核盘菌侵入油菜超微结构及侵染机制的研究

 通过电子显微镜观察核盘菌在油菜叶片上侵染过程,发现该菌首先在叶片上形成复合附着器。每个分枝末端一般生出一个侵染钉。侵染钉侵入叶表面腊质、角质层和表皮细胞壁时.不仅靠附着器产生的压力,而且供助于酶对寄主表面的软化、消解作用。该菌通过角质层和表皮细胞壁侵入油菜叶片,尚未发现通过气孔侵入的现象。侵入叶片后,该菌的继续生长,导致了油菜组织的溃烂。然后菌丝在腐烂的叶片上集结形成菌核。     

小麦雪霉叶枯病菌的侵染过程

 本文报道了小麦雪霉叶枯病菌Gerlachia nivalis的叶面侵染过程。该菌分生孢子发芽后相互结合,形成网状复合体,产生粗壮的叶面菌丝,经由气孔保卫细胞间隙侵入,不产生特化的侵染机构。侵染菌丝在叶肉细胞间和细胞内扩展,也可由气孔逸出在叶面蔓延。分生孢子梗由分生孢子座上产生,由气孔抽出。产孢细胞顶端有环痕。叶面菌丝亦能产孢。寄主组织病变特点表明该菌产生活性很强的胞外酶。     

栗疫病菌侵染板栗枝条的显微观察

栗疫病是一种严重危害栗属植物的病害。为了明确栗疫病菌侵染板栗枝条的过程及侵染的关键时间点,本研究利用病理组织切片技术、显微镜和扫描电镜技术对栗疫病菌侵染板栗枝条的过程进行了观察。结果表明:接种栗疫病菌后0～5 h,菌丝先降解枝条表皮,进行横向营养生长的同时沿着伤口纵向侵染,为进入皮层做准备;接种后6 h病菌开始在表皮定殖,并侵入皮层;接种后9 h在皮层可观察到侵染性菌丝沿着细胞间隙向相邻细胞延伸;接种后12 h栗疫病菌侵入韧皮部,在皮层的侵染面积扩大。随着侵染程度加深,皮层、韧皮部等处细胞被菌丝降解,最终在形成层附近聚集。接菌后9 h为栗疫病菌侵染板栗枝条的关键时间点。     

苹果树腐烂病树皮带菌部位和侵入途径

苹果树腐烂病菌是伤口寄生菌,其菌丝经带有死组织的伤口或经死组织侵入。但在田间,还常见到在没有伤口或死组织的部位也发了病。为此,作者试图通过试验的方法,明确苹腐菌经树皮表面死组织和经叶痕、果柄痕、皮孔侵入,并在其中潜伏的可能性。 病原菌侵入和扩展要求条件不同。苹腐菌侵入后,当侵染点周围组织健康时,一般不能立即扩展致病,而潜伏侵染。此时,往往不易判定菌丝是否已侵入。为此,做了以下三个试验:     

大丽轮枝菌侵染抗感棉种的组织学过程观察

 棉花黄萎病是一种极难防治的土传性真菌病害,研究病原菌侵染棉花的组织学过程对致病机理解析和抗病资源利用具有重要意义。本研究利用绿色荧光蛋白标记的大丽轮枝菌系统研究了其对抗病棉种海岛棉7124和三裂棉、感病棉种军棉1号和戴维逊棉的侵染过程。结果表明,大丽轮枝菌对抗/感棉种的初始侵染没有明显差异,接菌5 h后,分生孢子均能吸附在感病和抗病棉种的根表面。但侵染过程存在显著差异,侵染感病棉种中病原菌3~5 d到达皮层,5~7 d达到维管束,随后迅速扩展繁殖,侵染14 d后即完成系统侵染,并开始产生黄萎病症状;而病原菌侵染抗病棉种,5~7 d才侵入皮层,7~10 d到达维管束,14 d后仍无法扩展,病原菌的定殖与发展受到限制,无法形成系统侵染,较少形成黄萎病症状。本研究通过绿色荧光蛋白标记大丽轮枝菌对抗/感棉种的侵染过程研究,为大丽轮枝菌致病机理研究和抗性资源利用提供了强有力的理论依据。     

