Ethylene enhanced chlorosis and levels of 33-kilodalton cationic peroxidase

W. 1989. Characterization of inhibition of Rhizopus stolonifer germination and growth by Enterobacter cloacae. Can. J . Bot. 67: 2317-2323. Interactions between Enterobacter cloacae and Rhizopus stolonifer were evaluated to determine possible mechanisms by which E. cloacae protects peach fruit from postharvest rot caused by R. stolonifer. Inhibition of Rhizopus sporangiospore germination by E. cloacae was dependent on the concentration of the antagonist. Antagonist concentration (1 x loL0 cfu . mL-') needed to completely inhibit germination was similar to that needed to prevent fruit infection. Significant inhibition of in vitro hyphal growth was achieved at 1 x lo5 cfu. mL-' with simultaneous culturing of the fungus and antagonist. A reduction in inhibition occurred when addition of the antagonist was delayed. The presence of glucose in the growth medium did not prevent attachment of E. cloacae to hyphae and sporangiospores of R. stolonifer. Agglutination assays of sporangiospores by E. cloacae were positive whereas agglutination of cell-wall fragments was less distinct. Data indicate that nutrient competition, perhaps facilitated by bacterial attachment, may play a key role in E. cloacae and R. stolonifer interactions.WISNIEWSKI, M., WILSON, C., et HERSHBERGER, W. 1989. Characterization of inhibition of Rhizopus stolonifer germination and growth by Enterobacter cloacae. Can. J . Bot. 67 : 2317-2323. Les auteurs ont CvaluC les interactions qui existent entre Enterobacter cloacae et le Rhizopus stolonifer afin de determiner les mCcanismes possibles par lesquels 1'E. cloacae peut protCger les fruits de p&che contre la pouniture post-rkcolte causCe par le R. stolonifer. L'inhibition de la germination des sporangiospores du R. stolonifer par 1'E. cloacae dCpend de la concentration de l'antagoniste. La concentration de l'antagoniste (1 x 101° cfu. mL-I) nCcessaire pour empccher la germination est semblable 2 celle qui empgche l'infection des fruits. En cultivant simultanCment l'antagoniste et le charnpignon in vitro en presence de 1 x lo5 cfu. mL+, on observe une inhibition significative de la croissance mycelienne. I1 y a une rkduction de l'inhibition lorsque I'addition de l'antagoniste est retardCe. L'addition de glucose dans le milieu n'ernpgche pas l'attachement du E. cloacae aux hyphes et sporangiospores du R. stolonifer. L'agglutination du E. cloacae aux sporangiospores peut &tre obtenue expCrimentalement, mais ceci est rnoins evident avec des fragments de paroi. Les donnCes montrent qu'une compCtition pour les nutriments, possiblement facilitke par l'attachement des batteries, pourrait jouer un r6le clC dans les interactions entre E. cloacae et R. stolonifer.[Traduit par la revue]

As an alternative to fungicides, biological control of postharvest diseases of fruit has recently met with good success with peaches and apples and is an area of great potential. In contrast to previous study, we were particularly interested in finding antagonists that did not produce antibiotics as part of their mode of action. After extensive screening, several yeast and bacteria were identified that exhibited biocontrol of a number of postharvest disease organisms. In particular, the yeast, Debaryomyces hansenii, indicated great potential as a biocontrol agent without exhibiting antibiotic production as a mode of action. It has been recently shown to effectively control decay on citrus caused by Penicillium digitatum, Penicilliim italicum and Geotrichum candidum. The present report is the first to document the use of D. hansenii to control postharvest decay of apples by Botrytis cinerea and present possible inodes of action.To test for biocontrol activity, apples (cv Golden Delicious) ware wounded with a 4 nm cork borer to a depth of 5 mm.

Hot water and sodium hypochlorite (NaOCl) were evaluated to eradicate teliospores of the Karnal bunt fungus, Tilletia indica, for the purpose of decontaminating grain storage and handling equipment. The germinability of free teliospores and teliospores within the sori of infected wheat was assessed. Temperatures of 25, 60, and 80°C, NaOCl concentrations (wt/vol, pH 11.5) of 0, 0.53, and 1.60%, and immersion periods of 1, 5, 15, and 30 min were evaluated. In other tests, the influence of pH on NaOCl potency and of a delay between treatment and water rinsing were evaluated. Immersion at 80°C in water alone or with NaOCl killed both free teliospores and those within the sori of infected seeds within 1 min. NaOCl at 1.60% at 25°C killed teliospores suspended in water within 15 min, but some teliospores inside sori survived 30 min of this treatment. NaOCl adjusted to pH 8 before use was superior to NaOCl at pH 11.5. An application of 1.60% NaOCl at 25°C for 5 min followed by a 10-min delay before the seeds were rinsed in fresh water killed free teliospores but not all teliospores within sori. This treatment was more effective than the 5-min treatment alone but inferior to the 15-min treatment with NaOCl at a concentration of 1.60%. Because teliospores within the sori of infected seeds are partially protected and much more resistant to NaOCl, we recommend the removal and disposal of seeds from equipment before the treatments are applied. NaOCl radically altered the appearance of the teliospores, leaving a persistent visual indication that they had been treated, while hot water treatment alone did not. Therefore, it is beneficial to add NaOCl to hot water, although the improvement in the sporicidal efficacy was often small.

In the original description of Allonemobius walkeri Howard & Furth, 1986, the authors describe the species’ calling songs in a table that included trill length, length of the interval between trills, pulse rate, and carrier frequency for four individuals. Further investigation of the acoustics of this species reveals that the calling songs are composed of syllables organized into echemes composed of a varying number of syllables, and organized into groups of echemes, of variable length. The echemes are separated by intervals of various lengths. The calling song is pleasing to the ear, with ~27 syllables per second and a carrier frequency of ~7.7 kHz at 25°C. The characteristics of the echemes and echeme intervals are significantly different when the cricket is singing in sunlight compared to darkness. In sunlight, echemes are shorter, but echeme intervals are longer. There is no effect on calling bout lengths. Courtship songs are quieter than calling songs, with a random delivery of soft and loud chirps in addition to fainter, rhythmic sounds randomly distributed between the chirps. Courtship songs are interspersed with long bouts of calling songs with displays lasting hours.