The Occurrence and Pathogenicity of Cylindrocarpon, Cylindrocladium and Fusarium on Calluna vulgaris and Erica spp. in England and Scotland

Cylindrocarpon, Cylindrocladium and Fusarium spp. were often isolated from the woody roots, stem-base and lower foliage of diseased container-grown Calluna vulgaris and Erica spp. plants collected from English and Scottish nurseries. The highest isolation frequencies were obtained for Cylindrocarpon destructans, Cylindrocladium scoparium, Cylindrocladium ilicicola. Fusarium tricinctum, Fusarium avenaceum and Fusarium sporotrichioides . Isolations of these fungi were made more frequently from diseased plants that were at least 1-year-old. The percentage incidence of Cylindrocarpon, Cylindrocladium and Fusarium spp. did not differ between Scottish and English nurseries. Cylindrocarpon destructans. Cylindrocladium ilicicola and C. scoparium were more pathogenic to rooted C. vulgaris cuttings than F. tricinctum. F. avenaceum or F. sporotrichioides in laboratory and glasshouse tests. The high isolation frequency of Cylindrocarpon. Cylindrocladium and Fusarium spp., and their pathogenicity in tests, suggests that these fungi are involved in root, stem-base and lower foliage diseases in crops of C. vulgaris and Erica spp. The importance of these findings for the integrated control of diseases on ericaceous plant nurseries is discussed.     

健康与患病刺梨植株可培养叶际真菌菌群差异比较

本研究比较了健康与患叶斑病刺梨植株叶际真菌群落特征差异,以期探索病原菌的潜在来源,为人工构建具拮抗功能群落和刺梨叶斑病的生物防控提供参考。通过可培养方法对不同健康状况的刺梨叶际真菌进行分离培养,结合形态学和分子系统学对菌株进行综合鉴定;利用FUNGuild平台对真菌进行功能注释;结合根际、根部真菌作拆分网络分析探索病原菌的潜在来源。本研究结果表明：1）刺梨叶际真菌具有丰富的多样性。从刺梨叶际8个样品中共分离到真菌266株,其隶属于3门、6纲、13目、30科、46属中的61个种。其中,健康植株叶际内生真菌（LHE）包括8属10种27株,附生真菌（LHS）包括33属37种77株。患病叶际内生真菌（LDE）分离到7属10种38株;附生真菌（LDS）分离到31属35种124株。2）不同样品的真菌优势属和特有类群有差异。不同健康状况下叶际附生真菌的优势属均为拟盘多毛孢属Pestalotiopsis,但二者的相对多度存在差异,LHS为11.49%,LDS为32.26%;内生真菌优势属二者均为链格孢属Alternaria,但相对多度各异,LHE为33.33%,LDE为63.16%。其中,LHE特有类群为盘长孢状刺盘孢 Colletotrichum gloeosporioides和果生刺盘孢Colletotrichum fructicola等8种;LDE特有类群为茄链格孢 Alternaria solani和Didymella sinensis 等8种;LHS特有类群是草酸青霉Penicillium oxalicum和Peniophora crassitunicata等21种;LDS特有类群是尖孢镰刀菌Fusarium oxysporum、赭绿青霉Penicillium ochrochloron和易脆毛霉Mucor fragilis等19种。3）不同样品叶际真菌功能不同。经FUNGuild解析表明,LHS、LHE和LDE的叶际真菌功能群主要以腐生型为主,LDS则主要以植物病原菌群为主。本研究结果初步揭示刺梨植株健康与患叶斑病叶际间真菌多样性、群落组成及营养功能群存在差异,植株健康状况与其真菌群落特征密切相关;叶斑病病原菌主要源于刺梨叶际的附生微生物群。     

