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    ETIOLOGY
  • YAN Han, CHEN Lijie, HAN Tao, DONG Hai, XU Han, CHU Jin, MIAO Jiankun, YANG Hao, LI Zhiqiang
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    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.
  • ZHANG Shicai, ZHANG Jilin, DUAN Minjie, YANG Xiaomiao, HUANG Qizhong, HUANG Renzhong, LI Yifei, LUO Yunmi
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    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 (FST=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.
  • LU Xiuyun, SHANG Junyan, GAO Chi, SU Zhenhe, WANG Ying, ZHANG Xiaoyun, GUO Qinggang, LI Shezeng, MA Ping
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    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.
  • ZHANG Tianyi, YU Daihong, CAO Yulian, LU Hui, LAN Pingxiu, LI Meihui, TAN Guanlin, LI Fan
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    From 2021 to 2022, jasmine plants with virus-like symptoms of mosaic, yellowing, chlorosis, ringspot and mosaic were observed in Yuanjiang county, Yuxi city and Chenggong district, Kunming city in Yunnan Province, and a total of 95 symptomatic jasmine samples were collected. RT-PCR detection was performed using the virus universal primers of genera Begomovirus, Luteovirus, Polerovirus, Potexvirus, Potyvirus, Tobamovirus and Umbravirus, and the specific primers of cucumber mosaic virus (CMV), jasmine mosaic-associated virus (JMaV), jasmine virus C (JaVC), jasmine virus H (JaVH), jasmine virus T (JaVT) and tobacco streak virus (TSV) for the diseased jasmine samples. The results showed that the diseased jasmine samples collected in Yuanjiang county of Yuxi city and Chenggong district of Kunming city were infected with JaVT, JaVH, JMaV, JaVC and CMV with the detection rates of 60.00%, 57.89%, 15.79%, 13.68% and 6.32%, respectively. JaVT and JaVH were the dominant viruses infecting jasmine in Yunnan. All the five viruses occurred in Yuanjiang and Chenggong, and the dominant viruses in these two regions were JaVH and JaVT. Meanwhile, the virus detection rate in Chenggong was lower than that in Yuanjiang. Viruses mostly cause damage to jasmine in the form of mixed infection, with 11 types of co-infection in the 5 jasmine viruses. JaVC and CMV are usually co-infected with viruses such as JaVH and JaVT. The co-infection of JaVH+JaVT had the highest detection rate at 26.31%. This study was the first to detect CMV infection in jasmine. To gain deeper insights into the molecular variation and phylogenetic relationship between the CMV jasmine isolate (CMV-YYJMLH) obtained from Yunnan Pro-vince and other CMV isolates found in different regions and host plants, the cp gene sequence of CMV-YYJMLH isolate (GenBank accession number: OQ870529) was compared and analyzed with those of 35 other CMV isolates documented in the GenBank. The results showed that isolate YYJMLH shared 77.17%-99.09% nucleotide (nt) sequence identity with other CMV isolates, among them, isolate YYJMLH had the highest nt sequence identity of 99.09% with the CMV pepper isolate (GenBank accession number: MT786689) from Yunnan province. A phylogenetic tree was constructed using the cp gene sequences of different CMV isolates, and results showed that the CMV-YYJMLH jasmine isolate belonged to CMV subgroup I, and the YYJMLH isolate had the closest genetic relationship with the CMV pepper isolate (GenBank accession number: MTT86689). To our knowledge, this is the first report of CMV naturally infecting jasmine worldwide and the first record of JaVT in Yunnan province.
