Sylvia M. Blankenship

1-Methylcyclopropene: a review

Since the discovery of 1-methylcyclopropene (1-MCP) as an inhibitor of ethylene action, over 100 studies have examined details of its action, application and effects on ethylene inhibition. This plant growth regulator is a tool that can help scientists make major advances in understanding the role of ethylene in plants. 1-MCP prevents ethylene effects in a broad range of fruits, vegetables and floriculture crops. Effective concentrations are low and range from 2.5 nl l 1 to 1 m ll 1 . Concentration interacts with temperature such that low concentrations of 1-MCP applied over longer durations may be as effective as high concentrations. 1-MCP is most commonly applied at 68/77 8F (20/25 8C), but can be used at lower temperatures in some commodities. Generally, treatment durations of 12/24 h were sufficient to achieve a full response. A variety of factors may need to be considered when using 1-MCP including cultivar, developmental stage, time from harvest to treatment, and multiple applications. Depending on the species being treated, 1-MCP may hav ea variety of effects on respiration, ethylene production, volatile production, chlorophyll degradation and other color changes, protein and membrane changes, softening, disorders and diseases, acidity and sugars. This review compiles what is known about the technological uses for 1-MCP, defines where discrepancies exist between reports, and aims to define areas requiring further study. # 2003 Elsevier Science B.V. All rights reserved.

Competition of cyclooctenes and cyclooctadienes for ethylene binding and activity in plants

Abstracttrans-Cyclooctene, cis,trans-1,5-cyclooctadiene, and cis,trans-1,3-cyclooctadiene have been compared with the cis and cis,cis isomers and with 2,5-norbornadiene for competition with ethylene for binding in mung bean sprouts and tobacco and for action (induction of chlorophyll degradation) in banana. The compounds containing a trans double bond were much more effective in competition for binding and action than the cis and cis,cis compounds. trans-Cyclooctene and cis,trans-1,3-cyclooctadiene were in the general range of 50–90 times more effective than 2,5-norbornadiene.

Pal and ethylene content during maturation of red and golden delicious apples

Abstract Phenylalanine ammonia-lyase activity (PAL), a PAL inhibitor (PAL-IS) and fruit internal ethylene levels were measured during apple maturation in Red and Golden Delicious apples. In both cultivars internal ethylene and PAL increased at approximately the same time. Apple PAL-IS extract stimulated yeast PAL activity initially, but increased yeast PAL inhibition was observed as maturation progressed. PAL inhibitor levels were similar in both cultivars. The increase in yeast PAL inhibition with maturation, increased red skin colour development in Red Delicious and a comparable pattern of PAL activity and inhibition in Red and Golden Delicious indicates that PAL-IS was not closely involved with the regulation of anthocyanin synthesis in apple skin.

Relationship between apple fruit epicuticular wax and growth of Peltaster fructicola and Leptodontidium elatius, two fungi that cause sooty blotch disease.

Sooty blotch severity varied among apple cultivars or selections surveyed in 1989 and 1992. No mycelial growth was observed on russetted areas of the cuticle that are considered impermeable. Ursolic acid and n-alkanes were the most prominent components of the epicuticular waxes of the cultivars or selections evaluated. Although there were differences in the relative proportions of these compounds among the cultivars, the differences were not related to the severity of sooty blotch. Peltaster fructicola and Leptodontidium elatius were grown on compounds that comprise the epicuticular wax of the fruit to determine if one or more of these were needed for growth. The fungi did not grow on any of the five major components of the epicuticular wax unless dilute apple juice was included. Scanning electron microscopy studies showed that mycelia of P. fructicola grew on the surface of the wax and did not appear to degrade it. Our studies support the hypothesis that P. fructicola and L. elatius fungi are epiphytes and obtain their nutrients not from components of the cuticle, but more likely from fruit leachates.

Diazocyclopentadiene (DACP), a light sensitive reagent for the ethylene receptor in plants

Diazocyclopentadiene (DACP) has been shown to be an effective reagent for the ethylene receptor. Treatment of mung bean sprouts or tobacco leaves with DACP in the light or in the dark inactivates much of the ethylene binding. In the light, inactivation seems to be permanent, while in the dark, the site becomes active again after the DACP diffuses away. The compound is 10 times more effective in the light than in the dark. DACP inhibits banana ripening indicating the physiological receptor is involved. It also overcomes the inhibitory effect of ethylene on mung bean seedling growth (Km = 0.09 µl/1 E) at low ethylene levels. At high ethylene levels, an apparent high ethylene level site becomes apparent (Km = 50 µl/1 E) and growth is inhibited.

