Muscodor albus and its biological promise

We have found a novel fungal genus that produces extremely bioactive volatile organic compounds (VOCs). This fungal isolate was initially discovered as an endophyte in Cinnamomum zeylanicum in a botanical garden in Honduras. This endophytic fungus, Muscodor albus, produces a mixture of VOCs that are lethal to a wide variety of plant and human pathogenic fungi and bacteria. It is also effective against nematodes and certain insects. The mixture of VOCs has been analyzed using GC/MS and consists primarily of various alcohols, acids, esters, ketones, and lipids. Final verification of the identity of the VOCs was carried out by using artificial mixtures of the putatively identified compounds and showing that the artificial mixture possessed the identical retention times and mass spectral qualities as those of the fungal derived substances. Artificial mixtures of the VOCs nicely mimicked the biological effects of the fungal VOCs when tested against a wide range of fungal and bacterial pathogens. Potential applications for “mycofumigation” by M. albus are currently being investigated and include uses for treating various plant parts, and human wastes. Another promising option includes its use to replace methyl bromide fumigation as a means to control soil-borne plant diseases.     

Harnessing endophytes for industrial microbiology

Endophytic microorganisms exist within the living tissues of most plant species. They are most abundant in rainforest plants. Novel endophytes usually have associated with them novel secondary natural products and/or processes. Muscodor is a novel endophytic fungal genus that produces bioactive volatile organic compounds (VOCs). This fungus, as well as its VOCs, has enormous potential for uses in agriculture, industry and medicine. Muscodor albus produces a mixture of VOCs that act synergistically to kill a wide variety of plant and human pathogenic fungi and bacteria. This mixture of gases consists primarily of various alcohols, acids, esters, ketones and lipids. Artificial mixtures of the VOCs mimic the biological effects of the fungal VOCs when tested against a wide range of fungal and bacterial pathogens. Many practical applications for 'mycofumigation' by M. albus have been investigated and the fungus is now in the market place.     

An Endophytic <Emphasis Type="Italic">Phomopsis</Emphasis> sp. Possessing Bioactivity and Fuel Potential with its Volatile Organic Compounds

An unusual Phomopsis sp. was isolated as endophyte of Odontoglossum sp. (Orchidaceae), associated with a cloud forest in Northern Ecuador. This fungus produces a unique mixture of volatile organic compounds (VOCs) including sabinene (a monoterpene with a peppery odor) only previously known from higher plants. In addition, some of the other more abundant VOCs recorded by GC/MS in this organism were 1-butanol, 3-methyl; benzeneethanol; 1-propanol, 2-methyl and 2-propanone. The gases of Phomopsis sp. possess antifungal properties and an artificial mixture of the VOCs mimicked the antibiotic effects of this organism with the greatest bioactivity against a wide range of plant pathogenic test fungi including: Pythium, Phytophthora, Sclerotinia, Rhizoctonia, Fusarium, Botrytis, Verticillium, and Colletotrichum. The IC₅₀ values for the artificial gas mixture of Phomopsis sp. varied between 8 and 25.65 μl/mL. Proton transfer reaction-mass spectrometry monitored the concentration of VOCs emitted by Phomopsis sp. and yielded a total VOC concentration of ca. 18 ppmv in the head space at the seventh day of incubation at 23°C on PDA. As with many VOC-producing endophytes, this Phomopsis sp. did survive and grow in the presence of the inhibitory gases of Muscodor albus. A discussion is presented on the possible involvement of VOC production by the fungus and its role in the biology/ecology of the fungus/plant/environmental relationship.     

Muscodor fengyangensis sp. nov. from southeast China: morphology, physiology and production of volatile compounds

The fungal genus Muscodor was erected on the basis of Muscodor albus, an endophytic fungus originally isolated from Cinnamomum zeylanicum. It produces a mixture of volatile organic compounds (VOCs) with antimicrobial activity that can be used as mycofumigants. The genus currently comprises five species. Here we describe the isolation and characterization of a new species of Muscodor on the basis of five endophytic fungal strains from leaves of Actinidia chinensis, Pseudotaxus chienii and an unidentified broad leaf tree in the Fengyangshan Nature Reserve, Zhejiang Province, Southeast of China. They exhibit white colonies on potato dextrose agar (PDA) media, rope-like mycelial strands, but did not sporulate. The optimum growth temperature is 25°C. The results of a phylogenetic analysis based on four loci (ITS1-5.8S-ITS2, 28S rRNA, rpb2 and tub1) are consistent with the hypothesis that these five strains belong to a single taxon. All five strains also produce volatile chemical components with antimicrobial activity in vitro, which were different from those previously described for other Muscodor species.     

