A white sulfur slime produced by certain sulfur bacteria clogged drip irrigation emitters when the water contained H2S. Systems were cleaned by irrigating continuously for 3 weeks after first eliminating O2 leaks. After cleanout, growths of sulfur bacteria were prevented by keeping the lines full of water and free of O2 between irrigations. Intermittent injection of chlorine to yield a free residual level of 0.5 ppm prevented sulfur bacterial growths. Lowering the pH to 6.4 with SO2 or 6.0 with HCl also inhibited sulfur bacterial growths.
The fungicide benomyl (formulated as Benlate 50 DF) has been implicated in damage to several crops grown under warm, moist conditions. Although the target pathogen may be controlled, occurrence of population shifts in rhizosphere bacteria has been documented, with benomyl application. A growth chamber study to investigate the effects of benomyl on marigold (Tagetes patula) and subsequent effects on the populations of rhizosphere bacteria of marigold was performed. A one pound per one hundred gallon rate as foliar and drench treatments were applied to marigolds. Plant growth data and rhizosphere bacteria populations were recorded. Repeated application of the benomyl treatments significantly reduced the marigold root and shoot mass, 44% and 67% respectively, compared to controls. Repeated foliar applications of benomyl also resulted in necrotic lesions on marigold leaf margins. Rhizosphere bacteria total numbers differed between treatments, having a greater population for the drench rate than the foliar rate. These results suggest application of benomyl may have harmful nontarget effects, leading to production problems associated with its use.
Many tree crops belonging to the Rosaceae family translocate and metabolize sorbitol. We have determined that some species of bacteria belonging to the genus Agrobacterium, Pseudomonas, and Erwinia pathogenic to the Rosaceae demonstrate the ability to metabolize sorbitol while those that were isolated from other hosts could not utilize sorbitol. Employing cellulose acetate electrophoresis (CAE) we have been able to demonstrate the presence of isoenzymes of sorbitol dehydrogenase (SDH) that correlate with the ability to metabolize sorbitol in these organisms. In order to study the properties of SDH in these organisms we carried out a detailed enzymatic analysis of the enzyme from A. tumefaciens. We found that the enzyme displayed activity when mannitol or xylitol were used as substrates, in addition to sorbitol. Michaelis constants (Km) were 32.8 mM, 0.19 mM, and 38.2 mM for sorbitol, mannitol, and xylitol respectively. To further distinguish the reactions with the different substrates the enzymatic extracts were further characterized on CAE using different substrates to visualize patterns of isoenzymes for a particular sugar alcohol. These analyses revealed the presence of unique isoenzymes for SDH. In addition we observed the presence of mannitol dehydrogenase (MDH) representing in most species a non-specific polyol dehydrogenase.
Autotrophic nitrifying organisms were enumerated in soilless potting media using the most probable number (MPN) technique. Populations of NH4 + and NO2 - oxidizing organisms varied widely between two soilless media—Metro-Mix 220 and 350. Estimates for NH4 + oxidizing organisms ranged from 0.7 to 7.8 × 105 organisms/cm3, while NO2 - oxidizers ranged from 1.3 to 9.5 × 105 organisms/cm3. Population numbers were similar to those typically reported in soils. There was a significant effect of medium type, NH4 + N : NO3 - N fertilizer ratio, and planting on MPN counts of both groups of organisms, with significant interaction between several of the factors. Estimates of NH4 + oxidizers were not linearly correlated with NH4 + oxidizing activity, implying low counting efficiency, heterotrophic nitrification, or rate-limiting substrate NH4 + level. In a separate study, a soilless potting medium was inoculated with pure cultures of either Nitrosomonas europaea or Nitrobacter agilis. Rates of NH4 + and NO2 - oxidation increased, respectively, as inoculum volume increased. Inoculation with nitrifying bacteria may help in the overall management of N in the rhizosphere and be feasible alternatives for the prevention of either NH4 + or NO2 - phytotoxicity with fertilizers containing urea or NH4 +.
