Population Dynamics of Ice Nucleation Active Bacteria on Prunus Persica Cultivars
Populations of ice nucleation active (INA) strains of Pseudomonas fluorescens, Pseudomonas syringae, and Erwinia herbicola were assayed on four peach cultivars of known hardiness including Redhaven, Elberta, Loring, and Belle of Georgia. The addition of 0.85% NaCl to 0.1 M phosphate buffer (ph 7.0) containing 0.1% peptone was necessary for bacterial survival during the leaf washing process. Ice nucleation at -5 C was best detected from colonies grown on nutrient agar supplemented with 2.5% glycarol. Seasonal variations in populations of total and INA bacterial were observed over a ten week period with maximum populations at bud break followed by a gradual decline. A new INA species, Serratia liquifaciens was identified. The INA species were isolated in the following proportions: P. fluorescens 42%, P. syringae 24%, E. herbicola 19%, and S. liquifaciens 15%. Peach cultivar hardness is independent of INA bacterial concentration.
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