Endophytic microorganisms as potential growth promoters of banana

The potential of endophytic microorganisms in promoting the growth of their host plant was determined by artificially introducing five isolates (bacterial and fungal strains: UPM31F4, UPM31P1, UPM14B1, UPM13B8, UPM39B3) isolated from the roots of wild bananas into both healthy and diseased banana plantlets (Berangan cv. Intan). The response of the host plants to endophytic infection was assessed by measuring the change in four growth parameters: plant height, pseudostem diameter, root mass and total number of leaves. The endophytes tested as growth promoters were found to have a significant effect in both healthy and Fusarium-infected (diseased) plantlets. In both experimental systems, the bacterial isolate UPM39B3 (Serratia) and fungal isolate UPM31P1 (Fusarium oxysporum) showed promising growth-promoting properties. Isolate UPM39B3 (Serratia) induced the largest increases in all four growth parameters in healthy plantlets – 3.14 cm (height), 1.12 cm (pseudostem diameter), 2.12 g (root mass) and 1.12 (total number of leaves plant⁻¹) – followed by isolate UPM31P1 (Fusarium oxysporum). The beneficial effect of UPM39B3 (Serratia) and UPM31P1 (Fusarium oxysporum) was also reflected in the diseased plantlets, where pre-treatments with the isolates either singly (T6: UPM31P1; T8: UPM39B3) or in a mixture (T7: UPM31P1 + UPM39B3; T9: UPM14B1 + UPM13B8 + UPM39B3) were able to sustain the growth of plantlets, with significantly higher growth values than those in diseased plantlets that were not infected with endophytes (T10: FocR4). These results demonstrate the economic significance of these endophytic isolates, particularly UPM39B3 (Serratia) and UPM31P1 (Fusarium oxysporum), both as potential growth promoters of banana and as agents rendering tolerance towards Fusarium wilt as a strategy in the management of Fusarium wilt of banana via improved vegetative growth.     

Rhizosphere mycoflora of healthy and yellow vein mosaic virus infected okra (Abelmoschus esculentus) plants.

Investigations on the rhizosphere mycoflora of healthy and virus (YVMV) infected okra plants showed a higher fungal population in the rhizosphere of healthy plants at preflowering and post-flowering stages than in that of diseased ones. Maximum population was observed during flowering both in healthy and diseased plant rhizosphere as well as in non-rhizosphere soil. However, virus infected plants showed a higher population at the flowering stage than healthy ones. The quantitative differences in the rhizosphere of healthy and diseased plants during flowering seem to be due to a change in C/N ratio and amino acids. The drastic reduction in diseased plant rhizospheres during the post-flowering stage may be due to either change in C/N ratio unfavourable to mycoflora or production of some toxic substances inhibiting multiplication of the mycoflora.     

Colonization of root tissues and protection against Fusarium wilt of rye (Secale cereale) by nonpathogenic rhizosphere strains of Fusarium culmorum

Colonization of rye (Secale cereale) tissues by nonpathogenic rhizosphere Fusarium culmorum isolates DEMFc2 and DEMFc5 and a pathogenic strain DEMFc37, and their effect on plant fresh weight were studied in pot experiments. Both rhizosphere isolates colonized the epidermis and the cortex but were not found in vessels, while the pathogen colonized all three layers of root cells. The numbers of pathogen CFU isolated from plant tissues were much higher than those of the rhizosphere isolates in spite of the same number of macroconidia used as inoculum (1 × 10⁵ g⁻¹ of soil). Inoculation of seedlings with DEMFc2 resulted in a 20% increase, with DEMFc5 in more than a 20% reduction, and with DEMFc37 in a 38% reduction of shoot fresh weight of 14-day-old plants. Pre-colonization of plants with (either of) the rhizosphere isolates and subsequent inoculation with the pathogen resulted in plant weights the same as those observed in plants inoculated with the rhizosphere strain alone. The disease severity index for shoots of plants pre-colonized with DEMFc2 was reduced from class 4 (86% diseased plants) observed for plants inoculated with the pathogen alone to class 2 (average of 8% diseased plants) when pre-treated with the rhizosphere strain. The CFU number of the pathogen isolated from the interior of roots of plants pre-colonized with the rhizosphere isolates was as low as 10% of the number isolated from plants inoculated with the pathogen alone. A study of in vitro interactions between the rhizosphere isolates and the pathogen suggests that changes in plant colonization by the pathogen and its effect on fresh weight of plants pre-colonized with the rhizosphere isolates were not connected with inhibition of its growth by a direct action of the rhizosphere isolates. The results suggest that strain DEMFc2 can be considered as a potential biocontrol agent.     

