10 June 2023, Volume 53 Issue 3
    

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    REVIEW
  • Application of CRISPR/Cas gene editing system in plant antiviral defense
    SHEN Chuan, LI Xia, WU Yunfeng
    Acta Phytopathologica Sinica. 2023, 53(3): 343-357. https://doi.org/10.13926/j.cnki.apps.000803
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Plant virus diseases pose a serious threat to agricultural production worldwide, and protecting food crops from viruses is a major challenge in agriculture. Plant antiviral engineering using molecular biotechnology has become an effective strategy for the prevention and control of plant viruses. Recent advances in the CRISPR/Cas gene editing system-mediated targeting of DNA or RNA have made it a very attractive tool applicable to the field of plant protection and it is being widely used to produce virus-resistant cultivars of crops. This paper reviews the development of CRISPR/Cas systems and summarizes their application in the control of various plant viruses by targeting viral sequences or host susceptibility genes. In addition, some potential recessive resistance genes that can be used for virus resistance breeding are listed, and the importance of recessive resistance gene-based virus resistance breeding for generating developmentally defect-free transgenic plants is emphasized. Finally, the application of CRISPR/Cas technology for the detection and diagnosis of plant viruses in the field is described. The results of this emerging molecular technology can make a significant contribution to the development of agriculture and food security.
    • ETIOLOGY
  • The damage and etiology of the new disease Brown foot rot of wheat in China
    SHI Ruijie, XU Fei, SONG Yuli, LI Qianjin, LIU Lulu, FAN Zhiye, LI Yahong, HAN Zixing, ZHANG Jiaojiao, FENG Chaohong, WANG Junmei, ZHOU Yilin
    Acta Phytopathologica Sinica. 2023, 53(3): 358-366. https://doi.org/10.13926/j.cnki.apps.000810
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    In 2019-2020, a new disease, Brown foot rot of wheat was found in Henan Province. According to the survey of wheat disease at filling stage, the incidence of Brown foot rot was 35% in Xiangcheng City of Zhoukou City and slight occurrence in Anyang City, Luohe City and Nanyang City. The serious brown lesions of the lower leaf sheaths is visible. The isolates were white sparse fungus. According to the Phylogenetic tree analysis of the combined DNA sequences of ITS, β-tublin, RPB2, EF-1α and conidia morphology revealed that 22 isolates were Microdochium nivale and 52 isolates were M. majus. The conidia of M. nivale were in the shape of sickle, with a size range of (11.62-26.04) μm × (2.43-4.44) μm, the average size was 17.07 μm × 3.57 μm (n=240), with 1-3 septa. The conidia of M. majus were sickle-shaped and ranged in size from (15.63-33.82) μm×(3.36-8.95) μm, with an average size of 25.14 μm × 5.45 μm (n=240), they had 1-6 septa. The optimum growth temperature of M. nivale and M. majus was 20 ℃, and the average growth rates were 0.92 cm·d-1 and 0.89 cm·d-1. The average growth rate of M. nivale was higher than M. majus under the temperature 5-25 ℃. A large number of conidia piles were produced under 10 ℃ on PDA (Potato Dextrose Agar), while fewer conidia piles were produced at other temperatures. The results of pathogenicity test of represent isolates in ‘Aikang 58' at seedling stage showed that disease index of M. nivale and M. majus were 14.5-33.0 and 11.6-28.0, respectively. This study was first reported the Brown foot rot of wheat caused by M. nivale and M. majus in Nanyang City, Anyang City, Zhoukou City and Luohe City of China, which provides a theoretical basis for the monitoring of the Brown foot rot of wheat.
  • First report of Neopestalotiopsis foedans causing blueberry diseases
    CAO Ying, ZHANG Shuang, ZHANG Juan, WANG Yajuan, QIAN Shuojun, SUN Yan, YAN Xuerui
    Acta Phytopathologica Sinica. 2023, 53(3): 367-374. https://doi.org/10.13926/j.cnki.apps.001006
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    Pestalotiopsis-like fungi are an important class of pathogens on blueberry. Based on comparison analysis with reported Pestalotiopsis-like fungi on blueberry, 8 Pestalotiopsis-like isolates from blueberry were distinguished from those reported species and classified together in a single branch, which suggest that these isolates may be as a new record species or a novel species. Morphological and molecular phylogenetic methods were used to classify the 8 isolates, and the results suggested that they were Neopestalotiopsis foedans, which was the first report of N. foedans causing blueberry disease in the world. Further evidences showed that these 8 isolates had different virulence on five main blueberry cultivars in Liaoning Province. However, almost all tested cultivars were sensitive to the isolates with strong virulence, which should be considered in practice.
