辽西北半干旱地区枣树四大病害防治关键技术

辽西北半干旱地区光照充足,是栽植枣的优势区域,近年来发展速度很快,仅朝阳市就达到0.2万hm2。但是与之相应的枣树病害也随之严重发生。文章简述了辽西地区枣树枣疯病、枣锈病、枣缩果病和枣树黄化病等四大病害的系统防治技术。     

枣疯病和枣缩果病研究进展

枣树是山区丘陵区发展农村经济的支柱产业。但近年来因栽培区生态变化、感病寄主增加和管理较粗放等原因,枣树病害发生严重。本文介绍了枣疯病和枣缩果病研究进展以及防治技术。     

抗枣疯病枣树品种及品系的选择

测定了6个枣树品种的1个酸枣品种对枣疯病的抗性及河北太行山区主栽品种婆枣的45个单株对枣疯病的抗性。利用连续两年嫁接病皮的方法测定了采自山西果树研究所中国枣树基因库的5个枣树品种砘子枣、马牙枣、长红枣、哈蟆枣、壶瓶枣及河北唐县的婆枣和酸枣两个品种的抗病性。通过四年的跟踪观察，以上7种枣树的发病率分别是100％、78．5％、66．67％、0％、0％、100％、80％。结果表明，壶瓶枣和蛤蟆枣对枣疯病具有高度抗性。利用连续3年2次嫁接病皮和1次嫁接病枝的方法测定了采自河北太行山区七县的婆枣45个单株112株根蘖苗的抗病性，经4年观测，结果有3个单株6根蘖苗经过三次测定苗木未疯，表现出了很强的抗性。     

陕西清涧县枣疯病发生和危害调查及防治建议

根据对陕西清涧县枣疯病发生特点和危害状况进行调查和分析,提出了把好种苗带菌关、积极预防介体叶蝉传病、稳步地开展枣疯病治疗试验和示范、坚持因地适时清除病株或修除病枝,正确处理好枣果产量与枣疯病防治的关系等具体病害防治措施,以及黄土高原地区枣疯病综合治理原则。     

山西省枣树主要病虫害及防治历

山西省是我国枣的主产区之一,近年来因栽培生态的变化、感病寄主的增加和管理较粗放等原因,枣树病虫害发生严重。据调查研究,主要虫害有：枣尺蠖、枣粘虫、枣芽象甲、枣瘿蚊、枣龟蜡蚧、桃小食心虫,主要病害有：枣锈病、枣疯病、缩果病、枣黑顶病。最后针对各病虫害的发生规律,提出了枣树主要病虫害防治历。     

枣疯病的研究现状

枣疯病是枣树的毁灭性病害,在我省陕北、关中等枣区有日趋严重之势。该病症状为萎黄丛生及花、叶畸形,其病原为类茵原体(MLO)。除可通过嫁接传病外,中华拟菱纹叶蝉、凹缘菱纹叶蝉和红闪小叶蝉是三种重要的传病媒介昆虫。枣疯病的发生还与枣树的品种、枣园的土壤、海拔、坡向等有关。枣疯病的防治途径有药物治疗、砍疯枝、铲病株、热处理脱毒等,但以培育抗病品种、选育无病苗木和加强栽培管理、增强树势为其根本的防治措施。     

枣区枣疯病发生情况调查及防治建议

枣疯病是枣树毁灭性病害,由枣疯病植原体引起。针对河南省新郑、濮阳、镇平、灵宝、永城等县(市)枣区的枣疯病发生情况进行调查,发现新郑枣区发病情况较为严重,放任枣园较枣粮间作和集约管理的枣园发病严重。分析发病的原因,主要是疏于管理,导致树体营养失衡,抗性减弱,媒介昆虫增多,加速病原传播,防治措施缺乏,病树得不到处理造成的。建议采取平衡施肥,改善树势,做好枣园植被管理,防治害虫,防止病害传播,及时修剪,消除病原等措施,开展枣疯病综合防治。     