  • CELL BIOLOGY, PHYSIOLOGY, BIOCHEMISTRY, AND MOLECULAR BIOLOGY
  • SONG Xuantong, NIE Xiaofei, WANG Ziyao, BI Kai, ZHU Wenjun
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    Gray mold disease caused by Botrytis cinerea leads to severe crop yield reduction, and the secreted proteins play significant roles in the fungal infection. However, the functional mechanisms of these secreted proteins in B. cinerea remain largely unknown. In this study, a secreted protein, BcSGP1, from the secretome of B. cinerea during infection stages was identified. The expression level of BcSGP1 was upregulated during infection stages. Deletion of BcSGP1 caused reduction in pathogenicity, but not in growth rate, conidial production, or stress resistance. Transient expression of BcSGP1 in Nicotiana benthamiana leaves using agroinfiltration induced necrosis, and this necrosis-inducing activity depended on the plant receptor-like kinase BAK1, but not the SOBIR1. Furthermore, BcSGP1 could induce resistance against B. cinerea in N. benthamiana leaves. These results suggest that BcSGP1 is a pathogenesis-related secreted protein and involved in inducing plant resistance during the interaction between B. cinerea and plants. This study enhances our understanding of the pathogenic mechanisms of B. cinerea, providing a theoretical basis and genetic resources for effective control of gray mold disease.
  • ZHEN Jinpeng, LIU Jianhu, CAO Hongzhe, XING Jihong, DONG Jingao, SHI Chengmin, ZHANG Kang
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    In recent years, wheat scab, corn stalk rot and ear rot caused by Fusarium graminearum have led to substantial losses in crop yields. To investigate the genetic diversity and identify pathogenicity-related genes of F. graminearum, we performed population genetic diversity analysis and selective elimination analysis on 93 F. graminearum strains with released genome-wide resequencing data, using single nucleotide polymorphism (SNP) technology. The resequencing data of these F. graminearum strains were meticulously processed by using the Genome Analysis Toolkit 4 (GATK4), yielding a collection of 3,817,652 SNP markers. Based on these markers, a phylogenetic tree was constructed, and principal component analysis (PCA) and population structure analysis were conducted, effectively partitioning the 93 F. graminearum into 3 distinct groups. The selection elimination analysis of group 1 and group 2 revealed that group 1 exhibited a more pronounced response to selection pressure. A total of 70 regions were identified as candidate sites within the top 5% intersection region of population polymorphism (θπ) and population differentiation index (Fst). Furthermore, 76 protein-coding genes were identified in F. graminearum by leveraging the genomic location information. The results of Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed that these 76 candidate genes are mainly involved in metabolic pathways. Among them, eight genes (FGSG_05447, FGSG_05610, FGSG_10272, FGSG_10313, FGSG_01353, FGSG_05545, FGSG_10858 and FGSG_12745) are closely related to the pathogenicity of F. graminearum through further gene expression analysis. The result lays a basis for clarifying the pathogenic mechanism of F. graminearum and breeding F. graminearum-resistant wheat and maize varieties.
  • JIANG Yuxia, DAI Lili, XUE Xiaojing, YU Yue, ZHANG Jianli, DING Xinhua, ZHONG Weiran, CHU Zhaohui, LIU Haifeng
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    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.
  • MA Jiabing, YANG Mingming, ZHAO Yingjia, TAN Yunxiao, CHANG Bangshuai, WANG Nana, HUANG Lili
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    PilZ domain-containing proteins are the largest known receptors of second messenger c-di-GMP in bacteria, but the functions and underlying mechanisms have not been reported in Pseudomonas syringae pv. actinidiae (Psa). To reveal the contribution and regulation mechanism of PilZ domain-containing proteins to the pathogenicity of Psa and to provide new ideas for controlling kiwifruit bacterial canker. Firstly, genome analysis and sequence alignment of Psa M228 were performed to identify the PilZ domain-containing proteins of Psa and analyze the conserved c-di-GMP binding motif. Then, homologous recombination was used to construct deletion mutants, and the pathogenicity, motility and growth between mutants and wild type were determined by leaf discs vacuum infiltration, soft agar plate assays and growth curve measurment, respectively. The transcripts of pathogenicity- and motility-relative genes in WT and ΔPsa_2195 mutant were measured by qRT-PCR. The results show that there are eight PilZ domain-containing proteins in Psa M228, among them PSA_2195 and PSA_1975 have neither a conserved RxxxR motif nor a (D/N)xSxxG binding motif that binds to c-di-GMP. The pathogenicity of ΔPsa_1116, ΔPsa_2195, ΔPsa_2203, ΔPsa_762, ΔPsa_4490 and ΔPsa_4763 were significantly reduced. Deletion of PSA_1116 and PSA_2195, PSA_3989, PSA_762 affected swimming motility and swarming motility, respectively. The growth curve of all mutants are no significant difference with wild type M228. Among all PilZ domain proteins, PSA_2195 regulates the transcription of flagella genes flgA, filE and T3SS genes. Taking together, our research revealed the function of eight PilZ domain-containing proteins in regulating pathogenicity and motility of Psa and the simple molecular mechanisms of PSA_2195.
