Cassava (Manihot esculenta Crantz) is a vital food and energy crop in tropical regions, yet its yield is significantly threatened by cassava bacterial blight (CBB), caused by Xanthomonas axonopodis pv. manihotis (Xpm). Mildew resistance locus O (MLO) genes are known negative regulators of plant immunity, but their roles in cassava disease susceptibility remain unclear. In this study, we identified the MeMLO12 gene from cassava and investigated its function in response to Xpm infection. Subcellular localization revealed that MeMLO12 is specifically localized in the nucleus. Functional analysis via transient overexpression and virus-induced gene silencing (VIGS) demonstrated that MeMLO12 suppresses disease resistance: overexpression enhanced susceptibility to Xpm, while silencing conferred resistance. Furthermore, MeMLO12 modulated the expression of genes involved in jasmonic acid (JA) and salicylic acid (SA) signalling pathways, as well as reactive oxygen species (ROS) production and callose deposition, which are key components of plant innate immunity. These findings indicate that MeMLO12 acts as a susceptibility factor in cassava and may serve as a potential target for breeding bacterial blight-resistant varieties.

为对木薯细菌性萎蔫病菌 2个候选抗铜基因簇的功能进行验证和对病原菌抗铜机理进行分析,在进一步评价不同来源菌株抗铜性水平的基础上,开展 2个基因簇的克隆工作.结果表明,来自国内及密克罗尼西亚、马来西亚等国家的供试菌株对铜离子同样具有较高水平的抗性,不同国家的代表性菌株均编码有copTAB和XmeRSA两个抗铜基因簇.不同菌株的 2个基因簇具有高度同源性,分析其除参与抗铜代谢外,可能还和致病等其他保守功能相关.

Cassava (Manihot esculenta Crantz) is an important tropical tuber crop around the world. Cassava bacterial blight, caused by Xanthomonas phaseoli pv. manihotis, is a key disease that influences cassava production worldwide. Between 2008 and 2020, 50 X. phaseoli pv. manihotis strains were isolated from diseased plant samples or acquired from China, Uganda, Cambodia, Colombia, Malaysia, and Micronesia. Using multilocus sequence analysis, the genetic diversity of X. phaseoli pv. manihotis strains was evaluated. A neighbor-joining phylogenetic dendrogram was constructed based on partial sequences of five housekeeping genes (atpD-dnaK-gyrB-efp-rpoD). The strains clustered into three groups whose clusters were consistent with atpD and RpoD gene sequences. Group I contained 46 strains from China, Uganda, Cambodia, and Micronesia, and the other two groups were comprised of strains from Colombia and Malaysia, respectively. The resistance of all these strains to copper ion (Cu2+) was determined, the minimal inhibitory concentration was between 1.3 and 1.7 mM, and there was no significant difference between strains from different geographic region. During genome annotation of the X. phaseoli pv. manihotis strain CHN01, homologous gene clusters of copLAB and xmeRSA were identified. The predicted amino acid sequences of two gene clusters were highly homologous with the copper-resistant protein from Xanthomonas strains. CopLAB and xmeRSA were amplified from all these strains, suggesting that the regulation of copper resistance is associated with two distinct metabolic pathways. CopLAB and xmeRSA were highly conserved among strains from different geographic regions, possibly associated with other conserved function.

为明确国内木薯花叶病毒病(cassava mosaic virus disease)的危害情况、田间症状及其病原类型,本研究于2018—2019年调查了该病在国内的分布情况、症状特征及种质来源等数据,采集了8省(区)19地的384份样品,利用特异性引物检测2种木薯花叶病毒侵染引起的症状类型,并通过序列比对明确其病原特点.结果表明:木薯花叶病毒病已经在我国发生,种茎调运是该病远距离传播的主要原因;国内木薯花叶病毒病病原有斯里兰卡木薯花叶病毒株系(Sri Lankan cassava mosaic virus,SLCMV)和木薯普通花叶病毒(Cassava common mosaic virus,CsCMV)2种病毒,可分为单独感染、复合感染,其中SLCMV的检出率为21.1％,CsCMV的检出率为36.5％,SLCMV-CsCMV复合侵染率为15.1％;检测到的SLVMV与东南亚SLCMV序列同源性为99.4％～99.7％,检测到的CsCMV与拉丁美洲的CsCMV序列相似性为91％～96％.推测国内木薯花叶病毒病主要由2种病毒侵染引起,且普通花叶病毒有产生序列变异的可能性.

