GST family genes in jujube actively respond to phytoplasma infection

Jujube witches’broom(JWB)caused by phytoplasma has a severely negative effect on multiple metabolisms in jujube.The GST gene family in plants participates in the regulation of a variety of biotic and abiotic stresses.This study aims to identify and reveal the changes in the jujube GST gene family in response to phytoplasma infection.Here,70 ZjGSTs were identified in the jujube genome and divided into 8 classes.Among them,the Tau-class,including 44 genes,was the largest.Phylogenetic analysis indicated that Tau-class genes were highly conserved among species,such as Arabidopsis,cotton,chickpea,and rice.Through chromosome location analysis,37.1%of genes were clustered,and 8 of 9 gene clusters were composed of Tau class members.Through RT-PCR,qRT-PCR and enzyme activity detection,the results showed that the expression of half(20/40)of the tested ZjGSTs was inhibited by phytoplasma infection in field and tissue culture conditions,and GST activity was also significantly reduced.In the resistant and susceptible varieties under phytoplasma infection,ZjGSTU49-ZjGSTU54 in the cluster IV showed opposite expression patterns,which may be due to functional divergence during evolution.Some upregulated genes(ZjGSTU45,ZjGSTU49,ZjGSTU59,and ZjGSTU70)might be involved in the process of jujube against JWB.The yeast two-hybrid results showed that all 6 Tauclass proteins tested could form homodimers or heterodimers.Overall,the comprehensive analysis of the jujube GST gene family revealed that ZjGSTs responded actively to phytoplasma infection.Furthermore,some screened genes(ZjGSTU24,ZjGSTU49-52,ZjGSTU70,and ZjDHAR10)will contribute to further functional studies of jujube-phytoplasma interactions.

Detection and Identification of Phytoplasma of Cleome rutidosperma in Areca Palm Yellow Leaf Disease Field

[Objectives]The paper was to detect and identify the phytoplasma of Cleome rutidosperma in areca palm yellow leaf disease(YLD)field in Wenchang City,Hainan Province,China.[Methods]The nested PCR technique was employed to amplify the phytoplasma 16S rDNA of C.rutidosperma samples,followed by sequence analysis.Concurrently,this study examined C.rutidosperma in YLD field,collecting symptomatic leaves for phytoplasma detection.[Results]The 16S rDNA sequence of the C.rutidosperma witches'-broom phytoplasma was found to be identical to that of the HNWC5 strain associated with areca palm yellows phytoplasma,leading to the identification of this phytoplasma as belonging to the 16SrII-A subgroup.Field investigations revealed a higher incidence of C.rutidosperma in areca palm fields,with symptoms of leaf yellows observed in six of these fields.Quantitative PCR(qPCR)analysis confirmed the presence of phytoplasma infection in these instances.[Conclusions]Through the analysis of geographical distribution,sequence alignment,and field occurrence data,a significant correlation has been identified between witches'broom disease and YLD.It is proposed that the former may act as an intermediate host for the areca palm yellows phytoplasma.

A New Disease of Cherry Plum Tree with Yellow Leaf Symptoms Associated with a Novel Phytoplasma in the Aster Yellows Group

A novel phytoplasma was detected in a cherry plum（Prunus cerasifera Ehrh） tree that mainly showed yellow leaf symptom. The tree was growing in an orchard located in Yangling District, Shaanxi Province, China. The leaves started as chlorotic and yellowing along leaf minor veins and leaf tips. Chlorosis rapidly developed to inter-veinal areas with the whole leaf becoming pale yellow in about 1-4 wk. Large numbers of phytoplasma-like bodies（PLBs） were seen under transmission electron microscopy. The majority of the PLBs was spherical or elliptical vesicles, with diameters in range of 0.1-0.6 μm, and distributed in the phloem cells of the infected tissues. A 1 246-bp 16 S ribosomal RNA（rRNA） gene fragment was amplified from DNA samples extracted from the yellow leaf tissues using two phytoplasma universal primer pairs R16mF2/R16mR1 and R16F2n/R16R2. Phylogenetic analysis using the 16 S rRNA gene sequence suggested that the phytoplasma associated with the yellow leaf symptoms belongs to a novel subclade in the aster yellows（AY） group（16SrI group）. Virtual and actual restriction fragment length polymorphism（RFLP） analysis of the 16 S rRNA gene fragment revealed that the phytoplasma was distinguishable from all existing 19 subgroups in the AY group（16SrI） by four restriction sites, Hinf I, Mse I, Sau3 A I and Taq I. The similarity coefficients of comparing the RFLP pattern of the 16 S rRNA gene fragment of this phytoplasma to each of the 19 reported subgroups ranged from 0.73 to 0.87, which indicates the phytoplasma associated with the cherry plum yellow leaf（CPYL） symptoms is probably a distinct and novel subgroup lineage in the AY group（16SrI）. In addition, the novel phytoplasma was experimentally transmitted to periwinkle（Catharanthus roseus） plants from the tree with CPYL symptoms and then back to a healthy 1-yr-old cherry plum tree via dodder（Cuscuta odorata） connections.

