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  • Author or Editor: B. B. Rhodes x
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Abstract

Eleven of 39 varieties and lines resulted in good canned slice color in both unusually warm and unusually cool growing seasons for carrots. A number of lines showed seasonal interaction in color, with better color in the cool season, while others resulted in consistently fair or poor color in both growing seasons. No single pigment was highly correlated with color across the range of environmental and genetic diversity encountered in the study. Beta-carotene was the only single component showing a significant positive correlation with color. The highest multiple relationship with color considered beta-carotene, other carotenes except alpha carotene, and xanthophylls. Within a season this multiple correlation accounted for 47 to 50% of the color variance (R of .710 for spring and .686 for fall grown carrots).

Open Access

Abstract

Significant differences in oxalate levels were obtained with hybrid progeny of Dieffenbachia picta (Schott) ‘Exotica’ which indicate a potential for selection for low oxalate levels.

Open Access
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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

Watermelon (Citrullus Lanatus (Thunb.) Matsum and Nakai) and muskmelon (Cucumis melo) were regenerated from immature cotyledons cultured on MS medium containing 10 μM BA. Small population of watermelon and muskmelon regenerants contained tetraploids as variants. The tetraploid individuals were recognized by morphological features including enlarged leaves, tendrils, male flowers, and variable pollen grains. After self-pollination, seed lots reflected differences in size expected from tetraploid parents.. Cytological data from root tips of R1 populations will be presented.

Free access

Vitrification, a physiological disorder characteristic of in vitro grown plants, was observed in single-node cultures of sweet potato in mannitol-enriched medium during their second year of storage. Vitrified or vitreous sweet potato plantlets were watersoaked, translucent or glassy in appearance, with thick, swollen, leaves and stems, stunted shoot growth and poor root growth. These plantlets were not able to regenerate normal plants when transferred into fresh regeneration medium nor were they able to survive outside culture conditions.

Electron microscopy revealed changes in the ultrastructures of vitrified sweet potato plantlets. Vitrified plants had defective stomatal complex, starch grain-filled chloroplasts, disrupted cell wall, big air spaces (lacunae), high frequency of cell membrane separation from the cell wall, nuclear disintegration, and cytoplasmic disorganization. These changes in the internal structures of vitrified plants were reflected in their abnormal morphology and physiology.

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Vitrification, a physiological disorder characteristic of in vitro grown plants, was observed in single-node cultures of sweet potato in mannitol-enriched medium during their second year of storage. Vitrified or vitreous sweet potato plantlets were watersoaked, translucent or glassy in appearance, with thick, swollen, leaves and stems, stunted shoot growth and poor root growth. These plantlets were not able to regenerate normal plants when transferred into fresh regeneration medium nor were they able to survive outside culture conditions.

Electron microscopy revealed changes in the ultrastructures of vitrified sweet potato plantlets. Vitrified plants had defective stomatal complex, starch grain-filled chloroplasts, disrupted cell wall, big air spaces (lacunae), high frequency of cell membrane separation from the cell wall, nuclear disintegration, and cytoplasmic disorganization. These changes in the internal structures of vitrified plants were reflected in their abnormal morphology and physiology.

Free access

Tetraploids are needed to synthesize triploid watermelons, which produce “seedless” fruit with improved quality. Traditionally, the tetraploids are induced by applying colchicine to the growing apex of seedlings or soaking the seeds with colchicine solution. This method often produces low frequency of tetraploids and high frequency of chimeras. Breeding tetraploids takes much longer time than breeding diploids because of the low female fertility. We developed a tissue culture approach that allows breeders to develop desirable tetraploids with commercially acceptable volume of seed in 2 years. This tissue culture approach includes: 1) regenerate plants via shoot organogenesis from cotyledon tissue; 2) screen tetraploids based on leaf morphology (more serrated leaf margin and wider leaf shape) before transplanting, and confirm tetraploids based on pollen morphology (larger pollen with four copi) and/or seed characteristics; 3) self-pollinate tetraploids or cross the tetraploids with diploids to accurately estimate the female fertility; 4) micropropagate the best tetraploid(s) using axillary buds during the off-season; and 5) produce tetraploid seed from the cloned tetraploids in an isolation plot and evaluate the triploids derived from the tetraploid(s) in the following season. This approach has been practiced on more than 20 genotypes over the past 4 years.

Free access

Abstract

Watermelons Plant Introductions (PI) 189225, PI 271775, PI 271778, and PI 299379 were resistant to a population of Colletotrichum langenarium (Pass.) Ell. & Halst. in 3 states. Entries PI 203551, PI 270550, and PI 271779 were resistant in some field and greenhouse tests.

Open Access

Abstract

‘Green Ice’ is a green-fleshed muskmelon (Cucumis melo L.) adapted to the climatic conditions prevalent in the southeastern United States and is well-suited for both commercial and home garden production. It is a high-yielding ‘Honey Ball’-type muskmelon that produces round to oval, pale gray-green, medium-sized fruit that turn cream-colored and slip from the vine at maturity. The thick light-green flesh has a pleasing aroma and sweet flavor and is high in vitamin C. The vigorous plants are resistant to race 3 of powdery mildew [Spaerotheca fuliginea (Schlect ex Fr.) Poll.] and tolerant to most pests and environmental stresses of the region.

Open Access

Hybrid seed production can be facilitated by using male sterility coupled with a seedling marker. This research was initiated to combine the ms male sterility and dg delayed-green seedling marker into watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] lines. Male-sterile plants of the male-sterile line G17AB were crossed with plants of delayed-green breeding line Pale90, which has yellow cotyledons and pale-green, newly developed, true leaves. The double-recessive recombinants, male sterile and delayed green, from the F2 population were backcrossed to the male-fertile plants of G17AB. The pedigree method was used for selection in the progenies. The segregation ratios obtained from F2 and BC1F2 populations suggest that the male-sterile and delayed-green traits are inherited independently and that delayed green is inherited as a single recessive nuclear gene. Two male-sterile watermelon lines with delayed-green seedling marker have been developed. These lines will provide a convenient way to introduce male sterility and the delayed-green seedling marker into various genetic backgrounds. These two lines can be used for testing the efficiency of a new, hybrid, watermelon, seed production system.

Free access