  • GENETICS OF DISEASE-RESISTANCE AND PATHOGENICITY
  • HU Xiaohong, LI Hengjin, SHI Jun, LI Deqiang, FAN Jing, HUANG Fu, WANG Wenming
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    Rice blast disease is destructive to rice production. Breeding and utilization of resistant varieties are the most economical, effective and environmentally friendly methods to control the rice blast. Identifying the resistance genes of resistant varieties will be beneficial to the selection of new resistant varieties and the distribution of resistant varieties. ‘Yahui2115’ is an elite rice restorer line with broad-spectrum resistance to rice blast. Previous studies have shown that ‘Yahui2115’ contains Pi2. In order to identify other rice blast resistance genes in ‘Yahui2115’, we used the strain M14Ga089 virulent to the monogenic line harboring Pi2 to analyze the segregation of blast resistance in the F2 population of ‘LTH/Yahui2115’. The results showed that the resistance/susceptibility ratio was 3∶1 in the F2 population, indicating that the resistance from ‘Yahui2115’ to strain M14Ga089 was controlled by one dominant gene, which was named Pir2115-1(t). Through extreme recessive population method, Pir2115-1(t) was mapped between SSR markers RM6307 and RM208 on chromosome 2, a locus that contains a known blast resistance gene, Pib. Gene expression analysis showed that Pib in ‘Yahui2115’ was highly induced by Magnaporthe oryzae infection, and sequence analysis showed that the protein sequence encoded by Pib in ‘Yahui2115’ was completely identical to the reported Pib, indicating that ‘Yahui2115’ carries Pib. This study provides the basis for the application of ‘Yahui2115’ in breeding and the variety distribution of its combinations.
  • EPIDEMIOLOGY AND ECOLOGY
  • LÜ Qiushi, ZHAO Xinyu, YANG Xin, HUANG Fudan, LIANG Wusheng
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    Villosiclava virens can infect rice plants and cause rice false smut. At present, it is still controversial whether V. virens overwinters in the form of sclerotia or chlamydospores. In both 2021 and 2022, rice false smut was obviously observed in the rice fields in Xiaoshan District, Hangzhou City, Zhejiang Province. To clarify the overwintering form of V. virens in these fields, the survival of sclerotia and chlamydospores was continuously monitored from October 2021 to November 2022. The results showed that among all soil samples collected for 5 times (9 randomly selected sites in both rice-planting fields and ridges for each time), chlamydospores could be observed by microscope in at least 1 site for each sampling time except for ridge sites for 2 sampling times (January and May of 2022); V. virens could be detected by nested PCR in at least 1 sampling site from both rice-planting fields and field ridges; the survival periods of chlamydospores preserved at 23 ℃ and 4 ℃ were about 7 and 13 months, respectively; chlamydospores in soil samples still had the ability to germinate after storage for 6 months at 4 ℃. From October 2021 to October 2022, no sclerotium was found in our sampling fields and collected soil samples. Only a few sclerotia were found on rice false smut balls on November 9th, 2022. However, the sclerotium-bearing rate of rice false smut balls was only 3.14%. Taken together, it was concluded that V. virens overwintered by the form of chlamydospores in soils of the sampling rice fields in 2021, which became the main primary infection source in 2022 and caused rice false smut.
