Dye transport through vascular pathways was examined in tissues surrounding the graft union of second-leaf, field-grown trees of `Lapins'/Gisela 5 (`Gi 5') (dwarfing) and `Lapins'/'Colt' (nondwarfing). Excavated, intact trees were allowed to take up xylemmobile dye via transpiration for 6 h before sectioning the tree into scion, graft union, and rootstock tissue. `Lapins'/'Gi 5' had a significantly larger stem cross-sectional area in the central graft union than did `Lapins'/'Colt'. Per unit cross section, dye transport of both `Lapins'/'Gi 5' and `Lapins'/'Colt' was significantly less in the graft union than in rootstock sections, with still less transported to scion tissues in `Lapins'/'Gi 5'. `Lapins'/'Gi 5' had a tendency to produce vascular elements oriented obliquely to the longitudinal axis of the tree. Dye was distributed more uniformly axially and radially across the graft union in `Lapins'/'Colt' than in `Lapins'/'Gi 5', with an apparent accumulation of dye in `Lapins'/'Gi 5' graft union. Xylem vessel diameters and vessel hydraulic diameters (VDh) were smaller overall in `Lapins'/'Gi 5' than in `Lapins'/'Colt'; however, graft unions in both had smaller VDh than did rootstock sections. These observations suggest reduced transport efficiency of xylem vessels in the graft union in `Lapins'/'Gi 5' may be due to smaller vessels, vascular abnormalities and/or increased amounts of callus and parenchyma tissue.
Mercy A. Olmstead, N. Suzanne Lang, Gregory A. Lang, Frank W. Ewers, and Shirley A. Owens
Ebrahim M. Khah, Konstantinos A. Akoumianakis, and Harold C. Passam
As good quality irrigation water becomes increasingly scarce in the Mediterranean region, especially in coastal areas where greenhouses are located, methods of economizing water consumption are essential. Therefore, the effect of the duration of irrigation on the quality and yield of seed of two cultivars of dwarf green bean (`Larma' and `Montano', Phaseolus vulgaris L.) was studied during fall and spring in Greece. Seeds were sown on 11 Sept. 2000 (fall crop) and 23 Feb. 2001 (spring crop) in peat compost and when the plants had two expanded leaves (11 and 20 days after sowing, respectively), they were transplanted to the soil of an unheated, plastic-covered greenhouse. The following irrigation treatments were applied: 1) irrigation for the entire duration (control), 2) irrigation until the first pods were dry, 3) irrigation until ≈50% of the pods had filled, and 4) irrigation till flowering. Fall cultivation was not suitable for seed production due to low yield and reduced seed quality. By contrast, the spring crop had a higher yield, seed size and good germination. Stopping irrigation of the spring crop at the drying of the first pods achieved an ≈20% saving in water without significantly affecting seed yield or quality. Earlier discontinuation of irrigation to achieve greater savings of water caused a reduction in yield, but did not affect seed quality.
Hazel Y. Wetzstein*, Allan M. Armitage, Gwen N. Hirsch, and Stephanie L. Anderson
Tissue culture is a useful means to clonally propagate new ornamental plant selections, particularly when plant material is limited and/or conventional propagation methods are ineffective. An efficient in vitro multiplication protocol was established to propagate a new goatsbeard hybrid (Aruncus dioicus, × A. aethusifolia). The hybrid is of interest because it exhibits a dwarf habit, delicate white flower panicles and fern-like leaves, yet is tolerant to heat and humidity. Experiments were conducted to evaluate explant type (nodes, stems, leaves, and floral parts), disinfestation procedures, and media formulations including varying concentrations of 6-benzylaminopurine (BAP) and naphthalene acetic acid (NAA). Rapid plant regeneration was obtained with a shoot organogenesis system using a half strength Murashige and Skoog medium supplemented with 4.4 μmol BAP, 0.54 μmol NAA, 30 g·L-1 sucrose, and 3.0 g·L-1 GelGro. Studies compared the performance and yield of plants rooted using different in vitro and ex vitro methods. Ex vitro rooting of shoots during greenhouse acclimatization under mist was most effective. Regenerated plants exhibited uniform and rapid growth, and performed well in greenhouse and field evaluations.
