First Report of Fusarium Wilt of Blackberry Caused by Fusarium oxysporum f. sp. mori in North Carolina

Abstract

HomePlant DiseaseVol. 104, No. 3First Report of Fusarium Wilt of Blackberry Caused by Fusarium oxysporum f. sp. mori in North Carolina PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Fusarium Wilt of Blackberry Caused by Fusarium oxysporum f. sp. mori in North CarolinaA. M. Pastrana, W. O. Cline, T. W. Wong, D. C. Watson, J. Mercier, K. Ivors, J. C. Broome, L. M. Quesada-Ocampo, and T. R. GordonA. M. Pastranahttp://orcid.org/0000-0001-6540-4573University of California, Davis, CA 95616Search for more papers by this author, W. O. ClineNorth Carolina State University, Raleigh, NC 27695Search for more papers by this author, T. W. WongNorth Carolina State University, Raleigh, NC 27695Search for more papers by this author, D. C. WatsonUniversity of California, Davis, CA 95616Search for more papers by this author, J. MercierDriscoll’s Inc., Watsonville, CA 95076Search for more papers by this author, K. Ivorshttp://orcid.org/0000-0002-0930-3214Driscoll’s Inc., Watsonville, CA 95076Search for more papers by this author, J. C. BroomeDriscoll’s Inc., Watsonville, CA 95076Search for more papers by this author, L. M. Quesada-Ocampohttp://orcid.org/0000-0002-9072-7531North Carolina State University, Raleigh, NC 27695Search for more papers by this author, and T. R. Gordon†Corresponding author: T. R. Gordon; E-mail Address: trgordon@ucdavis.eduhttp://orcid.org/0000-0002-1715-6509University of California, Davis, CA 95616Search for more papers by this author AffiliationsAuthors and Affiliations A. M. Pastrana1 W. O. Cline2 T. W. Wong2 D. C. Watson1 J. Mercier3 K. Ivors3 J. C. Broome3 L. M. Quesada-Ocampo2 T. R. Gordon1 † 1University of California, Davis, CA 95616 2North Carolina State University, Raleigh, NC 27695 3Driscoll’s Inc., Watsonville, CA 95076 Published Online:22 Jan 2020https://doi.org/10.1094/PDIS-09-19-1980-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Beginning in 2015, wilting blackberry plants (Rubus L. subgenus Rubus) were observed in commercial plantings of cultivars BD467.1, BJ110.2, and Prime-Ark 45 in Pender County, North Carolina. Symptoms included chlorotic, wilted, or dried leaves on the entire cane. A dark, necrotic lesion on one side of the cane extending along the entire length of the cane was often visible. Complete or partial plant collapse was also observed, and up to 15% disease incidence occurred during fall 2018. Symptomatic blackberry plants of cultivar Prime-Ark 45 at one location in Pender County were sent to the North Carolina State University Plant Disease and Insect Clinic. To recover fungi from plants, infected tissues were surface sterilized in 1% NaOCl for 1 min. The tissue was rinsed in sterile distilled water, cut into small pieces, and placed on acidified potato dextrose agar (APDA). Two isolates, each from a different plant, were transferred from APDA to Nash and Snyder medium (Thies and Levi 2007), which is selective for Fusarium spp. Single strains (GL1963 and GL1964) were obtained by excising hyphal tips from recently germinated spores. Both isolates produced microconidia in false heads on short monophialides and macroconidia with elongated, bent apical cells and notched basal cells on carnation leaf agar, consistent with identification as Fusarium oxysporum Schlechtendahl emend. Snyder & Hansen (Leslie and Summerell 2006). Primer pairs iNL11/CNSa and iCNS11/NLa were used to amplify the intergenic spacer (O’Donnell et al. 2009). On the basis of a comparison of 2,281 bp, both isolates had identical sequences (GenBank accessions MN013360 and MN013361), which revealed a 100% match with sequences of F. oxysporum accessions in GenBank (AY527725.1) and Fusarium-ID (FD_00847_IGS) databases. A comparison with previously described blackberry isolates showed a 100% match with F. oxysporum f. sp. mori isolates from California (GenBank accessions KY515229 and KY515230). Complementary nit phenotypes obtained for each isolate, as described by Correll et al. (1987), were not compatible with F. oxysporum f. sp. mori strains previously identified in California. Both isolates from North Carolina were tested for pathogenicity to blackberry cultivar BJ110.2. For each isolate, five plants (approximately 8 months old) were inoculated by immersing roots for 10 min in a suspension of 5 × 106 spores/ml, which was obtained from cultures grown on PDA as described by Schmale and Gordon (2003). Thereafter, inoculated plants were placed in pots filled with Sunshine mix number 1 (SunGro Horticulture Canada). Each isolate was included in two independent pathogenicity tests, each of which included isolate GL1804 as the positive control (Pastrana et al. 2017). In each trial, five plants were immersed in sterile 0.1% water agar instead of a spore suspension to serve as negative controls. Inoculated and control plants were arranged in randomly assigned positions in a greenhouse with temperatures ranging from 15 to 30°C and relative humidity between 15 and 75%. By 6 to 7 weeks after inoculation, all inoculated plants were severely diseased or dead, and negative control plants remained healthy. F. oxysporum was recovered from stems and petioles of all symptomatic plants. This disease was previously reported in California and Mexico (Gordon et al. 2016; Hernandez-Cruz et al. 2015).The author(s) declare no conflict of interest.