我国部分枣树品种(系)的枣疯病抗性鉴定

收集了我国部分地区的不同枣树品种(系)的休眠期健康接穗材料,于2009年和2010年的4-6月嫁接到枣疯病砧木上,定期检查接穗发病状况,并采用PCR技术检测植原体感染.结果显示,不同枣树品种对枣疯病的抗性差异明显,根据接穗发病早晚、症状轻重、发病率和病情指数,将测定品种分为5个类型,其中高度抗病品系2个、中度抗病品系4个、一般抗病品系15个、感病品系7个、高度感病品系6个.高抗品系(交城骏枣、唐县和太原壶瓶枣)嫁接当年萌生枝条枣疯病无明显症状或嫁接早期无症状,后期症状较轻.嫁接到病树遮阴部位的接穗发病程度要重于向阳部位;存放期长和嫁接时间早的接穗,易诱发抗性品系发病.巢式PCR能检测到无症抗病接穗内低浓度植原体侵染.与以往所采用的昆虫自然传染和病皮或病枝嫁接到待鉴定的砧木品系上鉴定抗性技术相比,该方法具有接种强度大、诱导发病快、测定方法简便等优点,但对一般抗性、整株或成年株抗性、抗介体传毒等类型的抗性鉴定有局限性.     

太原市王家坟村提供优种枣苗

壶瓶枣是我省四大名枣之一,树体强健,适应性强,果形大,丰产,抗枣疯病,是全省重点推广品种之一。太原南郊王家坟村现有经过培育的二年生优种枣苗15万株,根芽苗100万株,愿以较低阶格外售,支援各县枣树基地建设。产品实行三包:包品种,壶瓶枣占95％以上,包质量,根系完整无病虫害;包成活,按科学方法运苗、假植、栽植及管理,死亡苗不付款。     

陕北枣树主要病虫害及综合防治历

红枣是陕北丘陵沟壑区重要的经济树种,生产管理较为粗放,加之树种配置单一,生态系统较为脆弱,枣树病虫害较易发生且危害严重。经调查,主要虫害有枣芽象甲、绿盲蝽、枣粘虫、枣瘿蚊、枣龟蜡蚧、桃小食心虫,主要病害有枣锈病、枣疯病、缩果病。针对各病虫害发生规律,提出了枣树主要病虫害综合防治历。     

抗病和感病泡桐无性系组培苗对嫁接传染植原体的不同反应

用感染了植原体并表现典型丛枝症状的组培苗作接穗或砧木，在无杂菌条件下嫁接７个表现不同田间抗性的无性系健康组培苗，并用ＤＡＰＩ荧光显微镜和１６ＳｒＲＮＡ基因扩增（ＰＣＲ）技术检验嫁接传病效果。Ｃ１２５和ＸｕＨ表现出较强的特异性接种诱发坏死反应，ＺＨ和Ｔ３５０２８坏死反应中等，ＱＬＭ、Ｃ０２０和Ｃ１６１的坏死反应较弱。培养基中添加植物生长调节剂（６ＢＡ或ＮＡＡ）可降低坏死程度，提高嫁接成功率，水杨酸处理或去掉健株砧木叶片和根系皆加重坏死反应程度。用病接穗嫁接抗病的ＱＬＭ无性系时，用ＰＣＲ检测到侵染砧木的植原体，但未表现丛枝症状，而将此无性系健康接穗嫁接到丛枝病砧木上时可诱致典型丛枝症状，从而表现出与根系和成熟叶相关的抗性反应。除Ｃ１２５外，其余６个无性系皆被嫁接传染，其继代培养表现出差异不显著的丛枝症状，其韧皮部金黄色自发荧光随着症状的加重而累积，也与抗病性有一定的联系。     