Cassava (Manihot esculenta Crantz) is a major staple food crop for more than a billion people in the world. Cassava mosaic virus (CMV), belonging to the Geminiviridae family, is a primary threat to cassava production. Sri Lankan cassava mosaic virus (SLCMV) is the only emergent CMV prevalent in South Asia and Southeast Asia since its identification in 2002. We reported the identification of two invasive strains of SLCMV, Col and HN7, in China in 2018. However, the occurrence and distribution of these known SLCMV strains and the presence of unknown geminivirus in China are still elusive. In this study, we firstly reported an improved CMV detection system based on molecular and serological methods, which was further used to determine the distribution of CMV in major cassava plantations in China. Two optimized PCR primer pairs based on the conserved regions of AV1 and AC1 genes were designed to detect different CMV species and distinguish SLCMV simultaneously. For a serological method, a polyclonal antibody against SLCMV AV1-encoded capsid protein was raised and used for enzyme-linked immunosorbent assay (ELISA). Consistent detection results were achieved by PCR- and ELISA-based methods. Among 62 examined samples collected in 2018, 10 were SLCMV positive, with 4 coinfection cases of two strains (HN7 and Col) in the same cassava plant. Two primer pairs could also be used to detect the presence of CMV in whitefly (Bemisia tabaci) sensitively. All positive samples were from Fujian and Hainan Provinces, indicating a limited distribution of SLCMV in cassava plants in China. Our detection methods could be used for future surveillance system to control and manage cassava mosaic disease in China and other countries.

木薯花叶病是由多种双生病毒引起的世界性木薯病害,已成为中国木薯产区发生普遍、危害较严重的病害之一.为明确怒江干热河谷区木薯各种质花叶病的发生危害情况,笔者采取踏查的方式对该区域木薯种质花叶病病株率、病情指数、烟粉虱种群数量进行调查.结果表明:2019年有42份种质发生花叶病,发病率在7.69％～100％,发病指数在1.67～40.00,烟粉虱种群数量高峰期集中在8月和9月,数量随着气温降低而减少;2020年有18份种质发生花叶病,发病率在1.69％～84.52％,发病指数在0.34～29.17;木薯主推品种均不抗花叶病,种茎带毒成为当年发病的主要侵染来源.调查结果可为下一步开展相关防控技术研究提供理论依据.

星油藤(Plukenetia volubilisL.)是一种重要的藤本油料植物,在我国华南地区广泛种植.青枯病是近两年在海南星油藤种植区发生的新病害,为探究星油藤青枯病菌的基本特性及种下分化情况,本研究对分离的6株代表菌株进行了相关分析.细菌学鉴定及致病性测定结果表明,该病害是由类茄科雷尔氏菌(Ralstonia pseudosolanacearum)侵染引起.同时,从传统分类及分子生物学不同层面分析了星油藤青枯病菌的遗传分化情况.生理小种及生化变种的测试结果表明,星油藤青枯病菌属于1号生理小种和生化变种Ⅲ;16S rDNA和egl基因部分序列聚类分析显示,星油藤青枯病菌属类茄科雷尔氏菌演化型Ⅰ即亚洲分支菌株,序列变种34.

