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Ecology and Epidemiology

Biological Control of Frost Injury: Establishment and Effects of an Isolate of Erwinia herbicola Antagonistic to Ice Nucleation Active Bacteria on Corn in the Field. 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 73:1102-1106. 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-73-1102.

Isolate M232A of Erwinia herbicola lacks ice nucleation activity, and has the ability to decrease both the population of epiphytic ice nucleation active (INA) bacteria and frost damage to plants inoculated with INA bacteria in growth chamber tests. Populations of this isolate and a streptomycin-resistant mutant of the isolate (M232ASR11) were established on corn (Zea mays L.) seedlings in the field by applications made shortly after emergence. Total bacterial populations present on corn leaves sprayed with either M232A or M232ASR11 were significantly higher than on control plants until ~20 July, and were composed almost exclusively of bacteria resembling either M232A or M232ASR11. After 20 July, total bacterial populations on leaves sprayed with the antagonists were not different from those on the control plants (~5 107 colony-forming units (cfu) per gram fresh weight), and M232A or M232ASR11 comprised ~10% of this population. Populations of INA bacteria in the presence of the antagonistic bacteria decreased significantly throughout the growing season relative to populations on control plants, eg. 30 cfu/g compared to 100300 cfu/g before 25 July and ~104 cfu/g versus 5 105 cfu/g on 20 September for treated and control plants, respectively. Populations of M232A were similar throughout the growing season regardless of whether the plants were treated two or eight times. Populations of M232ASR11 did not increase on plants treated with streptomycin (50 mg/L) relative to plants not sprayed with streptomycin. Exposure to 5 C caused significantly less damage to detached corn leaves colonized with M232A or M232ASR11 than to control leaves throughout the 1976 growing season. Reduction in bacterial populations by the application of these antagonistic bacteria significantly reduced the damage to corn exposed for 23 hr to a natural frost on 23 September 1976.

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