  • Epidemiological investigation of cucurbit chlorotic yellows virus in Shandong Pro-vince and whole genome amplification and sequence analysis of zucchini isolate
    SUN Xiaohui, ZHAO Jing, DAI Huijie, QIAO Ning, LIU Yongguang, ZHU Xiaoping
    Acta Phytopathologica Sinica. 2023, 53(3): 375-385. https://doi.org/10.13926/j.cnki.apps.000646
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    Cucurbit chlorotic yellows virus (CCYV) is causing severe economic losses to cucurbit crops in China. The occurrence of CCYV in Cucurbitaceae crop producing areas in Shandong province was continuously monitored from 2014 to 2019. The results showed that CCYV could naturally infect watermelon, melon, pumpkin, cucumber and zucchini, and the virus detection rate in samples increased from 1.7% in 2014 to 29.1% in 2019. The incidence of severe disease in zucchini plots showed a trend of further spread. The whole genome sequence of CCYV (zucchini-infecting isolate) was amplified by RT-PCR combined with RACE. The results showed that the similarity of genomic RNA1 and RNA2 of CCYV isolate from zucchini to GenBank isolates ranged between 99.6% to 100%. The phylogenetic evolutionary trees based on the whole genome sequences of CCYV displayed a clustering pattern that was consistent with the phylogenetic tree and homology results of protein sequences. The CCYV transmission process is not dependent on the host but probably related to geographical location. The outbreak of CCYV in China has seriously affected the economic benefits of cucurbitaceae crops. This study amplified and analyzed the genome sequence of CCYV zucchini isolates that will serve as a reference to study the genomic variability and evolutionary trends of CCYV.
  • Detection of camellia cryptic virus 1 in Fujian Province and molecular characterization of its complete genome
    XU Yuting, DING Ying, SHEN Jianguo, CHEN Xihong, ZHANG Shuling, DU Zhenguo, GAO Fangluan
    Acta Phytopathologica Sinica. 2023, 53(3): 386-394. https://doi.org/10.13926/j.cnki.apps.000658
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    The objectives of the study are to investigate the occurrence of camellia cryptic virus (CCV1) in the major tea plant planting regions in Fujian Province and to characterize the genomic structure of CCV1 isolates and its evolutionary relationship with reported CCV1 and camellia oleifera cryptic virus 1 (CoCV1) isolates. RT-PCR was used to detect leaves suspected of CCV1 infection collected from tea plant planting regions of 7 cities in Fujian Province. The genomic sequences of 18 viral isolates randomly selected from the positive samples were amplified and sequenced. Their genomic structure and the phylogenetic relationship tree were analysed subsequently. The results of RT-PCR showed that CCV1 was detected in 94 of 431 samples, with a mean positive rate of 20%. The complete sequence of dsRNA1, dsRNA2 and dsRNA3 of the 18 CCV1 isolates of the subsamples are 1 722-1 725, 1 504-1 506, 1 497-1 499 base pairs (bps) in length, respectively. The first 10-bp sequences(5'-GATAATGATC-3')of the 5'-UTRs in three dsRNAs of CCV1 are identical between these viral isolates and the reported representative CCV1 isolate Won. Sequence analysis indicates that RdRp, CP and mCP of 18 CCV1 isolates obtained in this study shares more than 91%, 84% and 90% amino acid sequence identity with known CCV1 Won isolate (GenBank accession numbers MH898482-MH898484) and camellia oleifera cryptic virus 1 (CoCV1) PXCS5 isolate (GenBank accession numbers MH814756-MH814758), respectively. These values exceed the threshold values of the species demarcation for the genus Deltapartitivirus. Further phylogenetic analysis indicates that CCV1 isolates sequenced in this study were clustered into a monophyletic clade with high confidence, together with known CCV1 Won and CoCV1 PXCS5 isolates. Taken together, the analyses suggest CCV1 and CCoV1 should be the same deltapartitivirus.
    • CELL BIOLOGY, PHYSIOLOGY, BIOCHEMISTRY, AND MOLECULAR BIOLOGY
  • Cytological study on the spots of rice leaf smut infected by Entyloma oryzae
    ZHANG Xiaomin, XIE Li, WANG Weilan, LAI Chaohui, LIANG Wusheng, LIN Fucheng, HU Dongwei
    Acta Phytopathologica Sinica. 2023, 53(3): 395-400. https://doi.org/10.13926/j.cnki.apps.001009
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    Rice leaf smut is a fungal disease caused by a basidiomycete, Entyloma oryzae, which infects rice leaves and leaf sheaths forming black strip spot. However, the cytological mechanism of the interaction between pathogen and host is still poorly understood. Here the preliminary cytological analysis was carried out on diseased leaves collected from the field. The results showed that the morphology of host epidermal cells on the spots remained basically intact after pathogen infection. The pathogen produced a large number of chlamydospores in the position of host mesophyll cells, and gradually replaced all the mesophyll cells. The hyphae of the pathogen expanded outside the host cell and did not penetrate into the host cell walls, nor did not produce typical fungal haustorium. The organelles in the host cells close to the hyphae of the pathogen were degraded, and the lipids produced by degradation condensed into large lipid spheres. The cell wall of the host vascular bundle tissue remained intact, and no pathogenic hypha was found to invade the vascular bundle. The pathogenic mycelia and spores were confined between two adjacent vascular bundles of the host. In the late stage of the infection, a large number of bacteria entered due to the structural integrity destruction of host leaf epidermis, which accelerated the senescence and death of host leaves. The results of this study showed that the pathogen infection mode is extracellular, similar to obligate parasitic fungi. On the other hand, pathogen infection leads to the degradation and death of nearby host cells as saprophytic fungi.