HomePlant DiseaseVol. 103, No. 6First Report of Sri Lankan Cassava Mosaic Virus Infected Cassava in China PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Sri Lankan Cassava Mosaic Virus Infected Cassava in ChinaD. Wang, X. M. Yao, G. X. Huang, T. Shi, G. F. Wang, and J. YeD. WangState Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China; University of the Chinese Academy of Sciences, Beijing, China; and , X. M. YaoState Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China; , G. X. HuangEnvironment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan, China, T. ShiEnvironment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan, China, G. F. WangEnvironment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan, China, and J. Ye†Corresponding author: J. Ye; E-mail Address: jianye@im.ac.cnhttp://orcid.org/0000-0002-7741-4354State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China; University of the Chinese Academy of Sciences, Beijing, China; and AffiliationsAuthors and Affiliations D. Wang1 2 X. M. Yao1 G. X. Huang3 T. Shi3 G. F. Wang3 J. Ye1 2 † 1State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China; 2University of the Chinese Academy of Sciences, Beijing, China; and 3Environment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan, China Published Online:25 Mar 2019https://doi.org/10.1094/PDIS-09-18-1590-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Cassava (Manihot esculenta Crantz, family Euphorbiaceae) is a tropical food crop for about a fifth of the world's population and one of the most efficient crops for converting solar energy to produce carbohydrates. China is the world's largest importer of cassava, mainly from Southeast Asian countries, such as Cambodia, Vietnam, Thailand, and Indonesia. Cassava production can be severely affected by cassava mosaic disease (CMD) caused by cassava mosaic geminiviruses (CMGs). In Southeast Asia, the first CMG was reported on a Euphorbiaceae plant, Jatropha curcas, in Singapore in 2013 (Wang et al. 2014) and later on cassava in Cambodia (Wang et al. 2016). In January 2017, several yellow-green mosaic and severe curling cassava plants were observed in a germplasm garden in Haikou, Hainan, China (E110.11, N20.02). In May 2018, yellow-green mosaic, curling, malformations, and size reduction symptoms were also observed from two other cassava germplasm gardens in Datian, Fujian Providence (E117.85, N25.69) and Liupo, Hainan Providence (E109.50, N19.51). Cassava (cultivar Limin) leaf DNA was extracted from each of the six samples of three cassava germplasm gardens with a DNeasy plant Mini Kit (Qiagen, Germany). The universal primers PA/PB (PA, 5′-TAATATTACCKGWKGVCCSC-3′; PB, 5′-TGGACYTTRCAWGGBCCTTCACA-3′) (Deng et al. 1994) were used to detect whether the plants were infected by geminiviruses, but no amplification of the expected size (520 bp) was obtained. Because these CMD plants originated from cassava stem cutting materials imported from Cambodia and propagated and distributed in China, polymerase chain reaction (PCR) was further performed using Sri Lankan cassava mosaic virus (SLCMV)-specific primers (Dutt et al. 2005; Wang et al. 2016) to amplify and clone the genomic components. All amplicons generated from 18 leaf samples of three germplasm gardens were sequenced and have totally identical sequences of DNA-A and DNA-B (GenBank accession nos. MH891840 and MH891841). The complete nucleotide sequences of the infectious DNA-A and DNA-B are 2,760 and 2,737 nucleotides in length, respectively. We performed pairwise sequence analysis of the SLCMV DNA-A with those of all known geminiviruses. The highest nucleotide sequence identity (99.9%) was found with the SLCMV Cambodia isolate SLCMV DNA-A segment (KT861468.1). The complete sequence of the DNA-B shares 99.6% nucleotide sequence identity with the corresponding genome components of the SLCMV Cambodia isolate DNA-B segment (KT861469.1). These data suggest that the causal pathogen of this cassava disease in China is an isolate of SLCMV according to currently accepted criteria, and accordingly, we named the isolate as Sri Lankan cassava mosaic virus-HN7. For further confirmation of virus infection on the symptomatic cassava, nonviruliferous whiteflies Bemisia tabaci MEAM1 (Middle East-Minor 1, formerly biotype B) were allowed to feed on one diseased cassava for 48 h. Six viruliferous whiteflies were transferred onto tomato (Solanum lycopersicum, Moneymaker) or Arabidopsis thaliana (Col-0) for 72 h. The presence of SLCMV-HN7 on both the recipient tomato and Arabidopsis plants were doubly confirmed by SLCMV-specific primers based on the PCR and sequencing methods used in Wang et al. (2014). The detection primers for DNA-A (AF/AR) and DNA-B (BF/BR) of SLCMV-HN7 are AF, 5′-ATCATTTCAACTCCCGCCTCGAAG-3′; AR, 5′- CACGCCATGTACAGCATCAATGCA-3′; BF, 5′-ATTTGGATCCTATTAGACTTGGG-3′; and BR, 5′-TAATAGGATCCAAATCCATGAGAT-3′. Therefore, we confirmed that SLCMV is a causal agent for CMD in three locations in China. To our knowledge, this is the first report in China of CMD, its probable origins being Cambodia.References:Deng, D., et al. 1994. Ann. Appl. Biol. 125:327. https://doi.org/10.1111/j.1744-7348.1994.tb04973.x Crossref, ISI, Google ScholarDutt, N., et al. 2005. Arch. Virol. 