First Report of Powdery Mildew caused by Erysiphe astragali on Sphaerophysa salsula.

Sphaerophysa salsula (Pall.) DC., also known as Yang Liao Pao, belongs to the Leguminosae family and is the only existing species in the Sphaerophysa genus. S. salsula is tolerance to cold, high salt, and alkaline soil, it is widely cultivated in China as a forage crop, and used as a Chinese folk medicine to treat hypertension (Ma et al., 2002). In 2023, signs and symptoms similar to powdery mildew were found on S. salsula planted in Tumd left (40.515°N, 110.424°E), Baotou City, Inner Mongolia Autonomous Region, China. The white powdery substance covered 90% of the leaf area, and the infected plants showed weak growth and senescence. More than 80% of plants (n=200) had these powdery mildew-like symptoms. Hyphal appressoria are solitary, conidiophores have few branches and septa. Conidia are cylindrical to clavate, 25-32 µm long and 8-15 µm wide (n=30), conidia form single subapical germ tubes, straight to curved-sinuous, with swollen apex or distinctly lobed conidial appressorium. Based on these morphological characteristics, the fungus was tentatively identified as an Erysiphe sp. (Schmidt and Braun 2020). Fungal structures were isolated from diseased leaves, and genomic DNA of the pathogen was extracted using the method described by Zhu et al. (2022). The internal transcribed spacer (ITS) region was amplified by PCR using the primers PMITS1/PMITS2 (Cunnington et al. 2003) and the amplicon sequenced by Invitrogen (Shanghai, China). The powdery mildew strain, named as KMD (GenBank accession no.: PP267067), showed an identity of 100% (645/645bp) with Erysiphe astragali, a powdery mildew reported on Astragalus glycyphyllos in Golestan, Iran (GenBank: OP806834) and identity of 99.6% (643/645bp) with Erysiphe astragali (GenBank: MW142495), a powdery mildew reported on A. scaberrimus in Inner Mongolia, China (Sun et al. 2023). Pathogenicity tests were conducted by brushing the conidia from infected S. salsula leaves onto leaves of four healthy plants, while four control plants were brushed in the same manner. All the treated plants were placed in separate growth chambers maintained at 19°C and 65% humidity, with a 16 h light/8 h dark photoperiod. Nine days after inoculation, the treated plants showed powdery mildew symptoms, while the control plants remained asymptomatic. The same results were obtained for two repeated pathogenicity experiments. The powdery mildew fungus was reisolated and identified as E. astragali based on morphological and molecular analysis, thereby fulfilling Koch's postulates. No report on the occurrence of powdery mildew on S. salsula plants has been found previously. The occurrence of this destructive powdery mildew may adversely affect the cultivation of S. salsula. Identifying the pathogen of powdery mildew will support future efforts to control and manage powdery mildew on S. salsula.

Identification and Genome Characterization of a Dahlia Common Mosaic Virus Isolate from China.

Dahlia (Dahlia variabilis) is a widely cultivated ornamental and medicinal plant in China. Recently, dahlia plants with symptoms of leaf mottling and distortion were collected in Hohhot, Inner Mongolia, China. The presence of dahlia common mosaic virus (DCMV), an unassigned species in the genus Caulimovirus, was confirmed by high-throughput sequencing. Three fragments of DCMV Inner Mongolia isolate (DCMV-IN) were PCR-amplified with specific primers, sequenced and assembled into the complete genome sequence with a GenBank accession number of OR494328. The double-stranded circular DNA genome of DCMV-IN consists of 7949 bp and contains six open reading frames (ORFs). Sequence analysis showed that DCMV-IN shared high sequence identities with other DCMV isolates available in the GenBank database. Phylogenetic analysis of DCMV isolates and other representative caulimoviruses based on genome sequence clustered four DCMV isolates to a single branch which was closest to dahlia mosaic virus (DMV). No recombination event was detected among the four DCMV isolates.

Genomic characterization of a novel torradovirus infecting Arctium lappa L. in China.

Burdock (Arctium lappa L.) is not only a popular vegetable crop but also an important medicinal plant. In burdock plants with symptoms of leaf mosaic, a novel torradovirus tentatively named "burdock mosaic virus" (BdMV) was identified by high-throughput sequencing. The complete genomic sequence of BdMV was further determined using RT-PCR and the rapid amplification of cDNA ends (RACE) method. The genome is composed of two positive-sense single-stranded RNAs. RNA1 (6991 nt) encodes a polyprotein of 2186 aa, and RNA2 (4700 nt) encodes a protein of 201 aa and a polyprotein of 1212 aa that is predicted to be processed into one movement protein (MP) and three coat proteins (CPs). The Pro-Pol region of RNA1 and the CP region of RNA2 shared the highest amino acid sequence identity of 74.0% and 70.6%, respectively, with the corresponding sequences of lettuce necrotic leaf curl virus (LNLCV) isolate JG3. Phylogenetic analysis based on the amino acid sequences of the Pro-Pol and CP regions showed that BdMV clustered with other non-tomato-infecting torradoviruses. Taken together, these results suggest that BdMV is a new member of the genus Torradovirus.

Correlation in endophytic fungi community diversity and bioactive compounds of Sophora alopecuroides.