  • The apoplastic effector Ps140300 inhibits innate immunity activated by XEG1
    WANG Lan, LIU Hanmei, ZHANG Mingmei, ZHU Jinyi, WANG Yan, ZHENG Xiaobo, WANG Yuanchao
    Acta Phytopathologica Sinica. 2023, 53(3): 401-411. https://doi.org/10.13926/j.cnki.apps.000799
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    The apoplastic effectors play important roles in promoting microbial colonization by interfering with plant immune responses. XEG1, an apoplastic effector secreted by Phytophthora sojae, belongs to the glycoside hydrolase 12 family. XEG1 is recognized by the pattern recognition receptor RXEG1, triggering immune response and cell death in plants. In this study, we found that the XEG1 homologous protein Ps140300 could suppress XEG1 induced-cell death. Ps140300 was a virulence factor of P. sojae and up-regulated at the early infection stage. Unlike XEG1, Ps140300 did not trigger cell death in plants. Ps140300 could inhibit XEG1-induced cell death and reactive oxygen species burst. Further studies found that Ps140300 did not affect RXEG1 interaction with XEG1, or the signaling transduction sectors BAK1 and SOBIR1. Ps140300 was conserved in oomycetes and fungi and homologues can also suppress XEG1-triggered cell death. These results suggest that the apoplastic effectors can promote microbial infection by inhibiting host basal immunity.
  • Functional analysis of autophagy related gene ChAtg26 in Colletotrichum higginsianum
    DUAN Lingtao, ZENG Miaolin, WANG Li, ZHU Yiming, HE Jiuqing, ZHOU Erxun
    Acta Phytopathologica Sinica. 2023, 53(3): 412-423. https://doi.org/10.13926/j.cnki.apps.001002
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    Colletotrichum higginsianum is an important plant pathogenic fungus that can cause severe cruciferous vegetable anthracnose, which has a great impact on vegetable production. In order to explore the function of the autophagy-related gene ChAtg26 in the pathogenesis of C. higginsianum, the cDNA of Arabidopsis thaliana Col-0 infected by C. higginsianum was used as a template in this study, and the expression pattern of the gene ChAtg26 during the infection process was determined by qRT-PCR. To characterize the function of ChAtg26, the gene knockout and mutant complementation were performed through homologous recombination technology, and the effects of the gene deletion on the growth, development and pathogenicity of C. higginsianum was evaluated. The result of expression pattern showed that the gene ChAtg26 reached the maximum expression level after 40 h of infection. When the deletion of this gene, no significantly effects were observed on the mycelial growth rate, conidium germination, appressorium formation, and sensitivity to oxidative stress, but the mutant showed the reduction of melanin accumulation in the colony, the sensitivity to cell wall stress, and the significantly decreased sporulation and pathogenicity. Taken together, our results suggest that ChAtg26 in C. higginsianum was involved in the melanin synthesis, cell wall stress response, conidia production and pathogenesis.
  • Inhibitory effect of fifteen small molecular compounds on the type Ⅲ secretion system of Xanthomonas oryzae pv. oryzicola
    LIU Jie, ZHU Kaixuan, WANG Guohua, ZHANG Linlin, YAN Xi, LIANG Xiangdong, HANG Xiaohong, JIANG Bole, YANG Mei
    Acta Phytopathologica Sinica. 2023, 53(3): 424-435. https://doi.org/10.13926/j.cnki.apps.000643
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    Type III secretion system (T3SS) is the virulence determinant of Xanthomonas oryzae pv. oryzicola (Xoc). A series of small molecule inhibitors of type III secretion system of Xanthomonas campestris pv. campestris (Xcc) have been identified in our laboratory before. Whether these inhibitors have the effect on T3SS of Xoc is worth investigating. In this study, the fusion reporter systems were constructed by fusing the luciferase gene (Lux) and the GUS gene with the promoter regions of T3SS-related genes respectively in Xoc. The small molecules inhibiting T3SS of Xoc were identified with the reporter system and quantitative PCR (qPCR). The results showed that Carmofur, 5-Fluorocytosine, A-3, and Dealkaline lignin also inhibit the expression of Xoc T3SS. Among them, A-3 and Dealkaline inhibit the growth of bacteria in XOM3. However, none of the four compounds could significantly reduce the disease symptoms caused by Xoc. In order to determine the quantitative hypersensitive response (HR) triggered by Xoc, and to check the biocontrol effects of the above inhibitors, the reporter strain GX01/avrBs1 was constructed by fusion PCR and homologous double exchange principle. The results indicated that GX01/avrBs1 could rapidly trigger HR on pepper ECW-10R, and Dealkaline lignin could significantly attenuate HR induction of Xoc on pepper ECW-10R, further indicating that Dealkaline lignin inhi-bits Xoc T3SS.
