Analysis of genetic variability of Fusarium oxysporum f. sp. cepae the causal agent of basal rot on onion using RAPD markers

Genetic variability among isolates of Fusarium oxysporum f. sp. cepae was obtained from different onion-growing areas of Tamil Nadu, India. Random amplified polymorphic DNA (RAPD) analysis was carried out using 12 random primers, each of them consisting of 10 base pairs. Four out of the 12 primers were differentiated between some of the tested F. oxysporum f. sp. cepae isolates. Analysis of the genetic coefficient matrix derived from the scores of RAPD profile showed that minimum and maximum per cent similarities among the F. oxysporum f. sp. cepae isolates were in the range of 14–85%. Cluster analysis, using the unweighted pair-group method with arithmetic average, clearly separated the isolates into two clusters (A and B) confirming the genetic diversity among the isolates of F. oxysporum f. sp. cepae from onion.     

Induction of defence-related enzymes in onion by combined application of fungal and bacterial biocontrol agents against Fusarium oxysporum f. sp. cepae

Basal rot disease of onion is a major problem in different onion growing regions of Tamil Nadu, India. Fungal and bacterial cultures were isolated and tested their efficiency against Fusarium oxysporum f. sp. cepae under in vitro conditions. Effective bacterial and fungal antagonists were tested alone and in combinations for the control of F. oxysporum f. sp. cepae in glasshouse experiments. Defence-related enzymes such as peroxidase, polyphenol oxidase and phenylalanine ammonia-lyase were induced and accumulated in onion treated with fungal and bacterial antagonists. Defence-related enzymes were significantly higher in onion pretreated with consortial formulation of Pf12 + Pf27 + TH3 at 5 days after the challenge inoculation with F. oxysporum f. sp. cepae and gave resistance to onion against basal rot disease.     

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%).     

香蕉枯萎菌基因组DNA提取方法的研究

以香蕉枯萎菌菌株为试验材料,在SDS～CTAB法和高盐沉淀法等基础上加以改进,对两种提纯香蕉枯萎菌基因组DNA的方法进行了比较研究。结果表明：高盐沉淀法是适合于香蕉枯萎菌基因组DNA提取的方法。该方法提取的DNA OD260／OD280的比值为1．841,DNA产量为0．81mgDNA／g菌丝体。基因组DNA经琼脂糖凝胶电泳得到一条带型较宽且清晰的DNA谱带,基本无DNA碎带;将提取的DNA直接用于PCR扩增,得到带多而且清晰、整齐、基本无拖尾的RAPD图谱。     

Fungus gnats vector Fusarium oxysporum f.sp. radicislycopersici1

Fungus gnat adults transported Fusarium oxysporum f.sp. radicis-lycopersici from Petri dish culture and infected host plants to the roots and hypocotyls of healthy tomato and bean plants. The source of the fungus did not affect the ability of fungus gnats to transport the fungus to healthy hosts. The presence of fungus gnat larvae in media in which young tomato plants were grown did not increase the incidence of plant infection by the pathogen. Fungus gnat adults appear to aid in the dissemination of F. oxysporum f.sp. radicis-lycopersici.     

香蕉枯萎病菌4号生理小种致病相关基因foABC1的分离

通过对香蕉枯萎病菌4号小种致病突变体B1233的进一步研究,分离了被突变的致病相关基因foABC1,同源性分析及保守结构预测该基因编码一类ABC转运蛋白,其功能可能同稻瘟病菌的ABC转运蛋白一样,负责真菌毒素的泵出,或是像其他真菌的ABC转运蛋白,在病原菌侵染寄主植物时能忍耐植物因防卫反应所释放的植保素或抗毒素类物质。     

Selection of bacteria able to control Fusarium oxysporum f. sp. radicis-lycopersici in stonewool substrate

AIMS: Tomato foot and root rot (TFRR), caused by Fusariumoxysporum f. sp. radicis-lycopersici (Forl), is an economically important disease of tomato. The aim of this study was to develop an efficient protocol for the isolation of bacteria, which controls TFRR based on selection of enhanced competitive root-colonizing bacteria from total rhizosphere soil samples. METHODS AND RESULTS: A total of 216 potentially enhanced bacterial strains were isolated from 17 rhizosphere soil samples after applying a procedure to enrich for enhanced root tip colonizers. Amplified ribosomal DNA restriction analysis, in combination with determination of phenotypic traits, was introduced to evaluate the presence of siblings. One hundred sixteen strains were discarded as siblings. Thirty-eight strains were discarded as potential pathogens based on the sequence of their 16S rDNA. Of the remaining strains, 24 performed equally well or better than the good root colonizer Pseudomonas fluorescens WCS365 in a competitive tomato root tip colonization assay. Finally, these enhanced colonizers were tested for their ability to control TFRR in stonewool, which resulted in seven new biocontrol strains. CONCLUSIONS: The new biocontrol strains, six Gram-negative and one Gram-positive bacteria, were identified as three Pseudomonas putida strains and one strain each of Delftia tsuruhatensis, Pseudomonas chlororaphis, Pseudomonas rhodesiae and Paenibacillus amylolyticus. SIGNIFICANCE AND IMPACT OF THE STUDY: We describe a fast method for the isolation of bacteria able to suppress TFRR in stonewool, an industrial plant growth substrate. The procedure minimizes the laborious screens that are a common feature in the isolation of biocontrol strains.     

