First report of Fusarium oxysporum Species Complex causing root and rhizome rot of Canna edulis in Colombia.

Achira, Canna edulis Ker, a plant native to South America, is the source of a starch used for food and industrial purposes. Since 2016, Colombian growers of the main cropping regions, Cundinamarca (CU), Nariño (NA), and Huila (HU) are experiencing yield losses due to rhizome rots. Surveys of the affected areas evidenced wilting and collapsed plants, with oxidized rhizomes and affected root masses. Disease incidence per field was around 10%, but diseased plants were found in all 44 visited farms. To study this problem, wilting plants were collected, and symptomatic tissues, pseudo-stems, roots, and rhizomes, were cut and disinfested in 1.5% hypochlorite, rinsed in sterile water, and plated onto PDA amended with 0.01% tetracycline. A total of 121 isolates were recovered; of these, 77 Fusarium-like isolates stood out, given their recovery frequency (64.7%) and cross-region distribution. To morphologically study the isolates, carnation leaf agar cultures of NA01, NA16, NA48, CU08-1 and HU02, were made. Isolates had hyaline, mostly aseptated microconidia, oval in shape, developing in false heads with short monophialides. Macroconidia were hyaline and falcate, straight to slightly curved, 2 to 4 septate, with apical cells curved and basal cells foot shaped. For NA01 the average size and width of the microconidia was 4.3 x 3.2 µm (n=80), while macroconidia averaged 18.9 × 5.7 µm (n =80); NA16 was slightly bigger (6.5 x 3 and 22.9 x 5.5 um respectively). This morphology resembles Fusarium oxysporum (Fox) (Leslie et al. 2006). Identity confirmation was obtained by Sanger sequencing of the rRNA internal transcribed spacer (ITS) and the translation elongation factor 1α (TEF1α) loci using protocols of White et al. 1994, and O'Donnell et al. 1998. Blast comparisons against NCBI databases, showed a very high identity (>99.5%) to MN528565.1 (ITS), and KU985430.1 (TEF 1α), both, F. oxysporum sequences. The identity of NA01 and CU08 was further confirmed by sequencing the DNA-directed RNA polymerase II (RPB1) locus (O'Donnell et al. 2015), observing more than 99% identity to CP052885.1 (RPB1) a F. oxysporum strain. BLAST check against the Fusarium MLSD database confirmed the identity. The obtained sequences were deposited in NCBI as MN963788, MN963793, MN963801, MN963782, MN963786 (ITS); OK143597, OK141601, OK143596 MW594202, OK169575 (TEF1α); and ON297670 and MZ670431 RPB1). To confirm causality, pathogenicity assays were conducted using NA01, NA48 and CU08. To this end, 25, 35 day-olds sprouted rhizomes, from each of the "purple", "green" and "white" varieties, were inoculated by drench with 30 ml of conidium suspension (1x106 conidia/ml) (Schmale 2003). Control rhizomes (25 per variety) were treated with sterile distilled water. Greenhouse conditions were 25 °C, 40% RH, and photoperiod 12h. Disease symptoms were detected 10 days after inoculation and evolved to resemble those from the field. While symptom and severity of infection varied with the isolate and host combination used, pathogen re-isolation and identification was successful fulfilling Koch´s postulates. Control plants remained healthy. The data shows that F. oxysporum species complex is the causal agent of this achira root and rhizome rot. To our knowledge, this is the first report of this problem in Colombia and clarifies local reports of Fusarium sp. causing disease in this crop (Caicedo et al. 2003). The disease affects the food security of local communities and strategies for control are being developed.

Identification and analysis of AP2/ERF gene family of Panax notoginseng and function of PnDREB84 gene / 药学学报

The AP2/ERF gene family is one of the largest transcription factor families in the plant kingdom, and plays an important role in response to biological and abiotic stresses, plant hormone responses, and plant growth and development. In this study, the AP2/ERF family of Panax notoginseng was identified by bioinformatics methods, and the physicochemical properties, structure, phylogenetic relationship, expression pattern and function of PnDREB4 gene of the family were analyzed. The results showed that 140 AP2/ERF family members were identified in P. notoginseng, which were divided into DREB, ERF, AP2, RAV and Sololit subgroups. The physicochemical properties and motifs of proteins were similar among the subgroups. There were 34 differentially expressed genes in the AP2/ERF family of Fusarium oxysporum infected P. notoginseng plants, and 19 genes were up-regulated. The expression level of PnDREB84 was up-regulated with the extension of Fusarium oxysporum infection time in the range of 0-96 h. The content of ABA and SA in P. notoginseng plants overexpressing PnDREB84 gene increased after 4 ℃ stress. The results showed that PnDREB84 gene plays a dual regulatory role in the process of biological stress and abiotic stress. PnDREB84 gene can be used as a potential molecular marker for the breeding of new varieties of P. notoginseng. The identification of AP2/ERF transcription factor and function analysis of PnDREB84 gene of P. notoginseng provided data support for the analysis of stress resistance mechanism of P. notoginseng and the breeding of new varieties.

