Tree peonies (Paeonia suffruticosa Andr. and hybrids) are well-known ornamental and medicinal plants cultivated in temperate and subtropical regions around the world. From June to September 2021, ...severe leaf spot disease was observed on 3 tree peony cultivars ('Luoyanghong', 'Moyushenghui', 'Roufurong') in Xinxiang (35º29´N, 113º95´E) and Luoyang (34º64´N, 112º49´E), Henan Province, China. Leaf spot incidence was as high as 28% ('Luoyanghong'), 45% ('Moyushenghui') and 67% ('Roufurong'), respectively. Symptoms appeared initially as small purple spots less than 1 mm in diameter in the middle and upper parts of the leaves, and then evolved to coalescent lesions, causing brown scorch ultimately. From each cultivar, 5 diseased leaves were collected. Leaflet tissues (3-4 mm2) cut from spot margins were surface sterilized in 75% alcohol for 45 s, washed 5 times with sterile distilled water, and then cultivated on potato dextrose agar (PDA) medium at 28 °C in the dark. Eleven isolates were obtained, and colonies grown from single conidia on PDA were 80-85 mm in diameter after 10 d, with scattered small, dark-based spikes on the surface of the colonies. The aerial mycelium was cottony, dense, and dark gray near the center on the reverse side. Conidia were cylindrical to clavate, with rounded apex and rounded base, and the conidia contents were granular, 8.44-14.06×3.60-4.31 μm (mean=11.28×3.69 μm, n=40). Appressoria were mostly subglobose or with a few broad lobes, pale to medium brown, 3.36-6.72×3.35-5.60 μm (mean=5.02×4.55 μm, n=20). Based on the culture representation and conidial morphology, the isolates were characterized as Colletotrichum gloeosporioides species complex (Weir et al. 2012; Fu et al. 2019). To further identity the species, the actin (ACT), calmodulin (CAL), chitin synthase (CHS-1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and the ribosomal internal transcribed spacers (ITS) loci of isolates PSW0002, PSW0008 and PSW0009 were amplified using ACT-512F/ACT-783R, CL1C/CL2C, CHS-79F/CHS-345R, GDF/GDR, and ITS1/ITS4, primers (Weir et al. 2012; Schena et al; 2014; Kim et al. 2021; Li et al. 2021). Fifteen sequences were deposited in GenBank (ACT for OP225605, OP225606, and OP225607, CAL for OP225608, OP225609 and OP225610, CHS for OP225611, OP225612 and OP225613, GAPDH for ON321897, OP225614, and OP225615, and ITS for ON323473, OP214349 and OP214350 ), which showed 100% sequence similarity to Colletotrichum aenigma (JX009443 and JX009519 for ACT, JX009683 and JX009684 for CAL, JX009774 and JX009903 for CHS-1, JX010244 and JX009913 for GAPDH, JX010243 and JX010148 for ITS). Three isolates clustered with C. aenigma (ex-holotype culture ICMP 18608) in the multi-locus phylogenetic tree with a bootstrap value of 100%. To achieve Koch's postulates, pathogenicity was tested on 5-year-old healthy potted plants ('Luoyanghong'). Thirty leaves were inoculated with 10 µL conidial suspension (isolate PSW0002, 1×106 conidia/mL) and the controls were inoculated with sterile water. Plants were placed in a greenhouse at 28°C under conditions with 12 h photoperiod and 90% relative humidity. After 5 to 10 days, distinct spots were observed on the inoculated leaves, while the control leaves showed no symptoms. C. aenigma was reisolated from all inoculated leaves, but not from the control. C. aenigma has been reported to cause anthracnose on Pyrus pyrifolia (Weir et al. 2012), Camellia sasanqua (Chen et al. 2019), Juglans regia (Wang et al. 2020), Paeonia ostii (Ren et al. 2020), and Capsicum annuum (Sharma et al. 2022). A previous study reported C. gloeosporioides as a pathogen of anthracnose in tree peonies in China (Xuan et al. 2017), the typical symptoms were big necrotic lesions (5-10 mm diam) on leaves，which were significantly different from those caused by C. aenigma. To our knowledge, this is the first report of C. aenigma causing anthracnose in tree peonies in China. This finding may help to take effective control of anthracnose in tree peonies.
