Detection of Sclerotium cepivorum within onion plants using PCR primers

Abstract

Primers were designed to amplify the 5·8S rRNA gene and part of the flanking ITS regions from S. cepivorum, the causal agent of white rot in onion ( Allium cepa). The primers amplified a DNA fragment of the same size from seven UK isolates of S. cepivorum and not from related fungi or the host plant while an atypical Egyptian isolate produced a different sized product. In a test of sensitivity, the primers amplified S. cepivorum DNA in the presence of 1000-fold excess onion DNA. A single band, corresponding to S. cepivorum, resulted from amplification of DNA extracted from field-infected onions. When infected onion seedlings were examined by electron microscopy, fungal hyphae were visible in the same regions where PCR detected DNA of S. cepivorum.