Ice nucleation active bacteria from pistachio in Kerman Province, Iran

Frost damage is one of the major factors threatening pistachio production in southern part of Iran. In the present study, an attempt was made to screen and characterize ice nucleation bacteria associated with frost damage among some predominant epiphytic microflora. A large number of epiphytic bacteria was isolated from different regions in Kerman province. 1200 bacterial isolates were obtained from bud, twig, leaf and green fruit surfaces. Sixty-four strains exhibited ice nucleation activity. Among these, a vast microbial diversity was observed. For preliminary characterization of the isolates, certain key biochemical and pathogenicity tests were performed. The preserved cultures were often checked for ice formation and loss of ice nucleation activity was found in most cultures. Furthermore, factors affecting the increment of ice nucleation activity were studied and the isolates that recovered their ice nucleation activity were selected for sequence analyses of 16SrDNA, rpoD and recA genes, then compared with other isolates in NCBI GenBank using blasts methods. Pseudomonas fragi, P. putida, P. moraviensis, P. virdiflava and Pantoea agglomerans were the major predominant ice nucleation active bacteria established on plant surfaces. This work reports for the first time the presence of two ice nucleation active bacteria, P. fragi and P. moraviensis, on pistachio plants.