COMPARISON OF PECTIC ZYMOGRAMS PRODUCED BY DIFFERENT CLONES OF SCLEROTINIA-SCLEROTIORUM IN CULTURE

The isozymes of polygalacturonase (PG) and pectinmethylesterase (PME), produced in vitro by 35 isolates belonging to 15 clones of Sclerotini a sclerotiorum, were detected by isoelectric focusing on polyacrylamid e gels and activity staining of agarose overlays containing the approp riate substrate. Analysis of the PG isozyme banding patterns (zymogram s) identified two distinct phenotypes among the isolates from canola, S. sclerotiorum zymogram group-1 (SSZG-1) and SSZG-2. Of the 11 clones tested, nine clones had the SSZG-1 phenotype, two clones had the SSZG -2 phenotype, and one clone had both SSZG-1 and -2 phenotypes. Therefo re, in this sample, there were fewer PG phenotypes than clonal genotyp es. One frequently sampled clone with wide geographic distribution inc luded two isolates of SSZG-1 and eight of SSZG-2. Two isolates, one fr om cultivated sunflower and one from a wild plant, Ranunculus ficaria, showed isozyme patterns different from the isolates obtained from can ola. The isolate from sunflower had the SSZG-3 phenotype, and the isol ate from R. ficaria had the SSZG-4 phenotype. There was no apparent co rrespondence between isozyme phenotype and either the pathogenicity or aggressiveness of the clones on canola. The isozyme analysis of PME s howed no variation among the isolates collected from canola.