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Abstract
In the laboratory, sections from leaves of peach [Prunus persica (L) Batsch. cv. Lovell] were treated with chemicals previously reported to have potential as peach fruit thinning agents. The resultant evolution of ethylene from the treated leaves was compared with the amount of peach fruit thinning by the same chemicals. A positive correlation exists between the level of ethylene evolution and the amount of fruit thinning by the chemicals tested.
Sap flow rates of three Cercis spp. exposed to supraoptimal root-zone temperatures were characterized in a controlled environment chamber using a water bath to control temperatures. Flow rates of sap in the xylem were measured every 15 sec. and averaged over 15 min. intervals. Sap flow measurements were correlated to root-zone temperatures recorded during the same time intervals. Whole plant transpiration was measured gravimetrically. Root-zone temperatures were maintained at 22C for three consecutive 24-hr cycles and then increased to 45C for an additional three 24-hr periods. All plants, regardless of species, had reduced sap flow patterns when exposed to high root-zone temperatures. Plants maintained at a constant temperature of 22C showed no extreme fluctuations in sap flow rate. Stomatal conductance rates and leaf water potentials showed similar trends to whole plant transpiration.
The species of section Batatas represent the primary potential source of wild germplasm for sweet potato breeding. Their wide distribution and adaptation make their use desirable, but their direct use is constrained by their ploidy level (2x, and 4x, in contrast with cultivated I. batatas which is 6x) and lack of storage root production.
We investigated 4x clones of interspecific origin (6x I. batatas 2x I. trifida) as bridges to introgress genes from several wild species of the section Batatas to I. batatas. Six 2x wild species from different origins were reciprocally crossed to the 4x clones. The crosses were successful only when the diploid wild species were used as females (2x × 4x) indicating unilateral interspecific incompatibility. The unsuccessful types of crosses (4x × 2x) were repeated using wild hybrid males containing I. trifida in their parentage. This time only those crosses involving a hybrid having I. trifida as its female parent produced seeds. Progenies from the successful 2x × 4x crosses were diploid instead of the expected triploid. Triploid progenies were obtained only in the 4x × (2x hybrid) crosses. Some triploid progenies produced 2n pollen in varying frequencies. These results show different levels of crossing barriers among Ipomoea species and give us alternative pathways for overcoming them. I. trifida was identified as a possible bridge species.
Root-zone temperature fluctuations and sap flow rates were characterized for several woody ornamental plants in a controlled environment using a water bath to control temperatures. Flow rates of sap in the xylem were measured every 15 seconds and averaged over 15 minute intervals. Sap flow measurements were correlated to root-zone temperatures recorded during the same time intervals. Whole plant transpiration was measured gravimetrically. Root-zone temperatures were raised from 22°C to 45°C (slightly below lethality between 9:00 am and 12:00 noon, held at that temperature until 4:00 pm, and then allowed to cool. There was a pronounced diurnal change in flow rate with peak flow during mid-morning declining in mid-afternoon. The decline in the rate of sap flow occurred at a faster rate than the decline in root-zone temperature. This diurnal flow rate was most pronounced during the first 24-hour elevated temperature cycle. Plants maintained at a constant temperature of 22°C showed no such extreme fluctuations in sap flow rate. Stomatal conductance measured with a porometer showed similar trends to whole plant transpiration.
More than 300 red raspberry cultivars and selections were screened for raspberry (Rubus idaeus L.) bushy dwarf virus (RBDV), tobacco streak virus (TSV), and tomato ringspot virus (TomRSV) using enzyme-linked immunosorbent assay in three naturally infected breeding program selection plots at Corvallis, Ore. All genotypes tested negative for TSV and TomRSV. The RBDV incidence in primocane-fruiting cultivars and selections was 67%; in floricane-fruiting genotypes, it was 34%. The pattern of RBDV infection in the field showed no discernible trend. The high incidence may have been due to use of infected parents, propagation of infected genotypes, and pollen transmission. `Willamette', considered to be immune to the common strain of RBDV, along with 14 clones that had been in the field 10 years or longer, tested negative. The high incidence of RBDV in the breeding plots may provide an opportunity to identify resistant parents for breeding programs. An early seedling screening method for RBDV susceptibility is desirable to eliminate highly susceptible genotypes from the program and maintain a lower incidence of RBDV within the breeding plots.