Maize (Zea Mays L.) is one of China's most widely grown cereals, a crucial food crop, and a vital source of feed and raw materials for various industries. In March 2023, a disease with typical white ...spot symptoms was observed on maize across 40% of the planted area in a farm field in Jiangcheng Hani and Yi Autonomous County, Yunnan Province, China. The disease initially showed water-soaked patches on leaves, which eventually faded to dark brown, forming irregular spots with yellow to brownish margins. The Dns14-1 strain, isolated from infected leaves, was identified as Diaporthe eres based on morphological and molecular identification. Pathogenicity tests found it to be one of the causal agents of white spots on maize leaves. To our knowledge, this is the first report of D. eres causing white spots on maize in China.
•Diaporthe eres was firstly reported to cause white leaf spots on maize.•The white leaf spot of maize could cause by multiple fungal infections.•Environmental factors could be considered when formulating management measures.
English/Persian walnut (Juglans regia L.) is grown as an economically valuable crop in temperate and subtropical regions. In August of 2018, serious fruit anthracnose, with brown to black circular or ...subcircular or irregular sunken lesions (Fig.1A), occurred on walnut trees ("Xiangling" and "lvling") in 33 ha., 23 ha. and 20 ha. orchards in Lincheng and Neiqiu county, in Xingtai, Hebei, China. Diseased fruits were observed on 41% (19,000 trees), 31% (13,300 trees) and 34% (11,400 trees) walnut trees. Diseased leaves, with circular or irregular brown to gray sunken lesions, were observed on 2% (19,000 trees), 2% (13,300 trees) and 1% (11,400 trees) walnut trees. From each orchard, 25 diseased fruits and leaves were collected, respectively. Twenty-one single spore isolates were obtained from fruits of three orchards and none from leaves as described by Cai et al. (2009). Six representative isolates 1811-1, 1811-4, 1811-7, 1811-8, 1811-11 and 1811-18, two from each orchard, were selected for further study. Colonies on PDA grew 11.8 mm d-1 at 25℃ under a 12/12 h light/dark cycle for 7 d. The upper side of colonies was milky (Fig.1 B), and reverse side was dark brown to brownish yellow. A few acervuli were observed on colonies. Conidiogenous cells were cylindrical to clavate, 10.6-29.7 × 3.1-5.3 μm (mean=21.3 × 4.0 μm, n=30) (Fig.1F). Setae were not observed. Conidia were smooth-walled, aseptate, straight or slightly distorted, cylindrical with one end slightly acute or broadly rounded ends, and 16.6-21.6 × 6.0-7.5 μm (mean=19.2 × 6.7 μm, n=30) (Fig.1 C). Appressoria were mostly irregular in outline, deeply lobed or lightly lobed, gray brown to dark brown, 8.3-16.6 × 7.1-14.5 μm (mean=12.5 × 9.7 μm, n=30) (Fig.1 D-E). Microscopic features were similar to the description of C. aenigma (Weir et al. 2012). To further identify isolates, the ribosomal internal transcribed spacers (ITS), β-tubulin 2 (TUB2), calmodulin (CAL), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), glutamine synthetase (GS) and chitin synthase (CHS-1) loci of representative isolates were amplified using ITS4/ITS5, Bt2a/Bt2b, CL1/CL2, GDF1/GDR1, GSF1/GSR1 and CHS-79F/CHS-345R primers (Prihastuti et al. 2009; Carbone & Kohn 1999). Sequences of representative isolate 1811-1 were submitted to GenBank (ITS: MN893316, TUB: MN893317, CAL: MN893312, GAPDH: MN893314, GS: MN893315, CHS-1: MN893313). Maximum likehood analysis of sequences of representative isolates and reference sequences of Colletotrichum spp. from GenBank revealed that six isolates clustered together with C. aenigma ex-type culture ICMP18608, and the bootstrap value was 100% (Fig.2). Pathogenicity tests were conducted on walnut fruit as described by Wang et al. (2017, 2018) and Cai et al. (2009). 10 wounded and 10 nonwounded fruits ("Xiangling", 35 mm diameter) were inoculated with isolates 1811-1, 1811-7 and 1811-11 conidial suspension (106 spore/mL) obtained from 10 d colonies grown on PDA at 25℃, respectively. 10 wounded and 10 nonwounded fruits were inoculated with sterile water. Inoculated and control fruits were incubated in containers at 25℃ in a 12/12 h light/dark cycle. After 10 days, necrotic lesions were observed in all inoculated fruits. The pathogen C. aenigma was reisolated from all inoculated fruits but not from control fruits. To our knowledge, this is the first report of C. aenigma causing walnut anthracnose in China. It is urgent to control walnut anthracnose caused by different species of Colletotrichum.
