First Report of Curvularia lunata on Red-Fleshed Dragon Fruit (Hylocereus polyrhizus) in Malaysia

Abstract

Red-fleshed dragon fruit (Hylocereus polyrhizus [Weber] Britton & Rose) is a newly introduced and potential crop in the Malaysian fruit industry. Besides its nutritious value, the fruit is being promoted as a health crop throughout Southeast Asia. In April of 2007, a new disease was observed in major plantations of H. polyrhizus throughout five states (Kelantan, Melaka, Negeri Sembilan, Penang, and Perak) in Malaysia with 41 and 25% disease incidence and severity, respectively. Stems of H. polyrhizus showed spots or small, circular, faint pink-to-beige necrotic lesions that generally coalesced as symptoms progressed. Symptom margins of diseased stem samples were surface sterilized with a 70% alcohol swab, cut into small blocks (1.5 × 1.5 × 1.5 cm), soaked in 1% sodium hypochlorite (NaOCI) for 3 min, and rinsed in several changes of sterile distilled water (each 1 min). The surface-sterilized tissues were placed onto potato dextrose agar (PDA) and incubated under alternating 12-h daylight and black light for 7 days. A fungus was consistently isolated from the stems of symptomatic H. polyrhizus and identified as Curvularia lunata (Wakker) Beodijn (1–3) that showed pale brown multicelled conidia (phragmoconidia; three to five celled) that formed apically through a pore (poroconidia) in sympodially, elongating, geniculated conidiophores. Conidia are relatively fusiform, cylindrical, or slightly curved, with one of the central cells being larger and darker (26.15 ± 0.05 μm). All 25 isolates of C. lunata obtained from diseased H. polyrhizus are deposited at the Culture Collection Unit, Universiti Sains Malaysia and available on request. Isolates were tested for pathogenicity by injecting conidial suspensions (1 × 106 conidia/ml) and pricking colonized toothpicks on 25 healthy H. polyrhizus stems. Controls were treated with sterile distilled water and noncolonized toothpicks. All inoculated plants and controls were placed in a greenhouse with day and night temperatures of 30 to 35°C and 23 to 30°C, respectively. Development of external symptoms on inoculated plants was observed continuously every 2 days for 2 weeks. Two weeks after inoculation, all plants inoculated with all isolates of C. lunata developed stem lesions similar to those observed in the field. No symptoms were observed on the control plants and all remained healthy. C. lunata was reisolated from 88% of the inoculated stems, completing Koch's postulates. The pathogenicity test was repeated with the same results. To our knowledge, this is the first report of C. lunata causing a disease on H. polyrhizus. References: (1) M. B. Ellis. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, Surrey, England, 1971. (2) R. R. Nelson and F. A. Hassis. Mycologia 56:316, 1964. (3) C. V. Subramanian. Fungi Imperfecti from Madras V. Curvularia. Proc. Indian Acad. Sci. 38:27, 1955.

The role of Ala231 and Trp227 in the substrate specificities of fungal 17β-hydroxysteroid dehydrogenase and trihydroxynaphthalene reductase: Steroids versus smaller substrates

“…It is a known plant and human pathogen, and thus it is a particularly interesting target for the development of novel fungicides and antimycotics [2][3][4]. In the present study, our attention was focused on two enzymes from this fungus: 17␤-hydroxysteroid dehydrogenase (17␤-HSDcl), with an unknown physiological function and trihydroxynaphthalene reductase (3HNR), which is involved in 1, 8-Abbreviations: 3HNR, trihydroxynaphthalene reductase; 17␤-HSDcl, 17␤-hydroxysteroid dehydrogenase from fungus Cochliobolus lunatus; DBO, 4,5-dihydroxy-2H-benzopyran-2-one; DDBO, 2,3-dihydro-2,5-dihydroxy-4H-benzopyran-4-one; PQ, 9,10-phenanthrenequinone; TLC, thin-layer chromatography.…”

Pitaya Nutrition, Biology, and Biotechnology: A Review

“…Pitaya stems are succulent and susceptible to various fungi such as Alternaria alternata [ 144 ], Aureobasidium pullulans [ 145 ], Neoscytalidium dimidiatum [ 146 , 147 ], Colletotrichum gloeosporioides [ 148 , 149 , 150 ], Bipolaris cactivora [ 151 , 152 , 153 ], Nigrospora sphaerica [ 154 ], Gilbertella persicaria [ 155 , 156 ], Botryosphaeria dothidea [ 157 , 158 ], Curvularia lunata [ 159 ], Fusarium solani [ 160 ], Fusarium proliferatum [ 161 ], Aspergillus flavus , Fusarium lateritium , and Aspergillus niger [ 32 , 162 ].…”

Fungal and Oomycete Diseases of Minor Tropical Fruit Crops

“…Fusarium oxyporum causes stem blight [47]. Stem necrosis is caused by Curvularia lunata [16] and stem canker by Neoscytalidium dimidiatum [37]. Two species of Nigrospora, namely Nigrospora lacticolonia and Nigrospora sphaerica, cause reddish brown spot [27].…”

“…Andaman Islands, India Abirami et al [15] Stem lesion/spot Curvularia lunata (stem of H. polyrhizus) Malaysia Masratul Hawa et al [16] Storage fruit rot Gilbertella persicaria (H. costaricensis) China Guo et al [17] Fruit blotch and stem rot Bipolaris cactivora (H. undatus)…”