To clarify the pathogen species and isolation frequency inside and outside of soybean seeds in Inner Mongolia, and to make clear whether soybean seeds carry quarantine pathogen Phytophthora sojae, a total of 218 isolates were obtained from the inside of seeds and 196 isolates were obtained from the outside of seeds using washing assay and medial culture method, respectively. P. sojae was not isolated from the soybean seeds tested. Combined with colony morphology observation and ITS-rDNA sequence analysis, the above isolates were preliminarily identified. The internal isolates of seeds belonged to 16 genera, and the external isolates of seeds belonged to 17 genera. In combination with literature reports, 24 candidate fungal strains belonging to 9 genera were selected and tested for virulence, it showed that they all could cause lesions on etiolated soybean seedlings. Finally, the tested soybean seeds were confirmed to be free of P. sojae by specific primer amplification. These results provide an important reference for the scientific control of soybean diseases caused by seed borne pathogens.

In order to clarify the the population structure types, pathogenicity and the potential risks to different crops of Verticillium wilt of watermelon, the physiological type, physiological races, mating types and pathogenicity differentiation of Verticillium dahliae from watermelon were measured and the pathogenicity of 20 strains was studied by using root-drenching method. At the same time, the pathogenicity to watermelon of V. dahliae from six crops and the pathogenicity to four crops of V. dahliae from watermelon were determined. The results showed that all the 20 strains were identified as nondefoliated stains, physiological race 2 and MAT1-2-1 mating type. There were significant differences in the pathogenicity among the tested strains, the AUDPC values were from 238.92 to 606.81, the AUDPC values of WM05 and WM14 strains were 606.81 and 514.72, respectively, which were significantly higher than those of the other 18 strains. The pathogenicity of WM05 and WM14 strains was relatively strong. However, the AUDPC values of WM01, WM20, WM24 and WM19 strains were only 238.92, 249.15, 256.11 and 257.45, which showed relatively weak pathogenicity. V. dahliae from cotton, eggplant, potato, sunflower, tomato and honeysuckle could infect watermelon, and there were significant differences in pathogenicity. V. dahliae from watermelon could infect cotton, eggplant, potato and sunflower. The pathogenicity was the strongest on eggplant and was the weakest on cotton, and was comparable to that of watermelon on potato and sunflower.

Viruses in the genus Polerovirus of the family Solemoviridae exhibit a broad host range and can infect plants from many families, including Fabaceae, Solanaceae, Cucurbitaceae, Brassicaceae and others. They are responsible for significant economic losses globally and frequently co-infect with umbraviruses, which are members of the family Tombusviridae, leading to severe plant diseases. In order to explore the occurrence and distribution of poleroviruses in Yunnan, along with the potential outbreak risk associated with co-infection involving umbraviruses, a comprehensive disease survey was conducted in commercial crops including vegetables and fruits, as well as in the weeds surrounding these crops in Yunnan. Additionally, virus species were also detected and identified by RT-PCR. A total of 669 samples of 5 families, comprising 25 species of commercial crops and surrounding weeds, including vegetables, tobacco, potatoes, passion fruit and others, were collected from 7 states and cities in Yunnan Province, including Kunming, Yuxi, Baoshan, Dali, Chuxiong, Xishuangbanna and Honghe. Among the 11 commercial crops, 6 species of poleroviruses were found, which were the species potato leafroll virus, the species cucurbit aphid-borne yellows virus, the species suakwa aphid-borne yellows virus, the species pepper vein yellows virus 1, the species pepper vein yellows virus 3, and the species brassica yellows virus, respectively. Among them, PeVYV-3 had the highest average detection rate of 6.73% and was the dominant virus species in vegetables and fruits in Yunnan province. It was the first report in domestic and abroad that BrYV infected pea, PeVYV-3 infected eggplant, PeVYV-1 infected pea and broad bean, CABYV infected tobacco and pea. Moreover, the occurrence of SABYV in Yunnan Province was first reported. The host range of poleroviruses is gradually expanding, especially in various parts of Yunnan, indicating that the harm of poleroviruses to crops is gradually increasing. In addition, there is a risk of disease outbreaks with umbravirus co-infection. The research results contribute to a deeper understanding of the main types, distribution, and occurrence trends of poleroviruses in Yunnan, providing reference for comprehensive prevention and control of plant diseases caused by poleroviruses and their combined infection with umbraviruses.

