species. Heritability of oleate and linoleate content was determined by regression of progeny values on midparent values and found to be approximately 0.86 in the first year, while palmitate gave no significant regression. In the second year, palmitate exhibited a heritability of 0.39, but oleate and linoleate had heritabilities near 0.4. The notable decrease in their heritability was examined by multiple regression analysis of progeny values with environmental parameters and midparent values. A significant regression was obtained with day length for oleate and linoleate content; however, correlations also were found with high and low temperatures during the seed maturation period. The various environmental parameters tested were too strongly correlated to distinguish the causative factor with certainty.