黑胫病感染对烟草茎秆及根际土壤真菌群落结构的影响

烟草黑胫病是由寄生疫霉烟草变种引起的一种对烟草生产造成巨大经济损失的土传病害。本文以健康烟株与感染黑胫病烟株茎秆和根际土壤为研究对象,通过PCR技术扩增样本中真菌转录间隔区的ITS1区域,采用Illumina Miseq高通量测序技术对扩增片段进行测序,旨在了解黑胫病感染对于烟草茎秆和根际土壤真菌群落结构与多样性的影响。本研究20个测序样品,共获得755 599条高质量序列片段,最短序列为200bp,最长序列为356bp,平均序列长度248bp。结果表明,健康烟株和发病烟株根际土壤的优势真菌为子囊菌门Ascomycota、接合菌门Zygomycota和担子菌门Basidiomycota,所有茎秆样品的优势真菌为子囊菌门、担子菌门。健康烟株与感染黑胫病烟株根际土壤样品相对丰度大于1%的属有镰刀菌属Fusarium、被孢霉属Mortierella、隐球菌属Cryptococcus、链格孢属Alternaria和赤霉菌属Gibberella等,其中,健康烟株根际土壤优势属为镰刀菌属（39.35%）和被孢霉属（14.19%）,发病烟株根际土壤镰刀菌属和被孢霉属相对丰度分别为40.26%和20.77%;健康茎秆样品优势属为隐球菌属（31.12%）、链格孢属（18.28%）、镰刀菌属（15.67%）和红酵母属Rhodotorula（13.34%）;病健交界茎秆样品优势属为镰刀菌属（41.36%）、隐球菌属（28.15%）和链格孢属（22.32%）;发病茎秆优势属为隐球菌属（62.14%）和链格孢属（27.75%）。烟株感染黑胫病后,其根际土壤与茎秆样品真菌优势属种类与健康烟株无明显变化,但属水平的相对丰度变化显著。发病烟株茎秆与根际土壤样品真菌群落Sobs、Chao1、Shannon指数较健康烟株降低,Simpson指数上升,表明烟株发病后根际土壤真菌与茎秆内生真菌群落丰富度与多样性降低。该结果对于研究烟草黑胫病发生的微生态机制及其生物防治具有一定的理论指导意义。     

Hummingbirds as vectors of fungal spores in Moussonia deppeana (Gesneriaceae): taking advantage of a mutualism?

Hummingbirds act as vectors of Fusarium moniliforme spores on protandrous flowers of Moussonia deppeana. The resulting interactions between the pathogen and plant-pollinator interactions were investigated in a 4-yr study to determine the pathogen's impact on host flowering phenology, flower longevity, nectar production, and fruit and seed production. We also evaluated hummingbird behavior on healthy and diseased plants and its effectiveness on spore transmission. Individual plants expressed the disease from year to year, and new infected individuals were detected every year. A fraction of the flowers in a plant expressed the disease, and this varied among and within years. Diseased plants produced more inflorescences, buds, and open healthy flowers than did healthy plants. Further, diseased plants bore proportionally fewer pistillate flowers than did healthy plants when considering only healthy flowers. Neither nectar nor fruit production differed between healthy and diseased plants, but healthy plants produced more seeds. Infected flowers were retained longer than uninfected ones, producing an additional 2 mg · μL(-1) · flower(-1) of nectar sugar. Hummingbirds visited more flowers on diseased plants than they did on healthy plants, regardless of number and sexual phase. Most pollen and spores were deposited within plants. These behavioral outcomes may promote geitonogamy and limit fungal spore mixing.     