Phytoplasmas and Phytoplasma Diseases: A Severe Threat to Agriculture

Several economically relevant phytoplasma-associated diseases are described together with an update of phytoplasma taxonomy and major biological and molecular features of phytoplasmas. Outlook about persepectives and future work to contain spread of these diseases are also reported.

Optimization of Expression Conditions for Immunodominant Membrane Protein Gene of Phytoplasmas in E.coli

[Objective] This study aimed to increase the expression level of immun- odominant membrane protein gene （Imp） of phytoplasmas in E. coil BL21 （DE3）. [Method] On the basis of orthogonal experiment, effects of different culture conditions on recombinant bacteria E. coil BL21-pET-28a（＋）-Imp were investigated. Based on the obtained optimal culture condition, effects of different induction conditions on the ex- pression level of Imp protein were explored. The expression level of Imp fusion pro- tein was analyzed by using SDS-PAGE and Gene Tools software. [Result] The re- sults showed that the optimal conditions for culture were at 37℃, pH 7.0, with liq- uid volume of 20% and oscillation speed of 200 r/min, for induction were at 37℃ for 6 h, with initial OD600 of about 1.5 and IPTG final concentration of 0.1 mmol/L. [Conclusion] The expression level of Imp achieved 70.98 mg/L under the optimal conditions. Optimized conditions for expression of Imp fusion protein in E. coil were determined.

Chemical composition of acid lime leaves infected with <i>Candidatus</i>Phytoplasma aurantifolia

The production of acid lime (Citrus aurantifolia) has declined in many parts of the world due to phytoplasmal infection by “Candidatus Phytoplasma aurantifolia”. The resulting Witches’ Broom Disease of Lime (WBDL) causes stem and leaf proliferation and clustering that starts on a few branches and continues to spread until trees are killed within 5-7 years. Recent studies have shown that Phytoplasma alters the chemical composition of leaves. Leaves from WBDL-symptomatic lime trees were collected to determine their volatile compound composition. Phytoplasmal infection was confirmed by a polymerase chain reaction (PCR) assay using primers P1/P7 and R16F2n/R16R2 in direct and nested PCR, respectively. Restriction fragment length polymorphism (RFLP) profiles of acid lime Phytoplasma were identical with those of WBDL Phytoplasma. The phytochemical composition of symptomatic (infected) and asymptomatic (healthy) leaves of acid lime were determined using GC-MS analysis of steam distilled extract. The WBDL-symptomatic leaves had higher concentration in ?-limonene, β-ocimene and trans-caryophyllene and a reduction in other compounds (i.e. citral, citronellal, cisverbenol, neryl acetate, and linalool). Variations in the leaf phytochemical concentration indicate a possible role in the development of the WBDL disease symptoms.

Molecular Study of a New Disease of Peach in Iran Associated with a Phytoplasma

In recent years, a disease has been reported to affect peach trees in Kurdistan province of Iran causing serious losses to the production. Main symptoms of disease include leaf stunting and yellowing, which lead to failure in fruit production at harvest. For diagnosis of disease and identification of the causal agent, symptomatic leaf samples were collected in Kurdistan orchards during summer 2010 and were carried to the laboratory. Total DNA was extracted from plant samples according to the standard procedures and indexed by grafting and nested PCR using phytoplasma generic primers, P1/P7 and R16F2n/R2. PCR products were characterized by RFLP technique and direct sequencing. The 16S rDNA sequences were compared with those of other phytoplasmas in GenBank. Phytoplasma rDNA was amplified from 20 out 35 samples. The 16S rDNA sequences of the phytoplasma were identified in Peach samples which showed 98% similarity to that of “Candidatus Phytoplasma phoenicium” which is considered to be the causal agent of Almond witches’ broom. Phylogenetic analysis of 16S rDNA sequences placed peach strains in Almond witches broom isolate as a member of pigeon pea witches broom (PPWB) group. Further studies on the epidemiology of “Ca. Phytoplasma phoenicium” and its vector(s) in Iran are recommended in order to identify new natural hosts and develop successful disease management programs.