枣疯病的综合治理措施

枣疯病是由植原体引起的枣树生产中发生最普遍、危害最严重的传染性检疫病害。主要从科学建园、病树治疗与康复及其他技术措施等方面对枣疯病的综合防治措施进行了概述。     

枣疯病和泡桐丛枝病原植原体分离物的组织培养保藏和嫁接传染研究

分别从河北唐县赞皇大枣、辽宁凌源梨枣和河南濮阳扁核酸3个品种的枣疯病和来自山东、江西和北京的不同无性系的泡桐丛枝病树上采集丛枝枝条作为组织培养材料,获得的枣疯病和泡桐丛枝病组培苗皆表现典型的丛枝症状。其中感染植原体的赞皇大枣组培苗(Ft)和扁核酸组培苗(HPD)在未加任何激素的MS培养基和其它培养基交替继代培养1a以上仍能维持丛枝苗生长;而发病梨枣(LD)除产生丛枝外,还出现叶片黄化和植株矮化、枯梢等衰退症状。泡桐丛枝病植原体可在不同无性系组培苗上通过各种培养基交替和单纯的MS培养基继代培养,并已在实验室内连续保藏达10a,其引致丛枝症状的能力无明显的改变。用枣树Ft染病材料作接穗,以健康冬枣(DJ)和抗病婆枣(W14)砧木进行组培苗间嫁接传病试验,可使部分DJ和W14发病;而嫁接未发病的砧木多数像健苗一样正常生长。用感染山东泡桐丛枝病植原体ZD株系丛枝组培苗为接穗,嫁接健康泡桐无性系组培苗致使无性系MB33、TY2T和C125发病。用植原体16SrDNA通用引物进行PCR,确证了泡桐和枣树发病苗和嫁接发病组培苗体内存在植原体。用DAPI荧光显微镜技术比较组培苗韧皮部筛管中的植原体浓度,结果显示,Ft和嫁接发病冬枣(DJ-Ft)筛管中植原体浓度相对较高,但仍低于各泡桐无性系染病丛枝组培苗;HPD和LD浓度中等,而发病的W14砧木含有植原体的筛管数量较少、且浓度很低。在嫁接不成功或未发病的DJ和W14砧木组织及健康对照组织中皆检测不到植原体荧光。     

Molecular characterization of a phytoplasma associated with Euonymus bungeanus witches’ broom in China

Euonymus bungeanus plants exhibiting symptoms of abnormal branches, small leaves and phyllody, which is indicative of E. bungeanus witches’ broom (EbWB) disease, have recently been found in Beijing, China. A phytoplasma from symptomatic E. bungeanus plants was identified by 16S rRNA polymerase chain reaction (PCR) using the phytoplasma‐specific universal primer pair R16mF2/R16mR1. Inoculation of healthy E. bungeanus plants by grafting with diseased scions was also performed. The rp and secY genes of the EbWB phytoplasma were cloned and sequenced as was the 16S rRNA gene. Sequence and phylogenetic analyses of 16S rRNA, rp and secY genes indicated that the phytoplasma associated with E. bungeanus belongs to the 16SrV‐B, rpV‐C and secY‐C subgroup, the same subgroup as the jujube witches’ broom (JWB) phytoplasma that is widely distributed among jujube trees in China. Comparative analyses based on virtual restriction fragment length polymorphism (RFLP) showed that the EbWB phytoplasma is more closely related to another 16SrV‐B subgroup strain: RPWB (Robinia pseudoacacia witches’ broom). To the best of our knowledge, this is the first report of a witches’ broom phytoplasma in E. bungeanus in China, and the findings add a new cultivated plant species to the already broad natural host range of 16SrV‐B subgroup phytoplasmas.     

寡核苷酸管芯片技术检测和鉴别我国不同组植原体

[目的]不同组植原体检测和鉴别的特异性探针已有报道,为了筛选出适合于我国不同组植原体检测和鉴别的特异性探针,建立管芯片检测和鉴别植原体技术,并对我国发生的疑似植原体病害进行鉴别。[方法]通过PCR扩增结合管芯片杂交技术,对收集到的15种植原体侵染的植物样品及其健康对照进行检测和鉴别。[结果]建立了管芯片检测和鉴别植原体技术体系。15种病害样品中,13种获得显著的阳性杂交信号,并且所有的健康对照都呈现为阴性。13种植原体病害依16Sr DNA直接测序可分为16SrⅠ、Ⅱ、Ⅴ、XIX四组植原体。在所有探针中,植原体的通用探针(Pp-502)可以检测到所有确定的植原体样品。16SrⅠ组特异性探针(PpⅠ-465)可以确定16SrⅠ组的泡桐丛枝、苦楝丛枝、桑树萎缩和莴苣黄化4种植原体样品。16Sr II组特异性探针(PpⅡ-629)仅可以确定16Sr II组的花生丛枝、甘薯丛枝和臭矢菜丛枝3种植原体样品。但16Sr V组的枣疯病、樱桃致死黄化和重阳木丛枝及16Sr XIX组的板栗黄化皱缩植原体与其他组专化性探针皆有明显的交叉杂交信号。相比于PCR扩增的凝胶电泳检测,管芯片检测的灵敏度提高了1 000倍。对疑似植原体病害的诊断结果显示河南濮阳的红花槐丛枝的病原应为16Sr V组植原体,福建福州的长春花黄化丛枝应为16SrⅠ组植原体;而北京戒台寺牡丹黄化皱叶和内蒙古包头柳树丛枝未出现任何植原体专化的杂交信号。[结论]管芯片杂交技术作为一种检测和鉴别植原体的方法,可应用于我国植原体病害调查和诊断,并为植原体的鉴别和分类提供可靠的依据。     

