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    植物细菌真菌合辑Plant Bacteria/Fungus

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    Identification and functional characterization of the MdHB-1 gene promoter sequence from Malus×domestica
    WANG Hao-jie, JIANG Yong-hua, QI Ying-wei, DAI Jie-yu, LIU Yan-li, ZHU Xian-bo, LIU Cui-hua, Lü Yan-rong, REN Xiao-lin
    2017, 16 (08): 1730-1741.   DOI: 10.1016/S2095-3119(16)61548-4
    Abstract724)      PDF in ScienceDirect      
        Homeobox 1 in Malus×domestica (MdHB-1) is a transcription factor that belongs to homeodomain-leucine zipper I (HD-Zip I) protein subfamily. According to previous reports, MdHB-1 could regulate ethylene synthesis by binding with the MdACO1 promoter, but other functions of MdHB-1 are still unknown. To reveal more clues concerning the characters of the MdHB-1 gene promoter and the functions of MdHB-1, the promoter region of MdHB-1 was cloned from the Royal Gala apple genome and recombined with the β-glucuronidase (GUS) gene in this study. This research was conducted in Nicotiana tabacum and supported by Agrobacterium-mediated transient transformation and bioinformatics analysis. Deletion analysis of the MdHB-1 promoter showed that the GUS gene could be activated by serially deleted promoters, and the activity promoted by 680 nucleotides (nt) was the lowest. The region, which is 266 nt upstream of the initiation code (ATG), was effective for GUS expression. Meanwhile, the activity of the MdHB-1 promoter (-1 057 nt), which was stronger than MdHB-1 promoter (-1 057 to -266 nt) and lack the 5´-untranslated region (5´-UTR), showed that 5´-UTR may have a positive effect on gene transcription. After the sequence analysis, the cis-acting elements that respond to hormones and environmental stresses were identified in the promoter region. The MdHB-1 promoter (1 057 nt) activity in Nicotiana tabacum was positively induced by ethrel and darkness, and it was suppressed by gibberellic acid (GA), whereas abscisic acid (ABA), salicylic acid (SA), wounding, and Pseudomonas syringae pv. tomato (DC3000) treatments revealed a slight auxo-action. These results reveal that the MdHB-1 promoter receive internal or external signals, and MdHB-1 may refer to many biological activities in apple, such as its stress response, development, and ripening.
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    MAPKs and acetyl-CoA are associated with Curvularia lunata pathogenicity and toxin production in maize
    NI Xuan, GAO Jin-xin, YU Chuan-jin, WANG Meng, Sun Jia-nan, LI Ya-qian, CHEN Jie
    2018, 17 (01): 139-148.   DOI: 10.1016/S2095-3119(17)61697-6
    Abstract592)      PDF in ScienceDirect      
    Mitogen-activated protein kinase (MAPK) cascades play an important role in extracellular signal transduction and are involved in the pathogenicity of fungal pathogens to host plants.  In Curvularia lunata, the roles of two MAPK genes, Clk1 and Clm1, have already been studied.  Clk1 is involved in conidia formation and pathogenicity, and Clm1 is closely related to pathogen cell wall formation and pathogenicity to maize leaves.  In this study, a third C. lunata MAPK gene, Clh1, which is homologous to hog1, was successfully cloned.  We found that a Clh1 deletion mutant had lower intracellular glycerol accumulation than the wild-type stain and was unable to grow normally under osmotic stress conditions.  Furthermore, the deletion mutants of three C. lunata MAPK genes (Clk1, Clm1 and Clh1) had lower levels of acetyl-CoA, which is an important intermediate product in the synthesis of melanin and furan toxin, and down-regulated expression of pathogenicity-associated genes.  Furthermore, pathogenicity and the ability to produce toxin were restored after adding acetyl-CoA to the culture medium, suggesting that acetyl-CoA is closely involved in the pathogen MAPK signaling pathway. 
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    The PhoR/PhoP two-component system regulates fengycin production in Bacillus subtilis NCD-2 under low-phosphate conditions
    GUO Qing-gang, DONG Li-hong, WANG Pei-pei, LI She-zeng, ZHAO Wei-song, LU Xiu-yun, ZHANG Xiao-yun, MA Ping
    2018, 17 (01): 149-157.   DOI: 10.1016/S2095-3119(17)61669-1
    Abstract675)      PDF in ScienceDirect      
    Bacillus subtilis strain NCD-2 is an excellent biocontrol agent for plant soil-borne diseases, and the lipopeptide fengycin is one of the active antifungal compounds in strain NCD-2.  The regulator phoP and its sensor kinase PhoR compose a two-component system in B. subtilis.  In this study, the phoR- and phoP-knockout mutants were constructed by in-frame deletion and the role of PhoR/phoP on the production of fengycin was determined.  Inactivation of phoR or phoP in  B. subtilis decreased its inhibition ability against Botrytis cinerea growth in vitro compared to the strain NCD-2 wild type.  The lipopeptides were extracted from strain NCD-2 wild type and its mutant strains by hydrochloric acid precipitate, and the lipopeptides from phoR-null mutant or phoP-null mutant almost lost the inhibition ability against B. cinerea growth compared to the lipopeptides from strain NCD-2 wild type.  Fast protein liquid chromatography (FPLC) analysis of the lipopeptides showed that inactivation of phoR or phoP genes reduced the production of fengycin by strain NCD-2.  The fengycin production abilities were compared for bacteria under low-phosphate medium (LPM) and high-phosphate medium (HPM), respectively.  Results indicated that the regulation of fengycin production by the PhoR/PhoP two-component system occurred in LPM but not in HPM.  Reverse transcriptional-PCR confirmed that the fengycin synthetase gene fenC was positively regulated by phoP when cultured in LPM.  All of these characteristics could be partially restored by complementation of intact phoR or phoP gene in the mutant.  These data indicated that the PhoR/PhoP two-component system greatly regulated fengycin production and antifungal ability in B. subtilis NCD-2 mainly under low-phosphate conditions.