  • PLANT DISEASE AND CONTROL
  • CHEN Zihan, HE Tao, SHI Benyi, LI Ke, CAI Hong, HE Xiahong, ZHU Youyong, ZHAO Yu
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    In order to explore the influence of Polygonatum sibiricum rotation on the soil microbial community of Panax notoginseng, evaluate the restoration ability of crop rotation and natural restoration. The influence of Polygonatum sibiricum rotation on the microbial structure and microflora change of soil continuous cropping with Panax notoginseng was studied. The results showed that seedling rate was 88.33%, significantly higher than the incidence rate of fallow treatment, which was less than 20%, but the difference was not significant. The diversity of soil fungi and bacteria was significantly reduced (P<0.01). The results showed that crop rotation could signi-ficantly affect the β diversity of soil fungi and bacteria in Panax notoginseng (P<0.001), and could significantly increase the relative abundance of Ascomycota and reduce the relative abundance of Basidiomycota and Triguta. Firmicutes, Budlesomonas, Chloritans, Acinetobacter, Bacteroidetes, etc. LEfSe results showed that after the rotation of the pathogens, Fusarium, Ilyonectria, and other fungi. Rhizosphere soil microbial fungi mainly saprophytic, pathological and mixed nutrition mode, after the rotation treatment, plant pathogen fungi abundance, pathogenic bacteria of decline, associated with the disease, at the same time after rotation bacterial L-valine biosynthesis pathway, L-isoleucine biosynthesis I (from threonine) pathway, L-isoleucine biosynthesis II, Aerobic respiration I (cytochrome C) pathway is significantly lower. The rotation of Polygonatum sibiricum can improve soil microorganisms and it’s potential to alleviate the obstacles of Panax notoginseng.
  • WANG Shaohua, CHU Tianran, LIAO Kai, SHI Yanxia, XIE Xuewen, LI Lei, FAN Tengfei, LI Baoju, CHAI Ali
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    Cucumber leaf spot caused by Corynespora cassiicola is an important disease in cucumber production, and diseased residues in soil have been proved to be the main source of its initial infection. To clarify the effect of droplet splash on the dispersal of the pathogen, a real-time fluorescence quantitative PCR (qPCR)-based system for rapid detection of C. cassiicola in soil was established. Through this system, C. cassiicola was detected in soil samples collected from greenhouses where Corynespora leaf spot was naturally occurred, with concentrations ranging from 27.00×100 to 7.95×105 pg DNA·g-1. The results of artificial simulation of droplet splashing experiment showed that the impact of droplets carrying C. cassiicola led to splash dispersal of the pathogen and increased disease severity, with disease index of 65.56 and 41.56 for C. cassiicola-infected soil and substrate, respectively. Mulching soil and substrate surface in the above experiment significantly reduced disease severity, with disease index of 13.79 and 13.83 for C. cassiicola-infected soil and substrate, respectively. The results of this study indicate that droplet splash is an important route for the transmission of soil-borne C. cassiicola, providing not only technical assistance for monitoring and early warning of Corynespora leaf spot but also theoretical basis for the prevention and control of the disease.
  • YUAN Jiasheng, HE Saiya, ZHANG JinHao, MENG Han, WANG Bowen, WEI Lanfang, JI Guanghai
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    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.
