First Report of Charcoal Rot Caused by Macrophomina phaseolina on Hemp (Cannabis sativa) in Missouri

HomePlant DiseaseAhead of PrintFirst Report of Charcoal Rot Caused by Macrophomina phaseolina on Hemp (Cannabis sativa) in Missouri PreviousNext DISEASE NOTE OPENOpen Access licenseFirst Report of Charcoal Rot Caused by Macrophomina phaseolina on Hemp (Cannabis sativa) in MissouriK. M. Goodnight, P. Tian, and K. M. BissonnetteK. M. Goodnighthttps://orcid.org/0000-0001-9142-2572Department of Biological Sciences, University of Missouri, Columbia, MO 65201Search for more papers by this author, P. Tianhttps://orcid.org/0000-0003-3479-0971Plant Diagnostic Clinic, Division of Plant Science and Technology, University of Missouri, Columbia, MO 65211Search for more papers by this author, and K. M. Bissonnette†Corresponding author: K. M. Bissonnette; E-mail Address: [email protected]https://orcid.org/0000-0001-5394-9031Division of Plant Science and Technology, University of Missouri, Columbia, MO 65201Search for more papers by this authorAffiliationsAuthors and Affiliations K. M. Goodnight1 P. Tian2 K. M. Bissonnette3 † 1Department of Biological Sciences, University of Missouri, Columbia, MO 65201 2Plant Diagnostic Clinic, Division of Plant Science and Technology, University of Missouri, Columbia, MO 65211 3Division of Plant Science and Technology, University of Missouri, Columbia, MO 65201 Published Online:23 Aug 2023https://doi.org/10.1094/PDIS-02-23-0385-PDNAboutSectionsView articlePDFSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat View articleCharcoal rot, caused by Macrophomina phaseolina, is abundant in the soil and pathogenic to soybean, corn, and many other hosts, including hemp (Cannabis sativa) grown for fiber, grain, and cannabinoids (Casano et al. 2018; Su et al. 2001). Hemp production in Missouri was a relatively new addition to the 2021 growing season. Charcoal rot was reported in Reynolds, Knox, and Boone counties in Missouri in commercial and experimental fields. One field had heavy disease pressure and uneven stand loss. The total loss was estimated at ∼60% and was attributed to charcoal rot. Charcoal rot signs and symptoms, microsclerotia on the lower stem and root tissue, wilting, and stem discoloration, were observed on a majority of hemp plants received at the University of Missouri Plant Diagnostic Clinic in July and late Fall of 2021, including samples from Bradford Research Farm in Boone County and Greenley Research Center in Knox County. Root and crown tissue from the plants from the Greenley Research Center were cultured on acidified potato dextrose agar (APDA). M. phaseolina and other fungi grew from the plated tissue after about 3 days of incubation at room temperature. M. phaseolina was confirmed based on the presence of melanized hyphae and microsclerotia (Siddique et al. 2021). The microsclerotia were black, round to ovoid, and about 34 to 87 (avg. 64) × 32 to 134 (avg. 65) μm (n = 44). A single-hypha isolation from a putative M. phaseolina isolate was conducted to obtain a pure culture. The M. phaseolina culture from the Greenley Research Center was used to complete Koch’s postulates of charcoal rot on four hemp cultivars. Sterilized toothpicks were added to pure cultures of M. phaseolina on APDA and incubated at room temperature for 1 week to allow for colonization and for use in greenhouse inoculation. Four hemp cultivars (Katani, Grandi, CFX-2, and CRS-1) were grown in sterilized silt loam for 3 weeks in a greenhouse. About four plants per cultivar were grown for inoculation and one plant per cultivar was used as a control. Plants were inoculated with the colonized toothpicks that were gently rubbed onto stem tissue and inserted into the soil at the stem. For 6 weeks, the plants were kept in greenhouse conditions of 25°C with a 12-h light and dark cycle and were watered when soil appeared dry. Plants were kept in a loosely sealed container constructed from wood and vinyl sheeting to minimize cross contamination with other plants in the same greenhouse. Plants were monitored weekly for charcoal rot symptoms. Symptoms that resembled charcoal rot, wilting and microsclerotia on the lower stem, were present on inoculated plants, but not controls, after about 4 weeks. Isolates resembling M. phaseolina in culture were recovered from symptomatic, inoculated plants, fulfilling Koch’s postulates. DNA was extracted from pure cultures of both the initial isolate and the isolate obtained from Koch’s postulates using GeneJet Plant Genomic DNA Purification Kit (Thermo Scientific, CA, U.S.A.) and the internal transcribed spacer (ITS) region of ribosomal DNA including ITS1, 5.8S, and ITS4 regions were amplified using universal primers ITS1 and ITS4 (White et al. 1990). The ITS region was sequenced and compared with reference sequences in GenBank by BLAST analysis. Recovered isolates (GenBank OQ455934.1) showed closest sequence similarity (100%) to M. phaseolina accession GU046909.1. Little is known about the life cycle, growth conditions, and possible inoculum buildup in the soil in hemp in Missouri. Also, M. phaseolina is a known pathogen of corn and soybean and effective management strategies are challenging for these crops due to the broad host range of the pathogen. Cultural management practices, such as crop rotations to reduce inoculum in the soil and close monitoring for symptoms, may reduce the severity of the disease.The author(s) declare no conflict of interest.References:Casano, S., et al. 2018. Plant Dis. 102:1665. https://doi.org/10.1094/PDIS-02-18-0208-PDN Link, Google ScholarSiddique, S., et al. 2021. Mycologia 113:92. https://doi.org/10.1080/00275514.2020.1810516 Crossref, ISI, Google ScholarSu, G., et al. 2001. Phytopathology 91:120. https://doi.org/10.1094/PHYTO.2001.91.2.120 Link, ISI, Google ScholarWhite, T. J., et al. 1990. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA. Crossref, Google ScholarThe author(s) declare no conflict of interest.DetailsFiguresLiterature CitedRelated Just PublishedSubscribeISSN:0191-2917e-ISSN:1943-7692 Metrics Article History Published: 23 Aug 2023First Look: 8 May 2023Accepted: 5 May 2023 Information© 2023 The American Phytopathological SocietyKeywordscharcoal rotfield cropsfungihemppathogen detectionThe author(s) declare no conflict of interest.PDF download