Early Events During Quiescent Infection Development by Colletotrichum gloeosporioides in Unripe Avocado Fruits

Inoculation of avocado pericarp tissue with Colletotrichum gloeospori-oides and treatment of avocado cell cultures with the cell wall elicitor of C. gloeosporioidesboth increased the production of reactive oxygen species (ROS). However, whereas the production of ROS could be detected within minutes in avocado cell suspensions, it was detected only after 2 h following inoculation of pericarp tissue. Protein kinase inhibitors such as K-252a and staurosporine and the phosphatase inhibitor microcystin-LR inhibited the release of H(2)O(2) from avocado cell suspensions. When 1 mM H(2)O(2) was exogenously applied to pericarp tissue, it enhanced ROS, phenyl-alanine ammonia lyase (PAL) activity, and epicatechin levels. But, when H(2)O(2) treatment was applied following staurosporine treatment, PAL activity was no longer induced. The uninduced ROS production in pericarp tissue of freshly harvested, unripe, resistant fruit was twice as high as in ripe, susceptible fruit. Challenge inoculation of resistant fruit further increased the ROS level; however, this increase did not occur in susceptible fruits. The current findings are consistent with the hypothesis that production of ROS is induced by fungal infection of unripe fruits and, consequently, may modulate resistance, resulting in the inhibition of fungal development and quiescence.     

Pathogenicity of Colletotrichum gloeosporioides to carrot

Abstract

Colletotrichum gloeosporioides was identified as the causal agent of carrot umbel blight in Brazil. Pathogenicity was evaluated on carrot and other host plants, as well as compared with the pathogenicity of other C. gloeosporioides isolates on carrot. C. gloeosporioides isolated from carrot umbel was able to infect tomato plants and ripe fruits of tomato and sweet pepper, in addition to carrot umbels and seedlings. This appears to be the first report of C. gloeosporioides attacking carrots.     

Development of Colletotrichum gloeosporioides Restriction Enzyme-Mediated Integration Mutants as Biocontrol Agents Against Anthracnose Disease in Avocado Fruits

ABSTRACT Reduced-pathogenicity mutants of the avocado fruit pathogen Colletotrichum gloeosporioides isolate Cg-14 (teleomorph: Glomerella cingulata) were generated by insertional mutagenesis by restriction enzyme-mediated integration (REMI) transformation. Following seven transformations, 3,500 hygromycin-resistant isolates were subjected to a virulence assay by inoculation on mesocarp and pericarp of cv. Fuerte avocado fruits. Fourteen isolates showed a reduced degree of virulence relative compared with wild-type Cg-14. Two isolates, Cg-M-142 and Cg-M-1150, were further characterized. Cg-M-142 produced appressoria on avocado pericarp similar to Cg-14, but caused reduced symptom development on the fruit's pericarp and mesocarp. Isolate Cg-M-1150 did not produce appressoria; it caused much reduced maceration on the mesocarp and no symptoms on the pericarp. Southern blot analysis of Cg-M-142 and Cg-M-1150 showed REMI at different XbaI sites of the fungal genome. Pre-inoculation of avocado fruit with Cg-M-142 delayed symptom development by the wild-type isolate. Induced resistance was accompanied by an increase in the levels of preformed antifungal diene, from 760 to 1,200 mug/g fresh weight 9 days after inoculation, whereas pre-inoculation with Cg-M-1150 did not affect the level of antifungal diene, nor did it delay the appearance of decay symptoms. The results presented here show that reduced-pathogenicity isolates can be used for the biological control of anthracnose caused by C. gloeosporioides attack.     

