Protein-Lipopolysaccharide Complexes Produced by Virulent and Non-Virulent Isolates of Vertidllium albo-atrum and V. dahliae are Non-Specific Toxins to Tomato and Potato.

Toxic protein-lipopolysaccharide complexes (PLPC) were isolated from culture filtrates of Verticillium albo-atrum (isolate WCS 800) and V. dabliae (WCS 070) isolates, both virulent to tomato and potato cultivars, and from an isolate of V. albo-atrum (V22W) which was non-virulent to these hosts. The virulent isolates each produced one major PLPC in culture and the non-virulent isolate produced two (fractions 1 and 2, characterized by their elution pattern after gel filtration). Virulence in these three isolates was not related to quantity of PLPC produced in culture. However, PLPC from the virulent isolates were toxic to tomato in a leaf bioassay at 4 μg ml-1 (WCS 800) and 20 μg ml-1(WCS 070) but the two PLPC from the non-virulent isolate required concentrations of 100 and 1000 jug ml"1 for toxicity. Production of a modified, less toxic PLPC in V22W may partly account for its non-virulence. Gel filtration of PLPC from the three isolates on a calibrated Sephacryl S-400 column, eluted in phosphate buffer plus NaCl, indicated a compound of heterogeneous molecular mass with an average of 126,000 daltons for the PLPC of WCS 800, WCS 070 and fraction 1 of V22W, and 25,000 daltons for fraction 2 of V22W. Attempts to extract a low molecular weight toxin from the PLPC by extended dialysis were unsuccessful. The susceptibility of 12 tomato and 19 potato cultivars to the Verticillium isolates was compared with their sensitivity to PLPC. Susceptibility was not correlated with toxin sensitivity and the PLPC were concluded to be non-specific toxins in these hosts. [ABSTRACT FROM AUTHOR]