Takuya Tetsumura, Ryutaro Tao, and Akira Sugiura
A potentially dwarfing rootstock for japanese persimmon (Diospyros kaki L.) was propagated by single-node stem cuttings taken from root suckers. When a mature tree was cut down at ground level and part of the roots was exposed to the air, numerous suckers formed on the exposed parts of the roots. Single-node stem cuttings 3 to 4 cm (1.2 to 1.6 inches) long survived and rooted better than 10-cm (3.9-inch) and 25-cm (9.8-inch) leafy stem cuttings with several buds. Dipping cuttings in 3000 mg·L-1 (ppm) IBA for 5 s or in 25 mg·L-1 IBA for 24 h resulted in similar rooting. Most of the single-node stem cuttings taken in late-June and July survived and rooted well, whereas those prepared in late August rooted poorly and few survived. The survival and rooting percentages were unaffected by the position on the suckers (top vs. base) from which cuttings were taken. High relativehumidity in the propagation frame appeared to enhance survival and rooting. This clonal propagation method will make a rapid multiplication of japanese persimmon, a difficult-to-root species, possible. Chemical name used: indole-3-butyric acid (IBA).
M. A. L. Smith, S. L. Knight, and M. J. Bass
A whole plant microculture (WPMC) screening system facilitated rapid, quantitative appraisal of salt stress effects on `Micro-Tom' miniature dwarf tomato. Axillary bud explants were micropropagated on a hormone-free control medium (conductivity = 3.3 dS m-1), gradually introduced to treatments with increasing NaCl or Na2SO4 concentrations via biweekly subculture to fresh media (7,6, 12.8, or 18 dS m-1), and monitored over a subsequent 5 week culture period. Non-intrusive video image analysis techniques were adapted to quantify morphometric (shoot growth rate, area, and length; root length and area) and photometric (ruler and tissue quality) plant responses. Shoot growth was only slightly inhibited at 7.6 and 12.8 dS m-1, but was severely stunted and distorted on high salt (18 dS m-1) media. Root growth inhibition (significantly shorter and thinner primary rants) was first evident at 12.8 dS m-1 after 3 weeks of treatment. At 18 dS m-1, conspicuous retardation of root growth relative to controls could be gauged after only one week. Shoot tip chlorosis was observed in the lowest salt-supplemented treatment after three to four weeks of culture, but overall shoot yellowing at the two highest conductivities was marked after only a few days. Chlorosis symptoms were not uniform within treatments. Cell osmotic concentration showed a linear increase with increasing medium salinity. The WPMC system expedited time course observations of stress symptom development, paralleled stress response trends observed in solution culture tests, and provided an excellent vehicle to investigate plant adaptation to saline conditions.
Nirmal K. Hedau, Shri Dhar, Vinay Mahajan, Hari S. Gupta, Karambir S. Hooda, and Vedprakash
al., 2004 ). Because of the dwarf plant habit, short duration, and quality pods, ‘Contender’ has been widely cultivated by the Indian farmers of northwestern Himalayan states (Uttarakhand, Himachal Pradesh, Jammu, and Kashmir). Hence, in this article
Shahab Hanif-Khan, Robert C. Bullock, Peter J. Stoffella, Charles A. Powell, Jeffrey K. Brecht, Heather J. McAuslane, and Raymond K. Yokomi
Silverleaf whitefly (SLW) (Bemisia argentifolii Bellows and Perring) feeding was associated with development of tomato irregular ripening (TIR) symptoms. `Micro-Tom', `Florida Basket', `Florida Lanai', and `Florida Petite' dwarf cherry tomatoes (Lycopersicon esculentum Mill.) were infested with adult SLW to observe oviposition preference, plant tolerance, and TIR symptom development in two experiments. There was no oviposition preference among the cultivars in either of the trials. TIR fruit symptoms were expressed as longitudinal red streaks with yellow, green, pink, or red blotches externally and white tissue internally. External TIR symptoms at the pink stage of ripening ranged from 32% (`Micro-Tom') to 82% (`Florida Basket') in Expt. 1 and 44% (`Micro-Tom') to 93% (`Florida Petite') in Expt. 2. In Expt. 1, external TIR symptoms disappeared from 18% (`Florida Lanai') to 37% (`Micro-Tom') and, in Expt. 2, 16% (`Micro-Tom') to 39% (`Florida Basket') of the fruit during ripening. SLW-infested plants exhibited 82% (`Florida Lanai') to 99% (`Florida Basket') and 76% (`Micro-Tom') to 90% (`Florida Petite') of fruit with internal white tissue regardless of external symptoms in Expts. 