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  • Author or Editor: P.W. Simon x
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Genes for reduced carotene content (white, yellow, and pale orange) and for anthocyanin pigmentation were identified in Daucus carota PI 173687 and in progeny derived from crosses of this Plant Introduction with orange-rooted inbred lines. Monogenic inheritance for each of these root color variants was examined. Mixed cell cultures of callus derived from white and orange roots indicated autonomy of carotene gene expression in carrot cell cultures. Strategies for incorporation of carrot genes conditioning pigment content will depend upon gene combinations sought.

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The effects of cold storage, photoperiod, and growth temperature on flowering incidence in four clones of garlic (Allium sativum L.) were studied. While flowering percentage was influenced most by clone, interactions with photoperiod, growth temperature, and storage occurred. Clone R81 flowered equally well in all conditions, whereas flowering percentage of clones D129, D130, and PI485592 was reduced by cold (4C) storage of either bulbs or plants, long (16-h) photoperiod, and at 18C relative to 10C. The highest flowering percentage in all garlic clones was achieved by growing plants at 10C under short (9- to 10-h) photoperiod with no cold storage of bulbs before planting.

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Three orange-mesocarp derivatives of the xishuangbannan cucumber (Cucumis sativus L. var. xishuangbannanesis Qi et Yuan), P100, P101, and P104; and NPI (P105), an unrelated cucumber (Cucumis sativus L.) reported to have orange flesh, were selected as parents for a diallel experiment to evaluate inheritance of orange cucumber mesocarp pigment over 3 years. Visual color intensity and carotenoid content were closely related. A preponderance of additive genetic effects for cucumber mesocarp pigmentation was observed in grade size 2 fruit (immature fruit used for pickling). Both additive and nonadditive genetic effects were important in grade size 4 fruit (mature). Years and yea× genotype interactions were highly significant for pigmentation of size 2 fruit, indicating the importance of environment on the expression of pigmentation in this size class. In contrast, color development was stable among years for size 4 fruit. P104 exhibited high general combining ability (GCA) estimates for size 4 fruit pigmentation across years, while P101 had high GCA estimates for size 2 fruit. The diallel analysis illustrated high fruit carotene content of parents per se. However, most hybrid combinations of the diallel reduced carotenoid content relative to parents, indicating both dominance for low carotenoid content for both fruit sizes and lack of genetic complementation among parents to enhance fruit color. Genetic control of pigmentation in size 2 fruit appeared to be independent of that for size 4 fruit.

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Despite its long history of obligate vegetative propagation, garlic (Allium sativum L.) exhibits a surprisingly large amount of variation between clones, as evidenced by both morphological and isozyme markers. As reported previously, several garlic clones which produce viable seed have been identified in the Wisconsin collection, and a possible correlation between clone fertility, morphology, and isozyme banding patterns was examined. The potential use of isozymes to analyze sexually-derived hybrid garlic lines, haploids, and interspecific hybridizations was also investigated.

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Garlic (Allium sativum L.) is an obligate apomict which reproduces almost exclusively by means of division of underground cloves or by propagation of topsets. The occurrence of viable, sexually-derived garlic seeds is rare. In order to assess the factors that limit garlic seed production, variables that affect flower initiation and development were studied. The effects on flowering of daylength, growing temperature, bulb and plant cold storage conditions, and cultivar were examined by observing flower development in plants grown under controlled greenhouse conditions. Correlations between isozyme markers and flowering, fertility, and morphological markers will be presented for a diverse collection of garlic clones, including six sexually-derived garlic plants.

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Abstract

Eighteen methods were evaluated to quantify reducing sugars in carrot (Daucus carota L.) roots using drops of juice spotted onto chromatography paper. Reducing sugar detection with dinitrosalicylic acid was rapid (12 to 30 samples per hr) and correlated very well with values obtained by use of high performance liquid chromatography (r = 0.88 overall, ranging from 0.76 to 0.98 in a genetically diverse range of populations). High reducing sugar, low sucrose (Rs/) roots could be distinguished from low reducing sugar, high sucrose (rs/rs) roots with little error. This method readily complements soluble solids measurement.

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Abstract

Four hybrids of carrot (Daucus carota L.) were analyzed raw, fresh-cooked, canned-cooked, or frozen-cooked for sensory and objective parameters. Processing reduced the carotenoid and volatile terpenoid concentrations of all hybrids. Relative to raw carrots, sugar content was reduced in canned-cooked and frozen-cooked carrots, but was increased in fresh-cooked samples. Depending on the hybrid, 6% to 32% of the free sugar was reducing sugar in raw samples; however, sugars in processed samples were 15% to 33% reducing sugar. Fresh-cooked and frozen-cooked carrots exhibited a 10-fold reduction in shear pressure texture relative to raw texture, while canned carrots had a 30-fold reduction. Harsh flavor was reduced greatly by canning and freezing, but was not reduced as much in fresh-cooked samples. These differences in harsh flavor could be accounted for by variation in volatile terpenoid levels. Differences in sweetness found between raw sampling hybrids also were observed for corresponding samples after processing. Reducing sugars and volatile terpenoids contributed to variation in sweetness and preference.

Open Access

Abstract

Reducing sugar (glucose and fructose) and sucrose are the major free sugars (total sugars) in the carrot root. Striking genetic variation exists for the reducing sugar/total sugar ratio (percentage of reducing sugar). Inbred carrot lines with high and low percentages of reducing sugar were used as parents in establishing various F1, F2, F3 and backcross populations to study the inheritance of root sugars. It was determined that a single major gene regulates the reducing sugar to sucrose balance in carrot roots with dominance for high percentage of reducing sugar. We propose that this gene be designated Reducing sugar, symbolized Rs. This relationship is of interest since sugars in the carrot root are a major storage carbohydrate and a primary component of carrot flavor.

Open Access

Nematodes impart significant damage to carrot production worldwide. Genetic resistance was studied for Meloidogyne javanica, one of the three major nematodes affecting carrots in warmer climates. F2, F3, and backcross families of `Brasilia' × B6274 were evaluated for resistance in inoculated seedlings. Resistance was conditioned by one, or two linked, dominant loci. Molecular markers were also evaluated with bulked segregant analysis. Three RAPD markers and AFLPs were associated with resistance loci.

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