蚕豆油壶菌火肿病的组织病理学

 为了解巢豆油壶菌（Olpidium viciae）侵染蚕豆叶片和茎引起细胞和组织的病理学变化,采用光学显微镜观察蚕豆叶和茎的病、健表皮组织及组织切片的解剖结构和病原物在寄主细胞中的动态。结果表明,巢豆油壶菌侵入叶和茎的表皮细胞后,定殖在被侵入的细胞内,菌体生长发育,整体产果,形成游动孢子囊和休眠孢子囊。病菌的侵染刺激了侵染点邻近的表皮细胞和其下的叶肉组织或茎的皮层组织细胞,这些已分化的组织细胞转为分生细胞,进行分裂,分裂方式为平周分裂。原有的正常基本组织细胞被未高度分化的薄壁组织细胞取代。这些细胞具有分生能力并不断分裂,细胞体积增大,造成蚕豆病组织细胞发生畸形增生的病理解剖改变,病部呈瘤状隆起。这是蚕豆油壶菌火肿病症状产生的病理组织学机制,也反映了巢豆油壶菌和蚕豆在细胞和组织水平上的相互作用。     

串珠镰刀菌引起玉米穗粒腐病防御酶变化及其电镜观察

 对串珠镰刀菌(Fusarium moniliforme)侵染引起玉米穗粒腐病的防御酶活性变化和病原菌侵染过程进行研究。采用人工接菌的方法,分别对抗(Bt鄄1)、感(掖478)玉米材料进行接种,取抗、感材料间隔24 h 的6 个时间段接菌部位的苞叶组织,分析玉米植株感病后部分防御酶、同工酶谱的动态变化,并用扫描电镜对病原菌入侵植株过程进行组织病理学观察。扫描电镜观察发现,菌丝首先要经过1 ~ 3 d 生长后,大约在72 h 左右开始侵入气孔,并且随着时间的推移,侵入气孔的菌丝量逐渐增多。这说明病原菌是直接通过气孔侵入寄主苞叶组织。同时,玉米受串珠镰刀菌侵染后,苯丙氨酸解氨酶 (PAL)和过氧化物酶(POD)的活性都是先上升后下降,在感病材料Ye478 中PAL 的活性要比抗病材料Bt鄄1 中增加的更快、更高;同样对于POD 来说,在感病材料Ye478 中的活性要比抗病材料Bt鄄1 中的高,但变化趋势在2 个材料中相似;而丙二醛(MDA)的含量则相反,在感病材料Ye478 中的活性要比抗病材料Bt鄄1 中的低;对POD 同工酶酶谱分析,2 个材料都增加了3 ~ 4 个条带,没有明显的区别,这说明玉米感病后会通过增加POD 的活性来抵御外源病菌的侵入。总体而言PAL和POD 活性水平与材料抗性呈负相关;MDA 与材料抗性呈正相关关系。对玉米植株感病后防御酶活性变化的分析和病原菌入侵寄主的电镜观察结果,可为深入研究玉米穗粒腐病抗病机制和抗病育种提供参考。     

草莓品种对白粉病菌抗性的组织病理学研究

以4个生产上主栽草莓品种为试材,采用曲利苯兰透明染色法,系统研究了草莓白粉病菌在不同抗性草莓品种上侵染过程的组织学特征。结果表明,草莓白粉病菌的侵染过程可分为：分生孢子萌发、附着胞形成、侵入寄主产生吸器、菌丝扩展和分生孢子链产生。而草莓不同品种对白粉菌的抗性表现在附着胞产生后的各侵染阶段,随品种抗病性增强,病菌侵入率降低,吸器数目减少,菌丝扩展缓慢,分生孢子数目减少。     