Muscodor sutura, a novel endophytic fungus with volatile antibiotic activities

Muscodor sutura is described as a novel species that is also an endophyte of Prestonia trifidi. Uniquely, this fungus produces a reddish pigment, on potato dextrose agar (PDA), when grown in the dark. In addition, the organism makes some volatile organic compounds that have not been previously reported from this genus, namely, thujopsene, chamigrene, isocaryophyllene, and butanoic acid, 2-methyl. These and other volatile compounds in the mixture possess wide-spectrum antifungal activity and no observable antibacterial activity. Most unusually, on PDA, the newly developing hyphae of this fungus grow in a perfect stitching pattern, in and out of the agar surface. The partial ITS–DNA sequence of this organism is identical to that of Muscodor vitigenus but it differs from all other Muscodor spp. Justification for a new species, as Muscodor sutura, is collectively based on morphological, cultural, chemical, and bioactivity properties.     

<Emphasis Type="Italic">Mycena</Emphasis> sp., a mycorrhizal fungus of the orchid <Emphasis Type="Italic">Dendrobium officinale</Emphasis>

An endophytic fungus, F-23, was isolated from the roots of Dendrobium officinale Kimura et Migo, an endangered Chinese medicinal plant. The sequence of the ITS region indicated that the isolate belongs to the genus Mycena. After 4 months of inoculation, the root systems of D. officinale that were inoculated with F-23 fungus were much larger than the control’s root systems. We also observed that the hyphae of F-23 penetrated the epidermal cells within the host’s roots and spread from cell to cell. A large number of pelotons existed in the root cortical cells of D. officinale inoculated with F-23 fungus. Intracellular hyphae crossing through the host walls were also observed using SEM (scanning electron microscopy). In contrast, light microscopy and SEM showed that the transverse sections of the roots of control plants remained uncolonized. Therefore, the F-23 fungus can form mycorrhizal associations with the roots of its host plant, D. officinale, and enhance the growth of seedlings and roots. In brief, Mycena sp. was identified and shown to be a mycorrhizal fungus of the epiphytic orchid, D. officinale. This might be of potential use to the mass cultivation of D. officinale under artificial conditions.     

Antibiotics and enzymes produced by the biocontrol agent Streptomyces violaceusniger YCED-9

Streptomyces violaceusniger strain YCED-9 is an antifungal biocontrol agent antagonistic to many different classes of plant pathogenic fungi. We discovered that strain YCED-9 produces three antimicrobial compounds with antifungal activity. These compounds were purified and identified, and included: AFA (Anti-Fusarium Activity), a fungicidal complex of polyene-like compounds similar to guanidylfungin A and active against most fungi except oomycetes; nigericin, a fungistatic polyether; and geldanamycin, a benzoquinoid polyketide highly inhibitory of mycelial growth of Pythium and Phytophthora spp. Antimicrobial assays were developed to estimate the production of each antibiotic independently. Medium composition had differential effects on the production of each metabolite. The hydrolytic enzymes chitinase and β-1,3-glucanase are also produced under induction by colloidal chitin and laminarin, respectively. Fungal cell walls induced the production of both enzymes. A potential for biological control of diseases caused by P. infestans was also suggested by strain YCED-9’s strong in vitro antagonism towards pathogenic isolates of this fungus. Received 27 October 1997/ Accepted in revised form 8 June 1998     

Clavatol and patulin formation as the antagonistic principle of <Emphasis Type="Italic">Aspergillus clavatonanicus</Emphasis>, an endophytic fungus of <Emphasis Type="Italic">Taxus mairei</Emphasis>