  • EXPERIMENTAL METHOD
  • ZHU Lijuan, BAI Yani, SU Lanyi, WANG Chi, HE Shiyun, HAN Yanhong
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    Jasmine plants often suffer from co-infection of multiple viruses during their growth. Due to the lack of research on the relationship between each virus and its symptom, it is challenging to accurately diagnose which type of virus is present solely based on viral symptoms. Therefore, the development of a rapid and simultaneous one-step multiplex reverse transcription PCR (RT-PCR) method is crucial for the diagnosis of jasmine virus diseases. This study successfully established a one-step multiplex reverse transcription PCR (RT-PCR) system capable of simultaneously detecting four types of jasmine viruses: jasmine virus T (JaVT), jasmine virus C (JaVC), jasmine virus H (JaVH) and jasmine virus A (JaVA). In a total reaction volume of 20.0 μL, the optimal reaction system is as follows: the final concentrations of upstream and downstream primers for JaVT, JaVC, JaVH, and JaVA were set at 200, 150, 100 and 150 nmol·L-1, respectively. The optimal quantities of One-step Enzyme Mix, 2×ES One-Step Reaction Mix, and jasmine RNA were determined to be 0.2 μL, 10.0 μL, and 1.0 μg, respectively. The RT-PCR parameters were set as follows: RNA reverse transcription at 50 ℃ for 30 min, Pre-denaturation step at 94 ℃ for 2 min, 30 cycles of denaturation at 94 ℃ for 30 s, annealing at 55 ℃ for 30 s, extension at 72 ℃ for 45 s, and a final extension at 72 ℃ for 10 min. The results demonstrated that the established one-step multiplex RT-PCR method can efficiently and accurately detect all four types of jasmine viruses simultaneously, significantly enhancing detection efficiency. This method has broad applications in laboratory-based accurate detection and field-based diagnosis of jasmine virus diseases.
  • QIN Yanhong, WANG Fengli, WEN Yi, ZHAO Zhengwei, GAO Suxia, ZHANG Desheng, LI Shaojian, LIU Yongkang, LIU Yuxia, LU Shuhao, WANG Fei, LU Chuantao
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    Youcai mosaic virus (YoMV) is one of the important viruses infecting Rehmannia glutinosa and Dioscorea oppositifolia. It decreases the yield and quality of these Chinese medicinal herbs. Based on reverse transcription loop-mediated isothermal amplification (RT-LAMP), a rapid, specific and sensitive method for detecting YoMV was developed. Five specific primers were designed according to the nucleotide sequence of YoMV coat protein (CP). The established RT-LAMP method for detecting YoMV was optimally performed at 60 ℃ for 60 min. This method can detect YoMV specifically. The sensitivity was 1 000 times higher than that of the conventional PCR, and it could detect 9.18×102 copies·μL-1. The RT-LAMP method established in this study provided a rapid and efficient diagnostic tool for correct detection of YoMV on Rehmannia glutinosa and Dioscorea oppositifolia.
  • SUN Qingfeng, LIU Zhifei, CHEN Ni, CHI Shengqi, YUAN Xuefeng, CAO Xinran
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    In this study, we analysed the RNA polymerase activity of the eukaryotically expressed RNA-dependent RNA polymerase (RdRp) of plum bark necrosis stem pitting-associated virus (PBNSPaV), a positive-sense single-stranded RNA virus belonging to the genus Ampelovirus in the family Closteroviridae. In an in vitro RNA transcription experiment using the 3′ untranslated region (UTR) of PBNSPaV RNA genome as a template, the purified recombinant PBNSPaV RdRp was able to synthesize the complementary strand of the RNA template, indicating that the purified protein has a polymerase activity. To examine whether the RdRP(s) of viruses of the family Closteroviridae share polymerase function with the same template, we used purified recombinant RdRP of little cherry virus-1 (LChV-1, genus Velarivirus, family Closteroviridae), which was shown to have polymerase activity in our previous study, in an in vitro RNA transcription experiment using the 3′ UTR of PBNSPaV as a template. The experimental result showed that LChV-1 RdRp was unable to synthesize complementary strand RNA of the template, suggesting that LChV-1 RdRp cannot recognize PBNSPaV RNA genome as a template for RNA synthesis. The purified recombinant PBNSPaV RdRP can be used for deeper molecular study of PBNSPaV replication.