瓜果腐霉游动孢子对番茄和秋海棠侵染过程的研究

 作者研究了瓜果腐霉游动孢子的附着特性和侵染过程。游动孢子主要附着在番茄苗根的根毛区和根冠上,休止孢子萌发的芽管在侵入根毛之前,能形成附着孢或前侵染丝;而游动孢子对秋海棠的附着主要集中在茎部和叶尖、叶缘处,芽管直接侵入茎、叶的表皮细胞及须根。     

小麦叶锈菌侵入方式的观测简报

小麦叶锈菌侵入方式的观测简报小麦叶锈菌的侵入方式，以往文献报道为萌发的芽管遇气孔后，形成附着胞覆盖在气孔上，长出侵入丝钻入气孔，并在气孔下腔内形成泡囊，再长出侵染丝侵入细胞内形成吸器，完成侵入过程。我们经３年的重复观察，发现除上述方式外，还有大量的锈...     

几种除草剂对胡麻田裸燕麦(莜麦)、皮燕麦的防除效果

本文开展了唑啉草酯等7种除草剂对胡麻田裸燕麦、皮燕麦的防除试验研究,结果表明,在胡麻株高5~7cm,裸燕麦、皮燕麦3~5叶期施药,50g/L唑啉草酯乳油、108g/L高效氟吡甲禾灵乳油、15%精吡氟禾草灵乳油、240g/L烯草酮乳油和10%精喹禾灵乳油有效成分剂量分别为90、145.8、315、432和90g/hm2时,药后45d对裸燕麦的株防效达95.39%以上,鲜重防效达97.21%以上,胡麻增产率在82.79%以上;50g/L唑啉草酯乳油、108g/L高效氟吡甲禾灵乳油、15%精吡氟禾草灵乳油、15%炔草酯可湿性粉剂、10%精喹禾灵乳油和12.5%烯禾啶乳油有效成分剂量分别为90、145.8、270、135、90和412.5g/hm2时,药后45d对皮燕麦的株防效在94.66%以上,鲜重防效达96.13%以上,胡麻增产率在80.25%以上,各药在上述剂量下防治裸燕麦和皮燕麦后均对胡麻表现安全,可大面积示范推广。     

Periodicity and gradients in dispersal ofAlternaria linicola in linseed crops

Conidia ofAlternaria linicola produced on infected linseed crops were mainly dispersed by wind. The numbers of conidia in the air above linseed crops collected by a Burkard spore sampler were greatest between 1200 h and 1300 h, when the relative humidity was lowest. Although numbers of conidia collected decreased with increasing height within and above the crop canopy, air-borneA. linicola conidia were present up to 80 cm above the crop canopy. Conidia ofA. linicola were transported by wind up to at least 40 m downwind from an artificial line inoculum source, but their numbers decreased with increasing distance from the source. In 1991, 1992, and 1993, the dispersal ofA. linicola conidia above linseed crops followed a seasonal periodicity which was influenced by weather conditions and cultural practices. The greatest numbers of conidia were collected during July, August and early September and coincided with periods favourable for sporulation and with an increase in the incidence of the disease in the senescent crop. Air-borneA. linicola conidia produced on point or line inoculum sources (naturally infected linseed stem debris) were responsible for the spread of the disease in linseed crops. In 1992 and 1993, the disease was first detected downwind from the sources, but by the end of the growing seasons, it had spread in all directions and up to 20 m and 60 m from the sources, respectively. Disease gradients were initially steep near the inoculum sources but they became flatter with time due to the secondary spread of the disease.     