; Sterrett et al., 1983 ; Vavrina, 1998 ). Plant- and animal-based fertilizers have been used as amendments in vegetable transplant production ( Koller et al., 2004 ). Mycorrhizal fungi and rhizosphere bacteria are, depending on formulation, permissible
The occurrence of bacteria in different tissues was studied using field-grown strawberries, in vitro-grown strawberries, wild strawberries, and aseptically germinated strawberry seedlings. Strawberry has a number of endophytic bacteria in its the internal tissue, most of which appear to be nonpathogenic. In the in vitro-grown strawberries, all identified isolates were in the genus Pantoea. In field-grown garden and wild strawberries the most common genera were Pantoea and Pseudomonas. Location of eubacterial inhabitants within strawberry tissue sections was studied by in situ hybridization. Bacteria were detected in flower stalks, leaf stalks, leaves, stolons, berries and aseptically germinated seedlings. The existence of bacteria in seeds and seedlings suggests that bacteria are able to move up to the generative tissue and, ultimately, to the next generation, forming a symbiosis-like chain of plant-bacteria coexistence.
Natural colonization of tomato transplants (Lycopersicon esculentum Mill. `Supersonic') by ice nucleation active (INA) bacteria was monitored during a warm, dry period in the spring and during a rainy period in the fall. Populations of INA bacteria and freezing temperatures were determined for seedlings on days 1 to 5, 7, 9, 12, and 15 after transplanting. During the spring experiment, plant freezing temperatures ranged from -6.4C to -3.6C. INA bacteria were detected from day 1 after transplant with populations ranging from 6 to 630 cells/g fresh wt. Most plants had detectable levels of INA bacteria after 3 days in the field, but some plants did not have detectable levels after 15 days. In the fall, populations of INA bacteria were similar to spring levels for the first week after transplant. Numbers of INA bacteria were higher and plant freezing temperatures warmer on days 9 through 15 in the fall compared with the same period in the spring.
Laboratory experiments were conducted using plants without INA bacteria. Seedlings with dry surfaces supercooled to lower temperatures than tomato plants with wet surfaces.
During Fall and Winter 1999-2000 and 2000-2001, a study was conducted to evaluate the effects of exogenous IBA application (0, 2000, or 4000 ppm) and inoculation with Agrobacterium rubi (strains A1, A16, or A18) alone or in combination with each bacterial strain on rooting of hardwood stem cuttings of two rose selections (ERS 14, Rosa canina, and ERS 15, Rosa dumalis). Treatments of hardwood stem cuttings with IBA, bacteria alone and in combination with IBA were found to promote rooting. The highest rooting percentage was obtained among ERS 14 cuttings when treated with 4000 ppm IBA plus A. rubi A16. However, optimal rooting of ERS 15 was obtained when treated with 2000 ppm IBA plus A. rubi A18. Better rooting was observed in thornless ERS 15 genotype than in thorny ERS 14 genotype in both years. Chemical name used: 1H, indole-3-butyric acid (IBA).
Cryoprotectants were applied at labeled rates to primary flowers of `Honeoye' strawberry (Fragaria × ananassa Duch.) plants at full bloom to determine their effects on the floral organs. Frostgard at 50 ml/liter or KDL at 22 ml/liter injured pistils and resulted in misshapened fruit. Floral buds that were closed when cryoprotectants were applied were uninjured. In other experiments, efficacies of cryoprotectants were determined after floral tissues of `Honeoye' strawberry plants were inoculated or not inoculated with the ice-nucleation-active (INA) bacteria, Pseudomonas syringae van Hall and subjected to sub-freezing temperatures. None of the products protected primary or secondary flowers against freezing injury regardless of the occurrence of INA bacteria. INA bacteria were not recovered from primary flowers of treated plants that were killed by low temperature exposure, indicating that non-bacterial nuclei may incite freezing in these tissues.
Including bacteria in the vase water of cut Gerbera jamesonii Bolus flowers resulted in an increase in scape curvature depending on the concentration of bacteria in the water, cultivar, and season. In the summer, a strain of Pseudomonas aeruginosa or a mixed population of bacterial species, all isolated from the vase water of cut gerbera flowers, resulted in curvature of >90° in `Liesbeth' at 108 cfu/ml and in `Mickey' at 1010 cfu/ml. In winter, the lowest bacterial concentrations that resulted in such bending were 106 and 108 cfu/ml, respectively. `Mickey' showed bending at a lower water potential than `Liesbeth'. Comparison between these results and the bacterial counts in vase water and water at retail shops indicates that frequently observed scape bending is at least partly due to bacteria.