乙烯产生的抑制与氟乐灵诱导棉苗对枯萎病的抗性有关(英文)

氟乐灵处理可诱发棉苗产生对枯萎病的诱导抗性,表现为推迟显症,降低发病率和病情指数。经1．0－4．0μg／g的氟乐灵处理后,棉苗受枯萎病菌侵染时其叶片和根茎部组织中乙烯的产生量明显下降（表1）,而且病菌侵染后氟乐灵处理棉苗中乙烯产生的抑制与其发病率和病情指数的下降呈正相关（图1）。经氟乐灵处理的棉苗受病菌侵染后喷以138．4μmol/L的乙烯利可同时提高其组织中乙烯的产生量以及发病率和病情指数（图2）,而未经氟乐灵处理的棉苗受病菌侵染后喷以乙烯合成抑制剂──2,4-二硝基苯酚和乙烯作用抑制剂──硫代硫酸银则明显降低发病率和病情指数（表2）。由此认为,乙烯产生的抑制可能与氟乐灵诱发棉苗产生对枯萎病的诱导抗性有关。     

Identification of resistance against Fusarium oxysporum f.sp. lini in linseed germplasm

Screening of germplasm/varieties was made to find out the sources of resistance against F. oxysporum f. sp. lini. Screening was conducted on 78 available germplasm/varieties during 2003–2004 and 2004–2005 in rabi season of linseed under natural conditions. Out of total 78 entries, 27 cultures were found to be resistant to disease as the disease incidence in these cultivars were between 0 and 10%. Twenty-three cultivars fell in moderately resistant category with 10.1–25% wilt incidence. Nine genotypes were found moderately susceptible sho'wing 25.1–50% disease incidence, 14 genotypes were found susceptible showing 50.1–75% and 6 genotypes were found highly susceptible to disease (above 75%).     

棉枯萎病菌异核体及其不同表型分离子在基因转录水平上的差异

采用银染mRNA差异显示技术,研究了棉花枯萎病菌异核体菌株(Ag149)及其两个不同表型分离子(Ag149-Ⅰ和Ag149-Ⅲ)之间差异表达的基因,观察到在300～700bp之间出现了19个差异条带,经反向RNA印迹,证实其中2条差异带为阳性：编号为C6的差异条带在Ag149和Ag149-Ⅰ菌株中呈高表达,而编号为G5的差异条带在菌株Ag149和Ag149-Ⅲ中呈高表达。这两条差异片段经测序后在GenBank中分别进行同源比较,发现由C6片段编码的氨基酸序列与多种生物(包括动物、植物和微生物)NADH脱氢酶的第6个亚基有不同程度的同源性(30％～70％);而编码G5片段的氨基酸序列与龟裂链霉菌(Streptomyces rimosus)的OtrB(tetracycline efflux protein)蛋白有35％的同源性。首次证明在异核体菌株及其不同表型分离子之间存在基因转录水平差异,为深入研究丝状真菌异核体形成的分子遗传机制提供了线索。     

Mineral Uptake in Fusarium oxysporum f. sp. vasinfectum

A method for growing Fusarium oxysporum, a mycelial fungus, and a technique for its use in mineral uptake studies have been described. Some general characteristics of the uptake process were determined. The fungus, grown for 54 hours, was found to take up as much K as 15 to 20 meq/100 g dry weight in 2 to 4 hours from a solution of 5 meq/l KCl. Approximately 3 to 5 meq of this uptake was readily removed by a CaCl₂ rinse. The uptake was only slightly sensitive to pH over the range of 4 to 9. Below pH 4 uptake dropped rapidly. The age of the culture appeared to be the dominant factor in determining the rate of uptake. In contrast to other fungi, the presence of glucose during uptake was detrimental to K uptake. Conditions unfavorable for metabolic activity as low temperature, anaerobiosis, or the presence of DNP markedly reduced the uptake rate. Although the fungus took up Na from single salt solutions nearly as well as K, the latter ion was much preferred in mixtures of the two ions. The organism showed no significant metabolic uptake of Ca or Cl. During uptake from KCl solutions, the organic acid content increased. The increase, chiefly in succinic acid and to a lesser extent in acetic and citric acids, amounted to about half the K uptake. The remainder of the K taken up was correlated with a roughly equivalent efflux of cellular Mg.     