Management of root-knot nematode,Meloidogyne incognita,infesting Egyptian henbane,Hyoscyamus muticus L., by the use of nematicides and oilcakes

Studies were carried out to evaluate the efficacy of various nematicides: aldicarb (Temik 10G), and carbofuran (Furadan 3G) at 3 kg a.i./ha, mocap (Ethoprop 10G) at 5 kg a.i./ha and oilcakes ofcastor ( Ricinus communis L., 4.2% N), groundnut ( Arachis hypogea L., 7% N), linseed ( Linum usitassimum L., 4.7% N), neem ( Azadirchta indica Juss, 5.4% N) and mustard ( Brassica compestris L., 4.8% N) at 1 g N/kg of soil in the form of soil amendments for the management of Meloidogyne incognita (Kofoid & White) Chitwood infesting Egyptian henbane ( Hyoscyamus muticus L.). All the treatments resulted in a significant increase in length, fresh and dry weights ofhenbane plants as compared with untreated inoculated plants. The maximum improvement in plant growth parameters was observed in plants treated with mocap followed by neem cake, aldicarb, carbofuran, castor, mustard, groundnut and linseed cakes respectively. Application of nematicides and oilcakes suppressed the pathogenic effect of M. incognita on Hyoscyamus muticus and resulted in significant reduction in gall intensity and population density ofroot-knotnematode in roots and soil. In comparison to untreated inoculated plants the highest reduction in root-knot index was noted in plants treated with mocap, whereas the lowest reduction was observed in plants treated with linseed cake.     

Thrips (Thysanoptera) associated with two genetically modified types of linseed (Linum usitatissimum L.)

Journal of Plant Diseases and Protection - The aim of this study was to determine thrips abundance, species composition and seasonal dynamics on two genetically modified types of linseed, i.e.,...     

Infection of Linseed by Alternaria linicola; Effects of Inoculum Density, Temperature, Leaf Wetness and Light Regime

Controlled environment studies were conducted to determine the effects of inoculum density, temperature, leaf wetness and light regime on the infection of linseed by Alternaria linicola. The % cotyledons and leaves with symptoms, and the disease severity (% leaf area with symptoms) increased linearly when the inoculum density increased from 1×10³ to 1×10⁵ conidiaml^–1. The first symptoms appeared on cotyledons and leaves 4 and 6 days after inoculation, respectively. Eight hours of leaf wetness were sufficient to initiate the disease at 25°C but not at 15°C, when 10-h periods of leaf wetness were required. % leaf area with symptoms was lower at 15°C than that at 25°C irrespective of the leaf wetness periods tested. Interruption of a continuous leaf wetness period by a 12-h dry period, occurring at any time between 1 and 18h after inoculation, decreased the % cotyledons with symptoms and the disease severity, with the greatest reductions (60% and 100%, respectively) being observed when the dry period began 6h after inoculation. A. linicola conidia were able to exploit successive 12-h periods of leaf wetness cumulatively to infect linseed plants. Disease incidence and severity were positively correlated with the dark period following inoculation, but they were negatively related to the length of the initial light period. Our findings suggest that infection of linseed by A. linicola and further development of symptoms can occur under unfavourable environmental conditions.     

Estimation of seed production by Stellaria media, Sinapis arvensis and Tripleurospermum inodorum in arable crops

Summary Seed production by Sinapis arvensis , Tripleurospermum inodorum and Stellaria media growing alone or in crops of spring wheat, spring field beans and spring linseed was studied in 11 experiments. Seed numbers for S. arvensis and T. inodorum were measured directly from samples harvested in late summer but for S. media were estimated from measurements of flower number and seeds/flower. Seed numbers were regressed against plant dry matter. In general, a linear log/log plot ( y  =  mx  +  c ) fitted the data for each species quite well ( R ² = 0.75, 0.89, 0.89 for S. arvensis , T. inodorum and S. media respectively), but there were small differences between crops and years in the individual regression lines, especially the intercept values. Estimated seed production for a 'mean' 10-g plant (dry matter) in the three crops for S. arvensis , T. inodorum and S. media was 590, 6300 and 8600, respectively. Seed production tended to be lower for the weeds in wheat than it was in field beans and linseed, or in the plants grown alone, primarily due to the differences in plant weight arising from the differing competition exerted by the crops involved .     