  • Functional study of effector protein AopK of Acidovorax citrulli
    LIU Jing, ZHAO Liping, GUAN Wei, YANG Yuwen, BAI Qingrong, ZHAO Tingchang
    Acta Phytopathologica Sinica. 2023, 53(3): 436-446. https://doi.org/10.13926/j.cnki.apps.000644
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    The type Ⅲ secreted effectors (T3Es) play important roles in the pathogenesis of Acidovorax citrulli, the causal agent of bacterial fruit blotch in watermelon and melon plants. XopK is a T3E with E3 ubiquitin ligase activity in Xanthomonas spp. The homolog of XopK, designated as AopK, in A. citrulli has not been investigated. To explore the function of AopK, the aopK deletion mutant and complementary strain were constructed in A. citrulli wild-type strain AAC00-1. The pathogenicity assay showed that the deletion of the gene aopK significantly reduces the virulence of A. citrulli on watermelon seedlings. Subcellular localization analysis of AopK was performed using Nicotiana benthamiana. Results revealed that AopK was delivered to the cytoplasmic membrane of N. benthamiana. The transcriptional expression level, secretory and BAX co-expression analyses showed that the expression of aopK was positively regulated by HrpX and HrpG. AopK was secreted into extracellular matrix through the Type Ⅲ secretion system. AopK can inhibit the production of reactive oxygen species, callose deposition and cell necrosis in N. benthamiana, and affects the virulence via inhibiting plant defense responses. In summary, our data indicated that AopK is a T3E in A. citrulli. Our data laid a foundation for further exploring the mechanism of interaction between A. citrulli and host plants.
    • GENETICS OF DISEASE-RESISTANCE AND PATHO-GENICITY
  • Biological characteristics of new Pyricularia species and resistance analysis of different rice varieties
    DU Yan, QI Zhongqiang, LIANG Dong, CUI Congcong, YANG Xiaoyun, LIU Yongfeng
    Acta Phytopathologica Sinica. 2023, 53(3): 447-454. https://doi.org/10.13926/j.cnki.apps.000816
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    Neck blast, caused by Pyricularia oryzae, seriously affect the yield and quality of rice. Previous results showed that a new species of Pyricularia, which was found by continuous monitoring in the rice fields in Jiangsu province, can cause neck blast-like with a high incidence and stable existence in different years. In order to understand the difference between the new pathogen and P. oryzae Guy11. The growth, sporulation, various stresses and resistance of different varieties to these two diseases were compared between the representative strain P. sp. jiangsuensis 18-2 and P. oryzae Guy11. The results showed that the growth of P. sp. jiangsuensis 18-2 on PDA, CM and SDC medium was significantly faster than that of P. oryzae Guy11, but the aerial mycelium of P. sp. jiangsuensis 18-2 was sparse. Under cell wall stress factor and oxidative stress, the tolerance of P. sp. jiangsuensis 18-2 to exogenous stress was significantly enhanced than that of P. oryzae Guy11, indicating that P. sp. jiangsuensis 18-2 was more adaptable to external stress response. Further analysis of the resistance of the main cultivars in Jiangsu province to panicle neck blast showed that some main cultivars had different resistance to panicle neck blast caused by P. sp. jiangsuensis 18-2 and P. oryzae Guy11. Varieties Zhendao 448, Yanjing 15, Jingliangyou 534 and Yongyou 2640 showed good resistance. In production, it is necessary to select the varieties with better resistance to these two diseases.
  • Establishment of an evaluation system for identification of litchi resistance indoor to Colletotrichum gloeosporioides
    LI Fang, ZHANG Lei, LIN Qiying, CAI Rupeng, LI Huanling, WANG Jiabao
    Acta Phytopathologica Sinica. 2023, 53(3): 455-462. https://doi.org/10.13926/j.cnki.apps.000835
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    Litchi anthracnose caused by Colletotrichum gloeosporioides is an important disease in litchi production, which occurs on leaves, flower clusters, fruits, and postharvest fruits. In this study, the investigation was performed on inoculation method, leaf development stage, infection position, incubation time, and measure pattern of disease spot to evaluate the resistance and select resistant litchi genotypes by using a detached leaf inoculation method indoor. The results showed that the optimal condition to evaluate the resistance was stab inocu-lation of a mycelial agar disk (5mm) on the back of fresh leaves which had just reached the maximum leaf area, and observing the incidence and measuring the disease spot area at 72 h after inoculation. Fifty-five germplasm litchi materials were analyzed by this method and their resistance level was divided into 5 grades: immune, highly resistant, moderately resistant, moderately susceptible and high susceptible by using the square Euclidean separation matrix analysis method. This evaluation method and grade division standard for litchi resistance to C. gloeosporioides provide the theoretical basis for litchi resistance breeding and gene selection.

