作物苗期立枯病和猝倒病的识别及防治

立枯病和猝倒病是许多花卉、蔬菜、果树、林木等苗期的根部病害。采用种子育苗和扦插育苗都可发生此病。病害普遍而严重。两种病害发生规律相似,防治方法基本相同。一、症状识别立枯病在早期发生,可引起烂种。苗期发病,茎基产生椭圆形暗褐色病斑,病斑逐渐凹陷,当病斑...     

玉米杂交种和自交系对多种病害抗病性的诱发病圃鉴定

在华农实验农场设置病圃,分区块重复分别接种大、小斑病、茎腐病、纹枯病、褐斑病和自然发生斑点病。从1980～1982年鉴定生产上推广的玉米杂交种和其亲本,以及培育中的材料共260份。其中多数抗3～4种病害;少数不抗到抗1～2病害,以至抗5～6种。湖北省低山地区推广三系杂交种“唐五”中抗到抗大、小斑病、茎腐病、褐斑病、斑点病,感纹枯病;二高山地区推广单交种“恩单2号”中抗大斑,中感小斑,中抗到中感茎腐、纹枯,中抗到抗褐斑和斑点。在培育中的新自交系“唐Mo17Ht_1cms-S”和“77cms-C”中抗到抗6种病害。根据国内外资料分析了抗小斑病材料“Mol7”含有加性显性抗病基因,并兼抗褐斑病;抗大斑病材料中包含Ht类加性显性抗病基因,以及抗茎腐病的多抗基因。又根据调查,讨论了进一步培育多抗材料,结合宽窄行套种、改夏播为春播、增施氮磷钾肥料、培土作垅等耕作栽培制度,保持和提高玉米品种的多种病害抗病性。     

荸荠秆枯病的发生与无公害化防治技术

荸荠秆枯病,又称荸荠瘟,是一种毁灭性病害.秆枯病一旦发生,致使大面积荸荠减产,部分荸荠田块甚至绝收,降低荸荠产量及品质.造成巨大的经济损失.为了降低或尽可能杜绝荸荠秆枯病的发生与危害,笔者于2004-2007年在镇宁县城关镇五里坪荸荠坝区,对荸荠秆枯病的发生危害情况进行调查,探索实施了无公害化防治技术,有效地控制了该病的发生与危害.     

芦笋主要病害及其防治

当年栽培的芦笋发病较轻 ,病害亦少 ,基本不用药剂防治 ,而栽培老区病害较重 ,主要有褐斑病、茎枯病、根腐病、紫纹羽病等病害发生 ;现就生产中芦笋病害的症状及其防治措施作简要介绍。1　褐斑病 Cerccsporq asparagi　　该病在我国发生较普遍 ,但为害较轻 ,其危害程度不及茎枯病。主要症状为 :病斑发生在茎秆、分枝及拟叶上 ,典型的病斑边缘红褐色或紫红褐色 ,中央淡褐色。在潮湿条件下 ,病斑表面生有灰黑色霉层 ,病斑外缘有黄色晕圈 ,病斑逐渐扩展呈不规则形 ,严重时分枝枯黄 ,拟叶提早脱落 ,病株早衰。　　高温多雨季节有利于该病发生 ,…     

芹菜软腐病的发生与防治

芹菜软腐病的发生与防治芹菜软腐病是一种细菌性病害，从苗期到成株期均有发生，引起植株死亡。病症主要发生在叶柄的基部和茎的基部，病斑初期为淡褐色，水渍状，纺锤形或不规则形的凹陷病斑，慢慢扩大为黄褐色或黑褐色的腐烂病斑，具有恶臭味，最后仅残留表皮和维管束。...     