Derivatives of N-(pyrid-2-yl)thiourea as root growth inhibitors

N-Benzoyl-N'-(3-methylpyrid-2-yl)thiourea has been shown to inhibit the elongation of linseed roots grown on nutrient agar, 50% inhibition being observed at a concentration of 0.18 μ. Similar effects were observed at higher concentrations on lettuce, ryegrass, cress, tomatoes and mustard. The effects were qualitatively similar to those caused by trifluralin. A structure-activity study of analogues of this pyridyl thiourea indicates that structural requirements for this biological activity are extremely specific. In soil tests, this compound exhibits pre-emergent herbicidal activity with a spectrum of selectivity different from that of trifluralin.     

Molecular Characterisation of Alternaria linicola and its Detection in Linseed

Nucleotide sequences of the ribosomal DNA (rDNA) internal transcribed spacers (ITS) 1 and 2 and a 1068bp section of the beta-tubulin gene divided seven designated species of Alternaria into five taxa. Stemphylium botryosum formed a sixth closely related taxon. Isolates of A. linicola possessed an identical ITS sequence to one group of A. solani isolates, and two clusters of A. linicola isolates, revealed from beta-tubulin gene data to show minor variation, were as genetically similar to isolates of A. solani as they were to each other. We suggest, therefore, that A. linicola falls within the species A. solani. Similar results suggest that A. lini falls within the species A. alternata. RAPD analysis of the total genomic DNA from the Alternaria spp. concurred with the nucleotide sequence analyses. An oligonucleotide primer (ALP) was selected from the rDNA ITS1 region of A. linicola/A. solani. PCR with primers ALP and ITS4 (from a conserved region of the rDNA) amplified a c. 536bp fragment from isolates of A. linicola and A. solani but not from other Alternaria spp. nor from other fungi which may be associated with linseed. These primers amplified an identical fragment, confirmed by Southern hybridization, from DNA released from infected linseed seed and leaf tissues. These primers have the potential to be used also for the detection of A. solani in host tissues.     

A small-scale method for the determination of pyrethroid insecticide residues in crops and soils

A small-scale method for the determination of pyrethroid insecticide residues in crops and soils is described. Compared with the conventional methods, the overall analysis time is reduced by approximately 60% and solvent usage is reduced by approximately 80% using this approach. Results obtained on a range of crops using the small-scale and conventional methods were in good agreement, and a repeatability study showed that the small-scale approach is unbiased and gives good precision. To date, linseed, tobacco, cotton foliage, cotton seed, wheat grain, sorghum, savoy, cauliflower, cabbage, cucumber, apple, peach, blackcurrant, gooseberry, raspberry and soil samples have been analysed using the method. Good recoveries were obtained with all these matrices.     

First report of the sexual stage of the flax pathogen Mycosphaerella linicola in France and its impact on pasmo epidemiology

We performed a 3-year field survey in France to characterize the dynamics of sexual reproduction in Mycosphaerella linicola, the causal agent of pasmo, during the interepidemic period. Cohorts of fruiting bodies were sampled from linseed straw during the autumn and winter and carefully observed, focusing on pseudothecia, asci, and ascospores. A sequence of experimental steps corresponding to Koch's postulates confirmed in July 2014, for the first time in France and continental Europe, the widespread presence of the sexual stage of M. linicola in plant host tissues. The developmental dynamics of pseudothecia on straw, expressed as the change over time in the percentage of mature pseudothecia, was similar in all three years. Pseudothecia appeared in late summer, with peak maturity reached in October. A temporal shift, thought to be due to early autumn rainfall, was highlighted in one of the three years. These observations suggest that sexual reproduction plays a significant role in the epidemiology of pasmo in France. A resurgence of M. linicola infections in spring flax is thought to have occurred in recent years, due to the increase in the area under flax. The presence of the sexual stage of this pathogen probably increased the quantitative impact of residues of winter linseed (used for oil) and flax straw (left on the soil for retting and used for fibres) as an interepidemic “brown bridge”. This case study highlights how certain parts of a disease cycle, in this case the sexual phase, can become crucial due to changes in production conditions.