Evaluation of Fusarium wilt disease in passion fruit species inoculated with Fusarium oxysporum f.sp. passiflorae

One of the main diseases that reduces production of passion fruit crops is Fusarium wilt, caused by the fungus Fusarium oxysporum f.sp. passiflorae (FOP). The use of resistant rootstocks, such as the species Passiflora cincinnata, is one of the management strategies used to control this disease. The objective of this work was to evaluate the pathogenicity of different isolates of FOP on P. edulis and P. cincinnata in order to identify its potential for use in areas with a history of the disease. Thirteen isolates of the fungus were used, and the inoculums were produced at a concentration of 10⁶ CFU/ml. Seedlings were produced in coconut fibre, and the root system was then immersed for five minutes in the conidial suspension before being replanted in the 770-ml pots. Inoculated seedlings of P. edulis and P. cincinnata at the three-leaf stage were daily evaluated from the second day after inoculation (DAI) until day 90. All isolates were pathogenic in both Passiflora species; however, the incidence, severity and mortality were higher in P. edulis. There was a statistically significant difference for the incubation period of the FOP 23 and FOP 57 isolates, being higher in P. edulis. We concluded that P. cincinnata was susceptible to FOP.     

韭菜对香蕉枯萎病菌生长及香蕉枯萎病发生的抑制作用

结合实验室抑菌试验和大棚人工接菌盆栽试验,研究韭菜对香蕉枯萎病菌4号生理小种(Foc4)的拮抗作用及其对香蕉枯萎病发生的防控效果.结果显示:离体条件下,韭菜粗提取液显著抑制Foc4菌丝的生长,造成菌丝变形、细胞的解体;也能显著抑制孢子的萌发并导致孢子失去活性.大棚盆栽试验中,韭菜处理的巴西香蕉苗枯萎病发病率降低70%,病情指数降低86.9%;韭菜处理的广粉1号粉蕉苗枯萎病的发病率降低76.7%,病情指数降低93.4%.研究表明,韭菜对Foc4有很高拮抗效果,而且对香蕉枯萎病有很高的防控作用.     

Gerbera jamesonii, a New Host of Fusarium oxysporum f.sp. tracheiphilum

The random amplified polymorphic DNA (RAPD) technique was used to analyze the total genomic DNA of pathogenic isolates of Fusarium oxysporum on Gerbera jamesonii by comparing them to representatives of the formae speciales chrysanthemi and tracheiphilum. A close genetic relationship was observed among most of the new isolates from G. jamesonii. They shared RAPD markers with the tested representatives of the forma specialis chrysanthemi . Some isolates of those tested from diseased G. jamesonii were placed in a different cluster, which included representative isolates of forma specialis tracheiphilum . This is the first report of F. oxysporum f.sp. tracheiphilum on G. jamesonii. A rapid protocol for DNA extraction directly from fungal colonies grown on potato dextrose agar allowed complete analysis in less than 4 h.     

Biocontrol efficacy of Trichoderma asperellum MSST against tomato wilting by Fusarium oxysporum f. sp. lycopersici

Tomato is a popular vegetable widely grown in the tropics, which is mainly attacked by fusarium wilt incited by Fusarium oxysporum f. sp. lycopersici (FOL). In the present scenario, an ecofriendly alternative strategy such as use of fungi from rhizosphere is being explored to combat the phytopathogen invasion. This study was carried out to evaluate the efficacy of Trichoderma asperellum MSST to promote the growth and yield parameters of tomato S-22, a susceptible variety. This study was also undertaken to manage fusarium wilt disease under in vitro and in vivo conditions. Significant increase in vegetative parameters like root length, shoot length, plant weight and chlorophyll content 60 days after sowing (DAS) was observed. There was reduction in the incidence of fusarium wilt in tomato up to 85%. Increase in the level of total phenol, peroxidase, polyphenoloxidase and phenylalanine ammonium lyase activity at 10th day of pathogen inoculation showed enhancement of plant defence mechanism by T. asperellum MSST against FOL. Overall study revealed that isolate MSST was proven to be potential biocontrol agent showing induced resistance against FOL.     