芒果胶孢炭疽菌漆酶lac1与致病力的相关性分析

为了明确芒果炭疽病病菌(Colletotrichum gloeosporioides)漆酶与该菌侵染相关致病因子之间的关系,本文以愈创木酚为底物筛选获得的高产漆酶菌株A2为材料,测定了漆酶粗提液对芒果炭疽病病菌致病力的影响,并通过半定量RT-PCR法,分析了在不同侵染时段漆酶基因lac1和其他酶基因的表达。结果表明,漆酶粗提液单独不能致病,但能促进该病原菌在寄主中的扩展;在侵染过程中,lac1表达与黑色素合成酶(thd和scd)基因表达相关性更高,与细胞壁降解酶(ecg和pel)基因表达也有一定相关性,但不及前者高。芒果胶孢炭疽菌分泌的漆酶有助于该菌在侵染芒果过程中的扩展,且对侵染相关致病因子黑色素合成酶和细胞壁降解酶基因的表达有一定影响。初步推测,漆酶lac1除了能通过降解芒果组织中的酚类物质、促进病原菌的扩展之外,也可以通过干扰与致病力相关的黑色素合成和细胞壁降解酶的产生来影响芒果胶孢炭疽菌致病力。     

不同杀菌剂对柑橘果实采后炭疽病菌室内毒力测定

[目的]为筛选出防治柑橘炭疽病的有效药剂.[方法]采用菌丝生长速率法测定了9种杀菌剂对柑橘炭疽病菌(Colletotrichum gloeosporioides)的毒力作用.[结果]25％吡唑醚菌酯、95％肟菌酯、96％戊唑醇、95％苯醚甲环唑、40％双胍三辛烷基、75％百菌清、75％肟菌酯戊唑醇、80％代森锰锌和70...     

Selection for Pathogenicity to Strawberry in Populations of Colletotrichum gloeosporioides from Native Plants

ABSTRACT Colletotrichum gloeosporioides causes a serious crown rot of strawberry and some isolates from native plants are pathogenic to strawberry. C. gloeosporioides from lesions on wild grape and oak were sampled at two sites adjacent to commercial strawberry fields in Florida and two distant sites. Random amplified polymorphic DNA (RAPD) marker data and restriction enzyme digests of amplified rDNA were used to determine whether isolates were from the same C. gloeosporioides subgroup that infects strawberry. There were 17 to 24 native host isolates from each site that clustered with a group of strawberry crown isolates based on RAPD markers. Among strawberry isolates, there were two rDNA genotypes identified by restriction enzyme analysis. Both genotypes were present among native host isolates sampled from all four sites. There was some evidence that the different rDNA genotypes differentiated two closely related subpopulations, although the proportion of pathogenic isolates from native hosts among the two different genotypes was not different. The incidence of isolates pathogenic to strawberry was greater at sites close to strawberry fields relative to sites distant from strawberry fields for isolates with a BstUI(-)/MspI(+) rDNA genotype (44 versus 13%), a BstUI(+)/MspI(-) genotype (57 versus 16%), or when both genotypes were analyzed together (46 versus 15%). Based on these results, it appears that the C. gloeosporioides subgroup that causes crown rot on strawberry is widely distributed in Florida and that selection for pathogenicity on strawberry occurs in the area where this host is grown in abundance.     

Survey of Fungicide Sensitivity in Colletotrichum gloeosporioides from Different Avocado and Mango Production Areas in South Africa

Pre-harvest fungicidal treatments aimed at reducing inoculum levels in the field include copper oxychloride and benomyl. Pre-harvest applications of benomyl are currently restricted if used on fruit destined for certain export markets. Isolates of Colletotrichum gloeosporioides collected during a three-year market survey were used to determine the incidence of resistance to benomyl, thiabendazole and prochloraz using an in vitro assay. A total of 17.7% of all isolates tested were resistant to benomyl, of which 8.5% were highly and 9.2% moderately resistant. Isolates from certain production areas were less sensitive to benomyl and thiabendazole, and mango isolates were generally more sensitive than avocado isolates. No isolates were resistant to thiabendazole or prochloraz.     

