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Ice Nucleation-Active Bacteria on Chinese Cabbage in Northern China: Population Dynamics and Characteristics and Their Possible Role in Storage Decay. Cindy E. Morris, Institut National de la Recherche Agronomique, Station de Pathologie Végétale, Domaine St. Maurice, 84140 Montfavet, France; Ai-Min Wen(2), Xiao-Hua Xu(3), and Yuan-Bo Di(4). (2)(3)Department of Microbiology; and (4)Department of Plant Protection, Beijing Agricultural University, Beijing 100094, People’s Republic of China; (2)Present address: Institute of Biological Engineering, Hebei University, Baoding 071002, Hebei Province, PRC. Phytopathology 82:739-746. Accepted for publication 25 November 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/Phyto-82-739.

Ice nucleation-active (INA) bacteria active at –5 C were detected on leaves of Chinese cabbage in the field and in storage facilities in the Beijing Municipality. Populations of INA bacteria in the field and those on plants in storage were as high as 2.45 × 106 and 3.12 × 106 cfu/cm2 of leaf, respectively. About 93% of the INA bacteria isolated were identified as Pseudomonas viridiflava. Other species of INA bacteria isolated from Chinese cabbage included P. fluorescens and nonfluorescent pseudomonads. Chinese cabbage is a half-hardy species that risks exposure to several periods of subzero temperatures during its cultivation and storage in northern China and that may suffer serious postharvest soft rot. Under experimental conditions, no significant differences in frost damage were detected between chamber-grown plants inoculated with or free of INA bacteria. Frost sensitivity of Chinese cabbage was reduced significantly by hardening at 8 C for about 1 mo, although outer leaves of hardened plants remained somewhat frost sensitive. Frost-damaged Chinese cabbage leaf tissue was colonized and decayed more rapidly at 5 C by P. viridiflava than was non-frost-damaged tissue. The progress of soft rot could be inhibited by spraying leaves with a nonpectolytic strain of P. viridiflava 48 h before introduction of the pectolytic strain.

Additional keywords: bacterial competition, Brassica campestris ssp. pekinensis, postharvest pathology.