A comparative evaluation of freezing criteria and molecular characterization of epiphytic ice-nucleating (Ice+) and non-ice-nucleating (Ice?) Pseudomonas syringae and Pseudomonas fluorescens

Bahareh Karimi | Bibi Sedigheh Fazly | Mirsasan Mirpour | Parviz Owlia | Rahim Nosrati | Mohammadali Malboob

---

URL :   http://research.shahed.ac.ir/WSR/WebPages/Report/PaperView.aspx?PaperID=116964
Date :  2019/09/03
Publish in :    Journal of Plant Pathology
DOI :  https://doi.org/10.1007/s42161-019-00402-7

Keywords :

Abstract :

---

The ice-nucleation-active bacteria that produce ice-nucleating proteins (INPs), especially Pseudomonas species, may play a critical potential role in frost injury. The ice-minus variant of bacteria is amutant, lacking the genes responsible for the production of INPs. The aim of the project was the isolation of relevant bacteria. Pseudomonas-like bacteria were screened from 66 leaves samples and were identified by biochemical as well as molecular methods with rpoD, 16S rDNA-flu and hrpl primers. The ice nucleation activity (INA) of isolates was performed using the drop-freezing method. The existence of the ina gene in isolates was investigated by specific inaZ and inaWprimers. The effect of various temperatures, salt concentration and pH on growth and INA were investigated. Finally, the pathogenicity and freezing of INA+ and INA− bacteria on tomatoes and oranges were estimated. In this study, 57 isolates were identified as Pseudomonas including five P. syringae strains and seven P. fluorescens strains. The freezing profiles revealed that P. fluorescens strain 22A as INA− bacteria and three strains of P. syringae 18A, 52A and 52B are also recommended as strong INA+ strains. Most of the P. syringae isolates were active at −2 to −8 °C (type I and II), whereas P. fluorescens strains had an efficient activity at −8 to −12 °C (type III). Unlike the selected P. syringae bacteria, P. fluorescens strains did not show signs of frost injury on tomatoes and oranges.