Clonostachys species are a group of fungi with various morphological and ecological characteristics, which are widely distributed in a variety of environmental conditions, especially in soil. Because Clonostachys can control plant diseases through direct or indirect mechanisms including antagonism, mycoparasitism, growth promotion and the induction of plant resistance, the application of Clonostachys as a biocontrol agent has attracted much attention. In this review, we summarized the progress in phylogeny and taxonomy of this genus, and the interactions of Clonostachys-plant pathogens and Clonostachys-plants. Then, the application status of Clonostachys was summarized and its application prospect was also prospected. Screening strains with excellent biological control characteristics from Clonostachys fungi will promote their commercialization in agricultural applications.

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.

Sho1 and Msb2 are respectively four-transmembrane membrane proteins and single-chain transmembrane protein. Resent research shows that they generally exist in fungi,and have conservative structures, including extracellular domain, transmembrane structure and cytoplasmic domain. Sho1 is located in the plasma membrane, and Msb2 is located in the plasma membraneand transported into the vacuole through endocytosis. Different domains of Sho1 and Msb2 bind to various signaling proteins, then participate in different pathways in the MAPK signaling pathway, so as to regulation of fungal growth and stress response. At present, the functions of Sho1 and Msb2 have been reported in Saccharomyces cerevisiae, Candida albicans, Aspergillus fumigatus, Verticillium dahliae, Fusarium oxysporum, F. graminearum, Ustilago maydis, Magnaporthe oryzae, Botrytis cinerea, Cryptococcus neoformans, and Histoplasma capsulatum, that mainly involved in filamentous growth, osmotic stress, oxidative stress, cell wall integrity, temperature response, and virulence regulation of fungi. However, their specific functions have fungal evolution specificity. This paper reviewed the structural characte-ristics of Sho1 and Msb2, summarized and analyzed the functions and action ways of Sho1 and Msb2 in different fungi, in order to provide reference for related research.

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.

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.

Peach latent mosaic viroid (PLMVd) is an important viroid infecting peach trees. PLMVd can cause various leaf symptoms including mosaic, yellowish and calico, etc. At present, the mechanism of PLMVd infection causing mosaic leaves is unknown. In this study, 86 full-length PLMVd sequences, in size of 336-338 nt, were isolated and cloned from the mosaic (M) and asymptomatic (N) leaves of nectarine trees collected in the field in China. By DnaSP 5.0 analysis, 31 haplotype (variant) sequences were obtained in the cloned sequences. The haplotype diversity (Hd) was relatively low as 0.79 for M isolates, while was high as 0.90 for N isolates. Compared with N isolates, sequence analysis showed that the sequence variation of M isolates mainly occurred in five regions of the whole sequence. MY1 haplotype sequence was dominant among those of M isolates, which clustered in phylogenetic group I with a few other variants and shared 89.4% identity with that of P1.148, a typical peach calico isolate. Through a comparative study of PLMVd cDNA infectious clones, gene synthesis and inoculation methods, the infectious PLMVd diploid cDNA clone construction and effective inoculation methods were established. The constructed MY1 diploid cDNA recombinant plasmid can infect the Prunus davidiana Franch systematically and exhibit typical mosaic symptoms after high-stressed stems slashing inoculation. The results will build a foundation for further study about the molecular mechanism of PLMVd inducing peach mosaic symptom.

Asarum plants showing leaf blight symptoms were collected from Xinbin County, Fushun City, Liaoning Province, China. To investigate the causal agent of the disease, pathogenicity test was carried out with XXY-2, a representative fungal strain that were isolated from the diseased plant tissues, and the result showed that it is the pathogen causing asarum leaf blight. Based on morphological characters, strain XXY-2 was identified as Talaromyces brevis. According to the results of multigene-combined (rDNA-ITS+BenA+RPB2) phylogenetic analysis, strain XXY-2 was grouped into the same branch of T. brevis model strains DTO 307^T and CBS 141833^T, further confirming that it belongs to T. brevis. Indoor toxicity tests of 8 fungicides against strain XXY-2 showed that pyraclostrobin and fludioxonil had a better inhibitory effect on mycelial growth of the strain, with EC₅₀ values of 0.0096 and 0.0056 μg·mL^-1, respectively. This is the first report of T. brevis as a pathogen of asarum leaf blight, making a theoretical basis for integrated control of the disease.

