Genetic control of plastid carotenoids and transformation in the skin of Cucurbita pepo L. fruit

The influence of allelic state of gene B on skin pigmentation in two cultivars of Cucurbita pepo L. has been studied. Total carotenoids were lower at early stages of fruit development in cultivar (cv.) 'Early Prolific' (EP) BB YY fruit skin, than in EP B⁺B⁺YY fruit skin, but no differences were observed in total skin carotenoids twenty days after anthesis. Total carotenoids were lower in cv. 'Fordhook Zucchini' (FZ) BB yy fruit skin, than in FZ B⁺B⁺yy fruit skin at all developmental stages from anthesis to maturity. Both green and yellow tissues contained typical foliar carotenoids. The carotenoids from yellow fruit skin of both EP genotypes and of FZ BB were characterized by a low carotene: xanthophyll ratio, with a high proportion of the xanthophylls esterified to fatty acids. The xanthophylls of the yellow tissues were esterified with 12:0, 14:0, 16:0 fatty acids. The carotenoids from the green fruit skin of FZ B⁺B⁺ had a higher percentage of carotenes (primarily β-carotene) and a lower percentage of esterified xanthophylls. Spectral shapes of carotenoid fractions from all yellow tissues were similar and distinguishable from those of green FZ B⁺B⁺ tissue. The results of these studies are discussed in terms of the genetic control of plastid transformation in Cucurbita pepo L.