Comparative Toxicity of Selected Insecticides to Phytoplasma Transmitted Leafhopper Cicadulina bipunctata （Melichar）

Leafhopper Cicadulina bipunctata is represented the main insect as a pathogen for phytoplasma disease occurring by insect-transmitted plant viruses in date palm orchards. Therefore, it is important to investigate the potential effect of some insecticides against such insect. The adults of leafhopper C. bipunctata were collected from date palm orchards in Alhasa, Eastern province, Saudi Arabia. Three insecticides from different classes--beta-cyfluthrin （pyrethroids）, imidacloprid （neonicotinoids） and abamectin （natural compounds）--have been evaluated in vivo against adults C. bipunctata. This stage was exposed to residual film of various concentrations of each insecticide on transparent plastic cups using a Potter precision laboratory spray tower. Bioassay test showed that both beta-cyfluthrin and imidacloprid caused 100% mortality by 500 ppm at 24 h after treatment, whereas abamectin gave the same mortality by 50 ppm at the same time. Toxicity values revealed that abameetin was the most potent insecticide compared with beta-cyfluthrin and imidacloprid, where the lethal concentrations LC50 and LC95 were 24.58 ppm and 116.73 ppm at 3 h after treatment, respectively. Therefore, abamectin can be a possible candidate to be applied on date palm or ground grass by the Ministry of Agriculture after successful field experiments.

Preliminary investigation and detection based on loop-mediated isothermal amplification(LAMP)of phytoplasmas associated with diseases in B.napus L.

In the last decade,some disease occurred on our experimental farms that had caused serious losses.They were not caused by fungi,bacteria or viruses.By loop-mediated isothermal amplification(LAMP)technique,the detection results pointed to the possible pathogen as phytoplasma.The investigation results implied that phytoplasmas could cause more than 13 kinds of symptoms in almost all parts of plants in B.napus L.,including witches’broom,multi-stems,aggregate main inflorescences,and flat stems.The incidences of these phytoplasma-associated diseases in our experimental farms rose from 1.61%in 2010 to 6.00%in 2021.Some phytoplasma infected plants died without any growing points.These studies would be helpful for detecting phytoplasmas diseases,selecting disease resistant germplasm and improving varieties with disease resistances in B.napus L.

Detection of ＂ Candidatus Phytoplasma asteris＂ in Brussels Sprout and Its Possible Association with Flower Bud Failure in Poland

Severe growth abnormalities including shoot stunting, leaf blade reduction and flower bud failure of Brussels sprout were observed in Poland. The presence of phytoplasma in diseased as well as in healthy looking plants, was demonstrated by nested polymerase chain reaction assay employing phytoplasma universal rRNA primer pairs-P1/P7 followed by R16F2n/R16R2. Products of PCR primed by R 16F2n/R 16R2 primer pair from naturally infected Brussels sprouts were sequenced. Comparison of the obtained 16S rDNAs revealed high nucleotide sequence identity between analyzed phytoplasma isolates （99.8%-100%）. They were also nearly identical with the sequences of other phytoplasmas isolates from sub-group 16SrI-B, and they were classified as members of ＂Candidatus Phytoplasma asteris＂.

国内外樱桃植原体（Phytoplasma）病害研究进展

植原体是一类无细胞壁、不能人工培养、存在于植物筛管内的专性寄生菌,世界各地已报道植原体可引起1000余种各类植物系统性病害,涵盖农作物、园艺、花卉、果树和林木等,该病害传播性强、症状明显、危害较大,可不同程度引起植物生长发育异常或变异,甚至造成植株死亡。樱桃植原体病害就是其中一种,近年来该病害已经成为威胁樱桃产业发展最为重要的病害之一,主要引起樱桃花变叶(绿)及花器官、叶片、果实的生长发育异常和变异,并最终导致植株2~5 a(年)内迅速死亡,对我国乃至世界樱桃产业造成了非常重大的损失。随着我国近几年不同地区樱桃植原体病害发生面积、规模及危害程度地不断增加,尤其是笔者研究发现的重庆地区大规模爆发引起了极大威胁,使得有关其致病机制、植株生长发育特性及防治方法的系统研究显得迫在眉捷、尤为重要。针对樱桃植原体病害研究的需求,笔者综述了国内外有关研究进展,主要从植原体的分类、检测与传播以及樱桃植原体病害等多个方面进行阐述,为进一步开展樱桃植原体病害研究与防治等提供重要基础,并对未来的研究前景与应用价值进行了分析。

