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Zhanao Deng, Fahrettin Goktepe and Brent K. Harbaugh

cross (8 of 94). Thus, the recombination frequency varied from 0.0% (‘Candidum’ × ‘Gingerland’) to 8.9% (‘Florida Blizzard’ × ‘Gingerland’) among the five test crosses, and the average recombination frequency across the crosses was 4.4%. Foliar

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Zhe Cao, Shunzhao Sui, Qian Yang and Zhanao Deng

modes of inheritance for certain foliar characteristics. For example, the color of the midribs and the leaf variegation pattern in Dieffenbachia are reportedly controlled by dominant nuclear genes W m and Pv 1 , respectively ( Henny, 1982

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P.A. Bowen and W.M. Kliewer

Two-dimensional partitioning of variation was used to determine the sources of relationships between the yield and vegetative characteristics of three `Cabernet Sauvignon' grape (Vitis vinifera L.) clones. Clonal differences were found in shoot growth rate, but not in duration or total growth. A weak positive relationship between total shoot growth and yield resulted from a positive relationship between fruit set and growth duration. Relationships between cluster number and foliar characteristics indicated that light exposure in the previous year may have influenced both vegetative and reproductive development. The mean number of clusters per bud was positively related to the mean area, dry weight, and nitrogen content of leaves.

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Fazal Sultanbawa, Sharad C. Phatak and Casimir A. Jaworski

Caphea glutinosa is a herbaceous, low-growing annual, bearing numerous attractive purple flowers and has potential as an ornamental and as a ground cover. Plants exhibit winter hardiness in USDA plant hardiness zone 8. Tissue culture techniques were developed to obtain large numbers of uniform plants. Whole leaf explants (approximately 1.0 cm2) callused profusely in MS (Murashige and Skoog, 1962) medium containing 84 mM sucrose, 1% (w/v) Difco Bacto agar and 8.8 μM N6benzyladenine. Shoot formation from calli was observed in the same medium 4 weeks after explanting. Detached shoots were rooted (100%) in half strength MS medium and rooted shoots were transferred to Promix® in the greenhouse 2 weeks after rooting. Tissue cultured plants flowered after 60 days in the greenhouse and no phenotypic differences were observed in floral or foliar characteristics.

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Ryan N. Contreras, Ron Determann and Mara Friddle

There is a great deal of variation among japanese-cedar cultivars with regard to growth form, foliar characteristics, and winter browning. Differences in winter browning have been observed and documented by a number of authors. Previous research has established that there are differences in winter foliage color between cultivars included in the current study; however, no quantitative analysis under standardized conditions was conducted. Because of a previous report that tetraploid forms of japanese-cedar remain green during winter as a result of increased antioxidant enzyme activity, we hypothesized that cultivars that exhibit reduced winter browning were polyploids. We screened 56 accessions of japanese-cedar using flow cytometry analysis of 4′,6-diamidino-2-phenylindole (DAPI)-stained nuclei and performed chromosome counts on three cultivars. All accessions were diploid (2n = 2x = 22), although there were significant differences in genome sizes among the cultivars. Holoploid genome sizes ranged from 18.9 pg for var. sinensis JCRA to 22.3 pg for ‘Viridis’ with a mean of 20.1 pg. Chromosome counts for cultivars Ogon, Oye Keme, and Viridis supported the flow cytometry results. Although the underlying cause of the variability in morphology and winter browning among cultivars is unclear, our results show that differences in ploidy level are not responsible, because all tested genotypes were diploid. Chemical name: 4′,6-diamidino-2-phenylindole (DAPI).

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Christopher S. Cramer, Narinder Singh, Neel Kamal and Hanu R. Pappu

Iris yellow spot is an economically important disease of onion that reduces bulb size and yield and is difficult to control. The disease is spread by Thrips tabaci (onion thrips) and disease symptoms are exacerbated by hot, dry climatic conditions that also favor rapid thrips multiplication and make control programs less effective. Currently, no onion cultivar is resistant to the disease and/or thrips. Certain onion foliar characteristics have shown nonpreferential feeding activity by thrips and may be the first step in developing Iris yellow spot (IYS)-tolerant onion cultivars. Seventy-five onion PI accessions from the U.S. germplasm collection were evaluated for leaf color, waxiness (bloom), and axil pattern; thrips number per plant; and IYS disease severity under conditions that favored thrips and disease buildup. Plants of PI 289689 were less attractive to thrips and had a lower number of thrips per plant than plants of most other accessions. These plants were rated as having light green to green-colored foliage and a relatively low amount of epicuticular leaf wax. Plants of PIs 239633 and 546192 generally exhibited less severe IYS disease symptoms than those of other accessions. Individual plants, that exhibited less leaf area exhibiting IYS disease symptoms, were selected at bulb maturity from 22 different accessions with PI 546140 producing the largest number of selected bulbs. Physiological plant development, environmental conditions, and tolerance to plant stress may influence the degree of disease symptom expression. Further work that examines the role of plant maturity and host plant tolerance to stress with respect to disease expression is needed.

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Stephen L. Love, Bruce K. Werner, Horia I. Groza and Asunta Thompson-Johns

Nine commercially available true potato seed (TPS) hybrids were compared to four standard clonal cultivars with respect to mean and uniformity of foliar characteristics and tuber traits important to the North American potato industry. The TPS hybrids were planted using second vegetative generation tubers derived originally from botanical seed. Ten plants from each plot were individually evaluated for plant height, vine maturity, early blight symptoms, and verticillium wilt symptoms. Following harvest, yield was determined and the tubers were rated or measured for appearance, shape, specific gravity, and french fry color. The TPS hybrids had mean values for all tuber and foliar traits, except plant height, that were not significantly different from those of one or more of the cultivars; generally, values for the hybrids fell amid those of the cultivars. Two of the hybrids were taller on average than any of the four cultivars. In contrast to the means, trait uniformity of the TPS hybrids was consistently less than for the cultivars. For all foliar traits, except plant height, the TPS hybrids were substantially less uniform than the standard cultivars. For specific gravity and french fry color, two important processing quality traits, the hybrids tended to be less uniform than the cultivars; however, the difference was much less pronounced than for the foliar traits. Four of the hybrids were not significantly less uniform than one or more of the cultivars for french fry color and seven were not less uniform for specific gravity. For many market uses, the TPS hybrids appeared to have the tuber yield and quality characteristics needed to compete with standard clonally propagated cultivars.

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Zhanao Deng, Brent K. Harbaugh and Natalia A. Peres

-leaved caladium cultivars with novel combinations of foliar characteristics. Leaves of ‘UF-331’ are characterized by large dark green veins and white interveinal areas, which result in an attractive coloration pattern. Although the white face with green veins is

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Zhanao Deng, Brent K. Harbaugh and Natalia A. Peres

performance of cultivars grown under full sun conditions was evaluated in 2005 on the same plots used for evaluating tuber production. Plant height, number of leaves, and foliar characteristics were recorded ≈3 and 4 months after planting. The overall plant

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Zhanao Deng, Brent K. Harbaugh and Natalia A. Peres

numerous sun-damaged areas or holes on leaves and 5 being resistant to sun burns and not showing any sun-damaged areas. At ≈4 months after planting, plant height, number of leaves, and foliar characteristics were measured. ‘UF-172’ was vigorous, ≈50% taller