Macrophomina phaseolina (Tassi) Goid. is a soilborne necrotrophic fungal pathogen causing charcoal rot on approximately 500 plant species worldwide (Mengistu et al. 2015). Charcoal rot occurs in ...eastern Canada and many regions of the USA, causing substantial yield losses in soybean Glycine max (L.) Merr. (Allen et al. 2017; Bradley et al. 2021; Wrather et al. 2001). However, it has not been reported in soybean in western Canada. Manitoba is the second largest soybean producer in Canada, comprising 31% of total seeded areas with 2.29 M acres in 2017 (Statistics Canada 2022). Still, soybean is a relatively new crop to Manitoba and annual surveys of soybean root diseases began in 2012. In August 2020, randomly selected soybean fields were surveyed for root diseases at 63 different locations in south-central and southwest Manitoba. A total of thirty diseased plants were sampled in a zigzag pattern at three random sites in each field and all samples were brought to the laboratory and rated for disease severity. All plants showed symptoms of root rot, and some samples exhibited wilting with yellowing-brown leaves attached to the stems by the petioles; when the taproot was sectioned longitudinally, black streaking could be observed. In the laboratory, 600 roots from 40 selected fields were processed for pathogen isolation and identification. A 1 cm section from each root was surface-sterilized in a 95% EtOH:5.25% NaOCl solution for 30 sec, rinsed in sterile water for 60 sec, and air-dried on sterilized filter paper in a laminar flow hood. Root tissues with two replicates were placed on potato dextrose agar (PDA) plates amended with streptomycin sulfate (2 mg/mL) and incubated at room temperature. Black microsclerotia were observed in cultures from three different fields and three individual fungal isolates were obtained from each field through isolation of a single microsclerotium and subsequent hyphal tip transfer. The mycelia were initially hyaline and turned gray to dark brown or black, forming numerous microsclerotia ranging in size from 13 to 61 µm long and 12 to 32 µm wide, based on measurements of approximately 100 microsclerotia per isolate using a Zeiss Axio Imager A2 microscope equipped with an AxioCam HRc (Carl Zeiss, Jena, Germany) and AxioVision software. The color of the microsclerotia was jet black and the shape was round to oblong or irregular, as described by Mengistu et al. (2015). Based on morphological characteristics and microscopic examination, three fungal isolates were identified as M. phaseolina (Mengistu et al. 2015). For molecular identification, genomic DNA was extracted from 10 to 14-day old mycelia and microsclerotia of each isolate using a ZymoBIOMICS™ DNA Miniprep Kit (Zymo Research Corp., Irvine, CA, USA) according to the manufacturer's instructions. The internal transcribed spacer (ITS) region, translation elongation factor-1α (TEF-1α), and calmodulin (CAL) genes were amplified using the primer sets ITS1/ITS4 (White et al. 1990), MpTefF/MpTefR, and MpCalF/MpCalR (Santos et al. 2020), respectively, according to the original reaction conditions. Subsequently, PCR products were sequenced at Eurofins Genomics (Louisville, KY, USA). BLASTn analysis in GenBank showed that the nucleotide sequences of these regions of the three isolates (NSRR20-MB-24, NSRR20-MB-34, and NSRR20-MB-40) matched multiple isolates of M. phaseolina with 100% query cover and 100% identity. Sequences were deposited in GenBank for the ITS (OK127887, OK142725, OK128266), TEF-1α (OR363103, OR363104, OR363105), and CAL (OR357627, OR357628, OR357629) regions. In addition, the ITS and TEF-1α sequences of the three novel isolates were further aligned with multiple previously reported isolates of M. phaseolina, M. pseudophaseolina, and M. euphorbiicola (Chen et al. 2013; Machado et al. 2019; Sarr et al. 2014) using Muscle and trimmed (Edgar 2004). Alignments were concatenated to generate a maximum likelihood tree. Once concatenated, sequences were re-aligned. The obtained alignments were employed to construct a phylogenetic tree using the max likelihood method and Tamura-Nei model (Tamura and Nei 1993) with 10,000 bootstrap replicates using MEGA 11 (Tamura et al. 2021). The ITS and TEF-1α