Red raspberry (Rubus ideas L.) selection fields in Oregon were screened to determine the incidence and prevalence of Raspberry Bushy Dwarf Virus (RBDV), a pollen-borne virus, using enzyme-linked immunosorbent assay (ELISA). In total, 365 genotypes were tested from three different fields which contained both junebearing (JB) and primocane fruiting (PF) clones. Positive RBDV infected genotypes were 29% JB and 65% PF; 30% JB and 72% PF; 42% JB and 64% PR in the 1991, 1989-90, and 1985-89 established fields, respectively. Examination of all pedigrees of RBDV positive and negative JB selections were very similar containing both susceptible and resistant cultivar parents, especially `Willamette,' considered immune. The PF selection pedigrees were very different from the JB pedigrees with the resistance status of the cultivar parents largely unknown. RBDV resistant genotypes from these selection plots could be useful parents in breeding programs.
Hydroponic greenhouse tomato production’s popularity has grown in the United States to meet the demands for year-round availability of fresh tomatoes. Although Salmonella has been the cause of several foodborne illness outbreaks linked to tomatoes, the potential for contamination in hydroponic production is not well understood. The objectives of this study were to determine whether biweekly inoculation of Salmonella in a hydroponic tomato nutrient solution would lead to Salmonella survival and contamination of the tomato fruit and plants, hydroponic nutrient film technique (NFT) troughs, and water receptacles. An avirulent strain of Salmonella Typhimurium was used to contaminate the nutrient solution at a concentration of 105 colony-forming units (CFU)/mL. Inoculation was conducted on day 0 and biweekly until the termination of project at 12 weeks; samples were filtered and plated on selective media. Leaves and biofilm coupons were collected on day 0 and every 2 weeks postinoculation. Leaf samples were analyzed using culture methods. The biofilm coupons were analyzed using tape fluorescence in situ hybridization (FISH) method. Fruit samples were collected 6 weeks postinoculation until termination of project and analyzed using culture methods. Typical Salmonella morphology of colonies on plates streaked from overnight cultures from plant samples were confirmed by automated ribotyping. A 2-log10 reduction of cells was observed in water samples 2 days post initial inoculation. Reduction continued over the 2-week period with few cells surviving until the next inoculation. S. Typhimurium was observed on the surface of the root systems. However, a splash incident resulted in low-level contamination of selected leaves and fruit samples. The results of the study indicate that although contaminated hydroponic nutrient solution led to surface contamination of roots, such an event may not pose a high risk of contamination of hydroponically grown fruit.
Abstract
Water uptake and movement in Thuja occidentalis pyramidalis Hort, during periods when soil was frozen were examined by use of deuterium as a tracer. Plants in containers were buried to the soil line and electric heating cables were placed below the pots. Deuterated water was added through access tubes when the soil was warmed above 0°C. The amount of deuterium tracer in the foliage was analysed with a gas chromatograph-mass spectrometer (GC-MS). Using this technique, it was found that no water moved from the roots to the foliage when the soil was frozen. When the soil temperature was raised above 0°C, tissue deuterium content increased 7 to 10 fold.
The objective of our experiment was to determine if the application of two deer repellents to six grape cultivars (Vitis vinifera L.) caused significant phytotoxic effects, production losses, or altered the sensory characteristics of wine. We evaluated fifteen single vine plants from six different cultivars in a randomized block design that included the two repellent treatments and an untreated control. During spring 1997, we applied repellents biweekly from budbreak until flowering (2 Apr. to 14 May). Plantskyyd was applied more frequently than recommended by the product label (for trees) due to rapid emergence of unprotected shoot growth in vineyards. Hot Sauce and Plantskydd caused some initial minor phytotoxicity during 1997, however, the yield and phytotoxicity of treated plants were similar to controls by harvest. A panel detected a significant difference in the color, aroma, or taste of `Chardonnay' wine made from grapes treated with repellents compared to wine made from untreated control grapes (P = 0.001 for Hot Sauce; P = 0.05 for Plantskydd). We conclude that Hot Sauce and Plantskydd did not cause serious production losses or phytotoxic effects for the six cultivars treated. However, both Hot Sauce and Plantskydd significantly altered the sensory attributes of Chardonnay wine, which may preclude the use of chemical repellents in wine grape vineyards under the experimental conditions applied in our study.