Factors affecting the autofluorescence response in infected onion epidermal cells

Abstract

Spore suspensions of Botrytis allii and Colletotrichum circinans were used to inoculate leaf-base pieces excised from white or red onion bulbs which had been either exposed, or not exposed, to ambient air before inoculation. Pre- and post-inoculation incubation was in light or dark. Autofluorescent areas formed beneath appressoria of both fungi on both cultivars 18 to 24 h after inoculation, and autofluorescence was found on anti- and periclinal walls. For C. circinans autofluorescence intensity was affected only by exposure, with exposed tissue producing greater autofluorescence intensity than covered tissue. For B. allii autofluorescence intensity was greater on exposed than covered tissue, and on exposed tissue incubated in light following inoculation than on dark-incubated, exposed tissue.