Stripe (yellow) rust caused by Puccinia striiformis f. sp. tritici is a devastating disease on wheat, which seriously affects the security production of wheat. Correct severity assessment is essential for disease forecasting and adopting effective disease management measures to reduce wheat yield losses. To realize accurately assess the severity of wheat stripe rust, in this study, the methods for the severity assessment of wheat stripe rust were investigated based on image processing and an automatic grading system of wheat stripe rust severity was developed. Based on the acquired disease images of single leaves of wheat stripe rust, manual disease image segmentation operations and pixel statistics operations were performed successively with an image processing software, and the segmented leaf region and lesion region images and the pixel numbers of the corresponding whole leaf regions and lesion regions were obtained. According to the obtained pixel numbers, the actual percentages of lesion areas in the areas of the corresponding whole diseased leaves were calculated. Based on image processing technology, four image segmentation methods were utilized to implement automatic segmentation to obtain leaf region images and lesion region images. Then, the results obtained by using the four automatic segmentation methods were compared with those obtained by using the manual segmentation method via the image processing software, and the optimal automatic segmentation method was achieved. Subsequently, based on the percentages of lesion areas in the areas of the corresponding whole diseased leaves obtained by using the optimal automatic segmentation method, the severity of each diseased leaf was assessed according to the midpoint-of-two-adjacent-means-based actual percentage reference range and the 99% reference range of the actual percentages for each severity class of wheat stripe rust, respectively. The results showed that the assessment method based on the 99% reference range of the actual percentages for each severity class of wheat stripe rust was the optimal, with the average accuracy of 88.19%. Finally, by using the optimal automatic image segmentation method and the optimal severity assessment method, in combination with the PyQt5 library, Qt Designer, and PyUIC5 design tools, an automatic grading system of wheat stripe rust severity was developed with the Python language. This study provided a basis for the automatic assessment of wheat stripe rust severity based on image processing technology, and provided methods and ideas for the severity assessments of other plant diseases.

Strawberry angular leaf spot is one of the important bacterial diseases in Yunnan in recent years. In this study, a bacterial strain isolated from the strawberry leaf lesion was identified as Xanthomonas fragariae based on morphological, physiological and biochemical analysis, pathogenicity detection, as well as the phylogenetic analysis of the 16S rDNA and hrpB genes. The physiological and biochemical detection showed that the pathogenic bacterium could utilize 26 carbon sources such as D-maltose, D-trehalose, D-cellobiose, sucrose and D-pintobiose. It can react with seven chemical sensitive substances such as nalidixic acid and lincomycin. The pathogenic bacterium had weak salt tolerance, sensitive to acid, and could use organic acids such as L-lactic acid and citric acid. The disease resistance evaluation experiment showed that ‘Benihoppeand’ and ‘Sweet Charlie’ were highly resistant varieties, with disease indexes of 5.95 and 4.76, respectively, and the proportion of highly resistant varieties was 14.28%. The moderately resistant varieties included ‘Portola’, ‘All star’, ‘Yuexiu’, ‘Snow White’, ‘Jingzangxiang’, and ‘Xiangye’, and the proportion of moderately resistant varieties was 42.85%. In conclusion, we identified the pathogenic bacterium of strawberry angular leaf spot, and obtained several disease-resistant strawberry varieties through screening. These results laid a foundation for further research on the characteristics of disease occurrence and prevention methods.

Potato common scab is caused by Streptomyces spp. Potato common scab disease is widely distributed in potato producing areas of the world. For many years, common scab has hampered the potato industry, especially the developing of seed potatoes industry. In this paper, the occurrence of common scab, pathogen distribution, disease detection, pathogenic mechanism, cultivar resistance research and green prevention and control technology were reviewed, and the urgent problems in potato common scab research were put forward in order to provide new ideas for in-depth research and green prevention and control of potato common scab.

In this study, the mating types, physiological race composition, and genetic structures of 66 Phytophthora capsici isolates, collected from Chongqing during 2019-2020, were revealed by antagonistic culture, root-irrigation inoculation of differential hosts, and simple sequence repeats (SSR) marker-based analysis. The results showed that there were 53 P. capsici isolates of A2 mating type and 13 isolates of A1 mating type; 11 isolates of race 1, 28 isolates of race 2, 1 isolate of race 3, and 2 isolates of race 6. Genetic variation analysis of the P. capsici population, which consists of 11 different geographical sub-populations, was carried out by using six common SSR markers, and 59 different genotypes were obtained in total, with effective alleles of 1.786-2.881, expected heterozygosity of 0.352-0.577, Shannon-Wiener index of 1.242-2.079, and percentage for polymorphic markers of 83.33%-100%, and high levels of gene exchange occurring within subgroups (Nm=0.133-7.680) were indicated by medium population differentiation (F_ST=0.113). It was concluded that the degree of genetic variation of P. capsici populations in different regions of Chongqing was different, while the whole population had a surplus of heterozygotes, indicating a rich genetic diversity. The mating type proportion, fixation index, Hardy-Weinberg balance and linkage disequilibrium analysis for each geographical population showed that asexual and sexual reproduction may co-exist in P. capsici populations of Chongqing. Analysis of molecular variance (AMOVA) further showed that genetic variation mainly occurred within populations. Discriminant analysis of principal components (DAPC) showed that there were obvious differences and group division among P. capsici isolates from Chongqing, which could be divided into two groups. Structural analysis showed that P. capsici in Chongqing may come from two different ancestral groups. The results lay a basis for the control of Phytophthora blight of pepper plants.