To study the species and genetic variation of yam viruses in Henan province, 188 yam samples suspected of viral diseases were analyzed by high-throughput sequencing and RT-PCR. The results showed that five viruses were detected from yam samples: Japanese yam mosaic virus (JYMV), youcai mosaic virus (YoMV), yam latent virus (YLV), broad bean wilt virus 2 (BBWV 2) and yam yellow spot mosaic virus (YYSMV). The detection rates of JYMV, YoMV, YYSMV, BBWV 2 and YLV were 94.15 %, 87.23 %, 68.09 %, 42.02% and 29.79 %, respectively. 98.94% of the yam samples had complex infection. In this study, there were 20 complex infection types in 188 samples, among which JYMV + YYSMV + YoMV was the main complex infection type, and the detection rate was 26.60 %. Molecular variation analysis showed that YoMV and JYMV were more highly conserved, followed by YYSMV, YLV and BBWV 2, which showed more variation. Phylogenetic tree analyses indicated that the isolates obtained in this study were closely related to those from the same region. At the same time, HTS analysis results showed that other unclassified virus species were detected on yam, so it is necessary to conduct a comprehensive and systematic study on the types of yam viruses in Henan Province.

In order to investigate the occurrence and population genetic structure of tobacco vein banding mosaic virus on tobacco in Xingyi City, Guizhou Qianxinan Prefecture, and understand the genetic variation mechanism of tobacco vein banding mosaic viruses on tobacco isolates in Guizhou, Detection and identification of tobacco samples with typical TVBMV symptoms collected from Xingyi City, Qianxinan Prefecture, Guizhou Province were performed using electron microscopy negative staining, ultra-thin section preparation observation and molecular biology methods. Phylogenetic analysis and population genetic structure analysis of Guizhou tobacco samples was based on CP gene sequence of virus isolates using bioinformatics software. The results showed that among the 22 tobacco samples collected, the detection rate of TVBMV was 13.64%. The consistencies of nucleotide and amino acid sequences between the obtained TVBMV Guizhou tobacco isolate and the other 42 isolates published in GenBank were 94.1%-99.6% and 93.4%-100%, respectively. Phylogenetic analysis based on the amino acid sequence of the CP gene divides the isolates into four groups corresponding to the geographical distribution. The clustering results have obvious geographical distribution characteristics. Genetic diversity analysis shows that each group of TVBMV isolates exhibits a high level of genetic diversity due to the influence of geographical distribution. The analysis of population genetic structure shows that negative selection, genetic drift and ecological environment are the important effoectors for the genetic variation of TVBMV population. The research results provide theoretical support for the prevention and control of tobacco virus diseases and disease resistance breeding in Guizhou.

To clarify the types of viruses infecting Siraitia grosvenorii (Luo han guo) in Guangxi and provide instruction for the prevention, small RNA sequencing technology was employed to identify viruses, followed by PCR analysis to verify the results with degenerate and specific primer pairs. Then, the primers of corresponding viruses were used to investigate the distribution of virus species in the main production areas of S. grosvenorii in Guangxi. For these new viruses discovered in S. grosvenorii,all nucleotide sequences were characterized and phylogenetic trees were reconstructed, based on their amplified whole genomes. The results were as follows: according to small RNA sequencing and validation of polymerase chain reaction (PCR), leaves of S. grosvenoriifrom Guangxi University were infected with both squash leaf curl China virus (SLCCNV) and ageratum yellow vein China virus (AYVV) in Begomovirus, and both zucchini yellow mosaic virus (ZYMV) and papaya ringspot virus (PRSV) in Potyvirus. Further investigation revealed that all samples from Yongfu County, Lingui District and Longsheng County in Guilin and Qingxiu District in Nanning were infected with SLCCNV and ZYMV, and samples from Lingui District and Longsheng County in Guilin were also infected with PRSV. Their full-length genomes were all cloned,for SLCCNV-DNA-A (2 736 bp) and its four defective molecules, DNA-B (2 648 bp) and its two defective molecules, and AYVV (2 745 bp), which encode seven, two, and seven proteins, respectively. Sequence alignment and phylogenetic analysis indicated that the sequence of SLCCNV-DNA-A exhibited the closest identity tothat of the isolate from Yunnan, China, with 99.56% identity; the sequence of SLCCNV-DNA-B exhibited the closest identity tothat of the isolate from Thailand, with 91.41% identity, whose defective molecules exhibited recombination with exogenous genes; and the sequence of AYVV exhibited the closest similarity to that of a common weed isolate in Guangxi, with 97.83% identity.These indicated that S. grosvenorii was a new host for viruses in Begomovirus, and S. grosvenorii in Guangxi was co-infected with several virusesof both Begomovirus and Potyvirus.