150:2101. https://doi.org/10.1007/s00705-005-0579-9 Crossref, ISI, Google ScholarWang, G., et al. 2014. Virus Genes 48:402. https://doi.org/10.1007/s11262-014-1034-3 Crossref, ISI, Google ScholarWang, H. L., et al. 2016. Plant Dis. 100:1029. https://doi.org/10.1094/PDIS-10-15-1228-PDN Link, ISI, Google ScholarFunding: Funding was provided by National Natural Science Foundation of China (grant nos. 31522046, 31672001, 31830073).DetailsFiguresLiterature CitedRelated Vol. 103, No. 6 June 2019SubscribeISSN:0191-2917e-ISSN:1943-7692 DownloadCaptionGreen mottle mosaic and leaf deformation symptoms on watermelon (Sui, Li, Shamimuzzaman, Wu, and Ling). Photo credit: K.-S. Ling. Postharvest rot on cucumber caused by Ceratocystis fimbriata (Li, Xu, Zhang, Song, Xie, Sun, and Huang). Photo credit: H. Song. Metrics Article History Issue Date: 6 Jun 2019Published: 25 Mar 2019First Look: 17 Dec 2018Accepted: 10 Dec 2018 Page: 1437 Information© 2019 The American Phytopathological SocietyFundingNational Natural Science Foundation of ChinaGrant/Award Number: 31522046, 31672001, 31830073Cited byDynamic analysis and bifurcation control of a fractional-order cassava mosaic disease model1 November 2022 | Journal of Applied Mathematics and Computing, Vol. 6Mitochondrial Genetic Diversity of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) Associated with Cassava in Lao PDR22 September 2022 | Insects, Vol. 13, No. 10Possible incursion of cassava virus diseases: risks and potential threats to the Philippine cassava industry5 September 2022 | Archives of Phytopathology and Plant Protection, Vol. 55, No. 15Susceptibility of Cassava Varieties to Disease Caused by Sri Lankan Cassava Mosaic Virus and Impacts on Yield by Use of Asymptomatic and Virus-Free Planting Material12 July 2022 | Agronomy, Vol. 12, No. 7Cassava mosaic disease and its management in Southeast Asia9 July 2021 | Plant Molecular Biology, Vol. 109, No. 3Evaluation of manihot glaziovii scion-cassava understock grafting for cassava growth and root yield during rainy and dry seasons13 June 2021 | Journal of Crop Improvement, Vol. 36, No. 2Development of a triple antibody sandwich enzyme-linked immunosorbent assay for cassava mosaic disease detection using a monoclonal antibody to Sri Lankan cassava mosaic virus18 May 2021 | Virology Journal, Vol. 18, No. 1A New Type of Satellite Associated with Cassava Mosaic BegomovirusesJournal of Virology, Vol. 95, No. 21Identifying New Resistance to Cassava Mosaic Disease and Validating Markers for the CMD2 Locus30 August 2021 | Agriculture, Vol. 11, No. 9Interspecies Recombination Has Driven the Macroevolution of Cassava Mosaic BegomovirusesJournal of Virology, Vol. 95, No. 17Bemisia tabaci Vesicle-Associated Membrane Protein 2 Interacts with Begomoviruses and Plays a Role in Virus Acquisition5 July 2021 | Cells, Vol. 10, No. 7Plant Defense Networks against Insect-Borne PathogensTrends in Plant Science, Vol. 26, No. 3Conversion and Validation of Uniplex SNP Markers for Selection of Resistance to Cassava Mosaic Disease in Cassava Breeding Programs25 February 2021 | Agronomy, Vol. 11, No. 3Assessing the diversity of whiteflies infesting cassava in Brazil15 July 2021 | PeerJ, Vol. 9Surveillance and distribution of the emergent Sri Lankan cassava mosaic virus in China3 August 2020 | Phytopathology Research, Vol. 2, No. 1Surveillance and diagnostics of the emergent Sri Lankan cassava mosaic virus (Fam. Geminiviridae) in Southeast AsiaVirus Research, Vol. 285First Report of Cassava common mosaic virus Infecting Cassava in Mainland ChinaD. C. Tuo, G. Y. Zhao, P. Yan, R. M. Li, X. Chen, W. Q. Wang, X. Y. Li, Y. Yao, H. G. Cui, W. T. Shen, and P. Zhou22 January 2020 | Plant Disease, Vol. 104, No. 3An efficient method of propagating cassava plants using aeroponic culture12 October 2019 | Journal of Crop Improvement, Vol. 34, No. 1A 7-Amino-Acid Motif of Rep Protein Essential for Virulence Is Critical for Triggering Host Defense Against Sri Lankan Cassava Mosaic VirusDuan Wang, Xuan Zhang, Xiangmei Yao, Peng Zhang, Rongxiang Fang, and Jian Ye11 November 2019 | Molecular Plant-Microbe Interactions, Vol. 33, No. 1