Isolation of fluorescent pseudomonads from the rhizosphere of banana plants antagonistic towards root necrosing fungi

Total aerobic bacteria and fluorescent pseudomonads were counted in bulk and rhizospheric soils of banana plants of 14 plantations in Martinique (French West Indies). Fluorescent Pseudomonas isolates were then identified and investigated for in vitro antagonism towards Cylindrocladium sp., a fungal pathogen of banana roots. Total aerobic bacteria and fluorescent pseudomonads were significantly more abundant in rhizospheric soils than in bulk soils. Among 58 fluorescent Pseudomonas isolates, 41 were identified as Pseudomonas fluorescens biovar V and 17 as Ps. putida biovar A. Six strains exhibited an antagonism towards Cylindrocladium isolates. Among them, Ps. putida strain 93.1 totally blocked fungal growth. No relationship was established between the antifungal effect and enzyme or hydrogen cyanide production by bacteria, suggesting that siderophores and other compounds were involved in fungal inhibition. Antagonistic fluorescent pseudomonads represent a potential for the biological control of banana root infections by Cylindrocladium sp.     

Use of Rhizobacteria in the Control of Root Rot–Root Knot Disease Complex of Mungbean

Thirty-two isolates of Pseudomonas aeruginosa and a Bacillus subtilis strain were isolated from rhizosphere and rhizoplane of four wild and 15 cultivated plants. Biocontrol and growth-promoting potentials of the bacterial isolates were tested under laboratory, greenhouse and field conditions. The bacterial isolates not only exhibited nematicidal activity by killing the second stage larvae of Meloidogyne javanica to a varying degree but also produced inhibition zones by inhibiting the radial growth of Macrophomina phaseolina, Fusarium solani and Rhizoctonia solani . Strain IE-2 and IE-6 of P. aeruginosa also lysed the fungal mycelium. P. aeruginosa and B. subtilis used as seed dressing or as soil drench significantly suppressed root rot–root knot infection and nematode population densities under greenhouse and field conditions and thereby enhanced plant growth and yield in mungbean.     

Illumina-based analysis of the rhizosphere microbial communities associated with healthy and wilted Lanzhou lily (<Emphasis Type="Italic">Lilium davidii</Emphasis> var. <Emphasis Type="Italic">unicolor</Emphasis>) plants grown in the field

Lanzhou lily (Liliumdavidii var. unicolor) is the best edible lily as well as a traditional medicinal plant in China. The microbes associated with plant roots play crucial roles in plant growth and health. However, little is known about the differences of rhizosphere microbes between healthy and wilted Lanzhou lily (Lilium davidii var. unicolor) plants. The objective of this study was to compare the rhizosphere microbial community and functional diversity of healthy and wilted plants, and to identify potential biocontrol agents with significant effect. Paired end Illumina Mi-Seq sequencing of 16S rRNA and ITS gene amplicons was employed to study the bacterial and fungal communities in the rhizosphere soil of Lanzhou lily plants. BIOLOG technology was adopted to investigate the microbial functional diversity. Our results indicated that there were major differences in the rhizosphere microbial composition and functional diversity of wilted samples compared with healthy samples. Healthy Lanzhou lily plants exhibited lower rhizosphere-associated bacterial diversity than diseased plants, whereas fungi exhibited the opposite trend. The dominant phyla in both the healthy and wilted samples were Proteobacteria and Ascomycota, i.e., 34.45 and 64.01 %, respectively. The microbial functional diversity was suppressed in wilted soil samples. Besides Fusarium, the higher relative abundances of Rhizoctonia, Verticillium, Penicillium, and Ilyonectria (Neonectria) in the wilted samples suggest they may pathogenetic root rot fungi. The high relative abundances of Bacillus in Firmicutes in healthy samples may have significant roles as biological control agents against soilborne pathogens. This is the first study to find evidence of major differences between the microbial communities in the rhizospheric soil of healthy and wilted Lanzhou lily, which may be linked to the health status of plants.     

