RESUMEN
Daphniphyllum macropodum Miq., an evergreen arbor, is widely cultivated in southern China for its ornamental and medicinal value (Su et al. 2013). In October 2019, a severe leaf spot was observed on D. macropodum in Jinggangshan National Nature Reserve in Ji'an city, Jiangxi, China (114°06'23â³E, 26°32'25â³N). The plants were about 15 years old, and the disease incidence was estimated to be 15% (4/26 plants). The disease primarily appeared as small black spots on the leaves. At the late stage, the spots enlarged and coalesced into regular or irregular gray necrotic lesions with dark margins. We collected five samples per plant and total 20 samples were collected to isolated the pathogen strains. The margin of the diseased tissues was cut into 5 mm × 5 mm pieces; surface disinfected with 70% ethanol and 2% NaOCl for 30 s and 60 s, respectively; and rinsed thrice with sterile water. Tissues were placed on potato dextrose agar (PDA) and incubated at 25°C in the dark. Pure cultures were obtained by single-spore isolation method, and the representative isolates, JRM3, JRM6, and JRM8 were used for morphological studies and phylogenetic analyses. The colonies of three isolates grown on PDA were white, cottony, and flocculent, contained undulate edges with dense aerial mycelium on the surface at 25 °C. Conidiomata was black conidial masses on PDA. Conidia were 5-celled, clavate to fusiform, smooth, 19.3 to 24.4 long × 6.1 to 8.6 µm wide (n = 50). The 3 median cells were dark brown to olivaceous, the central cell was darker than the other 2 cells, and the basal and apical cells were hyaline. All conidia developed one basal appendage (3.4 to 8.3 µm long; n = 50), and 2 to 3 apical appendages (18 to 32 µm long; n = 50), filiform. The morphological characteristics of the isolates are comparable with those of the genus Neopestalotiopsis (Maharachchikumbura et al. 2014). The internal transcribed spacer (ITS) regions, ß-tubulin 2 (TUB2) and translation elongation factor 1-alpha (TEF1-α) were amplified from genomic DNA for the three isolates using primers ITS1/ITS4, T1/Bt-2b, EF1-728F/EF-2 (Maharachchikumbura et al. 2014), respectively. The sequences of the isolates were submitted to GenBank (ITS, OQ372202 to OQ372204; TUB2, OQ390129 to OQ390131; TEF1-α, OQ390126 to OQ390128). A maximum likelihood and Bayesian posterior probability analyses using IQtree v. 1.6.8 and Mr. Bayes v. 3.2.6 with the concatenated sequences placed JRM3, JRM6, and JRM8 in the clade of N. clavispora. Based on the multi-locus phylogeny and morphology, three isolates were identified as N. clavispora. To confirm pathogenicity, eight healthy 10-year-old D. macropodum plants growing in the field were chosen, and 4 leaves per plant were wounded with a sterile needle and inoculated with 10 µL conidial suspension per leaf (106 conidia/ml). Eight plants inoculated with sterile water were used as control. All the inoculated leaves were covered with plastic bags to maintian a humidity environment for 2 days. The leaves inoculated with conidial suspension showed similar symptoms to those observed in the field, whereas control leaves were asymptomatic for 10 days. The same fungus were re-isolated from the lesions, whereas no fungus was isolated from control leaves. N. clavispora was determined as the pathogen of a variety of plant diseases, including Kadsura coccinea (Xie et al. 2018), Dendrobium officinale (Cao et al. 2022), Macadamia integrifolia (Santos et al. 2019). However, this is the first report of N. clavispora infecting D. macropodum in China. This work provided crucial information for epidemiologic studies and appropriate control strategies for this newly emerging disease.
RESUMEN
Cercis chinensis Bunge, commonly used as an ornamental plant, is native to southeastern China and extensively cultivated in gardens across major cities in the country. In August 2023, a new high-incidence disease was discovered at Huangshan University in Huangshan, Anhui Province, China. The symptoms initially began as small brown spots, which gradually expanded into large irregular brown spots with black-brown edges. The disease was investigated at both Jilingshan Park and Huangshan University, where C. chinensis Bunge was planted, revealing an average incidence rate of was 85 % at these sites. Seventy two leaf tissue samples (3 to 4 mm²) were collected from the margins of the lesion and subjected to surface sterilization with 75% ethanol for 30 seconds followed by 1% sodium hypochlorite for 90 seconds. Subsequently, the tissues were rinsed with sterile H2O, placed on potato dextrose agar (PDA) medium, and incubated at 25â for 5 days. The same fungus was isolated from 90% of the tissues, and pure cultures were obtained by monosporic isolation. Representative isolates ZJ 2-1, ZJ 2-2 and ZJ 2-3 were selected for morphological and molecular characterization. The colonies displayed a color range from white to gray, with white margins and aerial hyphae, while the reverse side of the colonies appeared gray to brown. Conidia were cylindrical, aseptate, with obtuse to slightly rounded ends, measuring 15.8±1.8×4.7±0.56 µm (n = 50). The morphological characteristics were generally consistent with those of Colletotrichum gloeosporioides species complex (Weir et al. 2012). Five conserved regions of isolates (ZJ 2-1, ZJ 2-2 and ZJ 2-3), including the internal transcribed spacer (ITS), glutamine synthase (GS), calmodulin (CAL), actin (ACT), and chitin synthase 1(CHS1) gene regions, were amplified using specific primers ITS1/ITS4 (Gardes et al. 1993), GSR1/GSF1 (Guerber et al. 2003), CL1C/CL2C (Li et al. 2018), ACT-512F/ACT-783R, and CHS-79F/CHS-345R (Zhu et al. 2019), respectively. Using the BLAST, ITS, GS, CAL, ACT and CHS1 gene sequences (GenBank accession nos. PP514751, PP448025, PP448026, PP448027 and PP448028, respectively) were 100% (594 out of 594 bp), 100% (864 out of 864 bp), 100% (299 out of 299 bp), 100% (732 out of 732 bp) and 100% (282 out of 282 bp) identical to C. gloeosporioides (GenBank accession nos. JX010152, JX010085, JX009818, JX009731 and JX009531, respectively). A Maximum Likelihood phylogenetic tree, constructed by combining all sequenced loci in MEGA7, showed that the isolates ZJ 2-1, ZJ 2-2 and ZJ 2-3 clustered within the C. gloeosporioides clade with 99% bootstrap support (Fig. S1). To fulfill Koch's postulates, five C. chinensis Bunge plants were tested for pathogenicity in the field with isolates ZJ 2-1, ZJ 2-2 and ZJ 2-3 at Huangshan University. Twelve leaves from each tree were wounded and inoculated with mycelial plugs (approximately 4 mm in diameter) and 10 µl of a spore suspension (1.0 × 106 conidia/ml) of C. gloeosporioides. Inoculation with sterile PDA plugs and pure water on leaves of each tree served as negative controls. Plastic bags were used to wrap the leaves, and sterile H2O was sprayed into the bags to maintain moisture conditions (Zhang et al.2020). The experiment was repeated two times, and within 5 days, all inoculated points displayed lesions similar to those observed in the field, whereas controls remained asymptomatic (Fig. S2). The same fungus was reisolated from these lesions with a frequency of 100%. Consequently, the pathogen responsible the disease in C. chinensis Bunge was identified as C. gloeosporioides. To the best of our knowledge, this is the first report of C. gloeosporioides causing leaf blight on C. chinensis Bunge in China. This study provides valuable insights for implementing targeted measures to control leaf blight on C. chinensis Bunge and lays a foundation for the prevention and treatment of the disease.