Effect of virulence and serial transfers of Xanthonomas campestris on xanthan gum production

ABSTRACT

The virulence of six Xanthomonas campestris isolates was evaluated using the percentage of lesion area of leaves in Brassica oleraceae host plant, compared to diameter of colonies, xantham production and gum viscosity. In terms of virulence, the isolates belonged to two statiscally different groups: isolates B, UPF and C(7), showed values between 52 and 69(per cent), while isolates CF, C and strain B-1459 gave 0-30 (per cent) of lesion area. Final xanthan concentration, gum viscosity and colony diameter did not correlate with virulence calculated by percentage of lesion area, showing that this parameter is not a good criterium for selection of potential xantham producer isolates. Serial transfers of X. campestris isolates in host plant did not show a significant effect on in vitro production of xanthan or on viscosity levels, suggesting that the increasing interaction between plant and bacteria did not stimulate the increase in xanthan production and viscosity.