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    Regionalization of wheat powdery mildew oversummering in China based on digital elevation
    ZOU Ya-fei, QIAO Hong-bo, CAO Xue-ren, Liu Wei, FAN Jie-ru, SONG Yu-li, WANG Bao-tong, ZHOU Yi-lin
    2018, 17 (04): 901-910.   DOI: 10.1016/S2095-3119(17)61851-3
    Abstract538)      PDF in ScienceDirect      
    Blumeria graminis f. sp. tritici, the pathogen that causes wheat powdery mildew, is one of the most important diseases affecting wheat production in China, and the oversummering is the key stage of wheat powdery mildew epidemic.  The more oversummering regionalization of wheat powdery mildew has played an important role in disease prediction, prevention and control.  In this study, we analyzed the correlation between oversummering data of wheat powdery mildew and the meteorological factors over the past years, and determined that temperature was the key meteorological factor influencing oversummering of wheat powdery mildew.  The average temperature at which wheat powdery mildew growth was terminated (26.2°C) was used as the threshold temperature to regionalize the oversummering range of wheat powdery mildew.  This regionalization was done using the GIS ordinary kriging method combined with the Digital Elevation model (DEM) of China.  The results showed that annual probability of oversummering region based on Model 26.2 were consistent with the actual survey of the more summer wheat powdery mildew.  Wheat powdery mildew oversummering regions in China mainly cover mountainous or high-altitude areas, and these regions form a narrow north-south oversummering zone.  Oversummering regions of wheat powdery mildew is mainly concentrated in the high-altitude wheat growing areas, including northern and southern Yunnan, northwestern Guizhou, northern and southern Sichuan, northern and southern Chongqing, eastern and southern Gansu, southeastern Ningxia, northern and southern Shaanxi, central Shanxi, western Hubei, western Henan, northern and western Hebei, western Liaoning, eastern Tibet, eastern Qinghai, western Xinjiang and other regions of China.
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    A study on the pathogen species and physiological races of tomato Fusarium wilt in Shanxi, China
    CHANG Yin-dong, DU Bin, WANG Ling, JI Pei, XIE Yu-jie, LI Xin-feng, LI Zhi-gang, WANG Jian-ming
    2018, 17 (06): 1380-1390.   DOI: 10.1016/S2095-3119(18)61983-5
    Abstract447)      PDF in ScienceDirect      

    In order to clarify the main pathogens of tomato Fusarium wilt in Shanxi Province, China, morphological identification, elongation factor 1 alpha (EF-1α) sequence analysis, specific primer amplification and pathogenicity tests were applied to study the isolates which were recovered from diseased plants collected from 17 different districts of Shanxi Province.  The results were as follows: 1) Through morphological and molecular identification, the following 7 species of Fusarium were identified: F. oxysporum, F. solani, F. verticillioidesF. subglutinans, F. chlamydosporum, F. sporotrichioides, and F. semitectum; 2) 56 isolates of F. oxysporum were identified using specific primer amplification, among which, 29, 5 and 6 isolates were respectively identified as F. oxysporum f. sp. lycopersici physiological race 1, race 2, and race 3; 3) pathogenicity test indicated the significant pathogenicity of F. oxysporum, F. solani, F. verticillioides, and F. subglutinans to tomato plant.  Therefore, among these 4 species confirmed as pathogenic to tomato in Shanxi, the highest isolation rate (53.3%) corresponded to F. oxysporum.  Three physiological species, race 1, race 2, and race 3 of F. oxysporum f. sp. lycopersici are detected in Shanxi, among which race 1 is the most widespread pathogen and is also considered as the predominant race.

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    In field control of Botrytis cinerea by synergistic action of a fungicideand organic sanitizer
    Fatima Ayoub, Najwa Ben oujji, Mohamed Ayoub, Athman Hafidi, Rachid Salghi, Shehdeh Jodeh
    2018, 17 (06): 1401-1408.   DOI: 10.1016/S2095-3119(17)61875-6
    Abstract456)      PDF in ScienceDirect      
    A new Integrated Pest Management program based on the combination of synthetic pesticide with a GRAS (generally recognized as safe)-classified sanitizer for the control of Botrytis cinerea in field conditions was described.  The aim behind this research was to determine whether the use of this mixture would enhance the efficiency of pesticides while decreasing the recommended dose.  Naturally infected tomato plants, grown in the greenhouse, were treated with two commonly used fungicides SWITCH (Syngenta, Switzerland) and SIGNUM (BASF, Germany) each alone or combined with a commercially available organic sanitizer PERACLEAN®5 (Evonik Industries, Germany).  A total of 27 treatments were tested consisting of three concentrations of synthetic fungicide (×1, ×1/2 and ×1/4 of the recommended dose) either applied separately or combined with three concentrations of the tested sanitizer (0.5, 1 and 1.5%).  The control efficacy achieved by the fungicides applied alone ranged between 0 and 66.7% while all fungicide-sanitizer mixtures resulted in up to 70% control of grey mould.  The treatment that provides the maximum control of B. cinerea was the result mixture of ×1/4 of the recommended concentration of SWITCH (15 g L–1) with 0.5% of PERACLEAN®5.  This combination suppressed 85% of grey mold infections while decreasing the usually used amount of this pesticide by 75%, reducing therefore the well known negative impacts of chemical pesticides on environment and consumers health.
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    Germination and appressorium formation of Pyricularia oryzae Cavara can be inhibited by reduced concentration of Blasin®Flowable with carbon dioxide microbubbles
    Tamaki Masahiko, Kobayashi Fumiyuki, Suehiro Keisuke, Ohsato Shuichi, Sato Michio
    2018, 17 (09): 2024-2030.   DOI: 10.1016/S2095-3119(18)61962-8
    Abstract372)      PDF in ScienceDirect      
    We investigated the possibility to reduce the usage of Blasin®Flowable (BF), a disinfectant inhibiting the germination and appressorium formation of Pyricularia oryzae Cavara conidia, by using carbon dioxide microbubbles (CO2MB).  Germination was significantly inhibited by 10 000-fold diluted BF solution containing CO2MB generated by the decompression-type generator compared to CO2 millibubbles (CO2MMB) and CO2MB generated by the gas-water circulating-type generator.  Appressorium formation in the 10 000-fold diluted BF solution containing both CO2MBs was less than that in CO2MMB.  Scanning electron microscopy showed wrinkles and dents on the surface of conidia treated with 5 000-fold diluted BF solution containing both CO2MBs.  Via transmission electron microscopy, we observed the expansion of the vacuole and the intracellular space and bloated or absent lipid granules in the conidia treated with BF solution containing both CO2MBs.  Our results show that inhibition of the conidium germination and appressorium formation of P. oryzae Cavara by 10 000-fold diluted BF solution could be achieved by using the decompression-type CO2MB.
