Validation of a duplex TaqMan real-time PCR for detection of Colletotrichum coccodes and Rhizoctonia solani AG-3 on potato tubers
Published 2025-11-03
Keywords
- quantitative PCR,
- diagnostics,
- black dot,
- black scurf,
- stem canker
- Solanum tuberosum ...More
How to Cite
Copyright (c) 2025 Martina SANNA, Vladimiro GUARNACCIA, Davide SPADARO, Monica MEZZALAMA

This work is licensed under a Creative Commons Attribution 4.0 International License.
Abstract
The potato pathogens Colletotrichum coccodes, (causing black dot), and Rhizoctonia solani anastomosis group 3 (AG-3) (causing black scurf and stem canker) are economically important, and are common in potato production regions, including Northern Italy. A duplex TaqMan quantitative real-time PCR, based on two previously validated singleplex methods, was tested for identification of these species in potato propagation material. This validation was carried out according to EPPO PM 7/98 standard guidelines. The limit of detection (LOD) for the method, assessed using serial dilutions of targets DNA, was 10 fg. Specificity was assessed by testing ten C. coccodes and four R. solani AG-3 isolates, and 19 non-target species including other Colletotrichum and Rhizoctonia spp. and potato pathogens, respecting inclusivity and exclusivity criteria. Selectivity of the test showed no influence of DNA obtained from potato tubers. Repeatability and reproducibility of the duplex qPCR were also validated. The assay was able to detect and distinguish, within a single run, the two fungi allowing early detection in potato tubers.
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References
- Anderson N.A., 1982. The genetics and pathology of Rhizoctonia solani. Annual Review of Phytopathology 20: 329–347. https://doi.org/10.1146/annurev.py.20.090182.001553
- Aqeel A.M., Pasche J.S., Gudmestad, N.C., 2008. Variability in morphology and aggressiveness among North American vegetative compatibility groups of Colletotrichum coccodes. Phytopathology 98(8): 901–909. https://doi.org/10.1094/PHYTO-98-8-0901
- Banville G.J., Carling D.E., Otrysko B.E., 1996. Rhizoctonia diseases on potato. In: Rhizoctonia Species: Taxonomy, Molecular Biology, Ecology, Pathology and Disease Control (B. Sneh, S. Jabaji-Hare, S. Neate, G. Dijst, ed.), Kluwer Academic Publishers, Dordrecht, Netherlands, 321–330.
- Belov G.L., Belosokhov A.F., Kutuzova I.A., Statsyuk N.V., Chudinova E.M., … Elansky, S.N., 2018. Colletotrichum coccodes in potato and tomato leaves in Russia. Journal of Plant Diseases and Protection 125: 311–317. https://doi.org/10.1007/s41348-017-0138-0
- Buonaurio R., Natalini G., Covarelli L., Cappelli C., 2002. Occurrence of black dot of potato caused by Colletotrichum coccodes in central Italy. Plant Disease 86(5): 562–562. https://doi.org/10.1094/PDIS.2002.86.5.562C
- Çalışkan M.E., Yousaf M.F., Yavuz C., Zia M.A.B., Çalışkan S., 2023. History, production, current trends, and future prospects. In: Potato production worldwide (M. E. Çalişkan, A. Bakhsh, K. Jabran, ed.), Academic Press, 1–18. https://doi.org/10.1016/B978-0-12-822925-5.00016-5
- Capote N., Pastrana A.M., Aguado A., Sánchez-Torres, P., 2012. Molecular tools for detection of plant pathogenic fungi and fungicide resistance. Plant Pathology 7: 151–202.