2016-2018年,笔者对柬埔寨木薯主栽区病害进行了调查.普查结果表明,花叶病、褐斑病、细菌性萎蔫病、丛枝病、炭疽病和根腐病是当地木薯种植中的主要病害.花叶病是为害最为严重的病害,而褐斑病发生面积最大.调查了引种至当地的中国木薯主栽品种发病情况,发现华南系列、桂热系列等品种均受花叶病严重为害.分子鉴定结果表明,引起当地花叶病的病原为斯里兰卡木薯花叶病毒株系.

2014年9月至2015年2月,笔者作为中国技术顾问参与了中英非农业合作项目,赴乌干达负责木薯种植方面工作.通过实地考察以及和乌干达农牧渔业部、国家农业研究组织、非洲创新研究所、马克累累大学等相关机构专家的交流,对木薯相关产业进行了初步调研,同时,开展了木薯主产区的病害联合调查,发现花叶病、褐条病、细菌性萎蔫病、褐斑病等为当地主要病害.

褐斑病是世界木薯种植中的常见病害,也是危害中国木薯的重要病害.在前期工作基础上,2011—2018年,笔者们对中国木薯主栽区开展了褐斑病的普查及发生规律研究工作.结果表明,褐斑病在中国木薯主要种植区域均有发生,部分地区发病严重,主栽品种均不具备抗病性.2地点3木薯品种的3年系统病情调查结果表明,病害通常在木薯生长中期发生,随后逐渐加重,中后期流行为害.田间试验结果表明,咪鲜胺、多菌灵、丙环唑、保叶清等杀菌剂对褐斑病的危害有较好的减轻作用,建议在生产中推广应用.

Sacha inchi (Plukenetia volubilis L.) is a little-known yet important perennial plant native to the Andes Mountains of Peru. It is a plant producing large, edible seeds rich in omega-3 fatty acids and proteins useful for promoting human health. The economic importance of sacha inchi has increased in recent years because its seeds produce significantly higher oil yields than those of other plants (Wong 2018). Sacha inchi was first introduced to grow in Xishuangbanna, Yunnan Province, southwest China in 2006, and then to Lingshui County, Hainan Province, southern China in 2014. However, just 2 years later, in April 2016, unusual wilting was observed on many sacha inchi plants in the fields of Lingshui County. The disease outbreak proved to be rapid and extensive, covering approximately 11 ha of sacha inchi growth and causing an 80% production loss in that crop’s area in just a few months. By 2017, the farmers had almost given up on continuing sacha inchi production owing to the severity and spread of this disease. In the fields, the disease caused the plant’s stem and leaves to wilt. On seedlings, their leaves wilted and drooped while still being photosynthetically active (i.e., green), followed by total plant collapse within a few days. Mature plants initially had symptoms of irregular, black necrotic lesions at their leaf base margins. But as the disease symptoms progressed, the necrotic leaves spread upward, and eventually the affected plants turned chlorotic and shed leaves and developed black stripes on their stems. Vascular necrosis and bacterial ooze were observed when longitudinal sections were obtained from the basal portion of infected stems. For identification, a total of 10 plants with the typical wilting symptoms were collected from the sacha inchi fields of Lingshui County. Six isolates were obtained from the roots and plantlets of six separate plants. All the isolates were gram negative, oblong to rod shaped, and 0.4 to 0.9 × 0.7 to 2.0 μm in size (n = 25) when viewed under electron microscopy. When cultured on Kelman’s tetrazolium chloride medium, the colonies appeared round to oval, fluidal, and entirely white with a pale red center after incubation at 30°C for 48 h. Three Ralstonia solanacearum-specific primer pairs, for the flagella subunit (Rsol_fliC-F/ Rsol_fliC-R) (Schonfeld et al. 2003), the polygalacturonase gene (pehA #3/ pehA #6) (Gillings et al. 1993), and 759/760 (Ito et al. 1998) yielded the expected amplicons. Two representative strains (ACCC60145 plu-3 and ACCC60146 plu-6) were identified as R. pseudosolanacearum phylotype I, sequevar 34, according to the phylotype-specific multiplex polymerase chain reaction (PCR) assay (Fegan and Prior 2005) and phylogenetic analysis of the partial egl gene sequences (GenBank accession nos. KY352419 and KY352421) (Safni et al. 2014). The two strains shared 99.9 and 100% sequence identity with R. pseudosolanacearum GMI1000 (AL646052), which had been identified using 16S ribosomal RNA (GenBank accession nos. KY346975 and KY346977) sequencing and sequence comparisons. For the pathogenicity test, stems of 30 1-month-old sacha inchi (cv. Pinto Recodo) seedlings were injected with 40-μl suspensions (10⁸ CFU/ml) of the representative isolates ACCC60145 plu-3 and ACCC60146 plu-6 (10 seedlings per isolate inoculation treatment). The injection point on the seedling stem was at 2 to 3 cm above the soil surface. Symptoms of wilt were observed 5 days after these inoculations of sacha inchi. To serve as a negative control, 20 healthy sacha inchi seedlings were likewise injected but with sterile water. No disease symptoms were observed on these control plants. Reisolations were done twice, as outlined above, on the symptomatic seedlings and control plants at 3 to 4 cm above the original injection points. To complete Koch’s postulates, the bacteria were then reisolated from the inoculated sacha inchi plants and reidentified by PCR. Following the same inoculation procedure, the bacterium also caused wilting in cherry tomato (Lycopersicon esculentum Mill.; 20 of 20 individuals), eggplant (Solanum melongena L. var. esculentum Nees.; 17 of 20), and pepper (Capsicum annuum var. conoide Mill. Irish; 18 of 20). To the best of our knowledge, this is the first report of R. pseudosolanacearum phylotype I sequevar 34 causing bacterial wilt of sacha inchi in China and around the world. These disease strain findings can be useful for developing effective strategies for control of the disease in the important oil and seed plant sacha inchi.

