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  • Author or Editor: C. V. Hall x
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Abstract

In leaves of carrot (Daucus carota L.) treated with 120 ppm 2-(4-chlorophenylthio)-triethylamine hydrochloride (CPTA), increased lycopene levels were found. Significant amounts of carotenes tentatively identified as gamma- and delta- were also found. Alpha- and beta-carotene levels were reduced. The effect of CPTA was modified by temperature and genotype. The data suggest that lycopene is a precursor of the carotenes mentioned and that alpha-ionone cyclase has a higher optimum temperature than beta-ionone cyclase.

Open Access

Abstract

Florisil column chromatography and silica-gel thin-layer chromatography were excellent preparatory steps for separation of cucurbitacins in cotyledons. It was difficult to identify closely related cucurbitacins by thin layer chromatography. Unstable cucurbitacin derivatives limited the use of gas-liquid chromatography for cucurbitacin identification; however, mass spectrometry was an effective method for cucurbitacin B.

Open Access

Abstract

Seedlings of 18 plant types from 5 genera of Cucurbitaceae were analyzed for cucurbitacins, total sugars, and fatty acids and these were correlated with spotted cucumber beetle feeding. The species were: Citrullus colocynthis L. (Schrad.), C. lanatus (Mansf.) Matsumara: Cucumis anguria L., C. dipsaceus Ehrenb., C ficifolius Bouche’C. longipes Hook f., C. melo L., C. myricarpus Naud., C. prophetarum L.: Cucurbita foetidissima H. B. K., C. pepo L.; Lagenaria siceraria (Mol.) Stamdl.; Luffa acutangula (L.) Roxb., and L. cylindrica Roem. Seedling injury ranged from 0 (none) to 3 (severe). Regression analysis indicated that cucurbitacins, total sugars, and the fatty acids (palmitic and linolenic) except linoleic contributed to insect feeding; correlation between concn and feeding was positive. Cucurbitacins, which cucumber beetles were able to locate without feeding, played the major role in seedling susceptibility; next in importance were palmitic acid, linolenic acid, and total sugars. All apparently related to the preference of beetles for specific strains or cultivars. In non-preferred seedlings, preference was induced by topical application of cucurbitacins A, B, C, D, E, and 1 and by the glycosides from C. foetidissimma roots. A barrier seemed to obstruct feeding of the beetles on the upper surface of the cotyledons, even when the attractant cucurbitacins were applied.

Open Access

Abstract

Seedlings in cotyledon stage of the F1, F2, and backcross generations from a cross between (susceptible) ‘Black Zucchini’ (BZ) and (resistant) ‘Early Golden Bush Scallop’ (EGBS) Cucurbita pepo L. were studied, with the parents, for inheritance of susceptibility to cucumber beetle injury, cucurbitacin, and total sugar content. BZ had a higher cucurbitacin content than EGBS. Highest cucurbitacin B in BZ cotyledons occurred at full cotyledon expansion. Inheritance of cucurbitacin in cotyledons was controlled by a single gene; both insect injury and total sugar content appeared to be controlled by polygenic mechanisms comprised of at least 2 or 3 gene pairs each. Environmental, additive, and dominance variance and epinstatic interactions were determined for the 3 traits. A quantitative relationship between cucurbitacin concn and cucumber beetle feeding was evident in segregating populations. Heritable resistance to the beetle was discernible and can be achieved in cultivars by selecting for nonpreferred seedlings low in cucurbitacin concn.

Open Access

Abstract

Seed production based on number of seeds per berry differed in 4 clones of lowbush blueberry, Vaccinium angustifolium Ait. Large seeds were more viable than small seeds.

Open Access