    • PLANT DISEASE AND CONTROL
  • Sensitivity of Cercospora beticola from sugar beet to carbendazim, difenoconazole, fenoconazole, and control efficacy of fungicides on Cercospora leaf spot
    LIU Mei, LIN Jie, HAN Chenggui
    Acta Phytopathologica Sinica. 2023, 53(3): 463-472. https://doi.org/10.13926/j.cnki.apps.000804
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    Sensitivity of 81 Cercospora beticola isolates to carbendazim, difenoconazole and flusilazole was determined by mycelial growth method. 57(70.37%) and 24 (29.63%) of the 81 isolates were sensitive and resistant to carbendazim. The range and mean EC50 values of C. beticola isolates were 0.003 5 to 3.818 0 μg·mL-1 and (0.162 7±0.544 6) μg·mL-1 for difenoconazole, 0.033 5 to 5.465 2 μg·mL-1 and(0.370 0±0.788 4)μg·mL-1for flusilazole. The highest EC50 value was 1 090 and 163 times greater than the lowest one for difenoconazole and flusilazole respectively.The ratio of lowest and highest EC50 values of difenoconazole for the isolates from the different regions ranged from 2.3 to 853, part of the isolates exhibited significant difference on the sensitivity to difenoconazole with the average EC50values from 0.031 0 to 1.915 9 μg·mL-1. The results of the frequency analysis revealed that subpopulation with less sensitivity to difenoconazole had been discovered, the average EC50 value of 82.7% isolates (0.037±0.002) μg·mL-1 which were conform to normal distribution, was used as the baseline sensitivity of C. beticola to difenoconazole. The ratio of lowest and highest EC50 values of flusilazole for the isolates from the different regions ranged from 1.3 to 65.6, part of the isolates exhibited significant difference on the sensitivity to flusilazole with the average EC50 values from 0.031 0 to 1.093 7 μg·mL-1. The results of the frequency analysis revealed that subpopulation with less sensitivity to flusilazole had been discovered, the ave-rage EC50 value of 75.3% isolates (0.145±0.007) μg·mL-1 which were conform to normal distribution, was used as the baseline sensitivity of C. beticola to flusilazole. The resistance frequency of the C. beticola isolates to difenoconazole and flusilazole was 20.99% and 16.05% respectively, most of them were low and high level. In field trials, after the second application, the control efficacy of 40% Flusilazole EC(24 g·hm-2) and 70% Thiophanate-methyl WP( 630 g·hm-2) was above 65% in 10 days, which was significantly higher than that of 70% Mancozeb WP (1 050 g·hm-2) and 50% Iprodione WP (600 g·hm-2). This study provides preliminary data support for appropriate application of fungicides and effective control of Cercospora leaf spot.
  • Screening, identification and detection of biocontrol effect of strain YC2-3 on wheat crown rot
    CHEN Jing, WANG Tongtong, MA Qing, WANG Yang
    Acta Phytopathologica Sinica. 2023, 53(3): 473-484. https://doi.org/10.13926/j.cnki.apps.000805
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    Crown rot of wheat, caused by the pathogenic fungal Fusarium pseudograminearum (Fp), is a de-vastating disease of wheat, which dramatically affects wheat production and its quality. To screen effective candidate biocontrol agents against Fp, streptomycetes were isolated from rhizosphere soil samples using dilution pla-ting method and plate confrontation method. In this study, 69 streptomycetes were obtained from 10 soil samples. Among them, strain YC2-3 demonstrated the strongest inhibitory activity against Fp, producing a radius of inhibition zone > 14 mm. Strain YC2-3 was identified as Streptomyces rectiviolaceus based on phylogenetic analyses, morphological characteristics, cultural characteristics, and biochemical characteristics. Strain YC2-3 exhibited a broad-spectrum antifungal activity. Under greenhouse conditions, the strain YC2-3 inoculated at 24 h before (protective effect) and 24 h after (curative effect) Fp inoculation, significantly reduced the incidence rate and disease index of wheat crown rot, and the biocontrol efficacy were 69.01% and 73.94%, respectively. Bioassays revealed that strain YC2-3 can produce various extracellular hydrolytic enzymes, siderophore, ACC deaminase, and has the ability to solubilize organic phosphate. Expression profiling of defense-related marker genes showed that the peroxidases gene TaPOD was activated at 12 h after the wheat was treated with YC2-3. These results suggest that S. rectiviolaceus YC2-3 has the potential to be used as a biological agent for the control of wheat crown rot.
  • Pathogen identification and fungicides screening for the control of leaf sheath brown spot of Zizania latifolia
    LI Yipeng, ZHENG Zhaisheng, SONG Ruiqi, YANG Mengfei
    Acta Phytopathologica Sinica. 2023, 53(3): 485-490. https://doi.org/10.13926/j.cnki.apps.000854
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    Some diseases cause the leaf sheath of Zizania latifolia to produce brown spots and the infected plants produce short and yellowish Jiaobai in Jinhua City and Lishui City, Zhejiang Province. XYQ3 strain was obtained from diseased samples by tissue isolation. The pathogen causing leaf sheath disease of Z. latifolia was identified as Microdochium seminicola by morphological characterization, sequence alignment analysis and pathogenicity test. Toxicity test of 12 fungicides commonly used in fields was carried out in laboratory conditions. The results showed that the inhibition effect on mycelium was best for prochloraz EC at 250 g·L-1 , with an EC50 of 0.067 mg·L-1; followed by 300 g·L-1 Benzo propiconazole EC and 60% Difenoconazole WG, with EC50 of 0.373 and 1.083 mg·L-1, respectively. In comprehensive consideration, 250 g·L-1 Prochloraz EC is the best as a fungicide agent, and 50% Iprodione WP can be used as an alternative. This study provided scientific basis for the identification and control of leaf sheath brown spot of Z. latifolia.