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    Conidia of one Fusarium solani isolate from a soybean-production field enable to be virulent to soybean and make soybean seedlings wilted
    ZHENG Na, ZHANG Liu-ping, GE Feng-yong, HUANG Wen-kun, KONG Ling-an, PENG De-liang, LIU Shi-ming
    2018, 17 (09): 2042-2053.   DOI: 10.1016/S2095-3119(17)61891-4
    Abstract348)      PDF (22206KB)(159)      
    Fusarium is usually thought to cause soybean root rot, which results in a large quantity of annual yield loss in soybean production, by its secretions including Fusarium toxins and cell wall degrading enzymes, but not by the conidia themselves that do not underlie any virulence so far.  Here we report that the conidia of one Fusarium solani isolate are able to be virulent to soybean and make soybean seedlings wilted alone.  We isolated them from the wilted plants in a soybean-production field and molecularly identified 17 Fusarium isolates through phylogenetic analysis.  Of them, except for one isolate that showed diversity of virulence to different soybeans (virulent to one soybean whereas avirulent to another soybean), the others were all virulent to the two tested soybeans: both conidia cultures and secretions could make soybean seedlings wilted at 5 days post infection, and their virulence had dosage effects that only conidia cultures of at least 5×106 conidia mL–1 could show virulence to soybean; however, the sole conidia of the F. solani isolate #4 also exhibited virulence to soybean and could make soybean seedlings wilted.  Finally, we developed the specific cleaved amplified polymorphic sequences (CAPS) markers to easily differentiate Fusarium isolates.  The isolate #4 in this work will likely be used to investigate the new mechanism of virulence of Fusarium to soybean.     
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    Effect of plant extracts on activity of some defense enzymes of apple fruit in interaction with Botrytis cinerea
    Jalal Gholamnezhad
    2019, 18 (1): 115-123.   DOI: 10.1016/S2095-3119(18)62104-5
    Abstract273)      PDF in ScienceDirect      
    The efficacy of seven plant extracts (neem, fennel, lavender, thyme, pennyroyal, salvia and asafetida) in controlling postharvest of apple (caused by Botrytis cinerea) was evaluated in vitro and in vivoIn vitro, all plant extracts treatments inhibited spore germination.  Inhibitory rates of pore germination was 17.41 and 20.83% for neem extract treatment (methanolic and aqueous extracts, respectively) with significant difference compared to control (73.6 and 85.33%) for aqueous and methanol extracts.  In the storage conditions, the application of aqueous extract of neem (at concentration of 25%) resulted in 89.11% reduction of disease severity compared with the untreated control.  Results of enzymes activity showed the plant extracts can increase the activity of peroxidase, phenylalanine ammonia-lyase, β-1,3-glucanase and polyphenol oxidase in the presence of pathogens, in apple fruits.  However, the results of this research revealed that application of neem extracts was more effective than the application of other plant extracts.  According to this study, it could be concluded that plant extracts may be useful to control postharvest disease as a safe alternative option to chemical fungicides. 
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    Soil application of Trichoderma asperellum GDFS1009 granules promotes growth and resistance to Fusarium graminearum in maize
    HE An-le, LIU Jia, WANG Xin-hua, ZHANG Quan-guo, SONG Wei, CHEN Jie
    2019, 18 (3): 599-607.   DOI: 10.1016/S2095-3119(18)62089-1
    Abstract174)      PDF (945KB)(200)      
    Of diseases affecting maize (Zea mays), Fusarium graminearum is one of the most common pathogenic fungi that cause stalk rot.  In the present study, the Trichoderma asperellum GDFS1009 strain was shown to be an effective biocontrol agent against stalk rot.  In a confrontation culture test, Trichoderma strain displayed an approximately 60% inhibition rate on the mycelial growth of F. graminearum.  In pot trials, the application of 2 g/pot of T. asperellum GDFS1009 granules had the best control effect on stalk rot at the seedling stage (up to 53.7%), while the average plant height and fresh weight were also significantly improved.  Additionally when fertilizer was added at 8 g/pot, the application of 3 g/pot of Trichoderma granules had the best control effect on maize stalk rot (40.95%).  In field trials, when inoculating F. graminearum alone, the disease index for inoculating was 62.45, but only 31.43 after treatment with T. asperellum GDFS1009 granules, suggesting a control efficiency of 49.67%.  Furthermore, in a naturally F. graminearum-infected field, Trichoderma granules, when applied for 3 consecutive years, showed significant control of stalk rot and increased yields.
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    Isolation and identification of Fusarium oxysporum f. sp. cubense in Fujian Province, China
    WU Kai-li, CHEN Wei-zhong, YANG Shuai, WEN Ya, ZHENG Yu-ru, Wilfred Mabeche Anjago, YUN Ying-zi, WANG Zong-hua
    2019, 18 (8): 1905-1913.   DOI: 10.1016/S2095-3119(18)62149-5
    Abstract172)      PDF in ScienceDirect      
    Fusarium wilt, caused by Fusarium oxyporum f. sp. cubense (Foc), is the most serious disease affecting banana production.  To clarify the distribution of the Foc races in Fujian Province of China, 79 soil samples were collected from four regions of Zhangzhou City, the primary banana production area in Fujian.  We isolated and identified 12 Foc strains based on internal transcribed spacer (ITS) sequence analysis, PCR amplification by using Foc-specific primers and pathogenicity assays.  Our analysis indicated that 11 isolates belong to Foc race 1, and 1 isolate belongs to the Foc tropical species race 4 (TR4).  Although TR4 has previously been reported to occur in primary banana-producing provinces, such as Hainan, Guangxi, and Guangdong of China, this is the first report of TR4 isolated from the soil in Fujian Province.  Monitoring the presence of Foc, in particular, the TR4 strains in the soil, is the basic strategy to prevent and control Fusarium wilt.