Screening of natural drug molecules against Fusarium oxysporum of ginseng root rot based on machine learning / 药学学报

italic>Fusarium oxysporum widely exists in farmland soil and is one of the main pathogenic fungi of root rot, which seriously affects the growth and development of plants and often causes serious losses of cash crops. In order to screen out natural compounds that inhibit the activity of Fusarium oxysporum more economically and efficiently, random forest, support vector machine and artificial neural network based on machine learning algorithms were constructed using the information of known inhibitory compounds in ChEMBL database in this study. And the antibacterial activity of the screened drugs was verified thereafter. The results showed that the prediction accuracy of the three models reached 77.58%, 83.03% and 81.21%, respectively. Based on the inhibition experiment, the best inhibition effect (MIC = 0.312 5 mg·mL-1) of ononin was verified. The virtual screening method proposed in this study provides ideas for the development and creation of new pesticides derived from natural products, and the screened ononin is expected to be a potential lead compound for the development of novel inhibitors of Fusarium oxysporum.

Analysis of Fusarium oxysporum infection on changes of Astragalus metabolism by metabolomic approach / 药学学报

italic>Astragalus is a commonly used Chinese medicinal material in traditional Chinese medicine (TCM), and with the increase of planting area in recent years, the damage of Astragalus root rot has worsened year by year, which seriously affecting its quality and yield. Fusarium oxysporum is one of the main pathogens causing root rot in astragalus. In this study, UPLC-Q-TOF-MS based metabolomic approach combined with multivariate statistical analysis were used to analyze the metabolite changes of Astragalus in response to F. oxysporum infection. The results showed that 62 metabolites in the Astragalus had significant changes after inoculation of F. oxysporum. Polar metabolites included 40 flavonoids, 8 saponins, 2 nucleosides, 1 vitamin, 1 organic acid, 1 amino acid; while lipid metabolites included 3 fatty acids, 1 diradylglycerols, 2 lysophosphatidylcholine, 1 lysophosphatidylglycerol, 1 phosphatidylinositol, 1 sterol lipid. Among these differential metabolites, the relative content of flavonoids, vitamin B2, tryptophan and salicylic acid were increased, while the relative content of saponins were decreased. Correlation analysis showed that the flavonoids were positively correlated with each other, and positively correlated with most lipids, but negatively correlated with most saponins. In addition, studies have shown that F. oxysporum infection is not an influencing factor for the generation of malonyl substitution of flavonoid. This study elucidates the effect of F. oxysporum infection on Astragalus from the perspective of plant metabolism, which provides a basis for exploring the interaction mechanism between the Astragalus and F. oxysporum and further promoting molecular breeding.

First Report of Fusarium oxysporum Causing leaf spot on Basella rubra in Malaysia.

Basella rubra (family Basellaceae), locally known as 'Remayong Merah', is an edible perennial vine served as leafy greens in Malaysia. In May 2021, leaves with circular brown spots ranging from 3 to 10 mm wide with purple borders were found on B. rubra growing in Penampang (5°56'55.6"N 116°04'33.5"E), Sabah province. The disease severity was 80% with 10% disease incidence on 50 plants. As the disease developed, the lesions grew larger and they developed necrotic centers. Leaves with brown spot symptoms from five plants were collected from the field. Five leaf pieces (5 x 5 mm) were excised from lesion margins, surface sterilized based on Khoo et al. (2022b), before incubation on water agar at 25°C. When five pure cultures were obtained, the fungi were cultured on potato dextrose agar (PDA) at 25°C. After 5 days, fluffy white mycelia tinged with pink pigmentation showing on the underside of the colony were observed on PDA. Mycelia became violet in color as the culture aged. The isolates were incubated on carnation leaf agar at 25°C with a 12-hour light/dark photoperiod for 10 days. Sickle-shaped, thin-walled and delicate macroconidia (n= 30), predominantly 3 septate, ranging from 21.6 to 38.3 µm long by 2.7 to 4.2 µm wide in size were observed. Kidney-shaped, aseptate microconidia (n= 30) ranged from 6.2 to 11 µm long by 2.6 to 3.9 µm wide in size, and were formed on monophialides in false heads. Chlamydospores were detected both terminally and intercalarily, singly or in pairs, with smooth or rough walls. Genomic DNA was extracted from fresh mycelia of a representative isolate from Penampang based on Khoo et al. (2022a). The primers ITS1/ITS4 (White et al. 1990) and EF1/EF2 (O'Donnell et al. 1998) were used to amplify the internal transcribed spacer (ITS) rDNA and translation elongation factor 1-α (TEF1α) region, respectively based on PCR conditions as described previously (Khoo et al. 2022b). The products were sent to Apical Scientific Sdn. Bhd. for sequencing. In BLASTn analysis, ITS sequence (OK469301) was 99% (506/507 bp) identical to isolate TSE07 (MT481761) of Fusarium oxysporum, and the TEF1α sequence (OM743433) was 100% (705/705 bp) identical to isolate BLBL5 of Fusarium oxysporum. The TEF1α sequence of Penampang was analyzed at the Fusarium MLST site (https://fusarium.mycobank.org/), and had 98% similarity to TEF1α of F. oxysporum (NRRL 22551). The pathogen was identified as F. oxysporum based on morphological (Leslie and Summerell 2006) and molecular data. A volume of 0.16 ml of spore suspensions (1 × 106 conidia/ml) were inoculated on a spot on each leaf of every three healthy B. rubra seedlings at the two-leaf stage. An additional three B. rubra seedlings were mock inoculated by pipetting sterile distilled water on similar aged leaf. The seedlings were maintained in a greenhouse at 25°C with a relative humidity of 80 to 90%. Six days after inoculation, all inoculated leaves exhibited the same symptoms as observed in the field, while the controls showed no symptoms. The experiment was repeated two more times. The reisolated fungi had the same morphology and DNA sequences as the original isolate obtained from the field samples, completing Koch's postulates. F. oxysporum has been reported previously in Bangladesh and India causing leaf spot disease on B. rubra (Dhar et al. 2015; Shova et al. 2020). To our knowledge, this is the first report of F. oxysporum causing leaf spot on B. rubra in Malaysia. The identification of leaf spot caused by F. oxysporum will enable plant health authorities and farmers to identify practices to minimize disease on this important crop.