Meloidogyne enterolobii, which is highly pathogenic to a wide range of host plants and spreads rapidly, can cause devastating damage to many crops. To deeply analyze the pathogenic mechanism of this nematode, here we take T106, a gene specifically induced in tomato roots in response to M. enterolobii infection based on previous transcriptome data, as our target. We silenced T106 in tomato plants via TRV virus-induced gene silencing technology, and then inoculated tomato seedlings with M. enterolobii to observe the difference in nematode and giant cell development in root system between T106-silenced and T106-unsilenced plants. The results showed that the silencing vector we constructed could effectively silence T106 gene in tomato plants, with a silencing efficiency of 85%; compared with T106-unsilenced control plants, there was no significant decrease in the percentage of root knots in T106-silenced plants, but the development of M. enterolobii in root knots was inhibited, and the number of eggs produced by M. enterolobii was reduced by 79.3%; meanwhile, the area occupied by giant cells was also decreased. In summary, T106 might be a susceptible gene targeted by M. enterolobii. Exploration of such susceptible genes in plants is vital for finding new ways to control root-knot nematodes including M. enterolobii.

Brown rot, caused by Monilinia spp., is a serious threat to both stone fruit and pome fruit, greatly affecting the long-distance transportation and exportation of fruits. Based on genomic and transcriptomic analysis of infection of Monilinia fructicola on peach fruit, it was detected that the expression patterns of MfHMG5 and MfHMG6 genes in early stages of infection were similar, and both down-regulated significantly at 1 h after inoculation and then gradually increased. In order to investigate the biological functions of these two genes, the knockout and overexpression transformants of MfHMG5, and knockout and complemented transformants of MfHMG6 were obtained and the corresponding phenotypes were investigated. It was found that the knockout and overexpression of MfHMG5 gene decreased the growth rate and sporulation ability, but did not affect the pathogenicity of M. fructicola. Knock out of MfHMG6 gene reduced the growth rate, virulence and sporulation ability of M. fructicola, and led to the increased expression of MfHMG5 gene. These results indicated that HMG-box family genes MfHMG5 and MfHMG6 were involved in regulating the growth and pathogenesis of M. fructicola.

The occurrence of Fusarium crown rot (FCR) caused by Fusarium pseudograminearum has been becoming increasingly serious in China, which has posed a severe threat to wheat yield and quality. The SEY1 belongs to the RHD3 (Root Hair Defective 3) family and encodes a dynamin-like GTPase protein participating in endoplasmic reticulum (ER) fusion. The ER is involved in the synthesis of deoxynivalenol (DON) in different pathogenic fungi, while its function in F. pseudograminearum has not been reported. In this study, subcellular localization of GFP-tagged Sey1 (FpSey1) protein in F. pseudograminearum was observed, and the results showed that FpSey1 was localized in the ER. The FpSEY1 deletion mutant (ΔFpSey1) was generated through PEG-mediated protoplast transformation and verified by Southern blot analysis, and complemented strains were obtained as well. Compared with the wild-type strain, the ΔFpSey1 mutant exhibited significant reduction in vegetative growth, conidiation, relative expression of DON biosynthesis related genes (TRI1, TRI5, TRI10) , and the virulence on wheat coleoptiles and barley leaves. In addition, the ΔFpSey1 mutant is more sensitive to salt stress, hydrogen peroxide (H₂O₂), but more tolerant to dithiothreitol (DTT) than the wild-type and complemented strains. These results indicate that FpSey1 localized in the ER plays important roles in the growth and infection of F. pseudograminearum.

