LIMITATIONS OF IN-VITRO STRAIN SCREENING METHODS FOR THE SELECTION OFSCLEROTINIA SPP AS POTENTIAL MYCOHERBICIDES AGAINST THE PERENNIAL WEED RANUNCULUS-ACRIS

Nineteen isolates of Sclerotinia sclerotiorum and three isolates of S. minor were inoculated an to excised tissues and intact plants of Ranu nculus acris (giant buttercup), to evaluate their pathogenicity. All i solates proved pathogenic, with S. sclerotiorum being more pathogenic than S. minor on both excised tissues and intact plants. Seven of the S. sclerotiorum isolates were more pathogenic than the others on excis ed tissues, but no significant differences in pathogenicity were found between any of the isolates when they were inoculated an to intact pl ants. The results of this study indicate that the excised tissue metho d cannot be used to predict whole plant mortality, nor, therefore, the mycoherbicide potential of strains of S. sclerotiorum for this perenn ial weed.