Sophora alopecuroides L. is a traditional Chinese medicine used for the treatment of several different disease states including bacillary dysentery and enteritis. But importantly, it also plays a role as an anti-tumor agent. That said, little is known about the role endophytes play regarding the clinically bioactive metabolites in S. alopecuroides. In order to explore the effects of endophytic fungi on the accumulation, quality, and correlation in the content of the medicinal compounds, the structural diversity of endophytic fungi in S. alopecuroides was analyzed. The relationship between endophytes and quinolizidine alkaloids (QAs), housed within the seeds of S. alopecuroides, which were interpreted based on established methods of high-throughput sequencing and high-performance liquid chromatography. A total of 1,034,418 effective sequence reads and 257 operational taxonomic units (OTUs) were obtained from 33 samples which were sourced from 11 different sampling sites and further classified into 9 phyla, 20 classes, 45 orders, 85 families, and 118 genera. Ascomycota was found to be the dominant phylum of endophytic fungi in S. alopecuroides, with a relative abundance ranging from 60.85 to 98.30%. Alternaria, Cladosporium, Filobasidium, and an unidentified Ascomycota were the core-shared endophytes, accounting for 49.96, 27.12, 14.83, and 7.88%, respectively. Correlation analysis showed that the Simpson's diversity index of endophytic fungal community in S. alopecuroides was significantly positively correlated with the Oxymatrine (OMA) content in different areas, while the Chao and Shannoneven indexes were significantly negatively correlated with OMA. The endophytic fungi of Alternaria were positively correlated with the content of OMA, Oxysophocarpine (OSC), and total QAs. This study has mastered the endophytic fungi resources of S. alopecuroides, explored potential functional endophytic fungi, and provided a scientific basis for using biological fertilization strategies to improve the quality of S. alopecuroides.

Occurrence of Powdery Mildew Caused by Erysiphe buhrii on Dianthus chinensis in Inner Mongolia, China.

Dianthus chinensis is widely cultivated for ornamental and medicinal use in China (Guo et al. 2017). The plant has been used in traditional Chinese medicine for the treatment of urinary problems such as strangury and diuresis (Han et al. 2015). In June and July 2020, powdery mildew-like signs and symptoms were seen on leaves of D. chinensis cultivated on the campus of Inner Mongolia Agricultural University, Hohhot city, Inner Mongolia Province, China. White powder-like masses occurred in irregular shaped lesions on both leaf surfaces and covered up to 50% of leaf area. Some infected leaves were deformed on their edges and some leaf senescence occurred. More than 40 % of plants (n = 180) exhibited these signs and symptoms. Conidiophores (n = 50) of the suspect fungus were unbranched and measured 70 to 140 µm long × 6 to 10 µm wide and had foot cells that were 25 to 48 µm long. Conidia (n = 50) were produced singly, elliptical to cylindrical shaped, 30 to 45 µm long × 12 to 19 µm wide, with length/width ratio of 2.0 to 3.2, and lacked fibrosin bodies. No chasmothecia were found. Based on these morphological characteristics, the fungus was tentatively identified as an Erysiphe sp. (Braun and Cook 2012). Fungal structures were isolated from diseased leaves and genomic DNA of the pathogen extracted utilizing the method described by Zhu et al. (2019). The internal transcribed spacer (ITS) region was amplified by PCR employing the primers PMITS1/PMITS2 (Cunnington et al. 2003) and the amplicon sequenced by Invitrogen (Shanghai, China). The sequence for the powdery mildew fungus (deposited into GenBank under Accession No. MW144997) showed 100 % identity (558/558 bp) with E. buhrii (Accession No. LC009898) that was reported on Dianthus sp. in Japan (Takamatsu et al. 2015). Pathogenicity tests were done by collecting fungal conidia from infected D. chinensis leaves and brushing them onto leaves of four healthy plants. Four uninoculated plants served as controls. Inoculated and uninoculated plants were placed in separate growth chambers maintained at 19 ℃, 65 % humidity, with a 16 h/8 h light/dark period. Nine-days post-inoculation, powdery mildew disease signs appeared on inoculated plants, whereas control plants remained asymptomatic. The same results were obtained for two repeated pathogenicity experiments. The powdery mildew fungus was identified and confirmed as E. buhrii based on morphological and molecular analysis. An Oidium sp. causing powdery mildew on D. chinensis previously was reported in Xinjiang Province, China (Zheng and Yu 1987). This, to the best of our knowledge, is the first report of powdery mildew caused by E. buhrii on D. chinensis in China (Farr and Rossman 2020). The sudden occurrence of this destructive powdery mildew disease on D. chinensis may adversely affect the health, ornamental value and medicinal uses of the plant in China. Identifying the cause of the disease will support efforts for its future control and management.

Preparative separation and enrichment of four taxoids from Taxus chinensis needles extracts by macroporous resin column chromatography.

An environment-friendly method was established for the preparative separation and enrichment of four taxoids, namely 10-deacetylbaccatin III (10-DAB III), 7-xylosyl-10-deacetyltaxol (7-xyl-10-DAT), cephalomannine and paclitaxel from Taxus chinensis needles extracts. Characteristics of seven widely used macroporous resins for four taxoids were compared, AB-8 resin offered better adsorption and desorption capacities than others. AB-8 resin column chromatography was used to study the desorption process for four taxoids. The optimum parameters for desorption were 30% ethanol 5 RV for removing impurities, following 15 RV for 10-DAB III, after the desorption of impurities with 35% ethanol 10 RV, 45% ethanol 30 RV for 7-xyl-10-DAT, then 65% ethanol 10 RV for cephalomannine and paclitaxel, the flow rate was 6 RV/h. After separation on AB-8 resin column chromatography, the contents of 10-DAB III, 7-xyl-10-DAT, cephalomannine and paclitaxel in the product reached 4.58, 13.17, 1.36 and 3.08%, respectively, which were 7.63-, 3.68-, 6.18- and 6.55-fold to those in T. chinensis needles extracts. The recovery yields were 94.96, 77.32, 88.09 and 95.25%. In general, the AB-8 resin column chromatography has the advantages of lower cost, high efficiency and simple procedure. Therefore, it may provide scientific references for the preparative separation and enrichment of taxoids from other T. species.