Leaf scald, caused by Xanthomonas albilineans (Xa), is a bacterial disease that seriously affects sugarcane production. Understanding the pathogenicity of this bacterial pathogen is crucial to preventing and controlling sugarcane leaf scald disease. Previous studies have shown that Phoq, a transmembrane histidine protein kinase in the two-component system of Xanthomonas, is a very important transduction factor, sensing extracellular signals, activating intracellular kinase activity, and subsequently regulating downstream gene expression. In this study, we collected Phoq protein sequences from eight pathogenic bacteria in the genus Xanthomonas, including Xa. The results of phylogenetic analysis and motif composition prediction showed that these Phoq proteins have conserved structure and similar physicochemical properties. To further investigate the biological role of phoq in Xa, we produced phoq knockout mutant in Xa-JG43 strain using the homologous recombination method. Compared with the wild-type strain Xa-JG43, the swimming ability and pathogenicity of the Xa-phoq knockout mutant were seriously weakened, but the swarming and stress response ability were not affected; In Xa-phoq complementary strain, the pathogenicity and swimming ability were restored to the level of the wild-type strain. This study provides a theoretical basis for further determination of the pathogenic mechanism of Xa.

Fusarium crown rot, mainly caused by Fusarium pseudograminearum, is a destructive disease in wheat production. To establish a rapid and reliable detection method for F. peasudeograminearum, the specific PCR primer pair (Fpg-F1/R2) was designed based on the RPB sequence, and real-time fluorescence quantitative PCR (qPCR) was used to validate the efficiency of the primer. The results showed that the primer pair had high specificity and sensitivity of 100 pg of DNA. Furthermore, the qPCR system for early and rapid detection of F. peasudeograminearum had an amplification efficiency of 87.5% and correlation coefficient of 0.99, and the pathologic threshold of F. pseudograminearum in soil was determined by using this detection system. It was found that F. pseudograminearum could cause Fusarium crown rot when the DNA concentration of F. pseudograminearum in field soil exceeded 213 pg·g-1. Hence, the qPCR-based method we developed for F. pseudograminearum detection has the advantages of high specificity and sensitivity, and can be used for rapid and early detection of F. pseudograminearum even in field soils.

To identify the pathogens causing root rot on Lonicera japonica, we collected diseased root samples and conducted microbe isolation. The causal agents of the disease were identified as Fusarium solani and Fusarium incarnatum through pathogenicity test, and based on morphological characteristics and phylogenetic analysis results, and combined infection by these two species of fungi led to more severe symptoms. The optimal tempera-ture for mycelial growth of the two pathogens is 28 ℃, and the growth was suppressed when the temperature was lower than 4 ℃ and above 50 ℃; The optimal temperature for spore germination of F. incarnatum is 28 ℃, and 25-28℃ for F. solani; The two pathogens are insensitive to pH and can grow at pH 5-11; A light/dark cycle of 12 h light/12 h dark is suitable for mycelial growth of F. incarnatum, while total darkness is suitable for F. solani; The lethal temperatures for mycelial growth of F. incarnatum and F. solani are 50 ℃ and 55 ℃ for 10 min respectively, and are 50 ℃ for 10 min for spore germination of both the pathogens; The most suitable carbon source for both fungal pathogens is pectin, and the most suitable nitrogen source is tryptone for F. incarnatum but peptone for F. solani. In addition, the utilization efficiency of F. incarnatum is low to the other tested nitrogen sources, whereas F. solani showed a broad-spectrum adaptability to carbon and nitrogen sources. To explore biocontrol agents against F. incarnatum and F. solani, bacterial strains were isolated from rhizosphere soil of healthy L. japonica. By confronting incubation test, enzyme activity test and pot experiment in greenhouse, two strains BG1 and BS37, which showed good performance in promoting the growth of L. japonica and controlling root rot, were obtained. BG1 and BS37 were identified as Paenibacillus polymyxa and Bacillus subtilis, with a control efficacy of 59.41% and 52.47%, respectively. The results provide good potential biocontrol resources for the control of L. japonica root rot.

