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Biological Control of Frost Injury: An Isolate of Erwinia herbicola Antagonistic to Ice Nucleation Active Bacteria. S. E. Lindow, Department of Plant Pathology, University of Wisconsin, Madison 53706, Present address: Department of Plant Pathology, University of California, Berkeley 94720; D. C. Arny(2), and C. D. Upper(3). (2)Department of Plant Pathology, University of Wisconsin, Madison 53706; (3)Plant Disease Resistance Research Unit, Agricultural Research Service, USDA, Department of Plant Pathology, University of Wisconsin, Madison 53706. Phytopathology 73:1097-1102. Accepted for publication 10 December 1982. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1983. DOI: 10.1094/Phyto-73-1097.

Treatment of corn (Zea mays L.) seedlings in a growth chamber with an Erwinia herbicola isolate (M232A) that was not active in ice nucleation decreased the amount of frost damage incited by ice nucleation active (INA) isolates of Pseudomonas syringae and E. herbicola at - 5 C. The percentage of leaves damaged by frost decreased significantly if M232A was applied at any time before, and up to 12 hr after, application of an INA E. herbicola isolate. Frost damage decreased with increased densities of M232A (105 to 109 cfu/ml) applied 24 hr before challenging with an INA isolate of E. herbicola (8 x 105 or 8 x 106 cfu/ml). Plants sprayed with 3 x 108 colony-forming units (cfu) per milliliter M232A 24 hr prior to application of INA isolates of E. herbicola or P. syringae sustained less damage than did plants without M232A populations, regardless of the cell densities of INA bacteria applied. From 88 to 100% reduction in frost damage was observed in the presence of M232A on plants challenged by less than ~106 cfu/ml of INA E. herbicola or 105 cfu/ml of INA P. syringae 48 hr before exposure to freezing temperatures. Populations of an INA E. herbicola isolate and a streptomycin-resistant mutant of M232A (M232ASR11) were estimated on seedlings treated with M232ASR11 at different times both before and after treatment with the INA E. herbicola. Total populations of bacteria at the time of freezing were nearly constant (~107 cfu/g fresh weight), but the fraction that was ice nucleation active decreased with increasing time of pretreatment with M232ASR11. A significant linear correlation was found between the logarithm of INA populations of E. herbicola present on leaves at the time of freezing and frost injury to those leaves. M232A significantly reduced frost injury incited by six different E. herbicola and two different P. syringae isolates.