Susceptibility of the three dragon fruit species to stem canker and growth inhibition of Neoscytalidium dimidiatum by ch

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ORIGINAL ARTICLE

Susceptibility of the three dragon fruit species to stem canker and growth inhibition of Neoscytalidium dimidiatum by chemicals John Darby Taguiam 1 & Edzel Evallo 1 & Jennelyn Bengoa 1 & Rodel Maghirang 1 & Mark Angelo Balendres 1 Received: 21 October 2019 / Accepted: 1 April 2020 # Società Italiana di Patologia Vegetale (S.I.Pa.V.) 2020

Abstract In the Philippines and other Southeast Asian countries, dragon fruits (Hylocereus species) have the potential to be a major “cash crop”. However, among the major problems currently faced by growers are yield- and quality-limiting diseases. In the Philippines, little is known of the dragon fruit diseases and measures that may be used in disease management. In this study, Neoscytalidium dimidiatum has been identified, by a combined morphological and molecular identification approach, as the cause of dragon fruit stem canker. The three dragon fruit species, H. monacanthus, H. undatus, and H. megalanthus, were susceptible to stem canker in both detached stems (3 laboratory trials) and rooted-stem cuttings (2 glasshouse trials) assays. The symptom was more severe in inoculated rooted-stem cuttings than in detached stems. Growth of N. dimidiatum was suppressed in potato dextrose agar (PDA) medium amended with B. subtilis (2 ml/400 mL, 100% fungal growth inhibition, fgi), mancozeb (2 g/ 400 mL, 100% fgi) and pyraclostrobin (1 mL/400 mL, 100% fgi) (chemical control). Citronella oil (1.25 uL/mL, up to 85.42% fgi) and isoprothiolane (2.25 mL/400 mL, up to 100% fgi) also showed promising results. However, the growth of N. dimidiatum was not inhibited in PDA medium amended with propamocarb (1.60 mL/400 mL). This is the first scientific report of N. dimidiatum as a pathogen of dragon fruit in the Philippines, the susceptibility of H. megalanthus to stem canker, and the growth inhibitory effect of B. subtilis and other chemicals that can be used alternatively or in rotation with synthetic chemicals. Keywords Hylocereus undatus . Hylocereus megalanthus . Hylocereus monacanthus . Bacillus subtilis . Plant disease susceptibility . Plant disease management

Introduction Dragon fruits (Hylocereus species) are a group of plants belonging to the cacti family (Nobel 2002). It produces an edible fruit, eaten as fresh or processed, which is also the economically important part of the plant. Dragon fruits have become an important plant in the import/export market. For instance, in Vietnam, the dragon fruit production area has tremendously increased in the last decade and income is largely generated from fruit export (Tel Zur 2015; Mercado-Silva 2018). In the Philippines and other Southeast Asian countries, dragon fruits have the potential to be a major “cash crop” (Eusebio and Alaban 2018). The three common dragon fruit species are

* Mark Angelo Balendres [email protected] 1

Institute of Plant Breeding, College of Agriculture and Food Science, University of the Philippines Los Baños, 4031 Los Baños, Laguna, Philippines

H. monacanthus (also known as H. polyrhizus), H. und