2007—2018年,本课题组在对中国木薯主栽区的病害调查中发现了一种国内尚未记载的叶斑病.病害主要危害叶片,形成圆形或不规则形、常密集分布的白色至黄褐色的病斑,故命名为白点病.该病在云南、海南、广西等地区均有发生,绝大多数主栽品种和部分新育成种质均受害.经病菌分离和回接实验以及病菌形态观察、核糖体基因间隔区和β-微管蛋白基因序列分析,将该病病原鉴定为链格孢(Alternaria alternata).病菌离体培养实验表明,菌丝生长最适条件为V9、OA、CA或CMA培养基,28℃,D-麦芽糖、D-山梨醇或D-乳糖,硝酸钠,光暗交替,pH 8.分生孢子萌发最适温度为28℃,而致死温度为60℃处理5 min.杀菌剂敏感性测定结果表明,在所测试的10种药剂中,10％苯醚甲环唑WG和25％吡唑醚菌酯WG的EC50值分别为0.12、0.47 mg/L,对菌丝生长抑制率最高.

NAC(NAM/ATAF/CUC)基因家族是广泛分布于陆生植物的一类转录因子,在植物生长发育和胁迫应答的调控中发挥重要作用.本文对该基因家族在木薯抗细菌性萎蔫病方面的作用机制进行了初步研究.采用RT-PCR技术从木薯cDNA中克隆了MeNAC29和MeNAC30基因,并采用qRT-PCR技术对抗、感种质受木薯萎蔫病菌(Xanthomonas axonopodis pv.manihotis,Xam)侵染后2个基因的表达变化进行了定量分析.结果表明,2个基因均含有3个外显子和2个内含子,且均有保守的NAM结构域.MeNAC29基因的开放阅读框全长888 nt,编码295 aa.MeNAC30基因的开放阅读框全长870 nt,编码289 aa.接种木薯萎蔫病菌后,抗病种质中MeNAC29和MeNAC30基因的表达量显著高于感病品种,表明这2个基因参与了木薯对细菌性萎蔫病菌的抗性反应.

由地毯草黄单胞木薯萎蔫致病变种引起的细菌性萎蔫病是国内木薯种植中危害最严重的病害.在前期工作基础上,本研究评价了4种新型药剂对细菌性萎蔫病的防治作用.室内毒力测定结果表明,炭特灵(25％溴菌腈EC)、乙蒜素(80％乙蒜素EC)和氨基乙蒜素(5％氨基寡糖素·20％乙蒜素ME)对不同来源的菌株有较好的抑菌作用,碧生(20％噻唑锌SC)效果较差,而海岛素(5％氨基寡糖素AS)效果最差.4个主栽品种的田间试验结果表明,碧生(20％噻唑锌SC)和乙蒜素(80％乙蒜素EC)防效最好,其次为炭特灵(25％溴菌腈EC)和氨基乙蒜素(5％氨基寡糖素·20％乙蒜素),而海岛素(5％氨基寡糖素AS)相对较差.

