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ARS Home » Southeast Area » Mayaguez, Puerto Rico » Tropical Crops and Germplasm Research » Research » Publications at this Location » Publication #379619
Research Project: Conservation and Utilization of Tropical and Subtropical Tree Fruit, Cacao and Bamboo Genetic Resources

Location: Tropical Crops and Germplasm Research

Title: First report of Neoscytalidium dimidiatum causing stem canker on Pitahaya (Hylocereus spp.) in Puerto Rico

Author
item SERRATO DIAZ, LUZ
item Goenaga, Ricardo

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2021
Publication Date: 2/25/2021
Citation: Serrato Diaz, L.M., Goenaga, R.J. 2021. First report of Neoscytalidium dimidiatum causing stem canker on Pitahaya (Hylocereus spp.) in Puerto Rico. Plant Disease. https://doi.org/10.1094/PDIS-10-20-2265-PDN.
DOI: https://doi.org/10.1094/PDIS-10-20-2265-PDN

Interpretive Summary: Dragon fruit or pitahaya is a tropical fruit native to Central and South America and commercially grown in South Asia, Australia, Israel, Central and South America. In the United States it is primarily grown in Southern California, South Florida, Hawaii and Puerto Rico. Symptoms of stem canker were observed in greenhouses at the USDA – ARS Tropical Agriculture Research Station (TARS) in Mayaguez and commercial orchards located in San Sebastian, Puerto Rico. In order to know which pathogen was causing the disease, a survey was conducted from April to June of 2020 at these two locations. Diseased tissue of 23 dragon fruit varieties were disinfested and plated on potato dextrose agar (PDA) amended with 60 mg/L streptomycin. Three representative isolates (17B-173-T3, 12C-118-T1 and 13B-131-T2) of Neoscytalidium dimidiatum (Nd) were identified using taxonomic keys and sequencing of the internal transcribed spacer (ITS) and translation elongation factor 1 alpha (TEF1-a) genes. Sequences were compared using the BLASTn tool with Nd deposited in NCBI GenBank. Accession numbers of genes sequences of Nd submitted to GenBank were MT921260, MT921261, MT921262, for ITS region; MT920898, MT920899, MT920900 for TEF1-a. Pathogenicity test was conducted on 12 healthy dragon fruit plants using three non-detached dragon fruit cladodes per plant. Cladodes were inoculated with 5mm mycelial disks from 8-day-old pure cultures grown on PDA. Three healthy dragon fruit plants were used as control and were inoculated with PDA disks only. The experiment was repeated once. For all isolates, sunken orange spots averaged 3 x 2 mm in length at 8 DAI. Necrotic blotch with chlorotic halos averaged 10 x 15 mm at 14 DAI; stem canker with water-soaked tissue was observed at 20 DAI, and black conidia on dry stem cankers at 30 DAI. Untreated controls had no symptoms of stem canker. Neoscytalidium dimidiatum has been reported to cause stem canker on Hylocereus spp. in China, Florida, Israel, Malaysia and Taiwan. This is a first report of N. dimidiatum causing stem canker in Puerto Rico. Identification of the fungus N. dimidiatum as causative agent of stem canker of dragon fruit is critical to develop an effective control of the disease.

Technical Abstract: Dragon fruit or pitahaya (Hylocereus spp.) is a tropical fruit belonging to the Cactaceae. It is native to Central and South America and commercially grown in the United States in southern California, south Florida and Puerto Rico. During a disease survey from April to June 2020, stem canker was observed in greenhouses and commercial orchards located in Mayagüez and San Sebastian, Puerto Rico with an incidence of 80%. Diseased cladodes (stems) of 23 dragon fruit varieties were disinfested with 70% ethanol, rinsed with double distilled water and plated on potato dextrose agar (PDA) amended with 60 mg/L streptomycin. Three isolates (17B-173-T3, 12C-118-T1 and 13B-131-T2) of Neoscytalidium dimidiatum (Nd) were identified using taxonomic keys (Crous et al., 2006) and sequencing of the internal transcribed spacer (ITS) and translation elongation factor 1 alpha (TEF1-a). Sequences were compared using the BLASTn tool with Nd deposited in NCBI GenBank. In PDA, colonies of Nd were initially powdery white and turned grayish-black with age. Arthroconidia (n=50) were dark brown, disarticulating, truncate or cylindrical at the base, thick-walled with 0 to 1 septum, averaging 9.1 x 5.5um in length. GenBank accession numbers of Nd DNA sequences were MT921260, MT921261 and MT921262 for ITS and MT920898, MT920899 and MT920900 for TEF1-a. Pathogenicity tests were conducted on 12 healthy dragon fruit plants using three non-detached cladodes per plant. Cladodes were inoculated with 5mm mycelial disks from 8-day-old pure cultures grown on PDA. Three healthy dragon fruit plants were used as controls and were inoculated with PDA disks only. The experiment was repeated once. Twenty days after inoculations (DAI), isolates of Nd caused stem canker on dragon fruit plants. For all isolates, sunken orange spots averaged 3 x 2 mm in length at 8 DAI. Necrotic blotches with chlorotic halos averaged 10 x 15 mm at 14 DAI; stem cankers with water-soaked tissue were observed at 20 DAI, and black conidia on dry stem cankers at 30 DAI. Untreated controls had no symptoms of stem canker, and no fungi were isolated from tissue. Neoscytalidium dimidiatum has been reported to cause stem canker on Hylocereus spp. in China, Florida, Israel, Malaysia and Taiwan (Chuang et al. 2012; Lan et al., 2012; Ezra et al., 2013; Sanahuja et al., 2016). To our knowledge, this is the first report of Nd causing stem canker in Puerto Rico.