Use of random amplified polymorphic DNA （RAPD） analysis to detect jujube witches＇ broom phytoplasmas

Jujube witches＇ broom is a devastating disease of Ziziphusjujube that occurs in various jujube regions of China. Nucleic acid extracted from midribs of samples collected from three jujube varieties （＂Suanzao＂, ＂Lajiaozao＂ and ＂Langzao＂） from symptomatic and asymptomatic shoots were tested by random amplified polymorphic DNA analyses. Using 13 different 10 and 11-bp random primers the amplification of jujube DNA was achieved from all the samples; AMI4 primer provided amplification of specific DNA fragments of about 400 bp, only from samples collected from symptomatic plants. No genetic variations in these varieties were identified using the other 11 arbitrary primers; only with primer AL07 it was possible to differentiate ＂Langzao＂ from the other two varieties tested. All the experiments were repeated 2 times and the results were consistent. Compared with PCR analyses with phytoplasma-specific primers, RAPD techniques resulted to be an alternative rapid and sensitive method for detecting jujube phytoplasmas presence in different jujube varieties.

植原体引起雪花木小叶病在中国的首次报道

2022年首次在广州市发现园林植物雪花木小叶病病株,采用分子生物学技术对其进行植原体的种类鉴定。以雪花木叶片总DNA为模板,利用植原体16S rRNA通用引物P1/P7进行PCR扩增,获得广东雪花木小叶病植原体(BLL-GD2022)16S rRNA基因片段(1811 bp,GenBank登录号为OQ625536)。16S rRNA序列相似性显示,BLL-GD2022与16SrVI组植原体株系的相似性最高,为97.05%~99.83%,其中与隶属于16SrVI-D亚组的10个植原体株系相似性为99.21%~99.83%。系统进化分析显示,BLL-GD2022与16SrVI组各植原体株系聚类在一个大分支,其中与16SrVI-D亚组成员聚类在一个小分支,亲缘关系最近。基于16S rRNA序列的i PhyClassifier限制性内切酶虚拟RFLP分析表明,BLL-GD2022与16SrVI-D亚组的参考株系Brinjal little leaf phytoplasma(GenBank登录号为X83431)的酶切图谱一致,相似系数为1.00。基于上述研究结果,明确广州市雪花木小叶病植原体隶属16SrVI-D亚组成员。本研究首次在园林植物雪花木上检测到植原体,通过16S rRNA序列分析明确为16SrVI-D亚组成员,为开展16SrVI-D亚组植原体在蔬菜、花卉和园林植物的发生监测及病害防控提供科学依据。

广东番茄巨芽病植原体的分子鉴定

2022年,对在广东省湛江市廉江市田间发现的疑似番茄巨芽病病株,利用分子生物学方法对其相关植原体进行了鉴定。以番茄病株叶片总DNA为模板,利用植原体16S rRNA基因通用引物R16mF2/R16mR1进行PCR扩增,获得了广东番茄巨芽病植原体(TBB-GD-2022)16S rRNA基因片段(1 430 bp, GenBank登录号为ON102780)。16S rRNA基因序列相似性分析显示,TBB-GD-2022与16SrⅡ组植原体菌株的相似性较高,为96.82%~100%,其中与隶属于16SrⅡ-V亚组的6个植原体株系相似性为100%。系统进化分析显示,TBB-GD-2022与16SrⅡ组各植原体株系聚类在一个大分支,并与16SrⅡ-V亚组成员聚类在一个小分支,亲缘关系较近。16S rRNA基因相似系数分析表明,TBB-GD-2022与16SrⅡ-V亚组的参照株系‘Praxelis clematidea’ phyllody phytoplasma (GenBank登录号:KY568717)的相似系数为1.00。上述研究结果表明,广东番茄巨芽病植原体隶属16SrⅡ-V亚组成员。本文首次报道在广东发现番茄巨芽病,通过其16S rRNA序列分析进一步确定了其相关植原体的分类地位,为该病害的防控提供了科学依据。