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    Combined application of Trichoderma harzianum SH2303 and difenoconazole-propiconazolein controlling Southern corn leaf blight disease caused by Cochliobolus heterostrophus in maize
    WANG Shao-qing, MA Jia, WANG Meng, WANG Xin-hua, LI Ya-qian, CHEN Jie
    2019, 18 (9): 2063-2071.   DOI: 10.1016/S2095-3119(19)62603-1
    Abstract104)      PDF in ScienceDirect      
    Southern corn leaf blight (SCLB) disease caused by Cochliobolus heterostrophus is one of the major threats to corn production worldwide.  The synergistic application of low toxic chemical fungicide and biocontrol agents could improve biocontrol stability and efficiency against plant diseases, which ultimately reduce use of chemical fungicide.  Trichoderma spp., well-known biocontrol fungi have been used to control some foliar diseases.  However, few works have been reported on synergistic application of chemical fungicide and Trichoderma against foliar diseases.  This study was aimed to investigate the control effect on the synergistic application of Trichoderma harzianum SH2303 and difenoconazole-propiconazole (DP) against SCLB.  Results showed that the synergistic application of DP and SH2303 reduced the leaf spot area compared to the control.  The efficacy of synergistic application of DP+SH2303 against SCLB could last for 15–20 d in pot trial under the greenhouse condition.  Under the natural field condition, maize treated with DP+DP and DP+SH2303 showed 60% control, which was higher than that of SH2303+DP (45%) and SH2303+SH2303 (35%).  All these treatments induced the synthesis of defense-related enzymes (phenylalanine ammonia lyase (PAL), catalase (CAT), and superoxide dismutase (SOD)) and the defence-related gene expression of SA pathway (PR1).  Taken together the in-vitro leaf test and field trial, the control of SCLB by synergistic application of DP+SH2303 was similar to that of DP+DP.  Among synergistic application, the sequential application of DP+SH2303 showed better control than the sequential application of SH2303+DP.  It was concluded that the synergistic application of chemical fungicide (DP) and biocontrol agent (T. harzianum SH2303) could be used to reduce the chemical fungicide and to reduce the SCLB diseases in maize, which provided alternative approach to realize an eco-friendly controlling of the foliar disease.
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    Fermentation, formulation and evaluation of PGPR Bacillus subtilis isolate as a bioagent for reducing occurrence of peanut soil-borne diseases
    Abdel-Gayed M. Ahmad, Abo-Zaid G. Attia, Matar S. Mohamed, Hafez E. Elsayed
    2019, 18 (9): 2080-2092.   DOI: 10.1016/S2095-3119(19)62578-5
    Abstract94)      PDF in ScienceDirect      
    Four isolates of Bacillus subtilis coded, B4, B7, B8 and B10 were examined as biocontrol agents for their abilities and antagonistic effect on the in vitro growth of certain phytopathogenic fungi of peanut, Rhizoctonia solani and Sclerotium rolfsii.  Bacillus subtilis isolate B4 (GenBank accession no. EF150884) was the highly effective one for inhibiting the fungal mycelial growth.  Batch fermentation of B. subtilis isolate B4 was carried out and the maximum biomass achieved was 4.53 g L–1 at 11 h.  Bacillus subtilis isolate B4 was formulated and evaluated as a biofungicide to reduce peanut soil-borne diseases under greenhouse and field conditions at the side of Rizolex-T (fungicide) as standard.  Treatments by formulated plant growth-promoting rhizobacteria (PGPR) B. subtilis B4 and Rizolex-T in a soil infested with R. solani, S. rolfsii and mixture of them were more effective in decreasing percentage of damping-off, root and pod rot disease incidence (%) in greenhouse and open field environment during the two seasons 2015 and 2016.  Treatments by PGPR gave highly dry weight and number of healthy pods compared to control of fungi treatment which was nearby to dry weights of healthy pods achieved by treatments by Rizolex-T in a soil infested with S. rolfsii, R. solani and mixture of them.  Formulated PGPR B. subtilis B4 gave higher increasing of yield percentage than treatment by Rizolex-T in the two evaluated seasons 2015 and 2016.  It can conclude that the produced bioforumlated agent was more efficient as fungicide when compared with the other chemical synthesized fungicides, safe for human and the environment and economy. 
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    Identification of three Berberis species as potential alternate hosts for Puccinia striiformis f. sp. tritici in wheat-growing regions of Xinjiang, China
    ZHUANG Hua, ZHAO Jing, HUANG Li-li, KANG Zhen-sheng, ZHAO Jie
    2019, 18 (12): 2786-2792.   DOI: 10.1016/S2095-3119(19)62709-7
    Abstract71)      PDF in ScienceDirect      
    Since the recent discovery of barberry (Berberis spp.) as an alternate host for the stripe rust pathogen Puccinia striiformis, many Chinese Berberis species have been identified as alternate hosts for P. striiformis f. sp. tritici.  However, little is known about Berberis species and their distribution in wheat-growing regions in Xinjiang, China, where stripe rust is endemic.  As the largest province or autonomous region, Xinjiang represents a relatively independent epidemic region for wheat stripe rust in China.  In this study, we conducted a survey of barberry plants in the main wheat-growing areas of Xinjiang.  We identified three Berberis species, B. heteropoda, B. nummularia and B. kaschgarica, and confirmed their roles as potential alternate hosts for P. striiformis f. sp. tritici in the laboratory. 
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    Screening of antagonistic Trichoderma strains and their application for controlling stalk rot in maize 
    LU Zhi-xiang, TU Guang-ping, ZHANG Ting, LI Ya-qian, WANG Xin-hua, Zhang Quan-guo, SONG Wei, CHEN Jie
    2020, 19 (1): 145-152.   DOI: 10.1016/S2095-3119(19)62734-6
    Abstract121)      PDF in ScienceDirect      
    Maize is one of the major crops in China, but maize stalk rot occurs nationwide and has become one of the major challenges in maize production in China.  In order to find an environment-friendly and feasible technology to control this disease, a Trichoderma-based biocontrol agent was selected.  Forty-eight strains with various inhibition activities to Fusarium graminearum, and Fusarium verticillioides were tested.  A group of Trichoderma strains (DLY31, SG3403, DLY1303 and GDFS1009) were found to provide an inhibition rate to pathogen growth in vitro of over 70%.  These strains also prevented pathogen infection over 65% and promoted the maize seedling growth for the main root in vivo by over 50%.  Due to its advantage in antifungal activity against pathogens and promotion activity to maize, Trichoderma asperellum GDSF1009 was selected as the most promising strain of the biocontrol agent in the Trichoderma spectrum.  Pot experiments showed that the Trichoderma agent at 2–3 g/pot could achieve the best control of seedling stalk rot and promotion of maize seedling growth.  In the field experiments, 8–10 g/hole was able to achieve over 65% control to stalk rot, and yield increased by 2–11%.  In the case of natural morbidity, the control efficiency ranged from 27.23 to 48.84%, and the rate of yield increase reached 11.70%, with a dosage of Trichoderma granules at 75 kg ha–1.  Based on these results, we concluded that the Trichoderma agent is a promising biocontrol approach to stalk rot in maize.
