The expression of a grapefruit gene encoding an isoflavone reductase-like protein is induced in response to UV irradiation.

Exposure of harvested grapefruit to UV-C (254 nm) irradiation was previously found to induce resistance against the green mold decay caused by Penicillium digitatum. In order to gain insight into the mechanism of this UV-induced resistance we initiated a study for isolation of genes induced during this process. Using the differential display method we cloned cDNA representing an mRNA which is accumulated in grapefruit peel upon UV irradiation.

Influence of CaCl(2) on Penicillium digitatum, Grapefruit Peel Tissue, and Biocontrol Activity of Pichia guilliermondii.

ABSTRACT Interactions between CaCl(2), grapefruit peel tissue, Penicillium digitatum, and the yeast antagonist Pichia guilliermondii strain US-7 were investigated. Application of 68 or 136 mM CaCl(2) to grapefruit surface wounds reduced the incidence of green mold caused by Penicillium digitatum by 43 to 52%. In laboratory tests, a cell suspension (10(7) cells/ml) of Pichia guilliermondii containing either 68 or 136 mM CaCl(2) reduced the incidence of green mold from 27 to 3%.

Are biological antagonists an alternative to synthetic fungicides for preventing postharvest diseases of fruits and vegetables?

In recent years, both the public and health authorities have become increasingly concerned about the presence of pesticides in our food supply and the environment. As a direct result of this mounting concern, research efforts for the development of alternative methods for the control of postharvest diseases of fruits and vegetables have been intensified. Considerable attention has been placed on assessing the potential of the use of biological antagonists as a viable alternative to the use of synthetic fungicides.

Application of Ultraviolet-C Light on Storage Rots and Ripening of Tomatoes.

The application of ultraviolet light (UV-C, 254 nm) hormesis on fruits and vegetables to stimulate beneficial responses is a new method for controlling storage rots and extending the shelf-life of fruits and vegetables. The present study was aimed at treating tomatoes ( Lycopersicon esculentum ) with different UV-C dosages (1.3 to 40 KJ/m) to induce resistance to black mold ( Alternaria alternata ), gray mold ( Botrytis cinerea ), and Rhizopus soft rot ( Rhizopus stolonifer ).

Characterization and reclassification of yeasts used for biological control of postharvest diseases of fruits and vegetables.

In previous studies workers have shown that three yeast strains (strains US-7, 82, and 101) have biological control activity against various postharvest fungal pathogens of fruits and vegetables, including Penicillium rots of apples and citrus and Botrytis rot of apples. In these reports the researchers have described these strains as Debaryomyces hansenii (anamorph, Candida famata) or Candida sp. strains.

Rhythmicity in cotton seedlings : Rhythmic ethylene production as affected by silver ions and as related to other rhythmic processes.

Ethylene production by detached cotyledons of cotton (Gossypium hirsutum L.) seedlings grown under cycles of 12 h darkness and 12 h light has been shown to be rhythmic, with a minimum and maximum 4 and 16 h, respectively after the start of the cycle (Rikin, Chalutz and Anderson, 1984, Plant Physiol. 75, 493-495).

Rhythmicity in ethylene production in cotton seedlings.

Cotyledons of cotton (Gossypium hirsutum L.) seedlings grown under a photoperiod of 12 hour darkness and 12 hour light showed daily oscillations in ethylene evolution. The rate of ethylene evolution began to increase toward the end of the dark period and reached a maximum rate during the first third of the light period, then it declined and remained low until shortly before the end of the dark period.

Enhancement by ethylene of cellulysin-induced ethylene production by tobacco leaf discs.

Cellulysin-induced ethylene production in tobacco (Nicotiana tabacum L.) leaf discs was enhanced several-fold by prior exposure of the leaf tissue to ethylene. This enhancement in the response of the tissue to Cellulysin increased rapidly during 4 and 8 hours of pretreatment with ethylene and resulted from greater conversion of methionine to ethylene.

Influence of enol ether amino acids, inhibitors of ethylene biosynthesis, on aminoacyl transfer RNA synthetases and protein synthesis.

The analogs of rhizobitoxine, aminoethoxyvinylglycine (AVG) (l-2-amino-4-2'-aminoethoxy-trans-3 butenoic acid) and methoxyvinylglycine (MVG) (l-2-amino-4-methoxy-trans-3-butenoic acid), that are potent inhibitors of ethylene biosynthesis at 0.1 millimolar also inhibited protein synthesis and charging of tRNA especially at 1 millimolar and higher concentrations. The saturated analog of MVG inhibited ethylene synthesis while the saturated analog of AVG did not.

Characterization of the Phosphate-mediated Control of Ethylene Production by Penicillium digitatum.

Characterization of the phosphate effect on ethylene production by Penicillium digitatum is reported. A low level of phosphate (0.001 millimolar) was about 200 to 500 times as effective as a high phosphate level (100 millimolar) in stimulating ethylene production and the stimulation was readily reversed by addition of phosphate.

Inhibition of Ethylene Production in Penicillium digitatum.

Production of ethylene by static cultures of Penicillium digitatum, which utilize glutamate and alpha-ketoglutarate as ethylene precursors, was inhibited by methionine, methionine sulfoxide, methionine sulfone, and methionine sulfoximine. Rhizobitoxine did not affect ethylene production but its ethoxy and methoxy analogues were effective inhibitors of ethylene production; its saturated methoxy analogue and kainic acid stimulated ethylene production. Tracer studies showed that the inhibitors blocked the conversion of [(3)H]glutamate into [(3)H]ethylene.

Methionine-induced Ethylene Production by Penicillium digitatum.

Shake cultures, in contrast to static cultures of Penicillium digitatum grown in liquid medium, were induced by methionine to produce ethylene. The induction was concentration-dependent, and 7 mM was optimum for the methionine effect. In the presence of methionine, glucose (7 mM) enhanced ethylene production but did not itself induce ethylene production.

Ethylene-induced Phenylalanine Ammonia-Lyase Activity in Carrot Roots.

Ethylene enhanced the activity of phenylalanine ammonialyase in carrot (Daucus carota L., var. "Nauty") root tissue.

Ethylene-induced Isocoumarin Formation in Carrot Root Tissue.

The concentrations of 3-methyl-6-methoxy-8-hydroxy-3,4-dihydroisocoumarin (MMHD) formed in carrot roots inoculated with certain fungi or treated with indole-3-acetic acid, 2,4-dichlorophenoxyacetic acid, or 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), were related to the amount of ethylene produced by the root tissue. Ethylene applied exogenously in concentrations above 0.3 ppm induced the formation of MMHD in carrot root discs.