CHARACTERIZATION OF RHIZOCTONIA-SOLANI AG-8 FROM BARE PATCHES BY PECTIC ISOZYME (ZYMOGRAM) AND ANASTOMOSIS TECHNIQUES

Isolates of Rhizoctonia solani AG-8 collected from Rhizoctonia bare pa tches at two locations in Western Australia were characterized by pect ic isozyme (zymogram) and anastomosis techniques. All isolates collect ed from the same patch at the same time and at different times up to 1 0 mo apart were members of the same zymogram group. Anastomosis techni ques demonstrated that these multiple isolates from the same patch wer e members of the same clone, as indicated by the clonal anastomosis re action. Anastomosis reactions also indicated that isolates from the sa me zymogram group but from different patches in the same field or farm may or may not be members of the same clone. In general, patches with the same zymogram group and in close proximity to one another are mor e likely to be of the same clone than are patches separated by greater distances. Thus, the zymogram technique demonstrated the existence of distinct groups (currently five) within R. solani AG-8, and the anast omosis technique demonstrated there may be many different clones withi n each zymogram group. In general, the chance of isolates collected fr om patches caused by the same zymogram group being members of the same clone decreases as distance between patches increases. However, clona l relationships have been detected between isolates of the same zymogr am group collected from patches separated by hundreds of kilometers in Australia and in one case in Oregon. Some possible explanations for t he spread of clones are presented.