First Report of Fusarium solani Causing Root Rot on Levisticum officinale in China

Lovage (Levisticum officinale Koch) is a long-stemmed perennial plant in the family of Apiaceae. It has been used as a medicinal herb in Europe for centuries (Segebrecht and Schilcher 1989). The herb was successfully introduced into China during the 1950s and the roots were used as a hematic tonic. Cultivation of lovage at a commercial scale has been established in recent years in China. From May to September of 2014, lovage plants grown in Fujian Province developed symptoms of yellowing, stunting, root rot, and finally wilting. A severe brown discoloration of vascular tissue along the roots was also observed. Symptomatic root tissue samples collected from plants in different fields were surface sterilized, plated on potato dextrose agar (PDA), and incubated for 7 days. A Fusarium species was consistently isolated and pure cultures derived from single spores were obtained. Colonies of the Fusarium isolates on PDA at 25 ± 2°C for 7 days were white to light purple with abundant cottony mycelia. Macroconidia were 25.5 to 36.4 × 4.2 to 6.5 μm with three to five septa, and microconidia were and 8.7 to 14.5 × 2.8 to 5.0 μm with zero to one septa. Genomic DNAs from three isolates (FJAT-30850, FJAT-30852, and FJAT-30854 from different plants) were obtained with a fungal genomic DNA extraction kit, and the internal transcribed spacer (ITS) rDNA regions were amplified and sequenced with universal primers ITS-4/ITS-5 (GenBank accession nos. KX229748, KX229749, and KX229750). The ITS sequences of the three isolates shared 99 to 100% sequence identity with those of Fusarium solani isolates (LN828155, KP292807, and KP264654). The fungus was identified as F. solani (Mart.) Sacc. based on both morphological and molecular characteristics (Booth 1977). To confirm the pathogenicity, the Fusarium isolates were grown on potato dextrose broth (PDB) media for 5 days and then inoculated on healthy lovage seedlings. Thirty of 2-month-old seedlings were inoculated with each of the Fusarium conidia suspension (1 × 106 conidia/ml) for 30 min using a root dipping method before being transplanted into a pot. All plants were maintained in a greenhouse at 28/20°C, with 70 to 80% humidity and a 14-h photoperiod. After 10 days, the disease symptoms started with leaf yellowing and the wilt; discoloration of roots occurred 18 days after inoculation. The incidence of diseased plants was 100, 80, and 86.67% for FJAT-30850, FJAT-30852, and FJAT-30854, respectively. Symptoms on the tested plants were similar to those on the diseased plants in the field; the reisolated isolates from root tissue of symptomatic plants were confirmed as F. solani by ITS rDNA region sequencing and the morphology characteristics on PDA plates. Control seedlings, treated with sterile water, did not develop symptoms. The identity of infectious agent was confirmed, which completed Koch’s postulates. The pathogenicity test for the three isolates has been repeated. Although F. solani has been reported as a pathogen in other Apiaceae, such as Angelica acutiloba (Chern et al. 2010), to our knowledge, this is the first report of root rot caused by F. solani on L. officinale in China. © 2017, American Phytopathological Society. All Rights Reserved.