Rice bacterial leaf streak, the main bacterial disease caused by Xanthomonas oryzae pv. oryzicola (Xoc), seriously affects rice production. Exploring safe and efficient biological resources is very important for the control of the disease. In this study, an endophytic bacterial strain XP-1 was obtained from rice leaves by confronting incubation method, with an inhibition zone diameter of (56.1±0.1) mm against Xoc. XP-1 also exhibited good antagonistic activity against 5 common bacterial phytopathogens (Ralstonia solanacearum, Xanthomonas oryzae pv. oryzae, Ralstonia solanacearum, Pectobacterium carotovorum subsp. carotovorum, Xanthomonas fragariae and Xanthomonas campestris pv. campestris). Physiological and biochemical test showed that XP-1 strain can produce IAA and siderophore, and solubilize phosphate but cannot solubilize potassium and fix nitrogen. Through indoor seed soaking test and greenhouse pot experiment, it was showed that the diluted fermentation broth of XP-1 could promote seed germination and seedling growth of rice plants, and inhibit leaf lesion on 3 rice varieties, with an inhibition rate of 63.72%-94.47%. The beneficial endophytic XP-1 strain, which has a wide antimicrobial spectrum, was identified as Pantoea ananatis based on morphological characteristics, physiological and biochemical properties and molecular identification results. This study provides the foundation for further exploration of biological resources for rice bacterial leaf streak control.

Watermelon planted in early spring is a characteristic fruit in hot area of Yunnan Province. Its viral diseases are more and more serious in recent years. To detect and identify the main viruses, the plants and fruits samples of watermelon were collected from Menghai county, Xishuangbanna state, and transmission electron microscope (TEM) observation, indirect enzyme-linked immunosorbent assay (ID-ELISA), RT-PCR amplification and analysis of viral genome sequences were carried out. The results showed that the viruses infecting watermelon were watermelon silver mottle virus (WSMoV) and cucumber mosaic virus (CMV). The detection rates of WSMoV and CMV using ID-ELISA were 70% and 20%, respectively, in leaf samples, and of complex infection was 15%. The detection rates of these two viruses by RT-PCR were 100% and 65%, respectively, and of complex infection was 65%. However, the complex infection rate of these two viruses detected by RT-PCR amplification could reach up to 100% in seeds. Phylogenetic analysis demonstrated that the genome sequences of WSMoV [21YV-40(GenBank accession no.:OP617563), 21YV-43(GenBank accession no.:OP867047)] isolated in this study were similar to the squence of WSMoV [Banna-2011 (GenBank accession no.:KM242056)] isolated from Yunnan watermelon in 2016, and the similarity was 99%. The genome sequences of CMV [CMVYN40(GenBank accession no.:OP617565), CMVYN46 (GenBank accession no.:OP617566)] isolated in this study were similar to the sequence of CMV [A27(GenBank accession no.:FN552545)] isolated from watermelon in Thailand, and the similarity was 98%. This study demonstrated that the early spring watermelon was mainly infected by WSMoV and CMV, and complex infection was also common. The complex infection of WSMoV and CMV to both the plant and the seed of watermelon was reported for the first time. This study supplied a basis for virus prevention in the early spring watermelon.

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.

Rice blast fungus has diverse polymorphism in paddy fields. To clarify the role of genetic recombination on biodiversity of Magnaporthe oryzae population in paddy fields, 336 single-spore isolates of M. oryzae were collected from five main rice-producing regions of Liaoning Province, and their difference on mating type distribution and fertility capacity were analyzed. The PCR amplification on mating type genes showed that all 336 isolates belonged to the same mating type, MAT1-2. The confrontation cultivations of all isolates with a standard strain P9 having an opposite mating type (MAT1-1) showed that the average proportion of fertile strains was 37.5% and the average number of perithecia of each cross was 38.8. Moreover, the fertility capacities of the isolates from the five main rice-producing regions were significantly varied. Taken together, these findings suggest that sexual reproduction of M. oryzae population in Liaoning Province is rare or probably non-existent though they retain certain fertility capacities, and the biodiversity of M. oryzae population in paddy fields may be attributed by other factors.