  • Pathogen identification and effective fungicides screening of root rot of Schisandra sphenanthera in Shaanxi Province
    WU Hao, YU Tingting, YUAN Zhichun, MIAO Jianqiang, HAN Lirong, LIU Xili
    Acta Phytopathologica Sinica. 2023, 53(3): 491-497. https://doi.org/10.13926/j.cnki.apps.000834
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    Schisandra chinensis planting has become a pillar industry for the local rural revitalization for Zhashui, Shiquan and Zhen'an counties in Shaanxi Province. With the continuous increasing of artificial planting areas, root rot has become a main problem which seriously affects the development of S. chinensis industry in Shaanxi Province. In order to identify the pathogen of S. chinensis root rot in Shaanxi Province, the specimens of diseased plants were collected from S. chinensis planting bases in Zhashui County and Zhen'an County in Shangluo City and Long County in Baoji City in Shaanxi Province. The pathogen of S. chinensis root rot was obtained by tissue isolation and pathogenicity testing. Pathogenicity test and phylogenetic analysis based on ITS- TEF-1α - β-Tubulin sequences showed that Fusarium proliferatum was the pathogen. The laboratory antifungal activity screening test showed that the selected 11 fungicides had certain inhibitory effects on the pathogen, among which Pyraclostro-bin, Metconazole, Saphire and Tebuconazole exhibited relative higher inhibitory effects, with EC50 of 0.021 0, 0.083 3, 0.380 7 and 0.403 5 μg·mL-1 respectively. This study provides an important guiding basis for the effective prevention and control of S. chinensis root rot in Shaanxi Province.
  • Effects of fludioxonil and tebuconazole mixtures on mycelial growth and disease of Fusarium crown rot
    LI Congcong, WU Yuxing, WANG Yajiao, JI Lijing, HAN Sen, KONG Lingxiao
    Acta Phytopathologica Sinica. 2023, 53(3): 498-507. https://doi.org/10.13926/j.cnki.apps.000795
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    In order to screen the safe and effective mixtures of fungicides for Fusarium cown rot, the toxicity of the mixtures of fungicides with different modes of action fludioxonil and tebuconazole against Fusarium pseu-dograminearum was detected by mycelial growth rate method, and the optimum synergistic mixture was selected. The safety and control effect of the fungicide mixture were determined by seedling bioassay in greenhouse. Finally, qPCR was used to detect the effects of the fungicide mixture on the pathogens in wheat rhizosphere soil and stem. The results showed that the toxicity of the mixture to hyphal growth of F. pseudograminearum was highest when the ratio of fludioxonil and tebuconazole was 1∶7 with the synergistic ratio of 7.22. The control effects of the seed coating agent for the mixture were 73.35%, 62.59% and 82.07% on three different disease resistant wheat varieties, respectively, which was significantly higher than the two single fungicides used at the same dose. It also had the growth promoting effect, and increased the root length and fresh weight of wheat by 2.81%-12.33% and 18.87%-49.21% respectively. Compared with the control, the contents of F. pseudograminearum in wheat rhizosphere soil and wheat stem treated with the mixture were decreased by 76.95%-90.37% and 92.00%-96.70%, reapectively. It was verified that the ratio of the mixture of fludioxonil and tebuconazole at 1∶7 could achieve the control effect by reducing the content of the pathogen in soil and wheat straw. This study provides a new reference for the chemical control of Fusarium cown rot.
    • RESEARCH NOTES
  • Alternaria and Curvularia species from maize leaf spot samples in Northern China
    ZHAO Lirong, ZHANG Mingyuan, ZHANG Huawei, NIU Yongchun, LU Guangxin, DENG Hui
    Acta Phytopathologica Sinica. 2023, 53(3): 508-513. https://doi.org/10.13926/j.cnki.apps.000808
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    In 2017, 2018 and 2020, a total of 191 leaf spot samples of maize were collected from representative sites of Beijing, Shandong and Jilin in Northern China. There were 293 strains -screened as Altarnaria sp. and 92 strains as Curvularis sp. based on rDNA ITS sequences analysis and morphological characteristics. Ten represen-tative strains of Alternaria were belonged to A. alternate by phylogenetic analysis with a combined dataset of rDNA-ITS, GAPDH, Tef1 and Alt a 1 gene fragments. Likewise, six representive strains of Curvularia were classified into C. lunata, C. intermedia and C. spicifera based on rDNA-ITS and GAPDH sequences. The pathogenicity by in vitro leaf assays were conducted for strains isolated from 102 samples and 42 samples of Alternaria and Curvularia, respectively, while by spraying with spore suspension were conducted for 20 representative strains. The result showed that all the strains mentioned above from four fungal species caused spot symptoms on maize leaves with the varied pathogenicity. In this study, the isolation frequency of Alternaria alternata and Curvularia lunata was significantly higher than that of C. intermedia and other species.
