First Report of Stem and Root Rot of Chinese Kale Caused by Fusarium incarnatum-equiseti Species Complex in China

Abstract

HomePlant DiseaseVol. 103, No. 7First Report of Stem and Root Rot of Chinese Kale Caused by Fusarium incarnatum-equiseti Species Complex in China PreviousNext DISEASE NOTESFirst Report of Stem and Root Rot of Chinese Kale Caused by Fusarium incarnatum-equiseti Species Complex in ChinaW. Akram, A. Ahmad, W. Luo, N. A. Yasin, T. Wu, J. Guo, Q. Wang, and G. LiW. Akramhttp://orcid.org/0000-0003-3811-6677Guangdong Key Laboratory of New Technology Research of Vegetables, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, ChinaVegetable Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, ChinaSearch for more papers by this author, A. Ahmadhttp://orcid.org/0000-0001-9097-2628Guangdong Key Laboratory of New Technology Research of Vegetables, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, ChinaVegetable Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, ChinaSearch for more papers by this author, W. LuoGuangdong Key Laboratory of New Technology Research of Vegetables, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, ChinaVegetable Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, ChinaSearch for more papers by this author, N. A. YasinInstitute of Agricultural Sciences, University of the Punjab, Lahore 54000, PakistanSearch for more papers by this author, T. WuGuangdong Key Laboratory of New Technology Research of Vegetables, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, ChinaVegetable Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, ChinaSearch for more papers by this author, J. GuoGuangdong Key Laboratory of New Technology Research of Vegetables, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, ChinaVegetable Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, ChinaSearch for more papers by this author, Q. WangGuangdong Key Laboratory of New Technology Research of Vegetables, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, ChinaVegetable Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, ChinaSearch for more papers by this author, and G. Li†Corresponding author: G. Li; E-mail Address: liguihua@gdaas.cnGuangdong Key Laboratory of New Technology Research of Vegetables, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, ChinaVegetable Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, ChinaSearch for more papers by this authorAffiliationsAuthors and Affiliations W. Akram1 2 A. Ahmad1 2 W. Luo1 2 N. A. Yasin3 T. Wu1 2 J. Guo1 2 Q. Wang1 2 G. Li1 2 † 1Guangdong Key Laboratory of New Technology Research of Vegetables, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, China 2Vegetable Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, China 3Institute of Agricultural Sciences, University of the Punjab, Lahore 54000, Pakistan Published Online:16 May 2019https://doi.org/10.1094/PDIS-02-19-0261-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Chinese kale (Brassica oleracea var. alboglabra) is an important green leaf crop in China. In October 2018, plants of cultivar ‘Sujie’ in the experimental field of the Vegetable Research Institute at the Guangdong Academy of Agricultural Sciences (VRI-GAAS) in Guangzhou, China, exhibited stem rot symptoms. Disease incidence was up to 30%. Symptom development was first observed on 2-month-old plants. Symptoms appeared as wilting and yellowing of leaves, followed by rotting of stem and root tissues. Infected plants had reduced growth, and severely infected plants died. Ten symptomatic plants were removed for pathogen isolation. Infected plant tissues were cut into pieces (5 × 5 mm) and surface sterilized with 1% NaOCl for 3 to 4 min followed by several washings with sterilized distilled water (SDW). Fungi were isolated by aseptically placing symptomatic plant tissues onto potato dextrose agar (PDA). The representative pathogen colonies were purified by single-spore technique onto 2% water agar followed by successive subculturing on PDA and carnation leaf agar (CLA) (Leslie and Summerell 2006). Cultures were incubated in a growth chamber at 25 ± 2°C with a 12-h photoperiod under fluorescent light for 2 weeks. Afterward, macroconidia and chlamydospores of isolates grown on CLA were examined. On PDA, colonies grew as white-colored, profuse, fuzzy mycelium with pale to dark brown pigmentation on the back side of the medium. Chlamydospores were globose, produced singly or in chains, measuring 7.1 to 9.6 μm in diameter with smooth outer walls. Macroconidia were relatively slender, 17 to 49 × 3 to 7 μm, bearing 3 to 5 septations, with a foot-shaped basal cell and a tapered or elongated apical cell. Microconidia were obovate, 8 to 11 × 3 to 4 μm, with a single septum. Mesoconidia were fusoid and had 1 to 4 septations. Morphological characters of the four fungi were consistent with F. semitectum Berkeley and Ravenel (syn. F. incarnatum) (Leslie and Summerell 2006). Molecular identification was performed by amplifying the internal transcribed spacer (ITS) region, the translation elongation factor 1a (EF-1α) gene, and the RNA polymerase II beta subunit (RPB2) gene using primer pairs ITS1/ITS4 (White et al. 1990), EF1/EF2 (Geiser et al. 2004), and RPB2AM-1bf/RPB2AM-7R (Miller and Huhndorf 2005), respectively. The ITS, EF-1α, and RPB2 sequences were deposited in GenBank (MK351313, MK439478, and MK487767). The ITS and EF-1α sequences had 99% homology with members of both F. incarnatum and F. equiseti in NCBI database; BLAST analysis of these in Fusarium-ID database (http://isolate.fusariumdb.org) showed 100 and 99% similarity with F. incarnatum-equiseti species complex (FIESC) (NRRL45997 [ITS] and NRRL36323 [EF-1α]), respectively. The RPB2 sequence shared 99% similarity with F. incarnatum strain ITEM6748 (GenBank LN901618) and FIESC (Fusarium-ID NRRL26417). The pathogen was identified as F. incarnatum, a member of FIESC, based on morphological and molecular evidence. Pathogenicity tests were conducted with all four isolates individually. Plants were grown in sterilized 15-cm-diameter plastic pots containing autoclaved commercial potting mix, and five replicate plants were included in each treatment. Sujie Chinese kale plants at four-leaf stage were inoculated by root-dip method in conidial suspension (1 × 106 conidia/ml) in SDW. Fungi were grown on CLA for 10 days at 25 ± 2°C under 12-h light/dark cycle. Control plants were dipped in SDW. Symptoms developed within 10 days postinoculation. Pathogen reisolations fulfilled Koch’s postulates, and identification was confirmed by morphological and molecular methods. The pathogen induced similar symptoms on the inoculated plants as in the field. The isolates were maintained in the VRI-GAAS culture collection (VRI 01 to 04). This is the first report of FIESC causing stem and root rot on Chinese kale in China. As the stem is the economically important part of the plant, serious measures must be taken to control this disease.The author(s) declare no conflict of interest.