Multiplex real‐time PCR assays for detection of four seedborne spinach pathogens

• Published in: Journal of applied microbiology 2014-08, Vol.117 (2), p.472-484
• Main Authors: Feng, C, Mansouri, S, Bluhm, B.H, du Toit, L.J, Correll, J.C
• Format: Article
• Language: English
• Subjects: Ascomycota - genetics; Ascomycota - isolation & purification; Biological and medical sciences; Cladosporium; Cladosporium - genetics; Cladosporium - isolation & purification; Cladosporium leaf spot; conserved sequences; Deoxyribonucleic acid; DNA; downy mildew; Economic importance; Food contamination & poisoning; Fundamental and applied biological sciences. Psychology; fungi; intergenic DNA; internal transcribed spacers; Microbiology; Multiplex Polymerase Chain Reaction - methods; Oomycetes; Pathogens; Peronospora; Peronospora - genetics; Peronospora - isolation & purification; Peronospora farinosa; Polymerase chain reaction; quantitative polymerase chain reaction; Real-Time Polymerase Chain Reaction - methods; real‐time PCR; saprophytes; seed assay,spinach; seed industry; Seeds - microbiology; Spinach; Spinacia oleracea; Spinacia oleracea - microbiology; Stemphylium; Stemphylium botryosum; Stemphylium leaf spot; Vegetables; Verticillium - genetics; Verticillium - isolation & purification; Verticillium dahliae; Verticillium wilt
• ISSN: 1364-5072; 1365-2672
• DOI: 10.1111/jam.12541

AIMS: To develop multiplex TaqMan real‐time PCR assays for detection of spinach seedborne pathogens that cause economically important diseases on spinach. METHODS AND RESULTS: Primers and probes were designed from conserved sequences of the internal transcribed spacer (for Peronospora farinosa f. sp. spinaciae and Stemphylium botryosum), the intergenic spacer (for Verticillium dahliae) and the elongation factor 1 alpha (for Cladosporium variabile) regions of DNA. The TaqMan assays were tested on DNA extracted from numerous isolates of the four target pathogens, as well as a wide range of nontarget, related fungi or oomycetes and numerous saprophytes commonly found on spinach seed. Multiplex real‐time PCR assays were evaluated by detecting two or three target pathogens simultaneously. Singular and multiplex real‐time PCR assays were also applied to DNA extracted from bulked seed and single spinach seed. CONCLUSIONS: The real‐time PCR assays were species‐specific and sensitive. Singular or multiplex real‐time PCR assays could detect target pathogens from both bulked seed samples as well as single spinach seed. SIGNIFICANCE AND IMPACT OF THE STUDY: The freeze‐blotter assay that is currently routinely used in the spinach seed industry to detect and quantify three fungal seedborne pathogens of spinach (C. variabile, S. botryosum and V. dahliae) is quite laborious and takes several weeks to process. The real‐time PCR assays developed in this study are more sensitive and can be completed in a single day. As the assays can be applied easily for routine seed inspections, these tools could be very useful to the spinach seed industry.