Botrytis cinerea was detected and quantified in pear stems from six orchards in the Pacific Northwest, and changes in fungal biomass in the stems after 6 and 8 months of cold storage in regular (air) atmosphere were studied. The fungus was detected by plating stem halves on selective medium and by enzyme-linked immunosorbent assay (ELISA) using the Botrytis-specific monoclonal antibody BC-12.CA4. Both methods demonstrated that the incidence of B. cinerea increased from 6 to 8 months, but ELISA was more sensitive than standard isolation. Quantitative ELISAs on stems indicated that over 200 μg of B. cinerea biomass per gram of stem tissue was present in the stems of visibly rotted fruits, but usually less than 35 μg/g was present in stems from fruits without visible gray mold. Aureobasidium pullulans, Penicillium spp., Alternaria spp., and Cladosporium spp. were commonly isolated from stem tissue. A. pullulans was present in 86% of the stems from which B. cinerea was detected. Use of the monoclonal antibody BC-12.CA4 could help in determining the infection path of B. cinerea in pear stems and detection of latent infections, enabling the timing and method of control of stem end rot to be optimized.
Keywords: antagonism.