新疆伊犁河谷发现向日葵黑茎病

2005～2007年在新疆伊犁河谷发现一种蔓延迅速、危害严重的向日葵病害,典型症状是病斑最初发生于叶柄基部,在茎秆上形成黑色椭圆形大病斑。经病原鉴定,病原菌无性态分类地位为半知菌亚门,茎点霉属,种名为Phoma macdonaldii Boerma;有性态分类地位为子囊菌亚门,小球腔菌属,种名为Leqtosphaeria lindquistii Frezzi,确定其为国内新病害——向日葵黑茎病。该病目前已在新疆伊犁河谷5县1市的向日葵产区普遍发生,造成严重危害。     

芹菜斑枯病的发生与防治

芹菜斑枯病又称叶枯病、晚疫病 ,俗称火龙。是芹菜生长中发生的严重病害 ,全国各地均有发生 ,主要危害叶片、叶柄及茎 ,此病危害叶柄及茎时 ,造成严重减产 ,在运输、销售、贮藏过程中仍会继续发生 ,造成一定损失。１受害症状芹菜斑枯病危害叶片时 ,先出现淡褐色油浸状小斑点 ,后逐渐扩大。扩大后的病斑表现出２种类型 :１．小斑型。即病斑较小 ,直径２ｍｍ～３ｍｍ ,边缘黄褐色 ,中间为白色 ,病斑外部有一圈黄色晕环 ,病斑上在边缘聚生很多小黑点（分生孢子器） ;２．大型斑。病斑直径３ｍｍ～１０ｍｍ ,病斑颜色较深。中间呈灰褐色 ,边缘红…     

花生网斑病的发生与防治

花生网斑病又叫褐斑病 ,纹斑病 ,是近年来发生趋重的一种新病害 ,2 0 0 0年滑县发生严重 ,造成花生中后期大量落叶 ,减产达 2 0 %～ 40 % .症状 :网斑病一般从花针期始始发 ,发病盛期在结荚期至成熟期 ,主要为害叶片 ,也为害叶柄和茎 ,植株下部叶片先受害 ,沿主脉主生圆形或不规则形黑褐色小点 ,周围有明显的褪绿圈 ,后形成边缘呈网纹状 ,不规则形褐色病斑 ,一般不透过叶面 ;若遇多雨天气 ,病斑较大 ;叶片一旦染病 ,极易脱落 ,叶槽茎受害 ,起初为小褐点 ,年扩展为边缘水渍状 ,中央凹陷、长条形成椭圆形病斑。病原及发病条件 ;该病病原为花生…     

三七上的一种新病害

三七上的一种新病害＊三七素称南国人参，是云南文山州的第一支柱产业。近年来在该地暴发一种新病害三七圆斑病。该病为害三七植株各个部位。叶片受害时，出现灰褐色圆形病斑，ｄ５～２０ｍｍ，随后病斑合并，腐烂脱落；茎顶与花轴顶受害后呈水渍状缢缩折垂；病菌落入土中...     

辽宁省药用植物白鲜病害种类调查及病原鉴定

白鲜为我国传统药用植物,具有较高的经济价值和药用价值,近年来在辽宁省大面积人工种植。为明确白鲜主要病害种类及发生危害情况,2018年-2020年生长季在辽宁省本溪、清原和西丰等主要种植地区进行了病害系统调查。调查和鉴定结果发现,危害白鲜生产的主要病害有5种,分别为由Phoma dictamnicola引起的茎点霉叶斑病、由Paracercospora dictamnicola引起的灰斑病、由Rhizoctonia solani引起的立枯病、由Fusarium oxysporum引起的根腐病和由Meloidogyne hapla引起的根结线虫病,并对各病害症状进行了详细描述。其中茎点霉叶斑病、灰斑病和立枯病分布广且危害较重,病害种类和发病情况地区间差异较大。立枯病主要发生在一年生育苗田,病株率一般为0.6%～19.0%,灰斑病和茎点霉叶斑病主要发生在生产田,病株率分别为38.2%～100.0%和17.6%～99.0%。研究结果将为白鲜病害的准确识别诊断及综合防控策略制定提供科学依据。     

Prepenetration stages in infection of clematis by Phoma clematidina

A detailed study of conidial germination, germ-tube growth and the formation of infection structures in Phoma clematidina , the causal agent of clematis wilt, is described for two clematis varieties differing in disease resistance. On both the resistant and susceptible varieties, the fungus entered leaves and stems by direct penetration of the cuticle, often, but not always, following the formation of infection structures. More germ tubes per conidium were formed on the susceptible host, but these germ tubes were on average shorter than on the resistant host. Although germ tubes regularly entered the plant via trichomes, stomata were not found to be sites of entry. Following penetration of the cuticle of resistant plants, germ-tube growth was sometimes restricted to the subcuticular region, and halo formation occurred at the sites where penetration was attempted. Subcuticular growth and halo formation were not observed on susceptible plants. These observations may partly explain the resistance of small-flowered clematis varieties to P. clematidina .     