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    Bioinformatic analysis and functional characterization of the cfem proteins in maize anthracnose fungus Colletotrichum graminicola
    GONG An-dong, JING Zhong-ying, ZHANG Kai, TAN Qing-qun, WANG Guo-liang, LIU Wen-de
    2020, 19 (2): 541-550.   DOI: 10.1016/S2095-3119(19)62675-4
    Abstract105)      PDF in ScienceDirect      
    Fungal secreted proteins that contain the Common in Fungal Extracellular Membrane (CFEM) domain are important for pathogenicity.  The hemibiotrophic fungus Colletotrichum graminicola causes the serious anthracnose disease of maize.  In this study, we identified 24 CgCFEM proteins in the genome of C. graminicola.  Phylogenic analysis revealed that these 24 proteins (CgCFEM1–24) can be divided into 2 clades based on the presence of the trans-membrane domain.  Sequence alignment analysis indicated that the amino acids of the CFEM domain are highly conserved and contain 8 spaced cysteines, with the exception that CgCFEM1 and CgCFEM24 lack 1 and 2 cysteines, respectively.  Ten CgCFEM proteins with a signal peptide and without the trans-membrane domain were considered as candidate effectors and, thus were selected for structural prediction and functional analyses.  The CFEM domain in the candidate effectors can form a helical-basket structure homologous to the Csa2 protein in Candida albicans, which is responsible for haem acquisition and pathogenicity.  Subcellular localization analysis revealed that these effectors accumulate in the cell membrane, nucleus, and cytosolic bodies.  Additionally, 5 effectors, CgCFEM6, 7, 8, 9 and 15, can suppress the BAX-induced programmed cell death in Nicotiana benthamiana with or without the signal peptide.  These results demonstrate that these 10 CgCFEM candidate effectors with different structures and subcellular localizations in host cells may play important roles during the pathogenic processes on maize plants.
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    A new Curvularia lunata variety discovered in Huanghuaihai Region in China
    CHANG Jia-ying, LIU Shu-sen, SHI Jie, GUO Ning, ZHANG Hai-jian, CHEN Jie
    2020, 19 (2): 551-560.   DOI: 10.1016/S2095-3119(19)62655-9
    Abstract102)      PDF in ScienceDirect      
    The purpose of this study was to identify the dominant pathogens of Curvularia leaf spot and their pathogenicity variation in Huanghuaihai Region of China in recent years.  In 2013 and 2016–2017, the occurrences of Curvularia leaf spots on maize were investigated in fields located in Henan, Hebei, Shandong, and Anhui provinces, and 292 fungi were isolated from diseased leaves.  These fungal isolates were subjected to morphological identification, and 232 isolates were found to have about 70% uncurved conidia and were identified as Curvularia lunata var.  Most of the conidia of 2 representative isolates, namely, HNWB-131 and HNWB-185, were oblong with parallel septations and were distinctly different from a reference isolate CX-3.  For further determination, the internal transcribed spacer (ITS), glyceraldehyde 3-phosphate dehydrogenase (GPDH), the large subunit (LSU), and translation elongation factor 1-alpha (EF1-α) sequences of HNWB-131, HNWB-185, and CX-3 were amplified and sequenced.  The results of sequence analysis showed that the 4 gene sequences from the 3 isolates had a similarity of more than 99% to C. lunata.  Based on the sequences of ITS and the combined data of the 4 genes, neighbor-joining trees were constructed for phylogenetic analysis.  The results indicated that these 3 isolates were clustered together with C. lunata. The expression of Clg2p and ClUrase genes in mycelia and conidia was significantly (P<0.05) higher in CX-3 than in HNWB-131 and HNWB-185.  This study found that the dominant pathogen of Curvularia leaf spot was a new variety of C. lunata with morphological variations in Huanghuaihai Region from 2013 to 2017.  The pathogenicity of the C. lunata var. was not significantly enhanced, and the expression of Clg2p and ClUrase genes of C. lunata var. was decreased.
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    Functional analysis and screening small molecules to RpfF protein in Xanthomonas oryzae involved in rice bacterial blight disease
    Mundla SRILATHA, Naina PATYAL, Madhu Sudhana SADDALA
    2020, 19 (3): 735-747.   DOI: 10.1016/S2095-3119(19)62813-3
    Abstract91)      PDF in ScienceDirect      
    Xanthomonas oryzae pv. oryzae (Xoo) is an important rice pathogen.  This is a vascular pathogen entering the plant via the hydathodes causing rice bacterial blight.  It has been known that most regulation of pathogenicity factor F (RpfF) genes in Xanthomonas regulates virulence in response to the diffusible signal factor (DSF).  The RpfF recognized as an attractive drug target in bacterial rice blight disease.  In this study, we performed the gene-gene interaction of RpfF and pathway functional analysis.  3D structure of RpfF protein was predicted using a homology modelling tool Swiss-Model and refined by molecular dynamics (MD) simulation.  The refined model protein was predicted structural assessment using various tools such as PROCHECK, ERRAT, and VERIFY-3D.  We have collected 2 500 rifampicin analogues from Zinc Database by virtual screening.  The screened compounds were docked into the active site of the RpfF protein using AutoDock Vina in PyRx Virtual Screening Tool.  Furthermore, docking result and in silico ADMET analysis described that the compounds ZINC03056414, ZINC03205310, ZINC08673779, ZINC09100848, ZINC09729566, ZINC11415953, ZINC12810788, ZINC24989313, ZINC27441787 and ZINC32739565 have best binding energies and less toxicity than reference compound.  This study revealed that the active site residues such as HIS-118, HIS-147, THR-148, ARG-179, ASP-207, ARG-240 and THR-244 are key roles in the pathogenicity.  It could be beneficial in the design of small molecule therapeutics or the treatment of rice bacterial blight disease.
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    Bacterial extracts and bioformulates as a promising control of fruit body rot and root rot in avocado cv. Hass
    2020, 19 (3): 748-758.   DOI: 10.1016/S2095-3119(19)62720-6
    Abstract72)      PDF in ScienceDirect      
    At least 20–40% of annual losses of avocado crops are caused by pathogenic fungi.  The chemical treatments of these diseases are inefficient, cause environmental pollution and are increasingly restricted by international laws.  This work aimed to assess the biocontrol capacity of a bacterial extract to protect avocado fruits and plants from pathogen infections.  Extracts from the bacterial isolate Serratia sp. ARP5.1 were obtained from liquid fermentations in a biorreactor.  A body rot postharvest infection model with Colletotrichum gloeosporioides on fruits was developed.  Moreover, packaging conditions were simulated using the bacterial extract and the commercial fungicide prochloraz as a positive control.  Additionally, seedlings infections with Phytophthora cinnamomi were performed on two types of avocado (West Indian race and cv. Hass).  The Area Under Disease Progress Curve (AUDPC) was recorded using the bacterial extract and a commercial product with fosetyl-aluminium as treatments.  The bacterial extract significantly reduced infections by C. gloeosporioides on injured avocado fruits at 31.1 µg mL–1.  Intact fruits were also protected against body rot infections at the same concentration and showed no significant differences with the commercial fungicide.  On the other hand, AUDPC in the seedlings was significantly reduced with the extract treatment at 3 µg mL–1 compared to the control.  However, a possible phytotoxicity effect of the extract was evidenced in the seedlings and confirmed by pathogen recovery and tests on Raphanus sativus seedlings.  Finally, formulations of the extracts (emulsion and emulsifiable concentrate) were prepared, and bioactive stability was assessed for 8 wk.  The emulsion formulates demonstrated very stable bioactivity against P. cinnamomi.  The extract and the emulsion formulate showed promising results for the control of avocado pathogens.  New bioproducts based on this type of active principles could be developed for the benefit of avocado industry.
