PCR Detection and RFLP Differentiation of Botrytis Species Associated with Neck Rot of Onion

Botrytis aclada and other Botrytis spp. can cause neck rot on onions, a storage disease that normally is very difficult to detect at harvest using traditional isolation techniques. Sequence characterized amplified region primers (BA2f/BA1r) were designed based on a previously cloned and amplified DNA fragment for direct amplification of isolates of Botrytis spp. associated with neck rot of onions. Digestion of the polymerase chain reaction (PCR) amplification product with the restriction enzyme ApoI makes it possible to distinguish the five groups: Botrytis aclada types AI and AII (B. allii); B. byssoidea; B. squamosa; and B. cinerea. The detection limit was 1 to 10 pg of pure fungal DNA. It was possible to detect B. aclada with the PCR method in artificially inoculated onion bulb tissue and in mature onion leaves showing no symptoms of the disease. The availability of a sensitive and specific PCR detection and identification method for Botrytis onion neck rot pathogens should facilitate ecological studies of this group of onion pathogens.