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The objective of this study was to determine if selected strains of Agrobacterium could infect microshoots of Rhododendron catawbiense. Fifteen microshoot stems of R. catawbiense var. album `America', `Joe Paterno', and `Cunningham's White' were inoculated with two drops (about 25 μL) of wild type Agrobacterium tumefaciens strains C58 or B6 or with wild type A. rhizogenes strain E8/73. Five control shoots were inoculated with 1.2 mM KH2PO4 buffer. Microshoots were grown on woody plant medium (WPM) supplemented with 4.9 μM 2iP. Six weeks after inoculation galls that formed were excised from the microshoots and placed on WPM that lacked plant growth regulators but contained 300 mg·L-1 cefotaxime. In another study, these wild-type bacterial strains were genetically modified by inserting the pBINm-gfp5-ER plasmid, which contained genes coding for NPTII and green fluorescence protein (GFP), into the bacteria. These modified strains were inoculated on 15 stems of the three rhododendron cultivars and one variety. Calluses that formed were excised, placed on basal WPM with cefotaxime, and allowed to proliferate. Wild type C58 induced galls to form on `Joe Paterno', R.c. album, and `Cunningham's White' stems, whereas wild type B6 caused galls to form only on the latter two types of rhododendron. Wild-type E8/73 failed to induce gall formation on the rhododendrons. Only genetically modified B6 caused galls to form on only `Cunningham's White' microshoots (seven of 15 inoculated stems). Three of these galls fluoresced green under ultraviolet light. Physical presence of the NPTII and GFP genes in the plant genome was determined by polymerase chain reaction. This study demonstrated that R. catawbiense is susceptible to Agrobacterium infection, and this plant can be genetically transformed.
An apple (Malus domestica cv. Empire on M9/MM111 rootstock) orchard groundcover management systems (GMSs) study has been underway since 1992 in Ithaca, N.Y. Four GMS treatments are applied each year in 2-m wide tree-row strips: Pre-emergence herbicides (Pre-H: diuron + norflurazon + glyphosate); Post-emergence herbicide (Post-H: glyphosate); mowed-sod (Grass); and composted hardwood bark mulch (Mulch) treatment. The soil (silty clay loam) physical and chemical conditions have been monitored continuously. In May and Sept. 2003, we sampled topsoil beneath trees in each GMS and used PCR-DGGE combined with sequencing to characterize soil microbial community composition. Mulch had more culturable soil bacteria than the Pre-H treatment. Soil in Grass plots had the most culturable soil fungi. Soil microbial respiration rates were higher in Mulch than Grass and herbicide GMSs. Surface vegetation in the Grass and Post-H plots strongly influenced soil bacterial community composition. In Principal Component Analyses, Post-H and Grass treatments comprised one variance cluster, and Pre-H and Mulch treatments another. The soil fungal community was less diverse (fewer DGGE bands) than the bacterial community, and was less affected by GMS. Treatments with more surface vegetation (Post-H and Grass) also had more free-living and phytonematodes than Pre-H and Mulch. A total of 47 clones from 12 DGGE bands yielded 31 unique DNA sequences. Of these, 15 were novel sequences with no matches in the GenBank (NCBI) database. Another 10 (27 clones) could be matched with known fungal species at 96-100% identity. The primer pair used, ITS1F/ITS2, amplified a considerable number of Basidiomycetes and Ascomycetes, but there was no amplification for Zygomycetes and Oomycetes.
Fruit from five apple (Malus domestica Borkh.) cultivars were pressure-infiltrated at 103 kPa for 6 min with a 0%, 0.73%, 1.46%, 2.91%, or 5.82% (w/v) Ca-equivalent solution of CaCl2, Ca EDTA chelate, or buffered CaCl2 solution (Stopit). The fruit were stored at 0 ± 1C for 18 weeks and then evaluated for Ca content, firmness, and injury. Fruit treated with Ca chelate had no increase in fruit Ca content and were injured at all treatment levels. No significant differences occurred in fruit Ca levels between CaCl2 and Stopit treatments across all cultivars tested. Apples treated with Stopit were firmer than apples treated with CaCl2, when averaged across cultivars. Fruit Ca levels, firmness, and incidence of injury were positively correlated with concentrations of CaCl2 and Stopit for all cultivars.
