Phymatotrichopsis omnivora (Duggar) Hennebert (syn. Phymatotrichum omnivorum Duggar) is a recalcitrant soilborne pathogen that causes serious root rot problems on numerous plant species in the southwestern United States and northern Mexico. Apple trees [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf. (syn. M. domestica Borkh. non Poir.)] are highly susceptible to P. omnivora with most tree death occurring in the summer months. Studies were conducted from 1996 to 1999 to examine when and at what rate infection and colonization of roots of apple trees by P. omnivora actually occurs. In three-year-old trees growing in orchard soils in 45-gallon containers (171,457 cm3) and inoculated with sclerotia in August 1997, infection occurred in the nursery after 12 weeks. For trees inoculated with sclerotia in February 1998, infection occurred within 15 weeks. After 18 weeks, 100% of trees were infected after inoculation in August and 80% of trees were infected after the February inoculation. This information is vital to understanding the epidemiology of Phymatotrichum root rot in apple orchards.
Wesley T. Watson*, David N. Appel, Michael A. Arnold, Charles M. Kenerley, and James L. Starr
Kevin R. Kosola, Beth Ann A. Workmaster, James S. Busse, and Jeffrey H. Gilman
roots from apple trees [ Malus sylvestris var. domestica (Borkh.) Mansf.] at the University of Wisconsin Peninsular Agricultural Experiment Station near Sturgeon Bay (lat. 44°52′51.96″ N, long. 87°20′7.8″ E) on 13 May 2004. The soil type was an Emmet
David R. Rudell, John K. Fellman, and James P. Mattheis
Repeated preharvest applications of methyl jasmonate (MJ) to 'Fuji' apple [Malus sylvestris var. domestica (Borkh.) Mansf.] fruit were evaluated for impacts on peel color, size, fruit finish, and maturation. MJ treatments at 2 week intervals began 48 days after full bloom (DAFB) (early season) or 119 DAFB (late season) and fruit were harvested 172 DAFB. MJ treatment stimulated significant increases in peel red color following the initial application and thereafter. Early season MJ treatment reduced fruit diameter and length to diameter ratio but slowed softening and starch hydrolysis. Fruit receiving late season MJ treatments had increased incidence of bitter pit and splitting, shorter green life, and slower softening. Results suggest preharvest application of MJ impacts apple color development and other aspects of fruit quality. Chemical name used: methyl 3-oxo-2-(2-pentenyl)cyclopentane-1-acetate (methyl jasmonate).
James D. Hansen
Durations of ultrasound treatments were evaluated for efficacy in removing or destroying external pests of apples (Malus sylvestris var domestica). Egg hatch of codling moth (Cydia pomonella; Lepidoptera: Tortricidae), was inversely related to time of ultrasound exposure, although egg mortality was less than 60% after 45 min of treatment. Mortality of twospotted spider mite (Tetranychus urticae; Acari: Tetranychidae), and western flower thrips (Frankliniella occidentalis; Thysanoptera: Thripidae), was directly related to ultrasound durations; adding detergent to the ultrasound bath increased treatment efficacy. Ultrasound did not remove san jose scale (Quadraspidiotus perniciosus; Homoptera: Diaspididae), from the fruit surface. Ultrasound, which can be incorporated in the packing line, shows promise as a postharvest phytosanitation treatment against external pests.
David R. Rudell and James P. Mattheis
`Golden Delicious' apple [Malus sylvestris var. domestica (Borkh.)] cortex disks suspended in solutions containing a nitric oxide (•NO) donor [S-nitrosoglutathione (GSNO) or sodium nitroprusside (SNP)], •NO gas, or nitrite (KNO2) were used to identify impacts of •NO on ethylene production and NO2 – on •NO and ethylene production. Treatment with GSNO or SNP reduced ethylene biosynthesis compared with control treatments containing equimolar concentrations of oxidized glutathione (GSSG) or Na4(CN)6 respectively. Apple disk exposure to •NO gas did not impact ethylene production. Treatment with NO2 – resulted in increased •NO production and decreased ethylene biosynthesis. Generation of •NO increased linearly whereas ethylene generation decreased exponentially with increasing NO2 – treatment concentration. •NO was enhanced in autoclaved tissue disks treated with NO2 –, suggesting that its production is produced at least in part by nonenzymatic means. Although this evidence shows •NO is readily generated in apple fruit disks by NO2 – treatment, and ethylene synthesis is reduced by •NO/NO2 – generated in solution, the exact nature of •NO generation from NO2 – and ethylene synthesis modulation in apple fruit disks remains to be elucidated.