Fusaric acid (FA) is highly phytotoxic and causes severe Fusarium oxysporum-induced vascular wilt. However, the molecular mechanisms of FA production in Fusarium oxysporum f. sp. cubense (FOC) are largely unknown. In this study, FoFUB4, a F. verticillioides FUB4 homolog was cloned from banana pathogenic fungus FOC and its deletion mutants were generated using homologous recombination. Our null mutation results showed that FoFUB4 did not affect fungal development and conidiation, but was essential for virulence on banana plantlets compared with wild type (WT) strain. Biochemical analysis showed that production of FA was not detected in mutant ΔFoFUB4 and FA production by WT was significantly reduced in Czapek Dox medium containing 6 compared with 120 mM NaNO3. Moreover, transcriptional analysis indicated that the expression levels of FoFUB4 were reduced in WT in Czapek Dox medium containing 6 compared with 120 mM NaNO3. Taken together, these results provide direct evidence for the vital roles of FA in virulence, and that nitrogen source regulated FA biosynthesis in FOC.

Three types of compound microbial fertilizer, CMF1, CMF2 and CMF3, were prepared from Bacillus subtilis BLG010 and Paecilomyces lilacinus E16 which could control Fusarium wilt of banana, and were used for pot culture trial to observe the effect of CMF1, CMF2 and CMF3 on disease incidence of Fusarium wilt, banana growth index, and colonization of Fusarium oxysporum f. sp. cubense (FOC), B. subtilis BLG010 and P. lilacinus E16 in banana rhizosphere. The results showed that treatments CMF1, CMF and CMF3 reduced significantly the disease incidence of Fusarium wilt to 60.00％, 44.44％ and 26.67％, respectively. Compared with control, the CMF1, CMF and CMF3 treatments could promote the biomass of banana, the plant height, the stem thickness, the fresh weight of aerial and underground part of banana by 24.46％～44.80％, 40.17％～101.43％, 18.78％～47.06％ and 75.88％～109.11％, respectively, reduced the number of FOC by 11.57％～49.07％ and increased colonization of BLG010 and E16 in the rhizosphere by 27.55％and 32.80％, respectively. The confocal laser scanning microscope showed that the volume and the fluorescence intensity of FOC were reduced. The correlation analysis showed that the number of FOC was positively correlated with the disease incidence, and that the number of BLG010 was positively correlated with the number of E16. Compound microbial fertilizer could not only increase the controlling effect on Fusarium wilt of banana, but also promote the growth of banana and the number of antagonistic strains, indicating a wide application prospect.

为探讨枯草芽孢杆菌对甜瓜白粉病的田间防控效果,以50％嘧菌酯水分散粒剂为对照,在甜瓜白粉病初期喷施不同浓度的200亿个活芽孢/g枯草芽孢杆菌可湿性粉剂.调查应用效果发现,该枯草芽孢杆菌制剂与嘧菌酯防效相当.施药处理后14 d,200亿个活芽孢/g枯草芽孢杆菌可湿性粉剂100倍液和500倍液对甜瓜白粉病的防效分别达96.72％和81.40％;对甜瓜株高、叶面横径、叶面纵径、果实横径、果实纵径和果实糖度指标的促生作用分别达24.28％～31.78％、36.85％～50.08％、42.42％～52.21％、61.14％～69.14％、39.58％～49.12％、23.29％～29.86％.

依据不同科属作物生态生理功能差异,检验了环境友好型跨年度瓜菜(辣椒、南瓜和芥菜)—香蕉轮作+花生间作提升土壤微生物多样性的影响.结果表明,跨年度轮作间作显著地提升了土壤可培养微生物细菌和放线菌群落,降低了真菌数量.土壤微生物高通量测序显示所有香蕉+花生间作系统Shannon生物多样性指数显著提升.花生覆盖地表保持水分和抑制杂草是间作提高土壤细菌和放线菌数量的影响因素.还田秸秆助长微生物.辣椒还田生物量高于南瓜和芥菜.因而,辣椒—香蕉+花生不同科属作物的协同作用可以更有效地提升土壤微生物多样性.