香蕉枯萎病菌Argonaute基因功能分析及其调控小RNA发生

尖孢镰刀菌古巴专化型Fusarium oxysporum f.sp.cubense是威胁香蕉生产的重要土传病原真菌,其中4号生理小种(Foc4)能感染几乎所有的栽培品系.Argonaute蛋白(AGO)介导的RISC复合体在RNAi干扰中起到重要作用.Foc4含有两个进化上高度保守的AGO蛋白,本研究利用同源重组技术获...     

基于RAPD、ISSR和AFLP对西瓜枯萎病菌遗传多样性的评价

利用RAPD、ISSR和AFLP分子标记技术对50个西瓜枯萎病菌株进行了分析。结果表明,21个RAPD引物、21个ISSR引物和21对AFLP引物分别对供试菌株扩增出113、134和389条带,三种分子标记的遗传相似系数比较一致,均可揭示西瓜枯萎病菌的遗传变异特点。三种分子标记产生的聚类分析结果存在一定差异,其中RAPD类群与生理小种和地理来源之间均不存在明显关系;而AFLP和ISSR类群与生理小种之间存在一定相关性,与菌株的地理来源关系不明显。     

基于RAPD、ISSR和AFLP对西瓜枯萎病菌遗传多样性的评价

利用RAPD、ISSR和AFLP分子标记技术对50个西瓜枯萎病菌株进行了分析。结果表明,21个RAPD引物、21个ISSR引物和21对AFLP引物分别对供试菌株扩增出113、134和389条带,三种分子标记的遗传相似系数比较一致,均可揭示西瓜枯萎病菌的遗传变异特点。三种分子标记产生的聚类分析结果存在一定差异,其中RAPD类群与生理小种和地理来源之间均不存在明显关系;而AFLP和ISSR类群与生理小种之间存在一定相关性,与菌株的地理来源关系不明显。     

应用PCR-RFLP和巢式PCR检测黄瓜尖镰孢菌

以3株黄瓜尖镰孢菌(Fusarium oxysporum f.sp.cucumarinum)、23株镰孢菌属(Fusariumspp.)真菌和分离自土壤的20株真菌、6株细菌和7株放线菌为材料,采用化学裂解法提取总DNA,进行PCR-RFLP和巢式PCR检测,试验证明PCR-RFLP程序不能完全区分Fusarium属内不同种,而巢式PCR对黄瓜尖镰孢菌具有特异性.运用优化的PCR-RFLP和巢式PCR检测程序对染病黄瓜组织进行了检测,结果表明,两种方法均可在接种发病早期(未显症时)检测出黄瓜枯萎病菌,PCR-RFLP在感病品种接种后3d即可检测到病原菌,而巢式PCR在接种后5d才能检测到病原菌.     

Purification and characterization of an exopolygalacturonase produced by Fusarium oxysporum f. sp. radicis lycopersici

Abstract An exopolygalacturonase produced by Fusarium oxysporum f. sp. radicis lycopersici , a fungus that produces root rot, was purified by gel filtration and ion exchange chromatography. It had a M _r 68 K, a pH optimum of 5.6 and an optimum temperature of 60°C. This polygalacturonase was inhibited by calcium ions and had a K _m of 0.64 mM using sodium polypectate as substrate. The exo mode of action of this enzyme was revealed by thin-layer chromatography of hydrolysed substrate.     

香蕉枯萎病菌Fow1基因的克隆及序列分析

为了解Fow1基因在尖镰刀菌古巴专化型侵染香蕉过程中的作用,及其与尖镰刀菌古巴专化型生理小种1号和生理小种4号之间的致病力差异的关系,采用PCR和RT-PCR方法扩增了2个生理小种的Fow1基因,并对扩增产物进行了克隆测序及相似序列搜索和比对,还对基因编码的蛋白进行了结构预测和功能分析。研究结果表明2个生理小种Fow1基因开放阅读框均为957bp,编码318个氨基酸,基因序列和氨基酸序列差异小,而且两个生理小种Fow1基因所编码的蛋白均具有酵母线粒体载体蛋白典型的结构特征,推测Fow1基因可能为香蕉枯萎病菌在香蕉组织中定殖所必需。从Fow1基因序列及其编码蛋白的氨基酸序列看,2个生理小种致病力的差异与Fow1基因并无明显对应关系,这为进一步研究Fow1基因功能奠定了基础。     

