2 MODIFIED CRYSTAL VIOLET PECTATE (CVP) MEDIA FOR THE DETECTION, ISOLATION AND ENUMERATION OF SOFT ROT ERWINIAS

Two modifications of the selective-diagnostic crystal violet pectate (CVP) medium for soft rot erwinias were developed using a new formulation of sodium polypectate; these were a single layer medium and a double layer medium consisting of an agar base with a pectate overlayer. Both media contained 0.1% tryptone to promote growth and cavity formation by erwinias and 40 mug ml-1 novobiocin instead of sodium lauryl sulphate to increase recovery rate and selectivity. Colonies of the three erwinias commonly associated with potatoes formed characteristic deep cavities in the single layer modified CVP. Cavities in the double layer CVP although deep were smaller but remained distinct longer. Recovery rate and selectivity with both media were better than with the original CVP.