The effects of organosilicone and more conventional hydrocarbon surfactants on postharvest radiolabeled calcium (Ca) and on Ca solution infiltration into `Golden Delicious' apples were examined to provide a direct and more efficient pressure infiltration technique to increase fruit Ca concentration. Both radiolabeled Ca infiltration and the proportional increase in fruit Ca estimated by fruit weight gain from Ca solutions of known concentration were significantly enhanced by a range of surfactants having differing chemical structures. Two organosilicone surfactants, Silwet L-77 and Silwet L-7604, known for their greater capacity to lower the surface tension of solutions than conventional hydrocarbon surfactants, were the best among the surfactants tested at augmenting Ca infiltration. Applications of surfactants to fruit were as effective or more effective when used as a pretreatment rather than by mixing with Ca solutions. The applied atmospheric pressure necessary to infiltrate Ca to levels considered sufficient to maintain fruit firmness and resist decay during storage could be lowered in fruit treated with organosilicone surfactants. Postharvest surfactant and Ca treatments may offer a practical means of increasing the Ca concentration of apple fruit.
A matriconditioning procedure based on the matric properties of Micro-Cel E and expanded vermiculite #5 has proved effective in improving seedling emergence in growth chambers. The major objectives of this study were to examine some physical characteristics of the carriers and their effectiveness as preplant conditioning media in improving stand establishment of vegetable seeds in field plantings. Carrier characteristics included no detectable solute or osmotic potential, low electrical conductivity (0.48-0.04 mmho/cm), high water-retaining capacity (450% to 600%), a pH range of 7.0 to 8.4, and ability to effectively control seed hydration (conditioning) at low matric potential. The seed: carrier: water ratio for seed conditioning ranged from 1:0.3-0.5:1-2 (by weight). In a field trial, conditioning of `Long Imperator' and `Nantes' carrot (Daucus carota var. sativus Hoffm.) seeds reduced the time to 10% of final emergence (T10) by 2.6 to 2.8 days and to 50% of final emergence (T50) by 2.1 to 3.0 days. Conditioning increased the final emergence percentage by 39% in 1-year-old `Long Imperator' compared to 150% in 4-year-old `Nantes' seeds. In another field trial, the effect of conditioning on stand establishment was evaluated in `Jackpot' tomato (Lycopersicon esculentum Mill.), `California Wonder' pepper (Capsicum annuum L.), and `BBL 47' snap bean (Phaseolus vulgaris) seeds. In tomato, conditioning reduced the T10 by 0.9 day, had no effect on T50, and increased the emergence percentage by 86%. In pepper, conditioning reduced the T10 and T50 by 1.5 days and increased the percentage emergence by 30%. In snap bean seeds, conditioning in Micro-Ccl E reduced the T10 and T50 by 0.8 day but adversely affected the percentage emergence. Further reductions in T10 and T50 (1.2 and 1.6 days, respectively) and restoration of percentage emergence to control level occurred upon addition of 0.001 mM GA3 during conditioning. Fungicides added to carrot, tomato, and pepper seeds, with or without conditioning, showed no additional improvements and, in a few cases, adversely affected emergence. A preplant conditioning in Micro-Ccl E, alone or in combination with GA3, smears to be a viable alternative to conditioning! seeds in liquid carriers. Chemical name used: gibberellic acid (GA3)
The effects of 36 organosilicone and conventional carbon-based surfactants on postharvest infiltration of radiolabeled and unlabeled Ca solutions into `Golden Delicious' apples (Malus domestica Borkh) were examined to devise a more efficient pressure infiltration technique to increase fruit Ca concentration. Radiolabeled Ca infiltration and the proportional increase in fruit Ca estimated by fruit weight gain from Ca solutions of known concentration were significantly enhanced by a range of surfactants having different chemical structures. Tween 60 and 80; Triton X-45, X-100, X-114, X-305, and X-405; and Silwet L-77 and L-7604 enhanced Ca infiltration. The two organosilicone surfactants, Silwet L-77 and Silwet L-7604, known for their greater capacity to lower the surface tension of solutions than conventional carbon-based surfactants, were the most effective at augmenting Ca infiltration. Applications of surfactants to fruit were as or more effective when used as a pretreatment rather than mixing the surfactant with the Ca solutions. The pressure necessary to increase Ca to levels considered sufficient to maintain fruit firmness and resist decay during storage could be lowered in fruit treated with organosilicone surfactants. Sequential postharvest surfactant and Ca treatments may be a practical means of increasing the Ca concentration in apples.