  • Isolation and identification of the pathogen causing pecan brown spot in Jurong, Jiangsu
    ZHAO Yuqiang, ZHUO Keer, GUO Yun, ZHU Qianli, ZHU Cancan, TIAN Yanli, HU Baishi
    Acta Phytopathologica Sinica. 2023, 53(3): 514-517. https://doi.org/10.13926/j.cnki.apps.000648
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    The pecan tree [Carya illinoinensis (Wangenheim) K. Koch] produces seeds with high nutritional value and medicinal properties. Brown spot is one of the most important diseases of pecan in China, especially in Jiangsu province. Disease incidence ranged from 10% to 20% in the affected fields, which seriously affected the yield and quality of fruits. In this study, by tissue separation method, two Colletotrichum-like isolates were isolated from diseased pecan in different planting areas in Jurong. In order to identify these isolates, typical morphological characteristics were analyzed, phylogenetic tree was constructed based on ITS-TUB2-GAPDH- CHS-1-ACT genes, and their pathogenicities were tested. The results showed that ten strains were pathogenic and identified as C. fructicola and C. viniferum. Pathogenicity tests showed that all of the isolates could induce leaf necrosis, displaying variable pathogenicites for different strains. This is the first report of C. fructicola and C. viniferum causing pecan blackspot in Jurong, Jiangsu province, which will provide theoretical basis for further study of disease monitoring and control and breeding of disease resistance in pecan cultivars.
  • Identification of the pathogen of papaya anthracnose in Guangxi
    ZHANG Yujie, SUN Wenxiu, TANG Lihua, HUANG Suiping, MO Jianyou, GUO Tangxun, CHEN Xiaolin, HUANG Huiye, LI Qili
    Acta Phytopathologica Sinica. 2023, 53(3): 518-521. https://doi.org/10.13926/j.cnki.apps.000819
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    Anthracnose caused by Colletotrichum spp. is an important postharvest disease, which severely affects the quality of papaya fruits. In this study, fungal colonies were isolated and identified from diseased papaya fruits collected from Guangxi Province. Koch's rule was fulfilled by inoculating three fungal strains, MG2, MG15-4 and MG15-7 on papaya fruits, resulting in the similar symptoms of anthracnose. The strains were identified as C. truncatum based on morphological characteristics and molecular biological identification. This is the first report of C. truncatum caused anthracnose on papaya in China.
  • Identification and biological characteristics of pathogen associated with Hippophae rhamnoides trunk canker
    JIA Xinyu, DONG Baozhu, MENG Huanwen, SONG Yang, BI Shujie, SI Qing, ZHOU Hongyou
    Acta Phytopathologica Sinica. 2023, 53(3): 522-526. https://doi.org/10.13926/j.cnki.apps.000806
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    Hippophae rhamnoides is a perennial shrub mostly used for water and soil conservation, wind break and sand fixation in western China. The fungal trunk canker disease on Hippophae rhamnoides is sometime very destructive in field. The authors isolated a pathogenic fungus strain A-1-2 from the diseased host plants in Erdos, Inner Mongolia. It was identified as Diaporthe eres by morphological and molecular methods. The pathogen grows fast on PDA, reaching 8 cm in diameter in 7 d. The most favorable temperature for mycelial growth was found at 25 ℃. Light was contributive to mycelial growth, while alternative light and dark was inducible to pycnidium formation. This paper is the first report for the pathogen Diaporthe eres causing trunk canker on H. rhamnoides in Inner Mongolia. The research results provide a preliminary base for further study on the disease cycle and management.
  • Identification of pathogen species of avocado leaf anthracnose in Chongzuo,Guangxi
    FAN Zhenzhen, LU Yanchun, WANG Wenlin, LIN Chunhua
    Acta Phytopathologica Sinica. 2023, 53(3): 527-530. https://doi.org/10.13926/j.cnki.apps.000812
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    The avocado (Persea americana) is a commercially valuable fruit crop and cultivated in tropical region. Leaf anthracnose is a common disease of avocado. In this study, we isolated and identified a Colletotrichum strain from leaf spot disease of avocado at the nursery of Guangxi, China. According to the morphological and phylogenetic analyses of multi-locus sequences (internal transcribed spacer, ITS; chitin synthase, CHS-1; actin, ACT; glyceraldehydes-3-phosphate dehydrogenase, GAPDH), the pathogen was identified as Colletotrichum fructicola. To our knowledge, this is the first report of C. fructicola from leaf anthracnose on P. americana in China. This finding will help us to recognize the leaf anthracnose disease of avocado and establish a foundation for future studies on C. fructicola to address effective management strategies.
  • Identification of the pathogen causing Baccaurea ramiflora southern blight
    WANG Tongtong, WANG Xiaoyu, LU Yanchun, TAN Dejin, XU Dongying, HE Wen, JIANG Ting, YANG Zhiqiang
    Acta Phytopathologica Sinica. 2023, 53(3): 531-533. https://doi.org/10.13926/j.cnki.apps.000809
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    In germplasm resource nursery of Guangxi South Subtropical Agricultural Science Research Institute, a stem disease of Baccaurea ramiflora was found at the seedling stage. The pathogen was determined by the Koch's postulates, morphological observation and ITS-TEF-SSU-LSU sequence analysis, and was identified as Athelia rolfsii. To our knowledge, this is the first report on A. rolfsii causing southern blight on B. ramiflora in China as well as in the world.