Effect of Bacterial Wilt on Fungal Community Composition in Rhizosphere Soil of Tobaccos in Tropical Yunnan

Bacterial wilt, which is a major soil-borne disease with widespread occurrence, poses a severe danger in the field of tobacco production. However, there is very limited knowledge on bacterial wilt-induced microecological changes in the tobacco root system and on the interaction between Ralstonia solanacearum and fungal communities in the rhizosphere soil. Thus, in this study, changes in fungal communities in the rhizosphere soil of tobaccos with bacterial wilt were studied by 18S rRNA gene sequencing. The community composition of fungi in bacterial wilt-infected soil and healthy soil in two tobacco areas (Gengma and Boshang, Lincang City, Yunnan Province, China) was studied through the paired comparison method in July 2019. The results showed that there were significant differences in fungal community composition between the rhizosphere soil of diseased plants and healthy plants. The changes in the composition and diversity of fungal communities in the rhizosphere soil of tobaccos are vital characteristics of tobaccos with bacterial wilt, and the imbalance in the rhizosphere microecosystem of tobacco plants may further aggravate the disease.     

Anther-smut infection of Silene alba caused by Ustilago violacea: factors determining fungal reproduction

Summary The anther-smut fungus Ustilago violacea sporulates in flowers of the dioecious host plant Silene alba. Growth chamber comparisons of healthy and diseased plants, with the genetic background of host and pathogen controlled, revealed that fungal infection increases the number of flowers produced per plant and decreases the size of individual flowers. There were few consistent effects of plant genotype or fungal isolate on diseased flower traits, but differences between the plant sexes were apparent. Stimulation of flower production is proportionally greater in females than males: thus, although healthy male plants produce many more flowers than healthy females, sexual differences in diseased flower number are reduced. Sexual differences in diseased flower size also exist, with male flowers smaller than females. A field inoculation study confirmed dimorphism in diseased flower size and demonstrated that spore production per flower was greater for males than females for all flower size classes.     

The endophytic fungi from wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

In order to study the species composition of endophytes from wheat healthy plants in Buenos Aires Province (Argentina) and to determine their infection frequencies from leaves, stems, glumes and grains, wheat plants were collected from five cultivars at five growth stages from crop emergence to harvest. A total of 1,750 plant segments (leaves, stems, glumes and grains) were processed from the five wheat cultivars at five growth stages, and 722 isolates of endophytic fungi recovered were identified as 30 fungal genera. Alternaria alternata, Cladosporium herbarum, Epicoccum nigrum, Cryptococcus sp., Rhodotorula rubra, Penicillium sp. and Fusarium graminearum were the fungi that showed the highest colonization frequency (CF%) in all the tissues and organs analysed. The number of taxa isolated was greater in the leaves than those in the other organs analysed.     

Effect of virus infection on the rhizosphere mycoflora of papaya plants

Summary Rhizosphere mycoflora of PLRV (Papaya Leaf Reduction Virus)- infected and healthy papaya plants have been investigated at the pre-flowring, flowering and post-flowering stages of plants. The fungal population per g of soil was higher in rhizosphere of diseased plants at all the three stages than that of healthy ones. The increased C/N ratio in the leaves of PLRV-infected papaya plants is responsible for the increased rhizosphere mycoflora concentration of infected plants.     

