Molecular detection of Fusarium subglutinans, the causal organism of internal fruit rot in greenhouse peppers

Abstract

Internal fruit rot of sweet peppers, caused by Fusarium subglutinans is a new disease found in commercial greenhouses in British Columbia and Alberta, which causes considerable yield losses. Experiments were conducted to develop a rapid and accurate assay for detection of F. subglutinans, by dot-blot hybridization. Internal transcribed spacers 1 (ITS1) and 2 (ITS2) and 5.8S rDNA were amplified by polymerase chain reaction, using universal primers, and a dot-blot assay was employed to detect the pathogen in culture and in the host. Among six probes tested, three (Fsub-1, Fsub-3, and Fsub-5) were selected because they differentiated F. subglutinans from other Fusarium spp. and greenhouse pathogens. Probe Fsub-3 hybridized with all F. subglutinans isolates. Fsub-1 hybridized only with F. subglutinans isolates from Monterey pine (Pinus radiata). Fsub-5 hybridized with F. subglutinans isolates from corn (Zea mays), peppers (Capsicum annuum), and Panicum miliaceum, but not with Pinus radiata isolates. None of these primers hybridized with Fusarium spp. other than F. subglutinans or with other pathogens of greenhouse crops. Dot-blot hybridization developed in this study differentiates F. subglutinans from other Fusarium spp. as well as from other fungal pathogens causing fruit rot of peppers. This technique may help to detect and identify F. subglutinans in culture and in pepper fruits.

Keywords:

• Capsicum annuum
• Fusarium subglutinans
• molecular detection
• dot-blot hybridization
• diagnosis
• identification