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    Regulation of the phytotoxic response of Arabidopsis thaliana to the Fusarium mycotoxin deoxynivalenol
    WANG Yan, YAN Hao, WANG Qi, ZHENG Ran, XIA Kai, LIU Yang
    2020, 19 (3): 759-767.   DOI: 10.1016/S2095-3119(19)62741-3
    Abstract82)      PDF in ScienceDirect      
    Phytopathogenic fungi, such as Fusarium spp., synthesize trichothecene family phytotoxins.  The type B trichothecene, namely deoxynivalenol (DON), is highly prevalent in small-grain cereals, such as wheat, corn and barley.  DON is thought to be a virulence factor allowing plant infections and has an elicitor activity.  We used the model plant Arabidopsis thaliana to evaluate the phytotoxic effects of DON in host plants.  The growth of A. thaliana on media was significantly inhibited by DON.  Moreover, DON induced cell death in detached leaves was observed by trypan blue staining.  This is consistent with the phenomenon of organelle changes observed at the ultrastructural level.  In our study, DON exposure stimulated oxidative bursts in the leaves, resulting in the concomitant down-regulation of antioxidant enzyme defense responses and up-regulation of lipid peroxidation.  In addition, a real-time PCR analysis revealed that the DON treatment rapidly induced the transcription of defense genes, like AtrbohC and AtrbohD, and up-regulated the transcriptional level of the ascorbic acid peroxidase gene.  These results suggested that DON phytotoxicity might result from reactive oxygen species pathways, and that DON production by the plant pathogen Fusarium graminearum can act as an elicitor influencing plant cell fate.
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    Rapid detection of potato late blight using a loop-mediated isothermal amplification assay
    KONG Liang, WANG Hui-bin, WANG Shuai-shuai, XU Ping-ping, ZHANG Ruo-fang, DONG Suo-meng, ZHENG Xiao-bo
    2020, 19 (5): 1274-1282.   DOI: 10.1016/S2095-3119(19)62816-9
    Abstract101)      PDF in ScienceDirect      
    Potato late blight caused by Phytophthora infestans is one of the most destructive plant diseases that threaten global food security.  Early and effective diagnosis of P. infestans is required before disease management decisions are made.  Here, we developed a quick protocol to detect P. infestans based on a loop-mediated isothermal amplification (LAMP) assay.  The P. infestans specific multiple copy DNA sequences (PiSMC), a transposon-like element, provides an ideal target for molecular detection of this pathogen.  We designed highly specific and sensitive primers allowing effective LAMP detection of the pathogen at 64°C in 70 min.  In the validation assay, all 15 P. infestans isolates collected from China, Europe and South America could be positively detected, but results of the other 9 Phytophthora species infecting different plants, fungal and bacterial plant pathogens tested were negative.  The detection limit of this assay is 1 pg P. infestans DNA.  Moreover, the LAMP-PiSMC assay is able to detect P. infestans from infected leaves, tubers and soil.  Taken together, this study reports the development of a specific and sensitive LAMP-PiSMC assay for early diagnosis of potato late blight.
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    FgHAT2 is involved in regulating vegetative growth, conidiation, DNA damage repair, DON production and virulence in Fusarium graminearum
    Lü Wu-yun, YANG Nan, XU Zhe, DAI Han, TANG Shuai, WANG Zheng-yi
    2020, 19 (7): 1813-1824.   DOI: 10.1016/S2095-3119(19)62819-4
    Abstract126)      PDF in ScienceDirect      
    Histone lysine acetylation is catalyzed by acetyltransferases (HATs), which is important in regulating gene expression and physiological function in eukaryotic cells.  HATs can be classified into two main types: A- and B-type HATs.  Recently, in Fusarium graminearum, it has been reported that A-type HATs are involved in hyphal development, conidiation, sexual reproduction and virulence.  However, the biological roles of B-type HATs are unknown.  Here we report the identification and characterization of two B-type HATs (FgHat1 and FgHat2) in F. graminearum.  Targeted deletion of FgHAT1 did not result in any detectable phenotypes.  However, ΔFghat2 mutants were severely defective in vegetative growth, conidia production and morphogenesis, deoxynivalenol (DON) biosynthesis and virulence.  Interestingly, deletion of FgHAT2 resulted in significantly increased sensitivity to the DNA-damaging agent methyl methanesulfonate (MMS).  Furthermore, double deletion mutants (ΔFghat1ΔFghat2) displayed similar phenotypes to the ΔFghat2 mutants.  Taken together, we conclude that FgHat2 but not FgHat1 plays essential roles in regulating morphogenesis, DNA damage repair, DON production and virulence in F. graminearum.
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    A LAMP-assay-based specific microbiota analysis reveals community dynamics and potential interactions of 13 major soybean root pathogens
    YE Wen-wu, ZENG Dan-dan, XU Miao, YANG Jin, MA Jia-xin, WANG Yuan-chao, ZHENG Xiao-bo
    2020, 19 (8): 2056-2063.   DOI: 10.1016/S2095-3119(19)62855-8
    Abstract114)      PDF in ScienceDirect      
    Soybean root diseases are associated with numerous fungal and oomycete pathogens; however, the community dynamics and interactions of these pathogens are largely unknown.  We performed 13 loop-mediated isothermal amplification (LAMP) assays that targeted specific soybean root pathogens, and traditional isolation assays.  A total of 159 samples were collected from three locations in the Huang-Huai-Hai region of China at three soybean growth stages (30, 60, and 90 days after planting) in 2016.  In LAMP results, we found that pathogen communities differed slightly among locations, but changed dramatically between soybean growth stages.  Phytophthora sojae, Rhizoctonia solani, and Fusarium oxysporum were most frequently detected at the early stage, whereas Phomopsis longicolla, Fusarium equiseti, and Fusarium virguliforme were most common in the later stages.  Most samples (86%) contained two to six pathogen species.  Interestingly, the less detectable species tended to exist in the samples containing more detected species, and some pathogens preferentially co-occurred in diseased tissue, including P. sojaeR. solaniF. oxysporum and F. virguliformeCalonectria ilicicola, implying potential interactions during infection.  The LAMP detection results were confirmed by traditional isolation methods.  The isolated strains exhibited different virulence to soybean, further implying a beneficial interaction among some pathogens.