analysis indicated that the isolates were grouped in three differentiated clades (Figure 1). Macrophomina phaseolina isolates clustered in the same clade at 98% similarity, with the three novel soybean isolates NSRR20-MB-24, NSRR20-MB-34, and NSRR20-MB-40 grouped closely in the cluster at 98% similarity and identified as M. phaseolina. In contrast, isolates of M. euphorbiicola formed another clade at 87% similarity and M. pseudophaseolina isolates grouped in a clade at 99%. The pathogenicity of the three isolates was evaluated under controlled conditions. Given that no information on charcoal rot resistance in soybean has been reported in Canada, one of the commonly grown varieties in Manitoba, "TH 32004", was selected for the pathogenicity test. Surface-sterilized soybean seeds, which had been pre-germinated for three days, were sown in a sterilized soilless growing mix (Sunshine #5) together with 5 g (approx. 1 × 105 microsclerotia) of macerated 10 to 14-day old inoculum grown on PDA-streptomycin agar medium at room temperature and applied using an inoculum layering technique. For the non-inoculated control, macerated PDA-streptomycin agar without mycelia was used. Twenty plants per treatment were maintained in a walk-in plant growth chamber with a 16 h photoperiod at 25/20 °C ± 1 °C (day/night) and 50% relative humidity. Plants were watered weekly but were subjected to water stress. Symptoms of charcoal rot were observed in the root systems of all inoculated soybean plants after 28 days, while no symptoms were observed in the control plants (Figure S1). There was production of microsclerotia on the roots inoculated with each isolate (data not shown). Three isolates of M. phaseolina were re-isolated from the inoculated plants and found to be identical to the inoculated isolates with respect to morphological characteristics in culture, as well as with respect to the ITS, TEF-1α and CAL DNA sequences. For each isolate and non-inoculated control, five seeds of 'TH 32004' were seeded per pot, and four pots were used for the inoculated and control treatments. The experiment was repeated twice in a randomized complete block design with similar results, fulfilling Koch's postulates. To our knowledge, this is the first report of charcoal rot caused by M. phaseolina on soybean in Manitoba, Canada.
Litsea cubeba, an economical important tree species originally from China, produces fruit from which essential oils are extracted and extensively used in the chemical industry (Zhang et al. 2020). In ...August 2021, a large-scale outbreak of black patch disease was first observed on the leaves of Litsea cubeba in Huaihua (27°33'N; 109°57'E), Hunan province, China (disease incidence 78%). A second outbreak in 2022, in the same area, lasted from June to August. Symptoms consisted of irregular lesions that initially appeared as small black patches near the lateral veins. These lesions grew along the lateral veins and formed feathery patches until almost the entire lateral veins of the leaves were infected by the pathogen. The infected plants grew poorly and eventually the leaves desiccated and the tree defoliated. To identify the causal agent, the pathogen was isolated from nine symptomatic leaves from three trees. Symptomatic leaves were washed with distilled water three times. Leaves were cut into small pieces (11 cm), surface sterilized with 75% ethanol for 10s and 0.1% HgCl2 for 3 min, and then washed 3 times in sterile distilled water. Surface disinfected leaf pieces were placed onto potato dextrose agar (PDA) medium with cephalothin (0.2 mg/ml) and incubated at 28°C for 4-8 days (about 16h light, 8h dark). Seven morphologically identical isolates were obtained, from which five were selected for further morphological examination and three for molecular identification and pathogenicity test. Strains from grayish white colonies with a granular surface and grayish black wavy edges; bottom of the colonies turned black over time. Conidia were hyaline and nearly elliptical, unicellular. The sizes of conidia ranged from 8.59 to 15.06 μm (n=50) in length and 3.57 to 6.36 μm (n=50) in width. These morphological characteristics are consistent with the description of Phyllosticta capitalensis (Guarnaccia et al. 2017, Wikee et al. 2013). To further confirm the identity of this pathogen, genomic DNA of three isolates (phy1, phy2 and phy3) were extracted to amplify the internal transcribed spacer (ITS) region, the 18S rDNA region, the transcription elongation factor (TEF), and actin (ACT) gene with ITS1/ITS4 (Cheng et al. 2019), NS1/NS8 (Zhan et al. 2014), EF1-728F/EF1-986R (Druzhinina et al. 2005) and ACT-512F/ACT-783R (Wikee et al. 2013) primers, respectively. Sequence similarity indicated that these isolates were highly homologous to Phyllosticta capitalensis. The ITS (Genbank No. OP863032, ON714650 and OP863033), 18S rDNA (Genbank No. OP863038, ON778575 and OP863039), TEF (Genbank No. OP905580, OP905581 and OP905582) and ACT (Genbank No. OP897308, OP897309 and OP897310) sequences of isolates Phy1, Phy2 and Phy3 shared up to 99%, 99%, 100% and 100% similarities with their counterparts (Genbank No. OP163688, MH051003, ON246258 and KY855652) in Phyllosticta capitalensis, respectively. To further confirm their identity, a neighbor-joining phylogenetic tree was generated using MEGA7. Based on morphological characteristics and sequence analysis, the three strains were identified as P. capitalensis. To fulfill Koch's postulates, conidial suspension (1×105 conidia per mL) collected from three isolates were independently inoculated on artificially wounded detached leaves and leaves on trees of Litsea cubeba. Leaves were inoculated with sterile distilled water as negative controls. The experiment was repeated three times. All pathogen-inoculated wounds exhibited necrotic lesions within 5 days on detached leaves and 10 days on the leaves growing on trees after inoculation, whereas no symptoms were observed on the controls. The pathogen was exclusively re-isolated from the infected leaves and showed identical morphological characteristics to those of the original pathogens. P. capitalensis is a destructive plant pathogen that has been shown to cause leaf spots or black patch symptoms on variety of host plants around the world (Wikee et al. 2013), including oil palm (Elaeis guineensis Jacq.), tea plant (Camellia sinensis), Rubus chingii and castor (Ricinus communis L.). To our knowledge, this is the first report of black patch disease of Litsea cubeba caused by P. capitalensis in China. This disease causes severe leaf abscission in fruit development stage of Litsea cubeba and leads to a large amount of fruit drop.
The problem in the production of biofertilizers is that raw materials are cheap, easy to get and apply. Another problem is determining the viability of the consortium microbes in a biofertilizer ...formulation. This study aims to determine the bacterial viability of various liquid media originating from organic waste as a liquid biofertilizer carrier. Three indigenous bacterial strains under consortium for phosphate soluble (Pantoea ananatis strain 53 (BC32)), non-symbiotic Nitrogen fixation (Bacillus li-cheniformis strain S45) and stabilizing soil aggregate (Pseudomonas plecoglossida strain PR19) were added to liquid biofertilizer. The study evaluated 10 treatments using a randomized design with three replicates. The treatments are as follows: Peptone, molasses, Compost wash from seaweed waste, Vermiwash, molasses + glycerol, compost wash from seaweed waste + glycerol, vermiwash+ glycerol, molasses + PEG (PolyEthylene Glycols)1%, compost wash seaweed waste + PEG 1%, and Vermiwash+ PEG 1%. This biofertilizer formulation (liquid) was kept for 16 weeks at optimum pH 5.5. VP3 (Vermiwashmade from vermicompost + PEG 1%) treatment showed the best viability of bacterial strains during the 16-week storage period. The pathogenicity test using green bean seeds Vima-1 showed that all liquid formulations of biological fertilizers with the three consortium bacterial isolates did not show signs of diseases and demonstrated better growth than the control treatment. Compared to other treat-ments, the best growth of bacterial strains was detected with MP2 (Molasses + glyc-erol) treatment. Formulations using vermiwashand PEG appear to maintain bacterial viability in the formulation effectively. However, the formulation of molasses and glycerol exerts a stimulating effect on sprouts growth.