Desmond R. Layne, Zhengwang Jiang, and James W. Rushing
Replicated trials were conducted in Summers 1998 and 1999 at two commercial orchards (A and B) to determine the influence of a metalized, high density polyethylene reflective film (SonocoRF) and aminoethoxyvinylglycine (ReTain), on fruit red skin coloration and maturity of `Gala' apples (Malus sylvestris var. domestica). There were four experimental treatments: 1) nontreated control; 2) reflective film (RF); 3) ReTain; and 4) RF + ReTain. RF was applied 4 weeks before anticipated start of harvest by laying a 5-ft-wide (150-cm) strip on each side of the tree row in the row middle. ReTain was applied 4 weeks before harvest at the commercial rate in one orchard and at 60% of the commercial rate in a second test. ReTain delayed fruit maturity. Fruit from RF trees had a significantly greater percent surface red color than fruit from trees not treated with RF. Fruit from RF + ReTain were significantly redder and had higher soluble solids concentration (SSC) than fruit from trees treated with ReTain alone. There were no differences in size, fruit firmness or starch content between fruit from RF and RF + Retain. RF appears to be a method to increase red skin coloration in `Gala' apples treated with ReTain without adversely impacting maturity.
Luiz Argenta, Xuetong Fan, and James Mattheis
The efficacy of the ethylene action inhibitor 1-methylcyclopropene (1-MCP) applied in water to slow ripening of `Golden Delicious' [Malus sylvestris var. domestica (Borkh.) Mansf.] apples was evaluated in comparison with 1-MCP applied as a gas in air. The material was applied by dipping fruit in 1-MCP water solutions (0, 0.03, 0.3 or 3 μM) for 4 min, or by exposing fruit to 1-MCP gas (0, 0.01, 0.1 or 1 μL·L-1) in air for 12 h. Fruit were held in air at 20 °C for 25 days after treatment or stored at 0.5 °C in air for up to 6 months followed by 7 days in air at 20 °C. Application of 1-MCP in water or air delayed the increase in respiration and ethylene production associated with fruit ripening, and reduced the amount of fruit softening, loss of acidity and change in peel color. Treatments applied in water required a concentration 700-fold higher compared to those applied in air to induce similar physiological responses. Fruit responses to 1-MCP varied with treatment concentration, and the maximum effects were obtained at concentrations of 0.1 or 1 μL·L-1 in air and 3 μM in water. Peel color change was impacted less than retention of firmness and titratable acidity for some 1-MCP treatments. Treatment with 1-MCP was less effective for slowing peel degreening when treated fruit were stored at 0.5 °C compared to storage at 20 °C. In 1 of the 3 years of this study, fruit treated with 1-MCP and stored in air at 0.5 °C developed a peel disorder typified by a gray-brown discoloration that is unlike other disorders previously reported for this cultivar.
Luiz C. Argenta, Xuetong Fan, and James P. Mattheis
The efficacy of the ethylene action inhibitor 1-methylcyclopropene (1-MCP) applied in water to slow ripening of ‘Golden Delicious’ [Malus sylvestris var. domestica (Borkh.) Mansf.] apples was evaluated in comparison with 1-MCP applied in air. The material was applied by dipping fruit in 1-MCP water solutions (0.03, 0.3, or 3 mmol·m−3) for 4 min or by exposing fruit to 1-MCP gas (0.42, 4.2, or 42 μmol·m−3) in air for 12 h. Fruit were held in air at 20 °C for 25 days after treatment or stored at 0.5 °C in air for up to 6 months followed by 7 days in air at 20 °C. Application of 1-MCP in water or air delayed the increase in respiration and ethylene production associated with fruit ripening and reduced the amount of fruit softening, loss of acidity, and change in peel color. Treatments applied in water required a 700-fold higher amount of active ingredient compared with treatments applied in air to induce similar physiological responses. Fruit responses to 1-MCP varied with treatment concentration, and the maximum effects were obtained at concentrations of 4.2 or 42 μmol·m−3 in air and 3 mmol·m−3 in water. Peel color change was impacted less than retention of firmness and titratable acidity for 1-MCP treatments applied at concentrations of 4.2 or 42 μmol·m−3 in air and 0.3 or 3 mmol·m−3 in water. Treatment with 1-MCP in air or water was less effective for slowing peel degreening when treated fruit were stored at 0.5 °C compared with storage at 20 °C. Fruit treated with 1-MCP and stored in air at 0.5 °C developed a peel disorder typified by a gray·brown discoloration that is unlike other disorders previously reported for this cultivar. Symptoms were present when fruit were removed from cold storage and no change in symptom appearance was observed during a 7-d holding period at 20 °C.
Yohei Kurata, Tomoe Tsuchida, and Satoru Tsuchikawa
apple ( Malus sylvestris var. domestica ), in which attenuance of peak maxima, time delay of peak maxima, and variation of full width at half maximum of the time-resolved profile were used as explanatory variables for multiple linear regression
Daniel Ferreira Holderbaum, Tomoyuki Kon, Tsuyoshi Kudo, and Miguel Pedro Guerra
Apples ( Malus × sylvestris var. domestica ) are an important source of polyphenols (phenolic compounds) in the human diet ( Hertog et al., 1992 ) and a classic example of fruit susceptibility to enzymatic browning, which is a major problem for