Light and Scanning Electron Microscopy Studies on the Infection of Oriental Lily Leaves By Botrytis Elliptica

Light, scanning electron and fluorescent microscopy were used to observe the infection process of Botrytis elliptica on leaves of oriental lily (cv. Star Gazer). At 20 °C and 100% relative humidity, conidia germinated on both adaxial and abaxial foliar surfaces, but germ tubes failed to invade epidermal cells on the adaxial surface. On abaxial surfaces, short (< 20 m) swollen germ tube appressoria penetrated through stomatal openings (19%), through the epidermis near guard cells (52%), or directly through epidermal cells (29%). Esterase activity was detected on germ tubes and conidia after 6 h of incubation, and deformation of the cuticle on abaxial surfaces of lily was observed surrounding infection sites. By 3 h after inoculation, almost 70% of the conidia had germinated, but no penetration was observed. At 6 h after inoculation, almost one-third of germinated conidia had penetrated epidermal cells, and water-soaked lesions were associated with 20% of the penetrations. By 9 h after inoculation, approximately 60% of the germinated conidia had penetrated plant tissues, and water-soaked lesions were associated with 60% of the infections. Fluorescent microscopy with a specific fungal stain allowed assessment of successful infection and visualization of sub-epidermal hyphae. We conclude that penetration of abaxial foliar surfaces of oriental lilies by B. elliptica occurs via short swollen germ tube appressoria mostly near stomata.     

Histological and ultrastructural characterization of the leaf infection events of Colletotrichum fructicola on Malus domestica ‘Gala’

Glomerella leaf spot (GLS), characterized by black necrotic spots and severe defoliation, is a destructive foliar disease of apple. Widely grown cultivars such as Gala and Golden Delicious are highly susceptible to GLS. Currently, the infection biology of the causal pathogen, Colletotrichum fructicola, on apple leaves is unclear. In the present study, the penetration and colonization processes of C. fructicola were characterized on apple (cv. Gala) leaves using light and transmission electron microscopy. C. fructicola conidia produced germ tubes 4 hours post-inoculation (hpi) and appressoria at 8 hpi. In melanized appressoria, funnel-shaped appressorial cones formed around the penetration pore. At 12 hpi, C. fructicola produced secondary conidia. After penetration, C. fructicola began to develop infection vesicles at 36 hpi. At 48 hpi, the primary hyphae of C. fructicola were produced from infection vesicles within host epidermal cells; the host epidermal cell plasma membrane remained intact, indicating a biotrophic association. Subsequently, secondary hyphae penetrated epidermal cells and destroyed cell components, initiating necrotrophic colonization. C. fructicola also produced biotrophic subcuticular infection vesicles and hyphae. Together, these results demonstrate that C. fructicola forms special infection structures and colonizes apple leaves in a hemibiotrophic manner, involving intracellular as well as subcuticular colonization strategies. Detailed characterization of the infection process of C. fructicola on apple leaves will assist in the development of disease management strategies and provide a foundation for studies of the molecular mechanism of the C. fructicola–apple leaf interaction.     

青杨叶锈病菌(Melampsora larici-populina Kleb.)侵染过程的超微结构研究

 采用电子显微镜技术对青杨叶锈病菌(Melampsora larici-populina Kleb.)的侵染过程进行了研究。发现该菌夏孢子萌发产生1~3个芽管,且具较多的树杈状分枝。芽管由气孔侵入,侵入前不形成明显的附着胞或仅个别芽管形成附着胞。芽管侵入气孔后在气孔腔内形成气孔下囊,再分化出圆形的膨大体而产生1~2支初生菌丝。初生菌丝在寄主细胞间扩展,与叶肉细胞壁接触后分化出吸器母细胞,吸器母细胞中的细胞器与胞间菌丝相同,双核。吸器母细胞产生侵入钉侵入叶肉细胞内部形成吸器,成熟吸器由细长具颈环的管状颈部和膨大的吸器体组成,此时胞间菌丝在吸器母细胞处分化出次生菌丝,在叶肉细胞间扩展形成次生菌落,产生孢子堆。病菌在寄主细胞间隙或沿寄主细胞壁延伸时,寄主细胞仍保持正常状态。     