Races and virulence of Fusarium oxysporum f.sp. cubense on local banana cultivars in Kenya

Virulence of 31 Kenyan isolates of Fusarium oxysporum obtained from bananas showing symptoms of Panama disease was tested against the differential banana cvs Bluggoe, Gros Michel, Dwarf Cavendish, and two other local cvs Muraru and Wang'ae. Seventeen isolates were assigned to either race 1 or race 2 of F. oxysporum f.sp. cubense (FOC). Race 4 was not apparent in this sample of 31 isolates from Kenya as none were pathogenic to cv. Cavendish, and no wilted Cavendish have been observed in field surveys in Kenya. Races could not be assigned to 12 isolates as they were virulent on more than one differential cultivar, and two were apparently not pathogenic. All isolates assigned to races 1 and 2 belonged to the VCG bridging complex 0124/5/8/20, but some other isolates belonging to this VCG complex could not be assigned to race. All five isolates assigned to VCG 01212 could not be assigned to known races. Considerable variability thus exists within FOC isolates within this region. Local cultivars of banana showed differential resistance to the pathogen. The interaction of cultivars and isolates on the level of disease was significant. Overall, cv. Wang'ae was the most susceptible to most of the isolates tested, regardless of their race, and could therefore be used as a reference cultivar in pathogenicity tests of isolates of FOC in the East African region. Of the cultivars tested that are widely grown on smallholder farms in Kenya, Muraru was the least susceptible.     

Sciarid and shore flies as aerial vectors of Fusarium oxysporum f. sp. cucumerinum in greenhouse cucumbers

The options for managing Fusarium wilt in greenhouse cucumbers are limited by our poor understanding of the modes of survival and dissemination of the pathogen. This study uses a specific quantitative real‐time PCR assay for Fusarium oxysporum f. sp. cucumerinum to investigate the significance of flying insects as aerial vectors of the pathogen in a commercial cucumber greenhouse. Shore flies were more frequently detected (35.5%) carrying F. oxysporum f. sp. cucumerinum than sciarids (25%), with both species carrying between 1 × 10² and 1 × 10⁶ pathogen genome copies/individual. Sciarid and shore flies acquired F. oxysporum f. sp. cucumerinum following exposures to agar cultures of the pathogen of up to 94 h. Light microscopy revealed that spores were carried externally on the bodies of the adult flies. The ability of adult sciarid flies to vector the pathogen from peat‐grown diseased cucumber plants and infect healthy cucumber plants was demonstrated in a caged glasshouse trial. An inoculum density trial showed that vascular wilt disease was initiated after inoculation of peat‐grown seedlings with as few as 1000 conidia. We conclude that sciarid and shore flies play significant roles as vectors of F. oxysporum f. sp. cucumerinum in greenhouse cucumbers and need to be recognized in developing integrated crop management strategies.     

水杨酸诱导普通菜豆镰孢菌枯萎病抗病性的研究

普通菜豆是人类主要食用豆类之一,其营养价值高、栽培面积大。镰孢菌枯萎病是普通菜豆典型的土传病害,给普通菜豆生产带来严重损失。水杨酸(SA)被认为是诱导植物抗病反应的重要信号分子之一,参与植物的过敏反应(HR)和系统获得性抗性反应(SAR)。本研究通过不同植物激素处理普通菜豆BRB-130,结果表明,SA处理普通菜豆叶片使植株根中SA的含量升高,并显著提高植株对枯萎病原菌FOP-DM01菌株的抗性。SA诱导普通菜豆根组织中苯丙氨酸解氨酶、过氧化物酶活性及过氧化氢的含量显著升高,从而诱导普通菜豆产生HR和SAR。因此,SA作为普通菜豆抗病信号途径中重要的化学激活因子,能够显著提高普通菜豆对枯萎病原菌的抗病性,为发展环境友好型化学农药提供新的思路。     

Genetic analysis of resistances to races 1 and 2 of Fusarium oxysporum f. sp. lycopersici from the wild tomato Lycopersicon pennellii

Summary Resistance to race 3 of Fusarium wilt in the wild tomato Lycopersicon pennellii (LA 716) was previously found to be controlled by one major locus, I-3, tightly linked to Got-2 on chromosome 7. This accession was also found to carry resistance to races 1 and 2; a genetic analysis of these resistances is reported in this paper. This analysis proceeded in two steps. First, allelism tests demonstrated that race 1 and 2 resistances carried by L. pennellii were not allelic to the I and I-2 genes originally incorporated into L. esculentum from L. pimpinellifolium. Second, an interspecific backcross with L. pennellii (BC₁) was used to determine the mode of inheritance of these new resistances and their chromosomal location by segregation and linkage analysis. BC₁ responses to each of the races were determined using progeny tests (BC₁S₁). BC₁S₁ plants were inoculated with race 1 or 2 and evaluated after 1 month using a visual disease rating system; mean disease ratings were calculated for each BC₁ individual for each race based on the progeny scores. A bimodal frequency distribution of the BC₁ mean disease ratings was observed for both races, indicating that one major locus controlled resistance in each case. Statistical comparisons of the mean disease ratings of homozygous versus heterozygous individuals at each of 17 segregating enzyme loci were used to map the resistances to races 1 and 2. Tight linkage was detected between the enzyme locus Got-2 and resistances to both races, as was previously reported for the I-3 locus. Therefore, the Got-2 locus can be used as a selectable marker for resistances to all three races. The relationship of these resistances is discussed in the paper. In addition, as previously reported for race 3, significance was also detected for the chromosome segment marked by Aps-2 on chromosome 8 for both races. Currently many cultivars carry I and I-2 resistances to races 1 and 2. Incorporation of the LA 716 resistances to these two races into cultivars may reduce the likelihood of new race development.Florida Agricultural Experiment Station, Journal Series No. R-00205     

