Leaf spot disease of Orychophragmus violaceus caused by Alternaria tenuissima in China

نویسندگان

چکیده

Orychophragmus violaceus (L.) O. E. Schulz, also called February orchid or Chinese violet cress, belongs to the Brassicaceae family and is widely cultivated as a green manure garden plant in China. During prolonged rainy period August 2020, leaf spot disease of was observed Northeast Agricultural University, Harbin, Heilongjiang province. One week after days, became more serious incidence ultimately reached approximately 80%. The symptoms began small brown spots on leaves, gradually expanded irregular circular spots. As progressed, withered with grayish-white centers surrounded by dark margins. Later on, collapsed into holes. For severely affected plants, coalesced large necrotic areas resulted premature defoliation. No conidiophores hyphae were present, not other tissues violaceus. To isolate pathogen, ten leaves typical collected from different individual plants. Small square pieces (5×5 mm) excised junction diseased healthy tissues, disinfected 75% ethanol solution for 1 min, rinsed sterile distilled water, then transferred Petri dishes (9 cm diameter) containing potato dextrose agar (PDA). After 3 days incubation at 25 oC darkness, newly grown-out mycelia onto fresh PDA purified single-spore isolation. Nine fungal isolates (NEAU-1 ~ NEAU-9) showing similar morphological characteristics obtained no fungi isolated. isolation frequency almost 90%. On plates, all colonies grey-white loose cottony aerial hyphae, turned olive-green eventually fungus formed pale sparsely branched chains carrot (PCA) plates darkness 7 days. Conidia ellipsoidal ovoid, light brown, ranged 18.4 59.1 × 9.2 22.3 µm size, zero two longitudinal septa one five transverse cylindrical beak (n = 50). Based cultural characteristics, tentatively identified Alternaria tenuissima (Simmons 2007). Genomic DNA extracted selected NEAU-5). internal transcribed spacer region (ITS) amplified sequenced using primers ITS1/ITS4 (White et al., 1990). Blast analysis demonstrated that these had same ITS sequence, sequence representative strain NEAU-5 (GenBank accession No. MW139354) showed 100% identity type strains alternata CBS916.96 CBS918.96. Furthermore, translation elongation factor 1-α gene (TEF), RNA polymerase II second largest subunit (RPB2), glyceraldehyde 3-phosphate dehydrogenase (GPD) EF1-728F/EF1-986R (Carbone Kohn 1999), RPB2-5F2/RPB2-5R (Sung 2007), Gpd1/Gpd2 (Berbee respectively. sequences RPB2, GPD, TEF submitted GenBank numbers MW401634, MW165223, MW165221, Phylogenetic trees based ITS, constructed neighbour-joining maximum-likelihood algorithms MEGA software version 7.0. results robust clade A. CBS918.96 (supported 99% 96% bootstrap values) trees. mentioned above, produced seldomly conidial PCA plates. pattern consistent (Kunze) Wiltshire, but distinct which could produce abundant secondary ramification Thus, its morphology phylogeny. Pathogenicity tests carried out inoculating unwounded suspension (approximately 106 conidia/ml) plants garden, an equal number inoculated sterilized ddH2O served negative controls. Inoculated control covered clear plastic bags 6 suspension, while such control. repeated three times. pathogenicity performed 2-month-old potted growth chamber (28 oC, 90% relative humidity, 12 h/12 h light/dark) repetitions. Five spraying 20 ml leaves. NEAU-5, whereas pathogen reisolated molecular methods. In tests, successfully infect violaceus, indicating direct interaction between tenuissima. It known high humidity fairly temperatures can favor epidemics (Yang 2018), this may explain why severe rain. Previously, it has been reported brassicicola japonica cause blight Hebei Jiangsu Provinces, China, respectively (Guo 2019; Sein 2020). Although pathogens lead easy distinguish them sequences. our knowledge, first report causing

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ژورنال

عنوان ژورنال: Plant Disease

سال: 2021

ISSN: ['0191-2917', '1943-7692']

DOI: https://doi.org/10.1094/pdis-10-20-2287-pdn