In this study, 155 isolates of Fusarium were isolated from the diseased roots of strawberry with the symptom of root rot, which were collected from thirteen provinces, municipalities, and autonomous regions across China from 2021 to 2022. The obtained 155 Fusarium isolates were identified to be eight species (namely F. acuminatum, F. asiaticum, F. commune, F. equiseti, F. fujikuroi, F. oxysporum, F. proliferatum, and F. solani) based on morphological characteristics and sequence analyses of internal transcribed spacer of ribosomal DNA (rDNA-ITS) and translation elongation factor-1 alpha (TEF-1α), with F. oxysporum (108 isolates, 69.68%) being predominant. Results of pathogenicity test confirmed that thirty-one representative isolates belonging to these eight species of Fusarium could induce the symptom of root rot on strawberry roots, showing that they were pathogenic on strawberry roots. The average disease incidence (98.62%) and disease index (79.87) of strawberry roots caused by F. oxysporum were higher than those of the seven other species of Fusarium. To the best of our knowledge, this is the first report of F. asiaticum, F. commune, F. fujikuroi, and F. proliferatum causing strawberry root rot in China.

Southern corn rust caused by Puccinia polysora Underw., is a fulminant and airborne disease, which can cause serious losses during epidemic years. Many studies at home and abroad have shown that the physiological races of P. polysora were very abundant, and the epidemic of plant diseases was mainly caused by the dominant races of P. polysora, but there were few research reports on the physiological races of P. polysora in China, so it brings many difficulties to the prediction and prevention of this disease, and has become a bottleneck in corn production. Based on the current research on the resistance genes and resistant inbred lines of southern corn rust in China, this study selected inbred lines containing known resistance genes and backbone inbred lines in maize production as differrential to be identified. Isolates of southern corn rust collected from different regions were used to identify these inbred lines resistance at the seeding in greenhouses, and the virulence frequency (VF) of different inbred lines. Then the inbred lines with the ability to identify different pathotype were selected to construct a set of differrential, and the pathotypes of southern corn rust in China was studied. 14 pathotypes were identified. Among them, pathotype 1, which can only infect Huangzaosi, with the highest frequency of 0.58, was the dominant pathotype of P. polysora in China, which could be found from 7 provinces such as Hainan, Guangxi, Guangdong, shandong, etc. in 2016 and 2017. This pathotype, which can be determined as a new physiological race of southern corn rust pathogen in China. This is the first physiological race of P. polysora identified in China, temporarily named as Nanzhong1(NZ1).

Late blight caused by Phytophthora infestans seriously affects the yield and quality of tomato. Previous research found that tomato plants contain age-related resistance (ARR) to P. infestans, but the underlying mechanisms are still unclear. Here, we used tomato variety ‘Micro Tom’ as the tested material and found that younger (4-week-old) plants are more resistant while older (8-week-old) plants are more susceptible to late blight. Through RNA sequencing and real-time quantitative PCR (qPCR) analysis, we observed that the transcription levels of genes involved in jasmonic acid (JA) synthesis, such as AOS1, AOS2 and AOC, are higher in 4-week-old plants than those in 8-week-old plants. We further examined the levels of several phytohormones and found that the concentration of JA in 4-week-old plants is significantly higher than that in 8-week-old plants. Transient expression of AOS1, AOS2 or AOC in tobacco leaves made them more resistant to late blight, suggesting that these JA biosynthetic genes can enhance tomato resistance to late blight. Tomato plants sprayed with MeJA were more resistant whereas tomato plants sprayed with JA synthesis inhibitor DIECA were more susceptible to late blight, suggesting that JA positively regulates tomato resistance to late blight. Thus, we provide evidence supporting a model in which genes involved in JA synthesis play important roles in the age-related resistance to late blight in tomato. Our results lay an important basis for using ARR to control tomato late blight.