1 and 2, respectively. Tomatoes with severe TIR symptoms rarely ripened to full red. Postharvest characteristics of ripening SLW-infested and control fruit were evaluated (Expts. 3 and 4). Generally, the SLW-infested fruit were lighter in color than the control fruit. The control fruit developed normal red color while the SLW-infested fruit developed a blotchy, streaky color that was overall more of an orange-red. SLW-infested fruit were firmer than the control fruit in both experiments. Ethylene production was higher in SLW-infested fruit. While the total soluble solids contents were not significantly different between the treatments, the SLW-infested fruit were more acidic than the control fruit. Each cultivar was susceptible to oviposition by SLW and induction of TIR symptoms. However, TIR symptom expression differed among the cultivars. Despite higher ethylene levels, the ripening process in the SLW-infested fruit appeared slower or may have been inhibited by factors induced by the SLW compared with the control fruit, which ripened normally.
Mikeal L. Roose, Frank Suozhan Cheng, and Claire T. Federici
The `Flying Dragon' cultivar of Poncirus trifoliata L. Raf. is a strongly dwarfing rootstock for Citrus cultivars, reducing canopy volume of 9 year-old `Valencia' orange trees to 1/3 that of trees on standard rootstocks Open-pollinated seed of `Flying Dragon' was screened with isozyme markers to distinguish zygotic from nucellar (apomictic) seedlings. All zygotics had genotypes consistent with an origin by self-pollination. Zygotic seedlings were budded with `Valencia' orange scion and planted in the field. Of 46 progeny evaluated as rootstocks, 35 produced small trees similar to those on nucellar `Flying Dragon' and 11 produced large trees. This ratio is consistent with the 3:1 segregation expected for a single dominant gene. The dwarfing gene was closely linked, or pleiotropic with a gene causing curved thorns and stems. Several RAPD markers close to the dwarfing gene were identified with bulked segregant analysis. `Flying Dragon' apparently originated as a mutation because it had au identical genotype to non-dwarfing strains of trifoliate orange at all 38 isozyme and RFLP markers tested
Darunee Thawornchareon, Unaroj Boonprakob, and Kriengsak Thaipong
‘KU Garnet No.1’ is a maroon-leaved dwarf guava suitable as an ornamental plant that can be grown either directly in the landscape or for container production. In addition, ‘KU Garnet No.1’ produces year-round sweet, edible fruits containing high
Robert M. Frymire and Janet C. Henderson
Uniform liners of pyracantha (Pyracantha coccinea Roem `Lalandei'), photinia (Photinia × fraseri Dress) and dwarf Burford holly (Ilex cornuta Lindl. and Paxt. `Burfordii Nana') were potted into 3.8 liter containers in a pine bark:sand medium. Ten weeks later, plants received uniconazole treatments as a media drench or foliar spray. The uniconazole drench rates were 0, 0.5, 1.0, and 3.0 mg ai per container for all three plant species. The foliar application rates were 0, 50, 100 and 150 ppm for pyracantha, 0, 25, 50 and 100 ppm for photinia, and 0, 10, 25, and 50 ppm for dwarf Burford belly. Plant heights and widths were recorded at 3 week intervals, and leaf chlorophyll content was determined by calorimeter at the same time as height and weight measurements. At harvest, leaf counts, leaf areas, and shoot, leaf and root dry weights were determined. Initial results indicate that both foliar and media drench treatments of uniconazole reduced growth of pyracantha and photinia at all rates. Only the two highest rates decreased growth of dwarf Burford holly when applied as either a media drench or a foliar spray.