Detection, quantification and classification of soft rot erwinias associated with potato tubers

Abstract

An improved method for detection, quantification and classification of soft rot bacteria associated with potato seed tubers, plant material, soil and water has been developed. The method is based on the use of a modified version of the crystal violet pectate selective medium (CVP), enrichment cultures under anaerobic conditions using pectate as the sole carbon source for recovery improvement, and the quantitative estimation ofErwinia spp. by employing a new solid medium - most probable number (MPN) method. The use of this method enabled an improvement in the recovery and identification of specificErwinia spp. in mixed populations. This was done by incubating CVP plates — used for the MPN counting — at three different temperatures (15, 28 and 39°C). These combined techniques were used for estimating low level populations at less than one cell per gram or ml tested ofErwinia carotovora subsp.carotovora, E. carotovora subsp.atroseptica, andE. chrysanthemi.