Apple sooty blotch (SB) is a disease complex caused by Gloeodes pomigina (Schw.) Colby, Leptodontidium sp. and other fungi. This study was undertaken to determine if G. pomigena and Leptodontidium sp. utilize some portion of the apple epicuticular wax as a carbon source for growth. Two isolates of G. pomigena and two of Leptodontidium sp. were used. Isolates were cultured on water agar coated with a thin layer of either nonacosane, ursolic acid, or complete apple wax and an uncoated control. Radial colony growth over a 30-day period was used to assess growth. Preliminary results suggest that G. pomigena differs from Leptodontidium sp. in carbon source preference. Gloeodes colonies were larger when ursolic acid and apple wax were used as a carbon source compared to nonacosane. Leptodontidium isolates grew best on apple wax. Also, growth was greater on nonacosane than ursolic acid. results from laboratory studies were compared to SB severity (percent surface area covered) in the orchard on cultivars of apples where the wax composition was determined. Although fungal genera were not detailed in the orchard, SB severity was positively correlated with the concentration of ursolic acid (r2=0.69) and nonacosane (r2=0.34).
Mature-green `Grande Naine' bananas (Musa AAA) were harvested 13 weeks after flowering, in June and Sept. 1993, and Feb. and Mar. 1994. Fruit were 1) held in storage for 36 days at 14C and 80% to 90% RH, or 2) after 8 days of storage, fruit were treated with ethylene, and held at 17C until color 6 of the standard color scale was observed. Although a similar grade and age, the length of the preclimacteric phase was different among months, which reflected different physiological maturities at harvest. Rate of respiration, pulp pH, and soluble solids were the most-useful variables to characterize the fruit. Increases in respiration after ethylene treatment varied from 4- up to 14-fold the respiratory level under storage conditions. The climacteric occurred at any point during ripening, ranging from color 2 to 5, except at very early stages. Ethylene increases were short in duration and magnitude, and occurred earlier than the respiratory peak. Sometimes, internal and external ripening stages did not match. The most dramatic seasonal effects were observed in CO2 evolution, pulp-to-peel ratio, and starch conversion.
Mature-green `Grande Naine' bananas from Costa Rica, Mexico, Ecuador, and Guatemala were harvested in June, Sept., and Dec. 1993 and Mar. 1994. Fruit were treated with ethylene and held at 17C and 80% to 90% relative humidity until they reached color 6 of the standard color scale. Guatemalan bananas had the highest respiration rate, followed by Costa Rican, Mexican, and Ecuadoran fruit. Peel color, ethylene production, and soluble solids content did not differ among the countries. Measurements made at arrival in the United States had a low correlation with days to reach color 5. Prediction equations showed significant linear relationships for most variables; however, correlations were very low. The highest coefficient of determination was observed with respiration rate (r2 = 0.289). Maximum R2 (0.342) was determined using CO2, C2H4, pH, and soluble solids in the model. pH and soluble solids were good variables to determine the physiological stage of the fruit, and they also detected ripening changes earlier than peel color or firmness.