  • RESEARCH NOTES
  • WANG Meng, WU Linna, CHEN Pengzhao, LI Xinghong, ZHANG Wei, YAN Jiye
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    White root rot is one of the most important root diseases of grape. From 2021 to 2022, the symptoms of white mycelium on the surface of grape roots were observed in several grapevines in Shanxi Province, China, with the incidence of 26.74%. Symptomatic root samples were collected and taken back to the laboratory to isolate the fungi. In this study, twenty strains were obtained by single hyphal purification. Based on the morphological characteristics and multi-gene (ITS, LSU and TUB2) phylogenetic analysis, these strains were identified as Rosellinia necatrix. To confirm the pathogenicity, the inoculation was performed by adding wheat seeds colonized by R. necatrix in the soil. The results showed that R. necatrix was pathogenic to the grape. To our knowledge, this is the first report of R. necatrix causing white root in Shanxi province, China.
  • ZHANG Ziyu, DONG Baozhu, MENG Huanwen, ZHAO yuan, MIAO Jianjun, BAO Lilan, ZHOU Hongyou
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    Gummy stem blight, usually seen on the stems, leaves and fruits, is one of the most serious threats to production of pumpkin (Cucurbita moschata Duch.) in Hebei with reduction of the quality and heavy losses in yield. The pathogenic organisms of the disease were still obscure because several fungal species with most similar morphology were reported to be the causative agents. A fungal pathogen NG2023021301-4 was isolated from the diseased tissue and purified by single-spore isolation. According to morphological characteristics and combinatory phylogenetic analysis of ITS region, TUB gene sequences, the pathogen was identified as Stagonosporopsis caricae. To our knowledge, this is the first report of S. caricae causing verticillium wilt of pumpkin fruits.
  • SHAN Changlin, LI Xiaojun, ZHOU Yuan, JI Wenbin, LU Zhuan, WU Ruoxuan, FAN Chaolu, SHAO Weidong
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    The fungal strain 98180-8 was isolated from the maize of Malaysian containers. The pathogenicity of the isolated fungus was confirmed in inoculating tests. To elucidate the strain, morphological observation, PCR detection and ITS sequence analysis were used in this study. Taken all, the strain 98180-8 was identified as Stenocarpella maydis, an ear rot pathogen of maize.
  • HE Chunping, HU Yue, WU He, LIANG Yanqiong, LI Rui, LIN Jinjing, LU Ying, WU Weihuai, YI Kexian
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    Ficus hirta (vahl) is a valuable medicinal plant as well as edible plants in southern China. In 2022, a new stem blight disease was observed to infect Ficus hirta (vahl) in Danzhou of Hainan province. The incidence of disease reached 47.5% in fields. In order to clarify the pathogen of Ficus hirta stem blight disease, ten isolates with the same morphology were isolated from blight tissue by using a conventional tissue separation method. MA2, a representative strain with excellent growth, was selected for pathogenicity test on Ficus hirta plants, observation of morphological characteristics, sequence analysis on ITS, TUB and TEF, and phylogenetic tree construction. The results showed that morphological characteristics of the isolate MA2 was similar to that of Lasiodiplodia pseudotheobromae. The isolate MA2 was clustered into one clade in phylogenetic tree with L. pseudotheobromae. The above results indicated that the stem blight of F. hirta was caused by L. pseudotheobromae. This is the first report of a stem blight disease on F. hirta in China was identified as L. pseudotheobromae.
  • LI Yanjie, PU Meiying, WU Hongzhi, YANG Yuyong, WANG Chao
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    In 2021, typical leaf samples of Rosa chinensis black spot disease were collected from the South Tropical Garden in Kunming, Yunnan Province, China, and a strains were obtained by tissue isolation method. According to Koch's rule, morphological characteristics and phylogenetic analysis of ITS, TEF1 and TUB gene sequences, the pathogen was identified as Gnomoniopsis rosae. This is the first report that G. rosae caused R. chinensis black spot disease in China.