叶下珠黄化植原体和丛枝植原体的分子鉴定

2022年8月在海南省文昌市一个槟榔黄化病园内,分别发现叶片黄化和丛枝症状的叶下珠,前期检测均为植原体感染。为了明确叶下珠黄化植原体和丛枝植原体的分类鉴定,本研究通过克隆16S rDNA基因和核糖体蛋白(rp)基因,并进行基因序列一致性、系统发育树及虚拟RFLP等分析。结果显示:克隆获得叶下珠黄化植原体16S rDNA片段1246 bp,rp基因1212 bp;叶下珠丛枝植原体16S rDNA片段1827 bp,rp基因1240 bp。基因序列一致性显示,叶下珠黄化植原体与丛枝植原体的16S rDNA基因序列均与16SrⅠ组的植原体一致性高达98%以上,与槟榔黄化植原体海南株系的16S rDNA序列一致性达100%;而二者的rp基因序列均与rpⅠ组的植原体一致性高达99%以上。系统发育树分析显示,叶下珠黄化植原体和丛枝植原体16S rDNA基因均与翠菊黄化组(16SrⅠ)植原体聚于一个大分支,且与16SrⅠ-B亚组的槟榔黄化植原体聚于同一个小分支,亲缘关系接近;而rp基因均与翠菊黄化组(rpⅠ)植原体集聚于一个大分支,且与rpⅠ-B亚组的翠菊黄化植原体聚于同一个小分支,亲缘关系接近。虚拟RFLP分析显示,叶下珠黄化植原体和丛枝植原体的16S rDNA基因序列虚拟RFLP图谱与16SrⅠ-B的洋葱黄化植原体的参考图谱相同,且相似系数为1.00。综上表明,叶下珠黄化植原体和丛枝植原体均属于16SrⅠ-B亚组成员。研究结果可对采用铲除槟榔黄化病中间寄主的防控手段提供理论依据。

槟榔黄化植原体TaqMan探针实时荧光定量PCR检测方法的建立

槟榔是海南省重要的热带经济作物,由植原体侵染引起的槟榔黄化病(areca palm yellow leaf disease,YLD)是当前我国槟榔生产上的一种毁灭性病害。为了建立精准高效的槟榔黄化植原体检测方法,本研究基于槟榔黄化植原体16SrDNA基因,设计并合成特异性引物AMf/AMr和探针AM-Prode,使用该方法进行准确性、敏感性、特异性及重复性测试,并在其他植物的植原体病害进行检测。结果显示:本检测方法能够准确的检测出阳性样品,健康样品无扩增曲线;在敏感性测试中,该检测方法能检测到1.16×10^(1) copies/μL样本浓度水平,其标准曲线方程为y=-3.4185x+43.624,扩增效率为96.12%,相关系数R^(2)=0.9833;在特异性测试中,该检测方法对YLD的检测具有较好的特异性,槟榔、槟榔其他病害病原及其内生菌的基因组对本方法未造成干扰;在重复性测试中,该检测方法对槟榔黄化病的检测具有较好的重复性;并且该检测方法可对苦楝黄化病、细圆藤丛枝病及辣椒黄化病等8种植原体病害进行检测,对植原体的检测具有一定的通用性。本检测方法的建立,有利于为槟榔黄化病的精准诊断、病原监测及媒介昆虫的检测等研究提供可靠的技术手段。

泡桐NLR基因家族分析及其对植原体的响应

为研究PfNLR基因家族在白花泡桐抗丛枝病过程中的作用,运用生物信息学方法全面分析了白花泡桐NLR(PfNLR)家族成员的组成、理化性质、染色体定位、进化、结构、顺式作用元件和组织表达特异性,结合植原体侵染白花泡桐前后的miRNA和转录组的表达量变化,筛选出与抗丛枝病相关的基因。结果表明:白花泡桐中的199个PfNLRs分属6个亚家族;91.9%的PfNLRs定位在白花泡桐18条染色体上,其中62.8%呈簇状分布,23个PfNLRs发生了10次染色体片段重复事件和1次染色体串联重复事件;PfNLR含激素类和胁迫类元件;miRNA和转录组的关联分析发现泡桐miRNA与PfNLR之间存在156对靶向关系;大多数PfNLRs在芽和根中表达;16个PfNLRs在白花泡桐感染植原体前后的表达水平显著差异。进一步分析发现,pf–miRNA482介导的PfNLR181在白花泡桐抗丛枝病中发挥作用,该结果可为解析白花泡桐NLR蛋白的功能提供理论依据。