Molecular diversity of native Trichoderma isolates against Fusarium oxysporum f. sp. lycopersici (Sacc.). A casual agent of Fusarium wilt in tomato (Lycopersicon esculentum Mill.)

Fusarium wilt in tomato caused by Fusarium oxysporum is the one of the problematic diseases. In this study, 12 native Trichoderma isolates were isolated from different land use types in Rayalaseema region of Andhrapradesh, India and were tested for antagonistic activity against F. oxysporum using dual culture method; the maximum inhibition occurred in WT₂ (78.4%) compared to the control. Molecular characterisation using random amplified polymorphic DNA (RAPD) technique reported 91.8% polymorphism among 12 isolates of Trichoderma. Internal transcribed spacer (ITS) region of rDNA amplification with genus-specific ITS1 and ITS4 universal primers produced amplicon size from 569 bp in all the isolates. The study resulted in identification of good competitive Trichoderma isolates against F. oxysporum. A relationship was found between the polymorphism showed by the Trichoderma isolates and their hardness to F. oxysporum during antagonism. Also, exhibition of sufficient genetic polymorphism aids further exploitation in genomic fingerprinting.     

己二酸二异丁酯对辣椒种子萌发及枯萎菌的化感效应

采用模拟的方式,利用生物测定和室内培养的方法,研究了不同浓度的己二酸二异丁酯对辣椒种子萌发、幼苗生长及辣椒枯萎菌的化感效应.结果表明:己二酸二异丁酯对辣椒种子萌发和幼苗生长具有低浓度促进、高浓度抑制的化感效应;己二酸二异丁酯对辣椒和茄子种子的化感效应存在较大差异,在低浓度时对辣椒种子萌发和幼苗生长的促进作用强于茄子种子,而高浓度时对辣椒种子萌发和幼苗生长的抑制强度弱于茄子种子;各浓度己二酸二异丁酯对辣椒枯萎菌菌丝生长有极显著的抑制作用,且作用强度随着浓度增加而增强,当浓度为1 mnol·L~(-1)时抑制作用最强,抑制率为10.75%;在田间抗病性调查期间内各浓度处理均提高了辣椒幼苗的抗病性,其中以1 mmol·L~(-1)处理抗病性最好,病情指数比对照降低了49.88%.

Abstract：

By the methods of laboratory incubation and bioassay, a simulation test was conducted to study the allelopathic effects of different concentration diisobutyl adipate on pepper seed germi-nation and its seedling growth and Fusarium oxysporum f. sp. vasinfectum. For the pepper seed germination and seedling growth, diisobutyl adipate exhibited allelopathic promotion at low con-centration, but allelopathic inhibition at high concentration. There existed greater differences in the allelopathic effects of diisobutyl adipate on the seed germination and seedling growth of pepper and eggplant. The promotion effects of low concentration diisobutyl adipate on pepper were stron-ger than those on eggplant, while the inhibition effects of high concentration diisobutyl adipate on pepper were weaker than those on eggplant. All test concentration diisobutyl adipate had signifi-cant inhibition effects on the mycelium growth of Fusarium oxysporum f. sp. vasinfectum, and the effects increased with increasing diisobutyl adipate concentration, being the strongest (an inhibi-tory rate of 10. 75%) at 1 mnol·L~(-1). Field text indicated that diisobutyl adipate at all test con-centrations enhanced the disease resistance of pepper seedlings. The best effect was observed at 1 mmol·L~(-1) of diisobutyl adipate, with the disease index decreased by 49.88%, compared to the control.     