Laccase Gene LAC1 of Colletotrichum lagenarium Is Not Essential for Melanin Biosynthesis and Pathogenicity

Laccase has been shown to oxidize 1,8-dihydroxynaphthalene (1,8-DHN) in the final step of melanin biosynthesis in several fungi. In this study, a laccase gene (LAC1) was cloned from Colletotrichum lagenarium that synthesizes 1,8-DHN melanin, and characterized. To clone the LAC1 sequences, genomic DNA was subject to polymerase chain reactions (PCR) with degenerate oligonucleotide primers that were designed on the basis of amino acid sequences conserved among characterized laccases from other ascomycetes Botrytis cinerea, Neurospora crassa, Aspergillus nidulans, and Cryphonectria parasiticus. The LAC1 gene contained an open reading frame composed of 589 codons and three introns of 51, 49, and 57 nucleotides. The deduced amino acid sequence of Lac1p had high similarity to that of laccase from N. crassa and significant homology with those of multicopper blue proteins. Under melanin-induced culture of this fungus, laccase activity significantly increased and LAC1 expression was also detected. However, the lac1Δ mutants retained laccase activity and had no significant phenotypic differences in melanin production or pathogenicity from the wild-type strain. Received 23 February 2001/ Accepted in revised form 29 March 2001     

火把对柑桔炭疽病菌的室内毒力试验

采用菌丝生长速率法,用杀菌剂火把对柑桔炭疽病菌进行了室内毒力测定,测得火把对柑桔炭疽病的EC50值为0.8110μg/mL,EC98值为10.5435μg/mL,确定了其在室内有效抑菌浓度。本试验有利于指导进一步的室外药效试验以确定实际应用中的最佳施用浓度。     

芽胞杆菌SM905的鉴定及其对铁皮石斛胶孢炭疽菌的抑菌活性研究

芽胞杆菌Bacillus sp.SM905是本实验室分离并保存的一株活性细菌,为进一步明确其分类地位及其对铁皮石斛胶孢炭疽菌Colletotrichum gloeosporioides的抑菌活性,利用形态学、生理生化特性及16S rDNA和gyrB序列分析对SM905进行种属鉴定;采用菌丝生长速率法、插片法和琼脂平板法测定了不同浓度的SM905发酵上清液对靶标菌菌丝生长和孢子萌发的影响;并通过盆栽试验考察其防效。结果表明,SM905为贝莱斯芽胞杆菌Bacillus velezensis。不同稀释倍数的SM905发酵上清液对胶孢炭疽菌均有一定的抑制作用,其中5倍稀释液对菌丝生长的抑制率最高,为97.89%,20倍稀释液的抑制率也达90%左右。处理组残留胶孢炭疽菌气生菌丝表现为畸形、空洞、色素积累等,基内菌丝产生大量的分生孢子。SM905发酵上清液不影响胶孢炭疽菌孢子的萌发率,但是导致萌发后的菌丝生长稀疏、膨大。盆栽试验结果表明,SM905粉剂100倍液间隔7 d喷施2次对铁皮石斛炭疽病的防效为80.74%,优于10%苯醚甲环唑水分散粒剂800倍液。本研究表明,芽胞杆菌SM905可以作为铁皮石斛炭疽病生物防治用生防菌,具有良好的应用前景。     

辣椒胶孢炭疽菌生物学特性初步研究

从广西南宁市采集辣椒炭疽病果实病害标本,进行病原菌分离培养、致病性测定及形态学鉴定,选择引起辣椒炭疽病的病原菌之--胶孢炭疽菌(Colletotrichum gloeosporioides)进行生物学特性研究,结果表明:在测试的不同温度、pH、湿度、光照和营养中,该菌的菌丝体生长和产孢的最适温度分别为25℃和30℃,菌丝体生长和产孢的最适pH值为7,光照对菌丝生长的影响不大,在光暗交替下可促进产孢;分生孢子萌发的最适温度为30℃,最适pH值为7,分生孢子在相对湿度为100%和100%+水滴中能萌发,在100%+水滴中萌发率最高,为99.5%,光照对孢子萌发影响不大;辣椒煎水和辣椒煎水+蔗糖可促进附着胞形成,附着胞在辣椒煎汁中形成率最高,达到90%.     

'Dead skin' on yams (Dioscorea alata) caused by Colletotrichum gloeosporioides

A storage rot of yams ( Dioscorea alata ), commonly referred to as 'dead skin', has recently become a major constraint to yam production in the Caribbean. The fungal pathogen Colletotrichum gloeosporioides was consistently isolated from affected tubers and re-inoculation of healthy yam tubers resulted in the development of typical symptoms of dead skin.     