Prestorage infiltration of `Golden Delicious' apples (Malus domestica Borkh.) with calcium (Ca) retarded texture changes during storage at 0C and inhibited ethylene production of the fruit at 20C. Infiltration of the fruit with the polyamines (PA) putrescine (PUT) or spermidine (SPD) also altered texture changes, but did not inhibit ethylene production. When the fruit were treated with Ca first and then with PA, cell wall-hound Ca concentrations increased 4-fold, but PA levels in the cell wall increased only slightly. When the fruit were treated with PA first and then with Ca, PA levels in the cell wall increased 3-fold, but Ca concentration increased only 2-fold. These results indicate that Ca and PA may he competing for the same binding sites in the cell wall and that the improvement of fruit quality during storage by these cations could involve strengthening of the cell wall.
Seeds of Aquilegia chrysantha Gray were germinated under a variety of temperature regimes. Germination was nearly 90% under a day/night cycle of 25/20C, but was reduced to ≤ 40% under constant 25C or a 25/10C day/night cycle. With days between 25 and 29C (night = 20C), germination percentage dropped gradually to ≈ 60% with increasing temperature. With days >29C, germination declined dramatically such that no germination occurred at 31C. Neither kinetin (4.6 to 46 μm) nor ethephon (6.9 to 207 μm) was able to reverse the inhibitory effects of 33C days. Our results indicate that germination of A. chrysantha seed is sensitive to temperature and that germination ≈ 75% can be obtained under a 25 to 27C day/20C night regime. Chemical names used: 2-chloroethylphosphonic acid (ethephon); 6-furfurylaminopurine (kinetin).
Factors affecting the greenhouse propagation of firebush (Hamelia patens) by leafy stem cuttings during winter were studied. Without bottom heat (BH), mid-day rooting medium temperature was 22 ± 3 C. About half of the auxin-treated cuttings without BH rooted. Maintaining the rooting medium at 29-39 C increased rooting for auxin-treated cuttings to 96-100% and increased root length and visual rating scores several-fold. Rooting percentage, root length, and visual ratings were consistently high in perlite and low in peat. Stem-tip cuttings and sub-terminal stem segment cuttings with basal stem diameters of 3-5 mm rooted slightly better than stem segment cuttings with basal diameters of 6-8 mm. Stem-tip cuttings not treated with auxin but with BH had rooting percentages of 81-86%. Treatment of stem-tip cuttings with auxin generally yielded 90% rooting or above. Despite this, plants grown from auxin-treated cuttings were indistinguishable from plants grown from non-treated cuttings 2 months after the rooting period. Of the variables studied, BH had the most dramatic effect on rooting of firebush cuttings during winter months.
Seeds of Aquilegia chrysantha Gray were germinated under a variety of temperature regimes. Germination was nearly 90% under a day/night temperature regime of 25/20C but was reduced to 40% or less under constant 25C or a 25/10C day/night temperature regime. At day temperatures between 25 and 29C (night temperature = 20C), germination percentage dropped gradually to about 60% with increasing temperature. Above a day temperature of 29C, germination declined dramatically such that no germination occurred at 31C. Neither kinetin (1-10 mg/liter) nor ethephon (1-30 mg/liter) were able to reverse the inhibitory effects of a 33C day temperature. Our results indicate that seed germination of A. chrysantha is quite sensitive to temperature and that germination percentages of 75% or greater can be obtained under a 25-27C day/20C night temperature regime.