Colletotrichum fructicola, belonging to the C. gloeosporioides species complex, is the dominant pathogenic species causing anthracnose on plum trees. In this study, multiple alignment of ApMat sequences of 36 strains in the C. gloeosporioides complex was performed, a pair of C. fructicola-specific primers: F2(5′-CGTGACCCAGGAGGCGACCACGCATCTGT-3′ ) and R2(5′-GGTGATCTCTCCTAGCGTTCGTACGTCTAAT-3′) was designed based on the specific sequences of the pathogen, and a PCR detection method was develo-ped accordingly. The results showed that a specific target amplicon of 132 bp could only be produced by C. fructicola with the primer pair F2/R2, with a detection sensitivity of 100 fg·μL^-1. Using this PCR detection system, the target pathogen C. fructicola can be quickly detected from the leaves of plum trees artificially inoculated with C. fructicola HN47-2 strain and the leaves of plum trees naturally infected with C. fructicola. The C. fructicola-specific PCR detection method established in this study provides an important technical support for early diagnosis, dynamic monitoring and accurate prevention and control of plum anthracnose caused by C. fructicola in the field.

In the autumn of 2019, a new leaf spot disease was discovered on Zizania latifolia plants in two locations, Langya in Jinhua, and Daji in Lishui, Zhejiang Province. We isolated the pathogen using tissue separation method, and identified it as Epicoccum sorghinum through multiple methods, including morphological observation, biological identification and pathogenicity test. Besides, to prevent the effect of E. sorghinum on the yield and quality of Z. latifolia, 12 chemical fungicides were screened. Among these, prochloraz showed the best inhibitory effect on the pathogen. Additionally it had the least side effect on the growth of Ustilago esculenta, another mutually beneficial organism associated with Z. latifolia. So prochloraz can be used as an effective fungicide for the disease management. This study provides a scientific basis for the identification and understanding the leaf spot disease in Z. latifolia. It offers insights into the selection of chemical fungicides for its control, which is valuable for agricultural and disease management.

In recent years, apple diaporthe neck and root rot has become one of the most important limiting factors for the development of apple production in Yunnan Province. In this study, the typical disease samples were collected and the fungal isolate M2g7-1 was obtained by tissue separation approach. The purified culture M2g7-1 was preliminary determined belonging to Diaporthe spp. based on the morphological features of colony, pycnidia, cirrus, two forms of conidia. The pathogenicity of M2g7-1 was further validated on apple young branches to fulfill the Koch's law. The taxonomic of pathogen M2g7-1 has been further determined with combining molecular phylogenetics. The phylogenetic tree was created with the data set of sequences from the internal transcribed spacer (ITS) of ribosomal DNA, the histone H3 (HIS) gene, the translation elongation factor 1-alpha (TEF) gene, and the beta-tubulin (TUB) gene. Based on morphological and molecular biology analysis, the pathogen M2g7-1 was finally identified as Diaporthe eres. This is the first report of D. eres as the pathogen of apple diaporthe neck and root rot. The research results provide a theoretical basis for the epidemic research and comprehensive control of this disease.

Bletilla striata is one of the genuine medicinal materials in Guizhou, and its planting area ranks first in China. In 2022, the leaf blight of Bletilla striata occurred in Guizhou Academy of Agricultural Sciences with a large area and was serious. In this study, the pathogenic fungus was isolated from the leaves with obvious symptoms, which was identified to be Rhizoctonia solani AG1-IB based on the results of morphological identification, ITS sequence analysis, and hyphal anastomosis. To our knowledge, there have been no reports on the isolation of R.solani AG1-IB from Bletilla striata in China as so far. This is the first report and the results will provide theoretical reference for effective control and further research of leaf blight on Bletilla striata.