Response of apples to diazocyclopentadiene inhibition of ethylene binding

Abstract Diazocyclopentadiene (DACP) is a light-activated compound that is thought to inhibit ethylene binding in plants. DACP was applied as a gas in the light for 24 hours to ‘Red Delicious’ apples harvested at a mature, preclimacteric stage. Treated apples held in air at 21°C for 30 days had lower internal ethylene concentrations than untreated fruits. Higher concentrations of DACP were more effective over longer periods of time. Untreated apples had a flesh firmness of 46 newtons after 30 days, while DACP treated apples were about 73 newtons. Starch conversion initially was slowed by DACP, but by 30 days all starch was lost. Retreatment of fruit with DACP during the 30 days did somewhat renew the effect on suppression of ethylene, but did not further effect flesh firmness or starch conversion. Apples treated once with DACP at harvest, then held in 0°C cold storage, contained much lower levels of internal ethylene and were approximately 10 newtons firmer after 18 weeks than untreated fruit.

Night-temperature effects on rate of apple fruit maturation and fruit quality

Abstract Potted ‘Red Chief’ apple trees were exposed to 26°C day and either 22°C (warm) or 11°C (cool) night temperatures during fruit development and maturation. The onset of fruit ethylene (C 2 H 4 ) production occurred at approximately the same time regardless of temperature. ACC (1-aminocyclopropane-1-carboxylic acid) levels in the fruits were not statistically different between temperature treatments during fruit maturation. Ethylene-forming enzyme (EFE) activity was measured by applying saturating amounts of exogenous ACC to fruit tissue and measuring C 2 H 4 production. Cool-night fruit developed EFE activity earlier than warm-night fruit. Firmness and soluble solid content of the fruit were not statistically different between the temperature treatments. Although fruit maturity was unaffected by night temperature, fruit abscission occurred earlier in cool-night fruit. Warm-night fruit had less red skin color than cool-night fruit. Fruit diameter and length were not affected by night temperature.

Effect of diazocyclopentadiene on tomato ripening

Diazocyclopentadiene (DACP) in the presence of fluorescent light delayed ripening of tomato fruits treated at the mature green (no visible red) stage. At 25 °C, ripening was delayed 10 days if DACP [185 µl/1 (gas)] was added as a single treatment and longer if DACP was added intermittently at 5-day intervals. The addition of 1000 µl/1 ethylene following DACP and light treatment did not hasten ripening. Little ripening delay was noted for fruit + DACP held in darkness. Tomatoes covered with aluminum foil so as to exclude light but not light-activated DACP, showed ripening inhibition. Apparently, the light-activated product from DACP is stable long enough to diffuse into fruit held in darkness. After an initial inhibition, ethylene production was greatly increased in tomatoes treated with DACP. Tomatoes with or without DACP treatment were held either in air or 5% O2/95% N2 for 12 days then treated with ethylene. Treatment with 5% O2 alone delayed ripening when compared to air alone, however, both groups reached 80% red color by 18 days. DACP treated fruit, whether held in air or 5% O2, still were green after 18 days and only approached 80% red color after approximately 27 days. Thus, 5% oxygen did not appear to slow the reversal of DACP inhibition of ripening.

Pathogenicity of fungi associated with crown rot of bananas in Latin America on Grande Naine and disease-resistant hybrid bananas

Fungi associated with crown rot of bananas were isolated and identified from fruit obtained from Mexico, Guatemala, Costa Rica, and Ecuador in October and November 1993. Fusarium semitectum and Penicillium spp. were isolated most frequently. In vitro and in vivo growth of five fungi isolated from Costa Rican bananas (F. semitectum, F. moniliforme, a Penicillium sp., Gliocladium roseum, and a Gliocladium sp.) was determined. The optimum temperatures for growth of F. moniliforme, F. semitectum, a Penicillium sp., a Gliocladium sp., and G. roseum were 24.3, >28.0, 21.8, 24.1 and 29.6°C, respectively. All fungi, except the Penicillium sp., grew profusely on the surface of crowns. After inoculation of crowns, F. moniliforme and F semitectum caused the greatest amount of rot. Hybrids recently released by the Honduran Foundation of Agricultural Research (Fundacion Hondurena de Investigacion Agricola, FHIA), FHIA 1 (Goldfinger) and FHIA 2, were partially resistant to the crown rot fungi. Isolates of F. semitectum and Penicillium sp. from Costa Rica grew on potato dextrose agar amended with 10 mg liter -1 of thiabendazole, which may indicate a reduced sensitivity of these species to thiabendazole.

Ethylene binding changes in apple and morning glory during ripening and senescence

Ethylene binding sites were measured during fruit ripening and morning glory flower senescence. Little change in ethylene binding was noted during these developmental stages, except a slight decline during the later stages of fruit ripening or flower senescence. The concentration of ethylene required to achieve 50% saturation of the binding sites was 0.14 μl/liter for both apple pulp and morning glory flowers. Ethylene binding sites were calculated to be 3.2×10−11 moles/kg and 3.8×10−9 moles/kg in apple and morning glory, respectively. It does not appear that changes seen in ethylene sensitivity during fruit ripening can be readily ascribed to changes in the number of ethylene binding sites in the tissue.