- Cullen D.W., Lees A.K., Toth I.K., Duncan J.M., 2001. Conventional PCR and real-time quantitative PCR detection of Helminthosporium solani in soil and on potato tubers. European Journal of Plant Pathology 107(4): 387–398. https://doi.org/10.1023/A:1011247826231
- Cullen D.W., Lees A.K., Toth I.K., Duncan J.M., 2002. Detection of Colletotrichum coccodes from soil and potato tubers by conventional and quantitative real‐time PCR. Plant Pathology 51(3): 281–292. https://doi.org/10.1046/j.1365-3059.2002.00690.x
- Damm U., Cannon P. F., Woudenberg J. H. C., Johnston P. R., Weir B. S., … Crous P.W. 2012. The Colletotrichum boninense species complex. Studies in Mycology 73(1): 1–36. https://doi.org/10.3114/sim0002
- EPPO, 2021. PM 7/98 (5) Specific requirements for laboratories preparing accreditation for a plant pest diagnostic activity. EPPO Bulletin 51: 468–498.
- Europatat, 2023. The EU potato sector in 2020: statistics on production & trade. European Potato Trade Association (Europatat). Accessed February 26, 2025, from https://europatat.eu/activities/the-eu-potato-sector/
- FAO, 2022. Food and agriculture data, Food and Agriculture Organization of the United Nations. Accessed February 26, 2025, from https://www.fao.org/faostat/en/#home
- Fiers M., Edel-Hermann V., Chatot C., Le Hingrat Y., Alabouvette C., Steinberg C., 2012. Potato soil-borne diseases. A review. Agronomy for Sustainable Development 32(1): 93–132. https://doi.org/10.1007/s13593-011-0035-z
- Gerin D., Pollastro S., Raguseo C., De Miccolis Angelini R.M., Faretra F., 2018. A ready-to-use single- and duplex-TaqMan-qPCR assay to detect and quantify the biocontrol agents Trichoderma asperellum and Trichoderma gamsii. Frontiers in Microbiology 9: 2073. https://doi.org/10.3389/fmicb.2018.02073
- Guerber J.C., Liu B., Correll J.C., Johnston P.R., 2003. Characterization of diversity in Colletotrichum acutatum sensu lato by sequence analysis of two gene introns, mtDNA and intron RFLPs, and mating compatibility. Mycologia 95(5): 872–895. https://doi.org/10.1080/15572536.2004.11833047
- Hariharan G., Prasannath K., 2021. Recent advances in molecular diagnostics of fungal plant pathogens: a mini review. Frontiers in Cellular and Infection Microbiology 10: 600234. https://doi.org/10.3389/fcimb.2020.600234
- Heltoft P., Brurberg M.B., Skogen M., Le V.H., Razzaghian J., Hermansen A., 2016. Fusarium spp. causing dry rot on potatoes in Norway and development of a real-time PCR method for detection of Fusarium coeruleum. Potato Research 59: 67–80. https://doi.org/10.1007/s11540-015-9313-5
- ISTAT, 2024. Coltivazioni: Cereali, Legumi, Radici Bulbi e Tuberi. Accessed February 26, 2025, from http://dati.istat.it/Index.aspx?QueryId=33702
- Lees A.K., Cullen D.W., Sullivan L., Nicolson M.J., 2002. Development of conventional and quantitative real‐time PCR assays for the detection and identification of Rhizoctonia solani AG‐3 in potato and soil. Plant Pathology 51(3): 293–302. https://doi.org/10.1046/j.1365-3059.2002.00712.x
- Lees A.K., Hilton A.J., 2003. Black dot (Colletotrichum coccodes): an increasingly important disease of potato. Plant Pathology 52(1): 3–12. https://doi.org/10.1046/j.1365-3059.2003.00793.x
- Lehtonen M.J., Somervuo P., Valkonen J.P.T., 2008. Infection with Rhizoctonia solani induces defense genes and systemic resistance in potato sprouts grown without light. Phytopathology 98: 1190–1198. https://doi.org/10.1094/PHYTO-98-11-1190
- Liu F., Cai L., Crous P.W., Damm U., 2013. Circumscription of the anthracnose pathogens Colletotrichum lindemuthianum and C. nigrum. Mycologia 105: 844–860. https://doi.org/10.3852/12-315
- Luchi N., Pepori A.L., Bartolini P., Ioos R., Santini, A., 2018. Duplex real-time PCR assay for the simultaneous detection of Caliciopsis pinea and Fusarium circinatum in pine samples. Applied Microbiology and Biotechnology 102: 7135–7146. https://doi.org/10.1007/s00253-018-9184-1
- Manici L.M., Caputo F., 2009. Fungal community diversity and soil health in intensive potato cropping systems of the east Po valley, northern Italy. Annals of Applied Biology 155(2): 245–258. https://doi.org/10.1111/j.1744-7348.2009.00335.x
- Manici L.M., Caputo F., Nicoletti F., 2016. Potato root infection by Rhizoctonia solani anastomosis group-3 and Colletotrichum coccodes under current and future spring weather in northern Italy. The Journal of Agricultural Science 154(8): 1413–1424. https://doi.org/10.1017/S0021859615001343
- McCartney H.A., Foster S.J., Fraaije B.A., Ward, E., 2003. Molecular diagnostics for fungal plant pathogens. Pest Management Science: formerly Pesticide Science 59(2): 129–142.
