Evaluation of ice nucleation ability of bacteria isolated from commercial sugarcane genotypes

Background and Objectives:

 Khuzestan is the only province with sugarcane cultivation. One of the limiting factors in the production of this crop is the occurrence of frost damages in some years. Since no comprehensive research has yet been conducted on detection and evaluation of bacteria with the potential to form nuclear ice in frostbite, this study was carried out to evaluate this subject.

 Materials and Methods:

 This study was carried out in the laboratory of Institute for Research and Training of Sugar and Auxiliary Industries. Endophytic and epiphytic strains of bacteria were isolated from sugarcane. To test the freezing potential of representative strains, four tests including, "determination of Ice nucleation activity by freezing in the tube", "freezing droplet test at -20 °C", "Ice nucleation test on sugarcane cut leaves in vitro" and "Ice nucleation test on sugarcane plant in greenhouse conditions" were performed. Also the genes of the nucleus were detected by 3076f / 3463r and 3308f / 3463r specific primers. 

Results:

 Results show that bacteria species B. gladioli, B. fungorum, B. cantaminans, M. huakuii, O. ciceri, M. proteolyticum, M. Foliorum, R. solanacearum , R. picketii and X. campestris had different degrees of symptoms. In addition, the genes of the nucleus were detected by 3076f / 3463r and 3308f / 3463r specific primers. For all of above mentioned bacterial strains, specifically strain X. campestris, no references have been reported of ice nucleation activity. To assess susceptibility or resistance of sugarcane, cultivar CP69-1062 were the most susceptible and highly damaged in the tests including "Ice nucleation test on sugarcane cut leaves in vitro" and "Ice nucleation test on sugarcane plant in greenhouse conditions". In addition, CP57-614 and CP48-103 cultivars showed minimum variation in frosting in compression to CP69-1062 cultivar. Two cultivars including CP73-21 and SP70-1143 exhibited a high degree of resistance to frostbite.

 Discussion:

 Due to the high variation among Ice-Nucleating bacteria and the sensitivity of commercial cultivars, our finding can be a suitable option for producers and encourage them to use resistant cultivars in the field.