氨基酸影响尖孢镰孢菌古巴专化型厚垣孢子的形成

香蕉枯萎病是由尖孢镰孢菌古巴专化型Fusarium oxysporum f. sp. cubense（Foc）侵染引起的一种土传真菌病害,已严重威胁香蕉产业的健康发展。该病菌产生的厚垣孢子可在土壤中存活多年,是香蕉枯萎病的初侵染源。本研究通过氨基酸添加试验,证明添加甘氨酸可抑制厚垣孢子的形成;通过对该病菌厚垣孢子形成前期、初期、中期和后期的转录组分析,发现氨基酸合成通路中有93个基因的表达水平在厚垣孢子形成过程中发生了显著变化;In silico 分析表明其中10个基因参与调控真菌的氨基酸合成,11个基因参与调控真菌种的生长发育和产孢,19个基因参与调控真菌种的致病性和毒素产生。由此推测,氨基酸合成通路不仅与尖孢镰孢菌古巴专化型厚垣孢子的形成相关,其有可能参与调控该病菌的致病性。     

Genetic Variability of Fusarium oxysporum f.sp. ciceris Population Affecting Chickpea in the Sudan

Fusarium wilt caused by Fusarium oxysporum f.sp. ciceris (Foc) is the most important soilborne disease of chickpea in the Sudan and many other countries. A total of 76 Foc isolates from six different chickpea‐growing states in the Sudan have been collected in this study to investigate the genetic diversity of Sudanese Foc isolates. Additional 14 Foc isolates from Syria and Lebanon were included in this study. All isolates were characterized using four random amplified polymorphic DNA (RAPD), three simple sequence repeats (SSR), five sequence‐characterized amplified region (SCAR) primers and three specific Foc genome primers. Based on the similarity coefficient, the results indicated two major clusters included seven subclusters. The isolates from the Sudan were grouped as identified as races 0, 2 and unknown races. The isolates from Syria and Lebanon were grouped together as they identified as races 1B/C and 6, respectively. This study identified a new race Foc (race 0) in the Sudan. The results of this study will be useful for breeders to design effective resistance breeding program in chickpea in the Sudan.     

Gerbera jamesonii, Osteospermum sp. and Argyranthemum frutescens: New Hosts of Fusarium oxysporum f. sp. chrysanthemi

The pathogenicity of five isolates of Fusarium oxysporum obtained from infected gerbera (Gerbera jamesonii), chrysanthemum (Chrysanthemum morifolium), Paris daisy (Argyranthemum frutescens) and African daisy (Osteospermum sp.) plants was tested on some varieties of the following Compositae hosts: C. morifolium, G. jamesonii, Argyranthemum frutescens (Paris daisy) and Osteospermum sp. and compared with the host range and pathogenicity of an isolate of F. oxysporum f. sp. chrysanthemi obtained from the ATCC collection. The results indicated that isolates of F. oxysporum from G. jamesonii as well as those from A. frutescens and Osteospermum sp. belong to the forma specialischrysanthemi. The isolate from gerbera was virulent on all tested varieties of gerbera, C. morifolium, A. frutescens and Osteospermumsp. Similar results were obtained testing the isolates obtained from A. frutescens and Osteospermumsp. The strain from C. morifolium infected cultivar of gerbera, A. frutescens and Osteospermum sp. The pathogenicity of isolate of F. oxysporum f. sp. chrysanthemi obtained from the ATCC showed a different cultivar range particularly in the case of chrysanthemum and gerbera.     

Common Bean Reaction to Fusarium oxysporum f. sp. Phaseoli, the Cause of Severe Vascular Wilt in Central Africa

During the September‐December season of 1990, severe symptoms of Fusarium wilt were for the first time observed on a popular climbing bean (Phaseolus vulgaris L.) cultivar. G 2333. introduced within the previous 5 years. Seventy‐three bean genotypes were screened for resistance lo the disease, using artificial inoculation. The effect of inoculation density on the reaction of four selected genotypes was also investigated. Of the 29 climbing bean genotypes evaluated, 19 were resistant, including 11 of the 15 pre‐release or released cultivars. Of the 44 bush bean cultivars evaluated, 28 were resistant, five were intermediate and 11 were susceptible. All susceptible cultivars showed vascular discoloration. In both susceptible and resistant genotypes, the fungus spread almost equally from the entry points in inoculated roots to the base of the plants, but colonization and vertical spread within the vascular system were markedly less in resistant than in susceptible cultivars. At 20 and 30 cm above soil level, the fungus was only recovered from susceptible cultivars. Increasing inoculum density from 10² to 10⁷ conidia/ml did not affect the resistance of cultivars RWR 950 and G 685 but. in the susceptible cultivars G 2333 and MLB‐48‐89 A. it resulted in early appearance, high incidence and severity of the disease.