Colletotrichum acutatum and C. gloeosporioides Cause Anthracnose on Olives

Morphological and cultural features and restriction fragment length polymorphism analysis of ITS regions, including 5.8S rDNA, from 26 isolates of Colletotrichum species revealed that isolates from olive fruits, previously identified as C. gloeosporioides, belong to two taxa: C. acutatum and C. gloeosporioides. Comparison of both ITS sequence data with reference isolates confirmed the presence of both species in olives affected by anthracnose disease.     

Ulvan effect on conidial germination and appressoria formation of Colletotrichum gloeosporioides

Ulvan is an algal polysaccharide known for its ability to induce resistance to plant diseases such as the Glomerella leaf spot of apple caused by Colletotrichum gloeosporiodes. This study was aimed at investigating microscopically, in tests in vitro and in vivo, whether ulvan interferes in the development of pre-infective structures of C. gloeosporioides. Conidial germination and appressoria formation were monitored hourly on agar and cellophane, and at 48 h on water- and ulvan-treated susceptible as well as resistant apple leaves. Amendment of agar with ulvan (10 mg ml^?1) enhanced the germination and resulted in longer germ tubes at 7 h of incubation. On cellophane it significantly delayed appressoria formation up to 8 h, but later after 14 h increased the number of appressoria per conidium. Spraying of susceptible leaves with ulvan 6 days before inoculation decreased disease severity by 50%. This was associated with inhibition of appressoria formation and stimulus in growth of germ tubes, without interfering with conidial germination, when compared with both water-treated control and resistant plants. Appressorium formation occurred preferentially on anticlinal walls of epidermal cells and its location was not influenced by host resistance or by ulvan treatment. This study suggests a new mode of action for ulvan interfering with appressorium formation that could protect apple plants against C. gloeosporioides infection.     

越南进境人参果炭疽病病原菌的分离鉴定

2008年4月从广州出入境检验检疫局送检的越南进境人参果样品(报检号:P02297)中发现果实表面密布近圆形褐色病斑,病斑直径约为3mm,中央黄褐色,边缘深红褐色,多个病斑可愈合成片.室温下放置1周,病果即完全腐烂,全果果皮及果肉均转成褐色.采用组织分离培养法获得分离物,经对分离物培养性状与形态特征观察、致病性测定,并辅助于分子生物学检测,将病害鉴定为人参果炭疽病,病原菌为胶孢炭疽菌(Colletotrichum gloeosporioides).Blast分析表明从病原菌基因组中扩增到的1.8 kbp 18S rDNA 片段与胶孢炭疽菌18S rRNA基因同源率为99%.迄今为止人参果炭疽病在国内外均未见报道,这是我国首次从进境人参果中截获并检验鉴定该病害.     

Effects of antagonistic microorganisms on the post-harvest development of Colletotrichum gloeosporioides on mango

Potential microbial antagonists of Colletotrichum gloeosporioides were isolated from blossom, leaves and fruit of mango and screened using a series of assay techniques. In total 648 microorganisms, including bacteria, yeasts and filamentous fungi, were isolated and tested for their inhibition of growth of C. gloeosporioides on malt extract agar. In vitro , 121 organisms inhibited the fungus and were tested further for their ability to affect conidial germination. Of these isolates, 45 bacteria and yeasts inhibited germination. These were inoculated onto mangoes artificially infected with C. gloeosporioides and assessed for their potential to reduce the development of anthracnose lesions. Seven isolates were chosen for use in a trial in the Philippines using freshly harvested fruit. This final screening procedure yielded two potential candidates for further trials, isolate 204 (identified as Bacillus cereus ) and isolate 558 (identified as Pseudomonas fluorescens ). In post-harvest trials under commercial conditions, isolates 204 and 558 were both tested in combination with different application methods including the addition of adhesive material, peptone, fruit wax or sucrose polyester. Application of isolate 204 did not reduce disease development, whereas application of 558 significantly reduced anthracnose development. No additional benefit was achieved by incorporating the bacteria in adhesive material, peptone, fruit wax or sucrose polyester.     