Fungal disease is an important factor restricting the high and stable yield of soybean. In order to clarify the taxonomic status of pathogenic isolates SoyITS1 and SoyITS12 isolated from the diseased soybean roots with the symptoms of root rot, the two isolates were identified on the basis of morphological traits and sequence analyses of translation elongation factor 1-α (EF1-α) and RNA polymerase II beta subunit (RPB2). The results showed that the colonies of isolates SoyITS1 and SoyITS12 were milky white when they were cultured on PDA medium. After 7 d of culture on CLA medium, the conidia were falciform with blunt apical cells and slightly crooked base cells, with 3 - 4 septa, the size of which was (20 - 40) μm× (3.5 - 6.8) μm (n = 50). BLAST sequence comparison showed that the consistency between strains SoyITS1 and SoyITS12 and Fusarium falciforme was 86.7% - 98.8%. In the two monogenic and polygenic phylogenetic trees, SoyITS1 and SoyITS12 strain was clustered in the same evolutionary branch as F. falciforme. Strain SoyITS1 and SoyITS12 were identified as F. falciforme based on morphological characteristics, homology analysis and phylogenetic tree analysis.

Myb transcription factors play important roles in the regulation of various biological processes in plants. However, the molecular mechanism underlying their roles in regulating late blight resistance remains elusive. Here, we report the cloning of NbMybl, a Myb-like gene from Nicotiana benthamiana, which has an open reading frame of 753 bp and encodes a protein of 250 aa. NbMybl contains a Myb-like DNA-binding domain. Real-time quantitative PCR (qPCR) revealed that NbMybl was induced by infection with Phytophthora infestans. Subcellular localization analysis showed that NbMybl is located in both the nucleus and the cytoplasm. Silencing of NbMybl by virus-induced gene silencing (VIGS) significantly increased the susceptibility of plants to P. infestans. Transcriptome profiling by RNA sequencing identified 8468 differentially expressed genes (DEGs) with fold change ≥ 2 and FDR < 0.01 between NbMybl silenced and non-silenced control lines in response to P. infestans infection, and the result of RNA-seq was further validated by qPCR with 10 randomly selected DEGs. KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis revealed that a total of 373 DEGs were involved in plant-pathogen interaction, 308 DEGs and 216 DEGs were involved in MAPK signaling pathway and plant hormone signal transduction, respectively. We speculated that these DEGs might be closely related to the reduced resistance of NbMybl-silenced N. benthamiana lines to P. infestans. Our study provides valuable insights into the molecular mechanisms of NbMybl in regulating resistance to P. infestans.

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.

The basal stem rot disease of belladonna (Atropa belladonna) occurred severely in the experimental farm of Shijiazhuang Academy of Agriculture and Forestry Sciences in May 2022. In order to effectively control the disease, identification, biological characteristics of the pathogen as well as disease control were carried out. The pathogen isolates causing belladonna basal stem rot disease was identified as Pythium aphanidermatum based on the morphological characteristics, rDNA-ITS sequence analysis and Koch's postulates testing. To our knowledge, the new disease is the first report in China. The optimum temperatures of mycelium growth, sporangium production and oospore formation were 35 ℃, 25-35 ℃ and 35 ℃, the optimum pH values were 7.0-9.0, 7.0-8.0 and 10.0, respectively. In addition, the optimum light condition and growth medium for culturing P. aphanidermatum were determined. The most suitable carbon sources of mycelium growth and sporangium production were soluble starch and glucose, and the most suitable nitrogen sources were ammonium nitrate and urea. Toxicity of nine chemical fungicides and one biological fungicide on mycelium growth of P. aphanidermatum were evaluated in the laboratory condition. The results showed that 35% metalaxyl-M FS, 250 g·L^-1 azoxystrobin SC, 98% hymexazol SP and 100 g·L^-1cyazofamid SC had strong inhibition abilities against the pathogen with EC₅₀ of 1.619, 2.069, 37.463 and 49.484 μg·mL^-1, respectively. All the work mentioned above provided a basic knowledge for rational control of belladonna basal stem rot.

In 2022, a study investigating viral diseases in three watermelon planting plots was conducted in Jiyuan, revealing an average incidence rate of approximately 97%. Twenty samples, comprising 14 watermelon samples, 4 melon samples, 1 pumpkin sample and 1 pigweed (Amaranthaceae retroflexus L.), were collected from the field. Three watermelon samples and one Amaranthaceae weed sample underwent small RNA sequencing, separately, and virus detect identified seven viruses from the four small RNA sequencing data sets. Subsequently, RT-PCR using primer pairs specific for 16 watermelon-infecting viruses identified the same seven viruses in all 20 samples. Watermelon mosaic virus (WMV) and zucchini yellow mosaic virus (ZYMV) had detection rates of 100% and 85%, respectively, making them the two most prevalent viruses in watermelon fields. WMV was also identified in pigweed, which could serve as an intermediate host of WMV in the field. The full genome sequences of four WMV isolates were derived from four data sets of small RNA sequencing. Comparing the identity and conducting a phylogenetic analysis based on the full genome sequences of WMV revealed that WMV isolates from Jiyuan have very high genetic diversity, suggesting that there could be multiple initial infection sources of WMV in the region. This study identified the causal agents of viral diseases in watermelon in Jiyuan; established a theoretical foundation for developing prevention and control strategies and conducting epidemiological research on viral diseases in watermelon in the region.