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    Diversity in metagenomic sequences reveals new pathogenic fungus associated with smut in Job’s tears
    LI Xiang-dong, SHI Ming, PAN Hong, LU Xiu-juan, WEI Xin-yuan, LU Ping, LIAN Qi-xian, FU Yu-hua
    2020, 19 (9): 2257-2264.   DOI: 10.1016/S2095-3119(20)63164-1
    Abstract99)      PDF in ScienceDirect      
    Smut is a serious disease in Job’s tears, also known as adlay, and contributes to the reduction of crop yield in agricultural fields.  In this study, the key pathogenic fungi in adlay smut disease were first identified by internal transcribed spacer region (ITS) high-throughput sequencing and then used to elucidate the composition and diversity of the fungal community in adlay smut.  Results indicate that an abundance of operational taxonomic units (OTUs) were detected in the infected involucres of flowering plants and the OTUs were classified to nine phyla, 20 classes, 45 orders, 90 families and 119 genera.  A total of 4 986 OTUs clustered together, sharing six core OTUs in all samples, while 145 OTUs were shared among four geographical groups.  The Shannon and Simpson indices ranged from 0.137–1.629 and 0.357–0.970, respectively.  Community diversity ranked as Anshun (AS)>Qinglong (QL)>Xingren (XR)>Xingyi (XY) among the four geographical groups by Shannon and Simpson indices, exhibiting complex community diversities among accessions and geographical groups.  The richness and diversity data imply a weak relationship between the accession community richness and geographical origins of samples.  Two closely related fungal genera, Sporisorium and Ustilago, were implicated as causes of smut disease.  The genus Sporisorium appears to be more commonly found among accessions and thus is more likely to be the fungal pathogen causing smut in adlay.  This work can facilitate strategies to control and prevent smut infection to improve adlay yield.
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    First report of a new potato disease caused by Galactomyces candidum F12 in China
    SONG Su-qin, Lü Zhuo, WANG Jing, ZHU Jing, GU Mei-ying, TANG Qi-yong, ZHANG Zhi-dong, WANG Wei, ZHANG Li-juan, WANG Bo
    2020, 19 (10): 2470-2476.   DOI: 10.1016/S2095-3119(20)63257-9
    Abstract64)      PDF in ScienceDirect      
    Potato (Solanum tuberosum L.) is an important crop throughout the world.  An uncharacterized disease has been observed on potato plants during the growing season and tubers during the storage period from Nileke County, Qitai County and other locations in Xinjiang, China.  A particular fungus was consistently isolated from the infected potato plants and tubers.  Based on its morphology, molecular characteristics, pathogenicity test and internal transcribed spacer (ITS) sequence, the pathogens was identified as Galactomyces candidum F12.  Further study also showed that the hyphae and conidia of the pathogenic fungus grew faster as the temperature was 30°C, pH was 7, soluble starch was used as optimal carbon source and yeast powder as optimal nitrogen source.  In addition, 12-h continuous illumination light was beneficial to the hyphal growth, while 24-h continuous illumination was beneficial to the sporulation of the strain at 30°C.  To our knowledge, this is the first report of Galactomyces candidum causing leaf wilt and postharvest tuber rot on potato in China.
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    Functional characterization of the catalytic and bromodomain of FgGCN5 in development, DON production and virulence of Fusarium graminearum
    WANG Qian-nan, HUANG Pan-pan, ZHOU Shan-yue
    2020, 19 (10): 2477-2487.   DOI: 10.1016/S2095-3119(20)63219-1
    Abstract88)      PDF in ScienceDirect      
    FgGCN5, a GCN5 homolog in Fusarium graminearum, plays a critical role in hyphal vegetative growth, asexual and sexual reproduction, deoxynivalenol (DON) biosynthesis and plant infection.  For nuclear localized GCN5, four conserved sequence motifs (I–IV) are presented in the catalytic domain and a bromodomain in the carboxy-terminus.  As a lysine acetyltransferase, conserved negatively charged residues are present to neutralize the protons from lysine substrates.  However, the role of conserved motifs/domains and residues in FgGCN5 are unclear.  Here, we generated deletion mutant strains for each the conserved motifs/domains and a glutamate residue 130 (E130) replacement mutant.  Deletion of each conserved motif in the catalytic domain and replacement of E130 site resulted in manifold defects in hyphae growth, asexual and sexual development, DON biosynthesis, and plant infection.  Phenotypic defects in the mutant strains were similar to deletion mutants.  The deletion of the bromodomain led a significant reduction in DON production and virulence, with no effects on hyphae growth, asexual or sexual reproduction.  FgGCN5 was further found to localize to the nucleus in conidia and hyphae cells.  In conclusion, FgGCN5 encodes a nuclear localized acetyltransferase.  The conserved motifs in the catalytic domain and E130 are essential for correct functions of the gene.  The conserved bromodomain is important for DON production and pathogen virulence.  This was the first report to identify the functions of conserved motifs/domains in FgGCN5, which will contribute to our understanding of the mechanism(s) by which FgGCN5 regulates F. graminearum
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    A novel glycoside hydrolase 74 xyloglucanase CvGH74A is a virulence factor in Coniella vitis
    QIN Jia-xing, LI Bao-hua, ZHOU Shan-yue
    2020, 19 (11): 2725-2735.   DOI: 10.1016/S2095-3119(20)63254-3
    Abstract53)      PDF in ScienceDirect      
    Grape white rot is a destructive fungal disease occurring worldwide.  Recently, Coniella vitis was identified as the predominant pathogen causing this disease in China.  As the periderms of grape shoots are severely degraded by C. vitis, it was speculated that cell wall-degrading enzymes (CWDEs) might play a key role in the pathogenesis of this disease.  Therefore, this study aimed to examine the hydrolytic activity of the CWDEs of C. vitis.  The results showed that xylanase (Xy) and xyloglucanase (XEG) had high levels of hydrolytic activity both in vitro and in vivo.  Furthermore, a high-virulence fungal strain exhibited higher levels of Xy and XEG activities compared with a low-virulence strain.  The genome of the fungus was found to harbor two XEG-coding genes CvGH74A and CvGH74B, which belonged to the glycoside hydrolase (GH)74 family.  The expression level of CvGH74A was found to be high during pathogen infection.  CvGH74A gene deletion mutants were generated using the split-marker method.  The deletion of CvGH74A decreased both the hydrolytic activities of XEG and Xy and also the ability of the fungus to infect the grape leaves.  No differences in the hyphal growth, morphology of colonies, or conidiation were found between the ΔCvGH74A mutant strains and the wild-type strain.  Together, these results suggested that CvGH74A acted as an important virulence factor, and its enzymatic activity might regulate the virulence of the pathogen.  This study was novel in reporting that GH74 XEG acted as a virulence factor in C. vitis.
