Detection of strawberry black spot (Colletotrichum acutatum) with monoclonal antibodies 1

Baiting with apple fruit and stimulation of sporulation with paraquat are sensitive tests currently used on strawberry planting/propagating material for the detection of Colletotrichum acutatum. A monoclonal antibody/ELISA technique could make testing shorter and easier. Several monoclonal antibodies distinguished C. acutatum in vitro; one recognized 45 out of 48 isolates believed to be C. acutatum, but not 18 out of 19 typical of closely related C. gloeosporioides. A less specific monoclonal antibody reacted positively with 66 out of 67 Colletotrichum isolates, indicating it was genus‐specific. The antigen was mainly associated with conidia. A dot‐blot test using PALL Biodyne membrane gave qualitative results more quickly and simply than ELISA, reducing time taken from 24 to 3 h. Specific monoclonal antibodies distinguished C. acutatum from C. gloeosporioides on strawberry petioles, but were less sensitive than either plating or paraquat tests, detecting only eight out of 50 potential positives compared with at least 30 out of 50 with the other tests. An immunofluorescence technique confirmed that conidia were the main source of antigen. A specific monoclonal antibody also reacting to mycelium was produced.