板栗黄化皱缩病检测方法优化及10个板栗品种抗性鉴定

为优化板栗黄化皱缩病检测方法,明确10个板栗品种的抗性,通过对巢式PCR引物添加量、退火温度的优化,结合植原体检出率和田间病情指数进行抗性评价。结果表明,巢式PCR在引物添加量为1.0μL、退火温度为54℃时,板栗植原体检出率最稳定;在毒源树嫁接400 d后,供试板栗品种均检测出植原体,其中‘燕山早丰芽变’叶片中植原体检出率最高,发病情况最严重,‘燕丽’叶片中植原体检出率最低,发病情况最轻;相关分析表明,植原体检出率和田间病情指数呈极显著正相关,相关系数为0.907,其线性回归方程为Y=0.276X+1.610;根据2种评价方法将供试板栗品种分为高抗、中抗和高感品种,其中‘燕秋’‘燕紫’‘燕龙’‘燕丽’为高抗品种,‘燕山早丰芽变’为高感品种。研究初步明确了10个板栗品种对黄化皱缩病的抗性差异,为选用抗性品种提供了基础数据。

两种林木植原体病害的分子鉴定

近年来,林木植原体病害发生日趋严重,对我国林业经济和生态造成了很大损失。2021年-2022年,在山西沙棘主产区的沙棘上和北京冬奥园区的油松上分别出现了典型的植原体病害症状;沙棘叶片皱缩,呈小叶状;油松过度分枝生长且出现球状结构等。本研究通过荧光显微观察,16S rRNA和tuf基因序列分析,并结合虚拟限制性片段长度多态性分析证实了这两种病害均由植原体引起。基于16S rRNA的系统进化分析显示:引起沙棘叶片皱缩的植原体与泡桐丛枝植原体(Paulownia witches’-broom phytoplasma,OP107515.1)的相似性最高(99.92%),引起油松丛枝的植原体与狗尾草丛枝植原体株系(Setaria viridis witches’-broom phytoplasma,FJ263625.1)的相似性最高(99.52%);基于tuf基因的系统发育树显示,二者同属于16SrⅠ组D亚组(16SrⅠ-D)。本研究首次明确了沙棘叶片皱缩病和油松丛枝病相关植原体的分类地位,为这两种植原体病害的准确诊断、快速检测及其防治提供了基础资料。

水稻橙叶植原体在病株中积累及其经电光叶蝉传播的主要特征

【目的】探究水稻橙叶植原体(Rice orange leaf phytoplasma,ROLP)在水稻植株体内的扩散和积累以及其经由主要介体电光叶蝉传播的特征,以加深对水稻橙叶病发生规律的认识,为病菌继代保存和田间病害防控提供科学依据。【方法】采用半定量PCR和实时荧光定量PCR检测ROLP在感病水稻植株不同部位积累动态及在叶蝉体内的增殖动态;以2~3龄电光叶蝉若虫为传菌介体,测定其在病程约20 d的菌源病株上取食不同时间的获菌率;采用稻苗感病试验测定病菌在叶蝉体内的循回期;通过单虫单苗共培养试验测定病菌经电光叶蝉向3~4叶期水稻幼苗传播的效率。【结果】水稻幼苗感病后,病菌先在受侵染叶片中缓慢增殖,10~15 d后经主茎向下扩展,随后在分蘖的茎和叶组织中大量增殖,约30 d后引致分蘖发病;病株受侵染叶片的上部茎和叶组织中仅有微量或没有病菌存在,根部仅实时荧光定量PCR检测到微量病菌。2~3龄电光叶蝉在菌源植株上取食15、25和35 d的获菌率分别为26.67%、71.11%和85.56%。病菌在叶蝉体内的循回期为25 d左右,度过循回期的带菌叶蝉单虫单苗取食12、24和48 h可分别使24.44%、46.67%和47.78%的水稻苗染病。【结论】ROLP在水稻植株体内呈不均匀分布,以感病30 d前后的分蘖茎和叶组织中含量最高,受侵叶片的上部茎和叶组织中无病菌分布。病菌经电光叶蝉高效传播的获菌取食时间、体内循回期和传菌取食时间分别为15 d、25 d和24 h。