Molecular profiling of fungal assemblages in the healthy and infected roots of <Emphasis Type="Italic">Decalepis arayalpathra</Emphasis> (J. Joseph &amp; V. Chandras) Venter,an endemic and endangered ethnomedicinal plant from Western Ghats,India

Decalepis arayalpathra, an endangered, endemic ethnomedicinal plant from southern Western Ghats, India, is targeted for its aromatic and medicinal properties. This study aimed at to identify fungal endophyte populations associated with healthy and diseased roots of this perennial shrub. Healthy and rotted root samples of D. arayalpathra were collected, fungal endophytes assemblages were identified both by culture-dependent and culture-independent approaches, further sequenced and the retrieved sequences were analysed with the reference sequences in GenBank to know their phylogenetic relationships. Analysis of the ITS rDNA region generated 24 different Ascomycota and three Basidiomycota taxa. Trichoderma sp. was most abundant in healthy and diseased root samples, while Penicillium and Aspergillus were confined to healthy roots. Furthermore, Fusarium solani, Fusarium oxysporum and Mucor velutinosus were found to be the most frequent fungi identified from the rotted root samples, thus substantiated to be the cause for D. arayalpathra decline in the wild. Interestingly, the strains assigned to Fusarium sp. were isolated from diseased roots showing typical clearly visible symptoms, such as a severe brown discolouration on the taproot. Molecular profiling of all the pure fungal isolates, viz., Trichoderma, Penicillium, Aspergillus, Fusarium and Mucor, revealed high sequence similarities (≥ 98 %) to corresponding reference sequences. Sequencing of Trichoderma pure cultures isolated from healthy and diseased roots revealed sequence similarities to Trichoderma harzianum, T. hamatum, T. koningiopsis, T. asperellum, T. pubescens and Hypocrea sp. This confirms the morphological examinations, as Hypocrea is the teleomorph stage of Trichoderma sp. This study signifies the first work pertaining to the taxonomy of the fungal endophytic community of D. arayalpathra, and the results reported in this work may help to ascertain the cause of root rot disease often perceived in D. arayalpathra. Also, it could be useful to identify the promising endophytic communities against the root rot diseases occurring in D. arayalpathra.     

Populations of the spinach wilt pathogen, Fusarium oxysporum f. sp. spinaciae, in the root tissues, rhizosphere, and soil in the field.

Populations of Fusarium oxysporum f. sp. spinaciae in root tissues and rhizosphere soil of diseased spinach plants were higher than in the root tissues and rhizosphere soil of healthy plants. Populations in soil rhizosphere were higher than in nonrhizosphere soil. The fungus populations were very low in the root tissues of the nonsusceptible strawberry, broccoli, chinese cabbage, and mustard grown in the infested field. The populations were low at the beginning of the season, increased, and remained high during the summer, then dropped in the fall. The fungus populations ranged from 1600 to 2600 propagules/g in the top 10 cm of soil, declined sharply between 11 and 20 cm, and were nondetectable between 41 and 60 cm.     

Molecular and phenotypic characterization of potential plant growth-promoting <Emphasis Type="Italic">Pseudomonas</Emphasis> from rice and maize rhizospheres

In this study, Pseudomonas species were isolated from the rhizospheres of two plant hosts: rice (Oryza sativa cultivar Pathum Thani 1) and maize (Zea mays cultivar DK888). The genotypic diversity of isolates was determined on basis of amplified rDNA restriction analysis (ARDRA). This analysis showed that both plant varieties selected for two distinct populations of Pseudomonas. The actual biocontrol and plant promotion abilities of these strains was confirmed by bioassays on fungal (Verticillum sp., Rhizoctonia solani and Fusarium sp.) and bacterial (Ralstonia solanacearum and Bacillus subtilis) plant pathogens, as well as indole-3-acetic acid (IAA) production and carbon source utilization. There was a significant difference between isolates from rice and maize rhizosphere in terms of biological control against R.  solanacearum and B.  subtilis. Interestingly, none of the pseudomonads isolated from maize rhizosphere showed antagonistic activity against R.  solanacearum. This study indicated that the percentage of pseudomonad isolates obtained from rice rhizosphere which showed the ability to produce fluorescent pigments was almost threefold higher than pseudomonad isolates obtained from maize rhizosphere. Furthermore, the biocontrol assay results indicated that pseudomonad isolated from rice showed a higher ability to control bacterial and fungal root pathogens than pseudomonad isolates obtained from maize. This work clearly identified a number of isolates with potential for use as plant growth-promoting and biocontrol agents on rice and maize.     