Histological investigation of stripe rust (Puccinia striiformis f.sp. tritici) development in resistant and susceptible wheat cultivars

The wheat cultivar Kariega expresses complete adult plant resistance against stripe rust, whereas cv. Avocet S is susceptible. Using confocal laser scanning microscopy, initial fungal penetration into flag leaves was identical in both cultivars, with directional germ-tube growth towards stomata that were penetrated without the formation of an appressorium, followed by differentiation of a substomatal vesicle, infection hyphae, haustorial mother cells and haustoria. During the following 4 days, further fungal development occurred more quickly in the resistant than in the susceptible cultivar. However, by 7 days postinoculation (dpi) the situation changed, with exponential growth of the pathogen occurring only in the susceptible line. Induced cellular lignification, a typical defence reaction of cereals, was observed at 4 dpi in the resistant cultivar, and 2 days later lignified tissue completely surrounded the fungal colonies. In the susceptible cultivar, isolated lignified host cells occurred at 6 dpi, and long, unbranched fungal hyphae outgrowing the resistance reaction were observed.     

Histopathology of the initial stages of the interaction between rose flowers and Botrytis cinerea

The early stages of the interaction between flowers of the cut rose cv. Sonia andBotrytis cinerea was investigated by scanning electron microscopy and light microscopy. Infection of petals by conidial germ tubes evoked a susceptible reaction. In contrast to general findings nutrient addition to the inoculum was not a prerequisite for this phenomenon. At the lower side of germ tube tips the cuticle was penetrated by infection pegs. Already at this early stage of the infection process, the infection sites were macroscopically visible as scattered white spots. After penetration, pegs enlarged to form infection hyphae, which invaded the periclinal wall of outer epidermal cells. At those sites, the petals formed outgrowths of variable appearance at their abaxial side. Thee outgrowths consisted of remanants of collapsed epidermal cells and of infection hyphae. Subsequent intra- and intercellular growth of hyphae led to a collapse of epidermal and mesophyll cells. The symptoms described generally developed within 24 h. After subsequent incubation the lesions became necrotic. Eventually, the necrosis would spread leading to the death of whole petals.     

Microscopical studies of the infection of gerbara flowers byBotrytis cinerea

The formation of lesions on ray florets of gerbera flowers caused by single conidia ofBotrytis cinerea was studied in two cultivars infected by two isolates of the pathogen. No differences in reaction after inoculation with conidia of either isolate were seen on either cultivar. The conidia produced usually one germ tube not longer than 10 m, but conidia with five germ tubes were also seen. Direct penetration of germ tubes through the upper cuticle of ray florets was observed. No appressoria or other specialised structures were observed before penetration, and degradation of the cuticle did not occur. Germination of conidia and subsequent flower infection was dependent on the availability of free water, but not on the addition of external nutrients.Between 18 to 25°C, fungal development usually stopped after cuticle penetration, two to four cells around the site of penetration becoming necrotic. This number did not increase when inoculated flowers were subsequently placed at 4°C, conditions conductive for the formation of spreading lesions. When flowers were incubated constantly at 4°C, lesions became visible 3 days after inoculation as a group of 10 to 14 cells. Initially from a vesicle-like structure, mycelium spread subcuticularly or in the lumen of epidermal cells resulting in the death of 40 to 50 cells at 18 days after inoculation. Ungerminated conidia and conidial germlings which has not yet penetrated the cuticle did not cause any visible symptoms in underlying epidermal cells.     