Detection of phytoplasma infections in declining Populus nigra ‘Italica’ trees and molecular differentiation of the aster yellows phytoplasmas identified in various Populus species

A disease of Populus nigra‘Italica’ associated with foliar yellowing, sparse foliage, stunting, dieback, and decline was observed in south-western Germany; a witches’ broom disease of Populus alba that is known in other countries was also detected in Hungary and Germany. The aetiology of the diseases was studied by fluorescence microscopy and polymerase chain reaction (PCR) amplification. Using fluorescence microscopy, phytoplasmas could be detected only in P. alba. However, most diseased trees of P. nigra‘Italica’ tested phytoplasma-positive by PCR. In some of the trees the phytoplasma numbers were so low that nested PCR was required to detect the infection. Very low phytoplasma numbers were also observed in diseased Populus tremula. The identity of phytoplasmas from P. nigra‘Italica’ sampled in Germany and France, P. alba and also P. tremula was examined by restriction fragment length polymorphism (RFLP) analysis of PCR-amplified ribosomal DNA. In all poplars, phytoplasmas of the aster yellows group were detected. However, three different RFLP groups were identified that consisted of (1) French strains from P. nigra‘Italica’, (2) German strains from P. nigra‘Italica’ and (3) strains from P. alba and P. tremula. The profile observed in the last group was probably the result of sequence heterogeneity in the two 16S RNA genes.     

Identification and characterization of the phytoplasma associated with elm yellows in southern Italy and its relatedness to other phytoplasmas of the elm yellows group

In the neighbouring regions Basilicata, Campania, and Calabria of southern Italy, diseased trees of European field elm (Ulmus minor) were examined for phytoplasmal infection using polymerase chain reaction (PCR) technology. All affected trees examined tested positively. Using a primer pair specific for the EY phytoplasma group and restriction fragment length polymorphism (RFLP) analysis of PCR-amplified ribosomal DNA, the organism detected was identified as the elm yellows (EY) phytoplasma. RFLP analysis of PCR-amplified ribosomal DNA was also employed to attempt differentiation within the EY group which includes, in addition to the EY agent, phytoplasmas infecting Rubus, alder, eucalypts, Spanish broom, and grapevine. Following separate digestion with AluI, RsaI, Sau3AI, MseI, HhaI, and KpnI, all PCR-products from EY-group phytoplasmas examined had similar RFLP profiles. When the same ribosomal DNA fragments were digested with TaqI restriction endonuclease, three different restriction profiles were detected among the EY-group phytoplasmas. These profiles represented, respectively, (1) the EY phytoplasma (2) the phytoplasmas causing rubus stunt and being associated with alder yellows, spartium witches broom, and eucalyptus little leaf, and (3) the flavescence dorée phytoplasma. RFLP analysis using TaqI endonuclease enabled for the first time the differentiation of the phytoplasmas associated with alder yellows, eucalyptus little leaf, and spartium witches broom from the EY agent.     

Campsisgrandiflora as a new host species harbouring two novel 16SrI subgroups of phytoplasmas

In September 2019, two diseased plants of Campsis grandiflora showing the main symptom of witches' ‐broom (CgWB) were found in a nursery garden in Yangling, Shaanxi province, China. Partial 16S ribosomal RNA (F2nR2 region) and ribosomal protein (rp) genes of phytoplasmas were generated from the symptomatic plants by PCR amplification, and phytoplasma bodies were observed in the sieve tube elements of the CgWB samples under a transmission electron microscope, indicating phytoplasma infection in the two CgWB plants. Restriction fragment length polymorphism analysis of the F2nR2 region and similarity coefficient results suggested that the two associated phytoplasmas belong to two novel subgroups of 16SrI (aster yellows) group, designated as AK and AL. On the reconstructed phylogenetic trees based on F2nR2 regions and rp genes of phytoplasmas, respectively, the CgWB‐associated phytoplasmas clustered together with members of 16SrI subgroups. This was the first record of phytoplasmas infecting C. grandiflora worldwide.     

北京市丰台区主栽枣品种对枣疯病抗性试验

采用以感染枣疯病的枣树作砧木嫁接健康休眠接穗的方式,对丰台区8个主栽枣品种进行了抗病性鉴定,并应用DAPI荧光显微方法和PCR方法对接穗进行了枣疯病植原体检测.结果表明,8个供试品种均能被感染,并表现丛枝症状,对枣疯病植原体均无免疫性,其中金芒果枣和冬枣为易感痛品种,尜尜枣和京枣39为相对抗性品种.