The application of molecular marker assisted breeding is limited in rice, which due to unclear resistance gene composition in most rice parent materials and the highly homology of allelic genes. In this study, we designed the functional nucleotide polymorphism markers for Pikp-1, Pikh-1, Pik-1, Pikm-1 and Pi1-1 at the specific polymorphism sites, respectively. Those sites were screened by the allelic genes alignment and then picked out the most specific sites by blasting with 155 rice genomes at Rice Resource Center. Based on those markers, we examined 24 monogenic lines and 109 rice parent lines which using for rice breeding in Sichun basin, and finally identified Pik-1, Pikh-1, Pikp-1, Pi1-1, and Pikm-1 gene from 0, 1, 5, 14, and 20 rice parent lines. Among them, the Pi1 gene was identified by sequencing in ‘Mianhui 365’, which verified the functional markers can distinguish those allelic genes at Pik site, effectively and accurately. It identified a number of rice parent resources with definite resistance gene composition at Pik site and provided reliable molecular markers for Pik-1, Pikh-1, Pikp-1, Pi1-1, and Pikm-1 gene.

Rhodococcus fascians is a gram-positive actinomycete that can cause plant diseases with a very wide host range. The pathogenic strains of Rhodococcus fascians make abnormal plant tissues form, such as leaf gall, cluster, flat stem, which affects plant growth and causes serious economic losses. As the identification and classification of the genus Rhodococcus were complex and is often confused with other plant diseases with similar symptoms, resulting in few studies being carried out. This review outlines the classification status, biological characteristics, pathogenic mechanisms, disease symptoms, isolation and identification methods, transmission routes of infection and prevention and control measures of R. fascians. It is expected to provide a reference for related research and precise prevention and control of leafy gall disease caused by R. fascians.

To understand the occurrence and genetic evolution of sweet potato chorotic fleck virus (SPCFV) in Shandong province, China, 131 sweet potato samples were collected for the detection of SPCFV in 2019 and 2020, and two complete sets of genome sequences were amplified and analyzed. The SPCFV detection rate in 2019 and 2020 was 7.1% and 5.6%, respectively. All positive samples were co-infected with SPCFV and other sweet potato viruses. The two complete sets of genome sequences (CFV-SD1, CFV-SD2) were obtained by RACE and RT-PCR, with a total length of 9 105 bp and a nucleotide similarity with the reported isolates was 72.9% to 89.5%. Phylogenetic analysis of genome sequences revealed that all SPCFV isolates clustered into two groups based on the CP genes of six Shandong isolates and that all Shandong isolates belong to the Asian group (Asian isolates 1). Amino acid preference analysis showed that the first 35 amino acids in the N-terminal region of the SPCFV CP protein exhibited variation. This study indicated that Shandong province has become a frequent occurrence area of SPCFV and the virus population was diverse. The results provide a theoretical basis for the effective prevention and control of SPCFV.

Oidium heveae is an incompatible pathogen of Arabidopsis Col-0, and triggers disease resistance in Arabidopsis in an EDS1 (ENHANCED DISEASE SUSCEPTIBILITY 1) and PAD4 (PHYTOALEXIN DEFICIENT 4) dependent manner, suggesting that TIR-NB-LRR (TOLL INTERLEUKIN 1 RECEPTOR, NUCLEOTIDE-BINDING, LEUCINE-RICH REPEAT) genes may involve in the disease resistance against O. heveae. In this study, the differentially expressed TIR-NB-LRR genes targeting O. heveae were screened, and the expression of WRR4C (WHITE RUST RESISTANCE 4C) gene was found to up-regulated induced by O. heveae. Through inoculation assay, O. heveae was observed to develop dense hyphal network and a few conidia in two wrr4c single mutants, and triggered significantly decreased defense responses including cell death, callose deposition and PR1 (Pathogenesis Related 1) gene expression, indicating that WRR4C positively regulated the disease resistance of Arabidopsis against the powdery mildew of Hevea brasiliensis. However, WRR4C gene did not participate in the cell pre-penetration resistance to O. heveae, and the expression of WRR4C reached to the highest level at 48 hours post inoculation, suggesting that WRR4C genes was mainly involved in the cell post-penetration resistance of Arabidopsis to O. heveae. In addition, we found WRR4C also positively regulated the disease resistance against Erysiphe polygoni in Arabidopsis.