Abstract
Key message
As a result of our research, we determined that
Cryptosporiopsis tarraconensis
—as a new species for Central Europe—is the causative agent of leaf lesions in natural populations ...of hazel (
Corylus avellana
). Until now, this species had not been described in a natural population of
C. avellana
or out of the temperate climate. This is the fifth notification of this rare fungus in the world and the first from Central Europe and the natural population of the host.
Litsea cubeba, an important industrial plant species that originated in China, produces fruit essential oil extensively applied in the chemical industry (Xiang et al. 2020). In July 2020, a ...large-scale outbreak of leaf spot disease on Litsea cubeba was first observed and then monitored over time in Yueyang (29°37'N; 113°13'E) and Changsha (28°06'N; 113°02'E), Hunan province, China. Symptoms of this disease consisted of round-shaped lesions that initially appeared as small light-brown spots. With the increase in number, these small spots coalesced into larger, dark-brown lesions leading to yellowing and abscission of the leaves. To identify the causal agent this disease, the pathogen was isolated with a tissue separation method (Gao et al. 2020). The infected leaf tissues surface-disinfected with 75% ethanol and 0.1% HgCl were aseptically cut into small pieces (11 cm) and then placed onto potato dextrose agar (PDA) medium with cephalothin (0.2 mg/ml) and incubated at 28°C for 3-5 days. The purified colonies on PDA exhibited fluffy white hyphae, secreted a dark red pigment that had been observed in previous studies (Xiao et al. 2015) and produced microconidia and macroconidia. The microconidia were single-celled, non-septate, ovoid, and ranged from 3.08 to 13.89 μm long and 2.17 to 3.62 μm wide (n=50). Macroconidia were three to five-septate, slightly curved, and ranged from 11.77 to 26.85 μm long and 3.31 to 4.50 μm wide (n=50). These morphological features suggested that theisolates were most likely Fusarium oxysporum (Savian et al. 2021). To further confirm the identity of this pathogen (designated as Fox-1), the TEF-1a gene (Genbank accession No. OM281065) and rDNA ITS region (Genbank accession No. OM250084) were cloned and then sequenced (Cui et al, 2021). Sequence alignments indicated that the ITS and TEF-1a sequences shared 99.8% (504/505) and 99.7% (665/667) similarities with that of F. oxysporum (Genbank accession No. MF667966, KT230848), respectively. Both of the morphological characteristics and molecular data were used to identify this pathogen as F. oxysporum Schltdl.: Fr. 1824. To further verify whether these isolates of F. oxysporum can cause leaf spot disease, Koch's postulates were tested (Gradmann 2014). The purified pathogens were inoculated on artificial wounds of detached Litsea cubeba leaves and the leaves on the field plants of Litsea cubeba, respectively. The wounds of leaves were inoculated with sterile distilled water as negative controls. The experiment was performed independently three times, each with three leaves and three inoculated wounds on each leaf. All pathogen-inoculated wounds developed dark brown or black lesions on detached leaves within 3 days and on leaves on plants within 9 days, whereas the controls showed no symptoms. Re-isolations from infected leaves confirmed that the re-isolated pathogens possessed identical morphological characteristics to those of the original pathogens. To our knowledge, this is the first report of leaf spot infection of Litsea cubeba caused by F. oxysporum in China. This disease severely delays plant development and significantly decreases the yield of essential oil of Litsea cubeba. Our results laid a foundation for the subsequent research into pathogenic mechanisms drug sensitivity tests, which will contribute to the prevention and cure of leaf spot disease of Litsea cubeba. References: Cui, L. X., et al. 2021. Plant Dis. 105:7. Gao, W., et al. 2020. Plant Dis. 105:501. Gradmann. 2014. J. Microbes Infect. 16:885-892. Savian, L. G., et al. 2021. Plant Dis. 104:1870. Xiang, Y. J., et al. 2020. J. Chin. Cereals Oils Assco. 35:186-195. Xiao, J. L., et al. 2015. Hunan Agric. Sci. 4:105-108.
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