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Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/23/1997 Publication Date: N/A Citation: N/A Interpretive Summary: Black rot, fungus induced, is an important problem in water- harvested cranberries cold-stored for fresh-market sales. In the water-harvesting process the fruit are forcibly picked while under water and some wounding of the fruit occurs. Spores of the black rot fungi can be present in the water and by contacting a needed wound site the black rot spores penetrate the fruit. Fungicides have not been effective in control thus resistant cultivars are needed. In our evaluation of ten cranberry cultivars for black rot resistance, it was found that large fruited cultivars such as Pilgrim, Stevens and Ben Lear were more susceptible than the medium sized cultivars, Cropper, Howes and Wilcox. The medium sized fruit may be more resistant to wounding in the water-harvesting process and thus have fewer would sites for the black rot fungi to gain entrance. The cultivars showing black rot resistance could be useful in a breeding program. Many other potential sources of black rot resistance exist and additional screening may reveal resistance levels superior to those found in this study. This information will be useful to producers, and is expected to improve the profitability of the industry. Technical Abstract: Resistance of ten cranberry cultivars to two black rot fungi, Allantophomopsis lycopodina and Strasseria geniculata, was evaluated utilizing a simulated water-harvesting process followed by cold storage. To produce a sufficient and consistent supply of inoculum needed for the resistance investigation, various incubation temperatures, media and light intensities were studied. The two fungi studied, A. lycopodina and S. geniculata sporulated well at 12 degrees C on oatmeal agar containing 100 g of oatmeal per liter with light intensities from 59-94u E-1 m-2. The cultivars Cropper and Howes were significantly more resistant to A. lycopodina than Pilgrim and Stevens. Large fruited cultivars such as Pilgrim, Stevens and Ben Lear were more susceptible than the medium sized cultivars, Cropper, Howes and Wilcox. The medium sized fruit may be more resistant to wounding in the water-harvesting process and thus have fewer wound sites for the black rot fungi to gain entrance. Many unexplored possibilities for black rot resistance exist and should be pursued. |