Root-knot disease, caused by Meloidogyne incognita, seriously threatens the production of many crop plants. To further explore biocontrol resources for this disease, two bacterial strains showing nematicidal activity were isolated from vegetable rhizopsheric soil in Yangzhou City, China. These two strains, named HJ03 and HJ04, were identified as Bacillus amyloliquefaciens and B. safensis, respectively, based on their morphologi-cal characteristics, biochemical properties, and phylogenetic analysis results. The corrected mortalities of HJ03 and HJ04 cell suspensions against second-stage juveniles (J2s) of M. incognita after 24 h of treatment were 77.3% and 79.3%, respectively, while those for culture filtrates of the two strains were 75.9% and 80.1%. No significant difference in corrected mortalities was observed between treatments with cell suspension and culture filtrate. Cell suspensions of HJ03 and HJ04 cultured for 24 h showed good nematicidal activity, and extended culture time did not significantly increase nematicidal activity. Cell suspensions (OD₆₀₀=1.2) of HJ03 and HJ04 diluted to 1:2 resulted in mortalities of 77.7% and 78.6%, respectively, similar to those caused by their mother solutions, but showed significantly decreased mortalities when diluted to 1:5. The biocontrol mechanisms of HJ03 and HJ04 against M. incognita were revealed as follows: HJ03 and HJ04 can inhibit egg hatching of M. incognita, with inhibition rates of 71.1% and 64.0%, respectively, compared to LB medium-treated control; significantly inhibit the chemotaxis of J2s. The number of J2s in tomato rhizosphere (1 cm) treated with HJ03 and HJ04 was reduced by 90.9% and 87.6%, respectively, compared with that of control; dramatically inhibit nematode infection, with inhibition rates of 85.4% and 85.2%, respectively, after treated with HJ03 and HJ04 for one week; inhibit gall formation, with gall indexes of 1.1 and 1.6 for HJ03 and HJ04, respectively, at 40 d after treatment, whereas 3.3 for control; inhibit the formation of egg masses, with inhibition rates of 75.7% and 73.1% for HJ03 and HJ04, respectively, at 60 d after treatment; reduce the size of M. incognita-induced giant cells. In addition, HJ03 and HJ04 can promote seed germination and seedling growth of tomato. This study enriches the biocontrol resources against root-knot disease and lays a basis for further development of biocontrol agents.

Fusarium wilt of cucumber, caused by Fusarium oxysporum f. sp. cucumerinum (Foc), is an important soil-borne disease that is difficult to control. The disease usually causes plant wilt, leading to significant yield loss. In this study, a Trichoderma strain 3199, which produces antimicrobial peptaibol, was obtained from the Agricultural Research Service Culture Collection (NRRL). The strain was identified as Trichoderma arundinaceum based on morphological characteristics and the result of molecular identification. Confronting incubation results showed that T. arundinaceum strain 3199 had obviously inhibitory effect on Foc. In pot experiment, root irrigation of cucumber seedlings with spore suspension (1×10⁸ spores·mL^-1) of strain 3199 showed 51.3% biocontrol effects against Fusarium wilt caused by Foc. Furthermore, the ethyl acetate extract (12 mg·mL^-1) from fermentation broth of strain 3199 could effectively inhibit the growth of Foc. The results indicate that T. arundinaceum strain 3199 has great potential for the biocontrol of Fusarium wilt of cucumber by producing bioactive secondary metabolites.

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.

After annotating the genome of Xanthomonas oryzae pv. oryzae strain PXO99A-GX, we found an atypical chemoreceptor gene PXO_01024, which encodes a protein with two transmembrane domains (TMD) and a methyl-accepting domain (MA) but without the ligand-binding domain (LBD). To understand the biological function of PXO_01024, we constructed the PXO_01024 deletion mutant DM01024 and its complemented strain CDM01024 by homologous double exchange method. Deletion of PXO_01024 resulted in the reduced formation of biofilm and almost loss of bacterial swimming, while in CDM01024 the swimming motility and biofilm formation ability were restored to wild-type levels. The virulence of DM01024 was not significantly different from that of the wild-type strain when inoculation of wounded host plants was performed. However, when unwounded plants were inoculated with the spraying inoculation method, the disease index caused by DM01024 was significantly reduced compared with that caused by the wild-type strain and complemented strain CDM01024, indicating that PXO_01024 played a role in early infection of Xoo. The chemotaxis of these strains was subsequently detected by capillary method, and the results showed that DM01024 showed significantly reduced chemotaxis to methionine, alanine, leucine, glycine, asparagine, phenylalanine, isoleucine, glucose, maltose, xylose, fructose, succinic acid, and tartaric acid compared with the wild-type strain. This study demonstrated that the atypical chemotactic receptor gene PXO_01024 is associated with chemotaxis, swimming motility, and early infection of Xoo.