- Niu Z., Zheng L., Yang P., Wang J., Tian M., … Zhu J., 2022. Detection of Alternaria solani with high accuracy and sensitivity during the latent period of potato early blight. Frontiers in Microbiology 13: 1016996. https://doi.org/10.3389/fmicb.2022.1016996
- Ortega S.F., Siciliano I., Prencipe S., Gullino M.L., Spadaro D., 2020. Development of PCR, LAMP and qPCR Assays for the Detection of Aflatoxigenic Strains of Aspergillus flavus and A. parasiticus in Hazelnut. Toxins 12(12): 757. https://doi.org/10.3390/toxins12120757
- Prencipe S., Sillo F., Garibaldi A., Gullino M.L., Spadaro D., 2020. Development of a sensitive TaqMan qPCR assay for detection and quantification of Venturia inaequalis in apple leaves and fruit and in air samples. Plant Disease 104(11): 2851–2859. https://doi.org/10.1094/PDIS-10-19-2160-RE
- Romero-Cuadrado L., López-Herrera C.J., Aguado A., Capote N., 2023. Duplex real-time PCR assays for the simultaneous detection and quantification of Botryosphaeriaceae species causing canker diseases in woody crops. Plants 12(11): 2205. https://doi.org/10.3390/plants12112205
- Ryazantsev D.Y., Chudinova E.M., Kokaeva L.Y., Elansky S.N., Balabko P. N., … Zavriev S.K., 2023. Detection of Colletotrichum coccodes by Real-Time PCR. Biology Bulletin Reviews 13(1): S108-S113. https://doi.org/10.1134/S2079086423070101
- Salamone A.L., Okubara P.A., 2020. Real-time PCR quantification of Rhizoctonia solani AG-3 from soil samples. Journal of Microbiological Methods 172: 105914. https://doi.org/10.1016/j.mimet.2020.105914
- Stevenson W.R., Loria R., Franc G.D., Weingartner D.P., 2001. Compendium of Potato Diseases. 2nd ed. The American Phytopathological Society, St. Paul, MN, USA. 520 pp.
- Tsror L., 2004. Effect of light duration on severity of black dot caused by Colletotrichum coccodes on potato. Plant Pathology 53: 288–293. https://doi.org/10.1111/j.0032-0862.2004.01011.x
- White T.J., Bruns T., Lee S.J.W.T., Taylor J., 1990. Amplification and direct sequencing of fungal ribosomal RNA genes for phylogenetics. In: PCR protocols: a Guide to methods and applications (M.A. Innis, D.H. Gelfand, J.J. Sninsky, T.J. White ed.), Academic Press, New York, 315-322.
- Woodhall J.W., Lees A.K., Edwards S.G., Jenkinson P., 2008. Infection of potato by Rhizoctonia solani: effect of anastomosis group. Plant Pathology 57(5): 897–905. https://doi.org/10.1111/j.1365-3059.2008.01889.x
- Woodhall J.W., Adams I.P., Peters J.C., Harper G., Boonham N., 2013. A new quantitative real-time PCR assay for Rhizoctonia solani AG3-PT and the detection of AGs of Rhizoctonia solani associated with potato in soil and tuber samples in Great Britain. European journal of plant pathology 136: 273–280. https://doi.org/10.1007/s10658-012-0161-8
