Purification and Partial Characterization of Host-Specific Toxins Produced byPericonia circinata

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Abstract
Host-specific toxins isolated from culture filtrates of P. circinata inhibited root growth of the susceptible sorghum [Sorghum bicolor] genotype by 50% at 1 ng/ml and had no effect on root growth of the near-isogenic resistant genotype at 2 .mu.g/ml. Purity of the isolated products was assessed by TLC, thin-layer electrophoresis (TLE), and high-performance liquid chromatography (HPLC) of the toxins or their dansyl derivatives. Two toxic substances were separated by preparative TLC; each contained only aspartic acid and 2 components with properties of polyamines. HPLC resolved each of those toxic fractions into 2 compounds, a biologically active one and an inactive one. In addition to aspartic acid, both active compounds contained the same polyamine, and boty inactive compounds contained another electrophoretically distinct polyamine. The Periconia toxins are low-MW, acidic compounds containing multiple residues of aspartic acid and one or more residues of a polyamine, which is responsible for ninhydrin reactivity and apparently responsible for selective biological activity.