Microplastics alter composition of fungal communities in aquatic ecosystems

Despite increasing concerns about microplastic (MP) pollution in aquatic ecosystems, there is insufficient knowledge on how MP affect fungal communities. In this study, we explored the diversity and community composition of fungi attached to polyethylene (PE) and polystyrene (PS) particles incubated in different aquatic systems in north‐east Germany: the Baltic Sea, the River Warnow and a wastewater treatment plant. Based on next generation 18S rRNA gene sequencing, 347 different operational taxonomic units assigned to 81 fungal taxa were identified on PE and PS. The MP‐associated communities were distinct from fungal communities in the surrounding water and on the natural substrate wood. They also differed significantly among sampling locations, pointing towards a substrate and location specific fungal colonization. Members of Chytridiomycota, Cryptomycota and Ascomycota dominated the fungal assemblages, suggesting that both parasitic and saprophytic fungi thrive in MP biofilms. Thus, considering the worldwide increasing accumulation of plastic particles as well as the substantial vector potential of MP, especially these fungal taxa might benefit from MP pollution in the aquatic environment with yet unknown impacts on their worldwide distribution, as well as biodiversity and food web dynamics at large.     

羊肚菌白霉病发生对土壤真菌群落结构的影响

【目的】了解羊肚菌白霉病发生对土壤真菌群落结构的影响。【方法】采用Illumina Mi Seq高通量测序技术,对未栽培羊肚菌土壤、正常生长羊肚菌和染白霉病羊肚菌根际土真菌群落结构进行研究。【结果】9个样品共得到393 347条有效序列。未栽培羊肚菌土壤真菌多样性指数和丰度显著大于羊肚菌根际土,染病羊肚菌根际真菌丰度和多样性大于正常生长的羊肚菌,各样品的群落组成和优势类群有较大差异。【结论】羊肚菌栽培后真菌多样性降低,白霉病发生后根际真菌种类增多,土壤真菌群落结构发生变化,优势真菌类群也产生了较大变化。     

Activities of cell wall degrading enzymes in autolyzing cultures of three Fusarium culmorum isolates: growth-promoting, deleterious and pathogenic to rye (Secale cereale)

Release of cell wall degrading enzymes, CWDE, (glucanases, chitinases, xylanases, endocellulases, exocellulases, pectinases and polygalacturonases) was compared for three Fusarium culmorum isolates, two nonpathogenic rhizosphere isolates (a plant growth promoting [PGPF] and a deleterious [DRMO]) and one root pathogen, grown on media supplemented with one of these C sources: glucose, chitin, plant (rye root) and fungal (Fusarium) cell wall. The degree of autolysis determined after 42 d in the medium containing glucose was 15% for PGPF and DRMO and 20% for pathogenic isolate. The organic compounds added to the growth medium differentially affected the activity of the individual enzymes released by the particular isolates. The activities of xylanases and endocellulases released to the plant cell wall-amended medium by the PGPF isolate were significantly lower than the activities of these enzymes released by the DRMO and the pathogenic isolates. The activity of pectinases was repressed by glucose. The activities of acidic hydrolases were greater than those of alkaline hydrolases. Principal component analysis revealed that the activities of the CWDE found in the supernatants of the autolyzing F. culmorum cultures could be clustered into two distinct groups. One group included pectinase, exocellulase and polygalacturonase and all the remaining tested hydrolases in the other, suggesting that enzymes from either group might act in synergy during cell wall degradation. The differences in the activities of the individual CWDE released to the culture by the particular isolates are considered to be one of the key factors responsible for the observed types of plant-fungal interactions.