The role of primary germ tubes in the life cycle of Blumeria graminis: The primary germ tube is responsible for the suppression of resistance induction of a host plant cell

When the conidia of Blumeria graminis f. sp. hordei (Bgh) are inoculated on barley coleoptile cells they produce short germ tubes called primary germ tubes (PGTs) about 2 h after inoculation. We evaluated the positive role of a PGT in inducing accessibility of the host cell under the germ tube. When an appressorium (APP) penetrated the same cell on which a PGT was present, the ratio of haustorium formation (penetration efficiency) was significantly higher than when an APP penetrated the cell adjacent to the one on which a PGT was present. When an APP penetrated the cell laterally adjacent to the one on which a PGT was present we killed the cell under the PGT by puncturing it with a microneedle and then investigated the penetration efficiency of the cell adjacent to the dead cell. As a control we killed the cell longitudinally adjacent to the one on which a PGT was present and investigated the penetration efficiency of the laterally adjacent cell. The results showed that the penetration efficiency of the former was significantly lower than that of the latter. This suggests that some accessibility factor might transfer from a cell on which a PGT is present to a laterally adjacent cell. The existence of a conidium body but not a PGT was not effective for induced accessibility of the host cell. Moreover, when a Bgh germling was removed 6 h after inoculation and another germling was transferred to the same cell, the penetration efficiency was significantly higher than that of control. As a control, a Bgh germling was transferred to a cell on which no germling was present. These results suggest that the existence of PGT is effective for induced accessibility of a host cell when penetrated by Bgh. However, it is unclear whether or not a PGT secretes some substance(s) which suppresses the resistance induction of a host cell.     

TMV侵染烟草诱导寄主产生细胞自噬

 细胞自噬(autophagy)—自体吞噬,是真核生物中一种高度保守并普遍存在的物质循环利用过程。为明确烟草花叶病毒(Tobacco mosaic virus,TMV)侵染烟草是否引起细胞自噬,本研究利用TMV-U1和普通烟(Nicotiana tabacum cv. Blight yellow)为主要研究材料,利用透射电子显微镜观察、单丹磺酰尸胺(MDC)荧光染色技术、自噬标记分子ATG8f-ECFP荧光观察和荧光定量RT-PCR(qRT-PCR)分别检测TMV侵染烟草后的烟草细胞内自噬结构的形成、酸性细胞器的存在和细胞自噬相关基因(Autophagy related gene,ATG)ATG3、ATG4、ATG5、ATG6、ATG7、ATG8a、ATG18a的表达特征。结果表明,TMV侵染72 h后,在液泡边际和液泡内发现大量疑似自噬体结构。利用MDC荧光染色和ATG8f-ECFP瞬时表达技术,通过激光共聚焦显微镜观察,在TMV侵染72 h后发现点状荧光信号。TMV侵染48 h后,除ATG5外,烟草ATG3、ATG4、ATG6、ATG7、ATG8a、ATG18a表达均上调并在72 h达到顶峰。表明TMV侵染后感病烟草均可检测到细胞自噬现象,推测TMV侵染普通烟可诱导寄主产生细胞自噬反应。     

Ultrastructure of the Infection of Sorghum bicolor by Colletotrichum sublineolum

ABSTRACT Ultrastructural studies of the infection of susceptible and resistant cultivars of Sorghum bicolor by Colletotrichum sublineolum were conducted. Initial penetration events were the same on both susceptible and resistant cultivars. Germ tubes originating from germinated conidia formed globose, melanized appressoria, that penetrated host epidermal cells directly. Appressoria did not produce appressorial cones, but each penetration pore was surrounded by an annular wall thickening. Inward deformation of the cuticle and localized changes in staining properties of the host cell wall around the infection peg suggests that penetration involves both mechanical force and enzymic dissolution. In compatible interactions, penetration was followed by formation of biotrophic globular infection vesicles in epidermal cells. Filamentous primary hyphae developed from the vesicles and went on to colonize many other host cells as an intracellular mycelium. Host cells initially survived penetration. The host plasma membrane invaginated around infection vesicles and primary hyphae and was appressed tightly to the fungal cell wall, with no detectable matrix layer at the interface. Necrotrophic secondary hyphae appeared after 66 h and ramified through host tissue both intercellularly and intracellularly, forming hypostromatic acervuli by 114 h. Production of secondary hyphae was accompanied by the appearance of electron-opaque material within infected cells. This was thought to represent the host phytoalexin response. In incompatible interactions, infection vesicles and primary hyphae were formed in epidermal cells by 42 h. However, they were encrusted with electron-opaque material and appeared dead. These observations are discussed in relation to the infection processes of other Colletotrichum spp. and the host phytoalexin response.