土槿皮乙酸对胶孢炭疽菌分生孢子萌发过程中核分裂的影响

为探究天然抑菌成分土槿皮乙酸对胶孢炭疽菌有丝分裂的影响,以多菌灵为药剂对照,以其亚致死剂量(EC30)处理了胶孢炭疽菌分生孢子,通过DAPI荧光染料染色观察了孢子萌发过程中的核相变化。结果表明,胶孢炭疽菌分生孢子在正常萌发过程的0~4 h,发生2次核分裂,之后菌体核分裂为1次/h,至12 h时共发生了10次核分裂;10 mg/L多菌灵处理胶孢炭疽菌12 h,菌体共发生了4次或5次核分裂,自第2次核分裂起,每次细胞核分裂的时间较未经药剂处理延迟5 h左右;5 mg/L土槿皮乙酸处理条件下,菌体12 h内共发生了7次核分裂,且自第3次核分裂后,每次核相发生变化的时间较未经药剂处理延迟3 h左右。可见,土槿皮乙酸能够抑制胶孢炭疽菌分生孢子萌发过程中细胞核的分裂,这可能与其抑制孢子萌发、芽管伸长及导致菌丝异常生长的作用有关。     

苹果炭疽叶枯病菌CgCMK1基因的克隆与功能分析

苹果炭疽叶枯病是由胶孢炭疽菌(Colletotrichum gloeosporioides)引起的苹果重要叶部病害,严重威胁苹果树的生长。CMK1-MAPK途径在植物病原真菌致病过程中具有重要的作用。本研究从苹果炭疽叶枯病菌中克隆了黄瓜炭疽病菌(C.lagenarium)CMK1的同源基因CgCMK1。CgCMK1基因ORF全长1 068 bp,编码355个氨基酸。CgCMK1敲除后不影响苹果炭疽叶枯病菌营养生长、色素沉积以及脂滴的转运。ΔCgCMK1突变体产孢能力显著下降、分生孢子萌发但不产生附着胞,外源添加cAMP不能诱导ΔCgCMK1突变体形成附着胞,在ΔCgCMK1突变体中,过表达cAMP信号途径依赖的蛋白激酶催化亚基基因CgCPK1也不能恢复突变体形成附着胞。CgCMK1基因参与氧化胁迫的应答反应,但不参与离子胁迫的应答反应。ΔCgCMK1突变体对苹果叶片完全丧失致病性,即使有伤接种也不能产生病斑。CgCMK1在苹果炭疽叶枯病菌分生孢子和附着胞中均有表达,定位于细胞质。上述结果表明,CgCMK1参与调控苹果炭疽叶枯病菌的分生孢子产量、附着胞的形成、氧化胁迫应答及致病性。     

苹果炭疽叶枯病菌CgCMK1基因的克隆与功能分析

 苹果炭疽叶枯病是由胶孢炭疽菌(Colletotrichum gloeosporioides)引起的苹果重要叶部病害,严重威胁苹果树的生长。CMK1-MAPK途径在植物病原真菌致病过程中具有重要的作用。本研究从苹果炭疽叶枯病菌中克隆了黄瓜炭疽病菌(C. lagenarium)CMK1的同源基因CgCMK1。CgCMK1基因ORF全长1 068 bp,编码355个氨基酸。CgCMK1敲除后不影响苹果炭疽叶枯病菌营养生长、色素沉积以及脂滴的转运。ΔCgCMK1突变体产孢能力显著下降、分生孢子萌发但不产生附着胞,外源添加cAMP不能诱导ΔCgCMK1突变体形成附着胞,在ΔCgCMK1突变体中,过表达cAMP信号途径依赖的蛋白激酶催化亚基基因CgCPK1也不能恢复突变体形成附着胞。CgCMK1基因参与氧化胁迫的应答反应,但不参与离子胁迫的应答反应。ΔCgCMK1突变体对苹果叶片完全丧失致病性,即使有伤接种也不能产生病斑。CgCMK1在苹果炭疽叶枯病菌分生孢子和附着胞中均有表达,定位于细胞质。上述结果表明,CgCMK1参与调控苹果炭疽叶枯病菌的分生孢子产量、附着胞的形成、氧化胁迫应答及致病性。