  • ZHANG Miaomiao, SUN Wenxiu, TANG Lihua, HUANG Suiping, GUO Tangxun, CHEN Xiaolin, LI Qili
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    Plum anthracnose caused by Colletotrichum Corda is one of the most important diseases of plum trees, which seriously affects the growth and production of plum. Screening of resistant plum varieties is the most effective method to control the disease. To find an inoculation method for accurate evaluation of plum resistance to anthracnose, we inoculated plum variety “Fortune” with 8 different methods, including inoculation of wounded or unwounded leaves (detached leaves or leaves of living plants) with spore suspension or mycelial plugs of Colletotrichum fructicola. The result revealed that disease incidence for inoculation of wounded leaves reached 100%. Disease severity for inoculation of both detached leaves and leaves of living plants were similar, with detached leaves showing additional rot symptom. In conclusion, inoculation of wounded leaves of living plants with spore suspension of the pathogen led to a better evaluation of plum resistance to anthracnose. Resistance evaluation of 40 plum varieties to anthracnose by this method showed five resistance types: immune, highly resistant, moderately resistant, moderately susceptible and highly susceptible. Among the tested 40 plum varieties, 11, 11, 12 and 6 were highly resistant, moderately resistant, moderately susceptible and highly susceptible, respectively, and no immune varieties were found. This study for the first time evaluates the resistance of different plum varieties to anthracnose. The results lay a basis for further research on screening and breeding of anthracnose-resistant plum varieties.
  • DU Dan, YANG Yan, YANG Xueping, SUN Dasheng, YUAN Xiangyang, SONG Xi’e, YANG Xuefang
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    Foxtail millet (Setaria italica (L.) Beauv.), a novel model species in C4 gramineae crops, plays a principal role in food security in Africa and Asia and in the adjustment of the crop planting structure in China. It is sensitive to continuous cropping, which is a serious constraint to the production and the quality. Root rot di-sease is typical for the diseased foxtail millet in continuous cropping fields. In this study, a fungus was obtained from the rotten root millet samples and grouped according to their colony morphology, namely, YDSi-1, YDSi-2 and YDSi-3. According to pathogenic tests fulfilling the Koch’s postulate, YDSi-3 showed a strong pathogenicity for root rot of foxtail millet. Based on morphological and molecular identification, YDSi-3 was identified as Fusarium oxysporum. This is the first report of F. oxysporum causing root rot of foxtail millet in China, and will provide a theoretical basis and technical support for the control on the continuous cropping of foxtail millet in the future.
  • WU Huijie, YAN Leiyan, WANG Chi, SUN Jianlei, WANG Chongqi, GAO Chao, KANG Baoshan, LIU Liming, LIU Xi, GU Qinsheng
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    During the disease survey in spring of 2023, watermelon in Shandong province and Zhenjiang province displayed silver grey and irregular mottled symptoms on leaves. In order to identify the virus, ten samples including the leaves, stem and the young fruit were collected, and total RNA was extracted from each sample. The RT-PCR method was used to amplify the conserved partial N gene sequence encoded by watermelon silver mottle virus (WSMoV) S RNA, and the partial N gene was cloned and sequenced. Sequence analysis showed that the sequence identity of WSMoV-Zhejiang and WSMoV-Shandong isolates with WSMoV-Thailand SN858 and WSMoV-Yunnan Banna-2011 isolates was over 99.0%. Furthermore, phylogenetic analysis showed that the partial N gene clustered with the Thailand and Yunnan-Banna-2011 isolates. The results showed that watermelon silver mottle virus (WSMoV) occurred in watermelon in Zhejiang and Shandong provinces. This is the first time the virus has infected watermelon in Zhejiang and Shandong provinces.