  • Identification and S RNA sequence analysis of watermelon silver mottle virus isolated from watermelon and melon in Guangxi
    LI Zhanbiao, YANG Shi'an, QIN Bixia, XIE Huiting, CUI Lixian, CHEN Jinqing, CAI Jianhe
    Acta Phytopathologica Sinica. 2023, 53(3): 534-538. https://doi.org/10.13926/j.cnki.apps.000813
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    During 2015-2016, Leaf samples of watermelon and melon exhibiting chlorotic and silver mottle symptoms were collected from Guangxi Zhuang Autonomous Region. Virus detection was done using double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) and reverse transcription-polymerase chain reaction (RT-PCR). The results showed that 38 out of 143 samples were reacted positively against the antisera of watermelon silver mottle virus (WSMoV). Total RNA of the 38 positive samples were extracted and analyzed by RT-PCR using WSMoV specific primers. PCR amplicons with an expected size of 455 bp were obtained from all of the 38 samples, confirming that these samples were infected with WSMoV. Gene cloning, sequence comparison and phylogenetic trees construction were applied for the identification of the viruses. Two complete S RNA genome sequences were obtained (GenBank No.:OK905442 and OK905443), and the two sequences had 97% nucleotide identity with WSMoV-GZ (JX177645). Phylogenetic tree analysis showed that the WSMoV Guangxi watermelon isolates formed a small branch with WSMoV-GZ based on the nucleocapsid gene sequence. The results indicated that the WSMoV Guangxi watermelon isolates shared a close evolutionary relationship with WSMoV-GZ.
  • Molecular characteristic of squash leaf curl china virus (SLCCNV) infecting Bolbostemma paniculatum in HeBei Province
    DU Jiang, ZHANG Li, CUI Liyan, MA Zhennan, WANG Chenyan, WANG Defu, NIU Yanbing
    Acta Phytopathologica Sinica. 2023, 53(3): 539-545. https://doi.org/10.13926/j.cnki.apps.001301
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    In order to clarify geminiviruses causing Bolbostemma paniculatum leaf shrinkage and mosaic in Anguo botanical garden, Hebei Province, China, the virus genome sequence was amplified by geminivirus degenerate primers and specific primers, and the phylogenetic tree of virus genome was constructed. The results showed that the squash leaf curl china virus (SLCCNV) was detected in Bolbostemma paniculatum plants in Hebei Province. The SLCCNV infected plants showed leaf shrinkage and mosaic, and the isolate was named SLCCNV-HB (DNA-A GenBank accession No: OL743525; DNA-B GenBank accession No: OM238222). The virus DNA-A genome was 2 736 bp and contained six open reading frames. The virus DNA-B genome was 2 718 bp and contained 2 open reading frames. The SLCCNV-HB DNA-A sequence shares the highest identity (96.30%) with SLCCNV-GDHY Pumpkin isolate (GenBank accession No: MW389917). The SLCCNV-HB DNA-B sequence shares the highest identity (95.37%.) with SLCCNV-GDHY Pumpkin isolate (GenBank accession No: MW389918). To our knowledge, this is the first report of SLCCNV that infects medicinal plant Bolbostemma paniculatum.
  • Identification of citrus yellow vein clearing virus from Diaphorina citri
    LIU Kehong, CUI Xuejin, ZHOU Yan
    Acta Phytopathologica Sinica. 2023, 53(3): 546-549. https://doi.org/10.13926/j.cnki.apps.000657
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    Citrus yellow vein clearing virus (CYVCV) belongs to the genus Mandarivirus, family Alphaflexiviridae and causes serious yield reduction of lemons and sour oranges. In this study, CYVCV was detected in Diaphorina citri collected from Yuxi, Yunnan province in August, 2019. A partial genome sequence (7 378 bp) was obtained after PCR amplification and sequence assembly. The sequence had a maximum nucleotide sequence identity of 98.88% to CYVCV isolate YN-SA. Furthermore, phylogenetic tree based on CP gene sequences showed that the isolate clustered with CYVCV isolates collected from China. To our knowledge, this is the first time that CYVCV has been detected in D. citri.
  • First report of cucurbit chlorotic yellows virus infection of Chinese yam in Guizhou
    WEI Jianming, YUE Ningbo, LI Yunzhou
    Acta Phytopathologica Sinica. 2023, 53(3): 550-552. https://doi.org/10.13926/j.cnki.apps.000647
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    Anshun is the main producing area of yam (Dioscorea oppositifolia) in Guizhou Province. Recently, field investigations found that yam in Anshun area was suspected to be infected with cucurbit chlorotic yellows virus (CCYV), which caused huge economic losses to local farmers. The leaves suspected of being infected with CCYV were collected. RT-PCR detection was performed on the suspected diseased leaf samples, and CCYV was determined in combination with the sequencing results. Phylogenetic analysis was performed by CCYV coat protein (CP) sequence. The results showed that the isolates detected by Anshun in Guizhou had small regional differences with the isolates in USA and Saudi Arabia and other countries, and the relatives were relatively close, while the isolates in Iran was relatively distant. The findings will facilitate further research and help develop strategies for the prevention and control of CCYV in yam.
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Editor in Chief: FAN Jun
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