Citrus bacterial canker caused by Xanthomonas citri subsp. citri (Xcci) is an important bacterial disea-se of citrus plants. Our previous work revealed that the homologous of XAC3126 (Accession no. AAM37971.1) of Xcci strain 306, which was predicted to be a single-domain response regulator, might be involved in the bacterial virulence in Xcci Guangxi wild-type strain N8. To investigate the biological functions of this gene (named embR), a deletion mutant was constructed with strain N8 as the starting strain. Simultaneously, a complemented strain was constructed using a recombinant plasmid harboring this innate gene. Phenotypic analysis revealed that the embR deletion mutant ΔembR showed obviously reduced virulence on the host plant Citrus reticulata Blanco 'Orah' compared with the wild-type strain, while the complemented strain exhibited similar virulence with that of the wild-type strain. Additionally, the ΔembR mutant displayed an obvious reduction in extracellular polysaccharide (EPS) production, cell motility and cell aggregation. Reverse transcription quantitative real-time PCR (RT-qPCR) revealed that the transcript level of a set of genes involved in EPS production and cell motility in the ΔembR mutant was decreased compared with that in the wild-type strain. These combined data indicate that the embR gene is required for multiple cellular processes including virulence in Xcci and modulates the expression of a series of virulence factor-related genes.

Potato Early Blight (PEB) is an important disease of the foliage of potatoes during the growing season and is widespread in all major potato producing areas worldwide. At present, there are no specific agents and potato varieties resistant to the disease completely. In this study, we identified the main cultivar ‘Cooperation-88’ (C88) in Yunnan Province was resistant to the potato early blight caused by Alternaria solani inoculated on leaves in comparison with the susceptible variety ‘Désirée’ by AUDPC. High-throughput RNA-seq in ‘Cooperation-88’ after infection at the early (A. so_e, 0-72 h), middle (A. so_m, 73-120 h) and late (A. so_l, >120 h) stages was performed on Illumina HiSeq PE150 platform. Transcriptome analysis revealed a total of 13 083 genes expressed differentially at A. so_e, of which 7 438 were up-regulated and 5 645 were down-regulated. At A. so_m, a total of 12 121 genes was differentially expressed, of which 3 299 were up-regulated and 8 822 were down-regulated. At A. so_l, a total of 10 530 genes was differentially expressed, of which 1 686 were up-regulated and 8 844 were down-regulated. A set of 2 720 identical genes was found in all the three periods, while 4 997 genes specific to A. so_e, 3 975 genes specific to A. so_m and 3 230 genes specific to A. so_l. Based on gene ontology (GO) term and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis and qRT-PCR validation along with the results of electron microscopic observations, it was speculated that the increased synthesis of pectin lyase and cellulose synthetase was involved in cell wall remodeling of ‘C88’ in the early stage of A. solani infection. The expression levels of glutathione S-transferase and cytochrome P450 were significantly up-regulated in ‘C88’ at mid-infestation, which were involved in the detoxification pathway. Late synthesis of large amounts of antioxidants to stimulate defence mechanisms. In the three periods, high expression levels of transcription factors, such as bHLH, ZIP, MYB, ERF, etc, associated with disease resistance and extensive involvement in the ubiquitination pathway. Overall, our findings could provide a theoretical basis for research on the early blight resistance in potato and accelerate the resistance breeding.

The bacterial wilt caused by Ralstonia solanacearum has brought a serious threat to tomato production. Coronatine (COR), structurally similar to JA-Ile (JA-isoleucine), is a compound produced by Pseudomonas syringae. In this study, we observed that pre-treatment of tomato seedlings with COR alleviated the symptoms caused by R. solanacearum. To investigate how COR affects tomato resistance to R. solanacearum, transcriptome sequencing of tomato seedlings inoculated with the pathogen 24 h after COR treatment was carried out. Analysis of RNA-seq data showed that COR treatment induced a total of 2122 differentially expressed genes (DEGs), including 998 up-regulated genes and 1124 down-regulated genes. DEGs annotation and pathway enrichment were conducted using GO database and KEGG database, and the results showed that COR affected the expression of genes related to plant-pathogen interaction pathway and plant hormone signaling pathways. Meanwhile, COR induced the up-regulation of genes involved in the jasmonic acid synthesis pathway and inhibited the expression of photosynthesis-related genes. Our results provide a theoretical basis for revealing the role of COR in plant-microbe interaction.