First Report on Ovate-leaf Atractylodes Damping-off Caused by Fusarium oxysporum species Complex in South Korea.

In South Korea, ovate-leaf atractylodes (OLA) (Atractylodes ovata) is cultivated for herbal medicine. During May to June 2019, a disease with damping off symptoms on OLA seedlings were observed at three farmer fields in Mungyeong, South Korea. Disease incidence was estimated as approximately 20% based on calculating the proportion of symptomatic seedlings in three randomly selected fields. Six randomly selected seedlings (two from each field) showing damping off symptoms were collected. Small pieces (1 cm2) were cut from infected roots, surface-sterilized (1 minute in 0.5% sodium hypochlorite), rinsed twice with sterile water, air-dried and then plated on potato dextrose agar (PDA, Difco, and Becton Dickinson). Hyphal tips were excised and transferred to fresh PDA. Six morphologically similar isolates were obtained from six samples. Seven-day-old colonies, incubated at 25 °C in the dark on PDA, were whitish with light purple mycelia on the upper side and white with light purple at the center on the reverse side. Macroconidia were 3-5 septate, curved, both ends were pointed, and were 19.8-36.62 × 3.3-4.7 µm (n= 30). Microconidia were cylindrical or ellipsoid and 5.5-11.6 × 2.5-3.8 µm (n=30). Chlamydospores were globose and 9.6 -16.3 × 9.4 - 15.0 µm (n=30). The morphological characteristics of present isolates were comparable with that of Fusarium species (Maryani et al. 2019). Genomic DNA was extracted from 4 days old cultures of each isolate of SRRM 4.2, SRRH3, and SRRH5, EF-1α and rpb2 region were amplified using EF792 + EF829, and RPB2-5f2 + RPB2-7cr primer sets, respectively (Carbone and Kohn, 1999; O'Donnell et al. 2010) and sequenced (GenBank accession number: LC569791- LC569793 and LC600806- LC600808). BLAST query against Fusarium loci sampled and multilocus sequence typing database revealed that 99-100% identity to corresponding sequences of the F. oxysporum species complex (strain NRRL 28395 and 26379). Maximum likelihood phylogenetic analysis with MEGA v. 6.0 using the concatenated sequencing data for EF-1α and rpb2 showed that the isolates belonged to F. oxysporum species complex. Each three healthy seedlings with similar sized (big flower sabju) were grown for 20 days in a plastic pot containing autoclaved peat soil was used for pathogenicity tests. Conidial suspensions (106 conidia mL-1) of 20 days old colonies per isolate (two isolates) were prepared in sterile water. Three pots per strain were inoculated either by pouring 50 ml of the conidial suspension or by the same quantity of sterile distilled water as control. After inoculation, all pots were incubated at 25 °C with a 16-hour light/8-hour dark cycle in a growth chamber. This experiment repeated twice. Inoculated seedlings were watered twice a week. Approximately 60% of the inoculated seedlings per strain wilted after 15 days of inoculation and control seedlings remained asymptomatic. Fusarium oxysporum was successfully isolated from infected seedling and identified based on morphology and EF-1α sequences data to confirm Koch's postulates. Fusarium oxysporum is responsible for damping-off of many plant species, including larch, tomato, melon, bean, banana, cotton, chickpea, and Arabidopsis thaliana (Fourie et al. 2011; Hassan et al.2019). To the best of our knowledge, this is the first report on damping-off of ovate-leaf atractylodes caused by F. oxysporum in South Korea. This finding provides a basis for studying the epidemic and management of the disease.