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    StKU80, a component in the NHEJ repair pathway, is involved in mycelial morphogenesis, conidiation, appressorium development, and oxidative stress reactions in Exserohilum turcicum
    GONG Xiao-dong, LIU Yu-wei, BI Huan-huan, YANG Xiao-rong, HAN Jian-min, DONG Jin-gao, GU Shou-qin
    2021, 20 (1): 147-158.   DOI: 10.1016/S2095-3119(20)63233-6
    Abstract75)      PDF in ScienceDirect      
    Homologous recombination (HR) and nonhomologous end joining (NHEJ) are considered the two main double-strand break (DSB) repair approaches in eukaryotes.  Inhibiting the activities of the key component in NHEJ commonly enhances the efficiency of targeted gene knockouts or affects growth and development in higher eukaryotes.  However, little is known about the roles of the NHEJ pathway in foliar pathogens.  Here we identified a gene designated StKU80, which encodes a putative DNA end-binding protein homologous to yeast Ku80, in the foliar pathogen Exserohilum turcicum.  Conserved domain analysis showed that the typical domains VWA, Ku78 and Ku-PK-bind are usually present in Ku70/80 proteins in eukaryotes and are also present in StKu80.  Phylogenetic analysis indicated that StKu80 is most closely related to Ku80 (XP_001802136.1) from Parastagonospora nodorum, followed by Ku80 (AGF90044.1) from Monascus ruber.  Furthermore, the gene knockout mutants ΔStKU80-1 and ΔStKU80-2 were obtained.  These mutants displayed longer septas, thinner cell walls, smaller amounts of substances on cell wall surfaces, and more mitochondria per cell than the wild-type (WT) strain but similar HT-toxin activity.  The mutants did not produce conidia and mature appressoria.  On the other hand, the mutants were highly sensitive to H2O2, but not to ultraviolet radiation.  In summary, the StKU80 plays devious roles in regulating the development of E.?turcicum.
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    The transcription factor FgNsf1 regulates fungal development, virulence and stress responses in Fusarium graminearum
    SHI Dong-ya, REN Wei-chao, WANG Jin, ZHANG Jie, Jane Ifunanya MBADIANYA, MAO Xue-wei, CHEN Chang-jun
    2021, 20 (8): 2156-2169.   DOI: 10.1016/S2095-3119(20)63339-1
    Abstract68)      PDF in ScienceDirect      
    Nutrient and stress factor 1 (Nsf1), a transcription factor containing the classical Cys2-His2 (C2H2) zinc finger motif, is expressed under non-fermentable carbon conditions and in response to salt stress in Saccharomyces cerevisiae.  However, the role of Nsf1 in filamentous fungi is not well understood.  In this study, the orthologue of Nsf1 was investigated in Fusarium graminearum (named FgNsf1), a causal agent of Fusarium head blight (FHB).  The functions of FgNsf1 were evaluated by constructing a FgNSF1 deletion mutant, designated as ΔFgNsf1, and its functional complementation mutant ΔFgNsf1-C.  Gene deletion experiments showed that the mycelial growth rate, asexual and sexual reproduction of ΔFgNsf1 were significantly reduced, but the pigment production of ΔFgNsf1 was remarkably increased compared with the PH-1 and ΔFgNsf1-C.  In addition, the tolerance of ΔFgNsf1 to osmotic pressures, cell wall-damaging agents and oxidative stress increased significantly.  Sensitivity tests to different fungicides revealed that ΔFgNsf1 exhibited increased sensitivity to carbendazim (MBC) and tebuconazole, and enhanced tolerance to fludioxonil and iprodione than PH-1 and ΔFgNsf1-C.  The virulence of ΔFgNsf1 to wheat coleoptiles and flowering wheat heads were dramatically decreased, which was consistent with the decrease in the yield of deoxynivalenol (DON).  All of these defects were restored by target gene complementation.  These results indicated that FgNsf1 plays a crucial role in vegetative growth, asexual and sexual reproduction, stress responses, fungicide sensitivity, and full virulence in F. graminearum.
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    Wheat straw biochar amendment suppresses tomato bacterial wilt caused by Ralstonia solanacearum: Potential effects of rhizosphere organic acids and amino acids
    TIAN Ji-hui, RAO Shuang, GAO Yang, LU Yang, CAI Kun-zheng
    2021, 20 (9): 2450-2462.   DOI: 10.1016/S2095-3119(20)63455-4
    Abstract84)      PDF in ScienceDirect      
    Complex interactions based on host plant, rhizosphere microorganisms and soil microenvironment are presumed to be responsible for the suppressive properties of biochar against soil-borne diseases, although the underlying mechanisms are not well understood.  This study is designed to evaluate the efficacy of biochar amendment for controlling tomato bacterial wilt caused by Ralstonia solanacearum, and to explore the interactions between biochar-induced changes in rhizosphere compound composition, the pathogen and tomato growth.  The results showed that biochar amendment decreased disease incidence by 61–78% and simultaneously improved plant growth.  The positive ‘biochar effect’ could be associated with enhanced microbial activity and alterations in the rhizosphere organic acid and amino acid composition.  Specifically, elevated rhizosphere citric acid and lysine, but reduced salicylic acid, were induced by biochar which improved microbial activity and rendered the rhizosphere unsuitable for the development of R. solanacearum.  In addition, nutrients which were either made more available by the stimulated microbial activity or supplied by the biochar could improve plant vigor and potentially enhance tomato resistance to diseases.  Our findings highlight that biochar’s ability to control tomato bacterial wilt could be associated with the alteration of the rhizosphere organic acid and amino acid composition, however, further research is required to verify these ‘biochar effects’ in field conditions.
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