Citrus is one of the most important fruits in China and is cultivated extensively in southern China. Fusarium fujikuroi has been reported to cause diseases on various plants excluding citrus worldwide. In this study, by using tissue separation method, 23 Fusarium-like isolates were isolated from diseased citrus leaves from eight different citrus planting areas in Hubei province. STJ-4 was selected as a representative isolate for further analysis, which included analyses of morphological characteristics, partial sequences of ITS, EF-1α, and RPB1 genes, phylogenetic trees based on the three genes and pathogenicity. Results showed that the STJ-4 isolate was identified as F. fujikuroi, which is the first report of F. fujikuroi causing leaf rot disease on citrus. Our study is important for developing the prevention strategies against F. fujikuroi in the future.

Brown rot symptoms on fruit of Lucuma nervosa were observed in Guangxi South Subtropical Agricultural Science Research Institute. The samples were collected from the field, the pathogen was isolated by tissue isolation, and its pathogenicity was verified by the Koch′s rule. The pathogen was identified as Lasiodiplodia pseudotheobromae by combining morphological characteristics and ITS-TUB-RPB2-TEF1 sequence analysis. This is the first report of Lasiodiplodia pseudotheobromae causing brown rot on Lucuma nervosa fruit in the world.

As an important ornamental plant, hollyhock (Alcea rosea L.) plays an important role in landscape architecture. In May 2023, a new rust disease on A. rosea was observed in Guiyang, Guizhou Province. Rust infected various parts of A. rosea and seriously reduced the ornamental value. In this study, the teliospores were collected from the diseased leaves of A. rosea. Based on the morphological characteristics and phylogenetic analyses of internal transcribed spacer (ITS) and large subunit (LSU) sequences, the rust pathogen was identified as Puccinia modiolae. This is the first report of P. modiolae causing rust disease on A. rosea in China. These findings will promote further research on rust disease on A. rosea and provide a scientific basis for its control.

As a famous fruits of the tropics and subtropics,the overall growth of Hylocereus polyrhizus have been seriously affect by a mature stem blight disease found in the regions of H. polyrhizus plantations in Danzhou city,Hainan province of China in 2022. It caused extensively grayish-white blight of the diseased stems. The pathogen isolated from the diseased plants was identified as Diaporthe passiflorae,based on pathogenicity test,morphological traits and phylogenetic analyses of multi-loci (ITS,TUB2,CAL,TEF1-α and HIS3). The results provide a theoretical basis for the field control of stem blight of H. polyrhizus.

Cherry tomato (Solanum lycopersicum var. cerasiforme) is an important crop in Hainan Province, and its production is seriously damaged by viral diseases. To identify the viruses infecting cherry tomato, LncRNA sequencing was performed using leaf samples from diverse geographical locations with typical viral symptoms. The virome of cherry tomato comprises eight viruses─ageratum yellow vein virus (AYVV), cucumber mosaic virus (CMV), southern tomato virus (STV), tobacco mosaic virus (TMV), tomato chlorosis virus (ToCV), tomato mosaic virus (ToMV), tomato mottle mosaic virus (ToMMV) and tomato yellow leaf curl virus (TYLCV). The PCR detection results of 234 cherry tomato leaf samples from nine cities and counties indicated that the dominant viruses are TYLCV (69.23%), ToCV (49.57%) and ToMMV (35.47%), followed by STV (23.50%), ToMV (17.52%), CMV (17.52%), AYVV (16.24%) and TMV (10.68%). The ratio of mixed virus infection was 81.62%. Complete genomes of two AYVV isolates (AYVV-tomato-LS1 and AYVV-tomato-LS2) and one TYLCV isolate (TYLCV-tomato-LS) in the genus Begomovirus were obtained using PCR with back-to-back primers. The pairwise comparison of genomes of AYVV-tomato-LS1 and AYVV-tomato-LS2 were 98.98% nucleotide identical to each other, sharing their maximum nucleotide identities at 92.71% and 92.81% with AYVV-SY08 (GenBank accession no.: KC810890), and were phylogenetically closely related to the AYVV isolates from diverse hosts from Hainan. TYLCV-tomato-LSs shared their maximum nucleotide identities at 96.52% with TYLCV-HNLS (GenBank accession no.: MK908814), and were phylogenetically closely related to the TYLCV isolates from diverse hosts from Hainan, followed by Capsicum annuum isolates from Spain (GenBank accession no.: AJ489258). Our findings provide support for sustainable control strategies for cherry tomato virus disease in Hainan, China.