尖孢镰刀菌古巴专化型MAPK FoSlt2敲除突变体的转录组分析

尖孢镰刀菌古巴专化型Fusarium oxysporum f. sp. cubense（FOC）是威胁香蕉生产的重要土传病原真菌。丝裂原活化蛋白激酶（mitogen-activated protein kinase,MAPK）FoSlt2信号通路在调控尖孢镰刀菌古巴专化型的生长发育、细胞壁完整性和致病性方面发挥着重要作用。为了揭示FoSlt2信号通路的致病机理和寻找农药靶标,本研究利用高通量RNA-seq技术对该病菌野生型菌株和FoSlt2敲除突变体菌株的转录组进行了比较分析,结果表明差异表达基因共有2 164个,其中上调表达基因有1 184个,下调表达基因有980个。Gene Ontology（GO）功能分析结果表明,差异表达基因主要参与在结合、催化分子功能组和代谢过程、细胞过程生物学通路中。KEGG 功能富集分析结果表明,差异基因主要参与戊糖和葡糖醛酸盐转换、氨基糖和核苷酸糖、氨基葡聚糖降解、磷酸肌醇和碳类物质代谢通路,说明这些通路与尖孢镰刀菌古巴专化型的生长发育和致病性相关。该研究为尖孢镰刀菌古巴专化型致病机制的阐明奠定了理论基础。     

Characterization of Fusarium oxysporum f.sp. cepae from Onion in Turkey Based on Vegetative Compatibility and rDNA RFLP Analysis

Seventy‐five isolates of Fusarium oxysporum f.sp. cepae, the causal agent of basal plate rot on onion, were obtained from seven provinces of Turkey. The isolates were characterized by vegetative compatibility grouping (VCGs) and restriction fragment length polymorphism (RFLP) analysis of the nuclear ribosomal DNA intergenic spacer region (IGS). Forty‐eight vegetative compatibility groups were found, each containing a single isolate. Only one isolate formed strong heterokaryons with the reference isolates of VCG 0423. Five isolates were heterokaryon self‐incompatible. Restriction fragment analysis with six different enzymes revealed 13 IGS types among 75 F. oxysporum isolates from Turkey as well as 16 reference isolates from Colorado, USA. The majority of single‐member VCGs produced identical RFLP banding patterns with minor deviations, considerably different from those of the reference VCG isolates. These results suggested that isolates of F. oxysporum f.sp. cepae in Turkey derived from distinct clonal lineages and mutations at one or more vegetative compatibility loci restrict heterokaryon formation.     

A rapid serological test for detecting Fusarium oxysporum f.sp. narcissi in Narcissus

Polyclonal antiserum was elicited against a strain of Fusarium oxysporum f.sp. narcissi (GCRI80/26) and a specific and sensitive enzyme-linked immunosorbent assay developed. Antiserum raised to cell wall fractions gave better recognition than that to cytoplasmic fractions. Recognition was equally good in artificially and naturally infected bulbs. Little cross-reactivity in bulb tissue was shown by three other bulb-rotting fungi. Nine isolates of F. oxysporum f.sp. narcissi from a wide geographic area gave similar results in an indirect ELISA of mycelial extracts, although some cross-reactivity was observed with two other Fusarium spp. Four Fusarium spp. and four other fungi showed little cross-reactivity. Ten days after inoculation the pathogen was readily detected in the base plate area of three Narcissus cultivars and points remote from the inoculation site in the most susceptible cultivar. A direct correlation was observed between positive results in the enzyme-linked immunosorbent assay and recovery of the pathogen on selective medium.     

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.     

Biological control of Fusarium oxysporum f. sp. radicis-cucumerinum by some Trichoderma harzianum isolates

The purpose of this study was to investigate the effects of isolates T₂₂, T₉ and T₆ of Trichoderma harzianum on isolate F₄₂ of Fusarium oxysporum f. sp. radicis-cucumerinum. The effect of T. harzianum isolates on controlling disease was examined under greenhouse conditions. Results showed that these three isolates, respectively, had the high effect on inhibition of pathogen growth. In examining the severity of disease in the greenhouse, it was found that isolate T₂₂ had the greatest effect on controlling the pathogen. The results of volatile compounds showed that these isolates, respectively, were effective in reducing mycelial growth of isolate F₄₂. The highest peroxidase activity was observed on the fourth day in isolate T₆ and the highest phenylalanine ammonia lyase enzyme activity was observed on the fifth day in isolate T₂₂. Based on the results, isolate of T₂₂ showed the greatest effect on the induction of resistance against F₄₂ and may be a successful agent for biological control of root and stem rot of cucumber.     

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.