Many endophytic fungi are known to protect plants from plant pathogens, but the antagonistic mechanism has rarely been revealed. In this study, we wished to learn whether an endophytic Aspergillus sp., isolated from Taxus mairei, would indeed produce bioactive components, and if so whether (a) they would antagonize plant pathogenic fungi; and (b) whether this Aspergillus sp. would produce the compound also under conditions of confrontation with these fungi. The endophytic fungal strain from T. mairei was identified as Aspergillus clavatonanicus by analysis of morphological characteristics and the sequence of the internal transcribed spacers (ITS rDNA) of rDNA. When grown in surface culture, the fungus produced clavatol (2′,4′-dihydroxy-3′,5′-dimethylacetophenone) and patulin (2-hydroxy-3,7-dioxabicyclo [4.3.0]nona-5,9-dien-8-one), as shown by shown by NMR, MS, X-ray, and EI-MS analysis. Both exhibited inhibitory activity in vitro against several plant pathogenic fungi, i.e., Botrytis cinerea, Didymella bryoniae, Fusarium oxysporum f. sp. cucumerinum, Rhizoctonia solani, and Pythium ultimum. During confrontation with P. ultimum, A. clavatonanicus antagonized its growth of P. ultimum, and both clavatol as well as patulin were formed as the only bioactive components, albeit with different kinetics. We conclude that A. clavatonanicus produces clavatol and patulin, and that these two polyketides may be involved in the protection of T. mairei against attack by plant pathogens by this Aspergillus sp.     

Evolution of <Emphasis Type="Italic">Salmonella</Emphasis> nomenclature: a critical note

Salmonellae are widely distributed but nomenclaturally controversial pathogens of both humans and animals. Despite elaborate studies, much still remain to be discovered about these organisms. Although Salmonella nomenclature has proved to be rather complex, in 2005, Salmonella enterica finally gained official approval as the type species of the genus Salmonella. In addition, one other species has been approved and recognised in the genus Salmonella, namely, Salmonella bongori. New serovars (serotypes) are continually being discovered each year and reported in the journal Research in Microbiology. Salmonella serovars and their antigenic formulae are listed in the White–Kauffmann–Le Minor scheme and updated by the World Health Organization’s Collaborating Centre for Reference and Research on Salmonella at the Pasteur Institute, Paris, France.     

Response of plants to ectomycorrhizae in N-limited conditions: which factors determine its variation?

In the present work, the following hypotheses were tested: (1) the negative effects of mycorrhization over host plant productivity in N-limited conditions are due to N retention by the fungal partner and not due to excessive C drainage; (2) If mycorrhization results in decreased N uptake, the host plant decreases its C investment in fungal growth. The effects of mycorrhization over a wide range of combinations between N availability, N concentration in plant tissues, and degree of mycorrhizal colonization were studied in Pinus pinaster L. mycorrhizal with Pisolithus tinctorius. Several plant productivity parameters, the seedlings’ N status, chl a fluorescence (JIP test), and mycorrhizal colonization were measured. N was always limiting. A gradient of mycorrhizal effects over the host plant’s growth and vitality was successfully obtained. The mycorrhizal effects on plant growth and N uptake were very strongly and positively correlated, and no evidence was found of a C limitation to growth, confirming hypothesis 1. Indications were found that the plants continued to provide C to the fungus although the N supplied by it was increasingly lower, denying hypothesis 2. A new index, the mycorrhizal N demand–supply balance, was found to efficiently explain, and to have a curvilinear relation with, the variation in response to mycorrhization. The mycorrhizal effect on host plant growth was not related to a negative effect on its photosynthetic performance and, therefore, reflected changes in resource allocation between host plant and mycorrhizal fungus, not in plant vitality.     

Molecular and morphological evidence support four new species in the genus Muscodor from northern Thailand

The genus Muscodor comprises fungal endophytes which produce mixtures of volatile compounds (VOCs) with antimicrobial activities. In the present study, four novel species, Muscodor musae, M. oryzae, M. suthepensis and M. equiseti were isolated from Musa acuminata, Oryza rufipogon, Cinnamomum bejolghota and Equisetum debile, respectively; these are medicinal plants of northern Thailand. The new Muscodor species are distinguished based on morphological and physiological characteristics and on molecular analysis of ITS-rDNA. Volatile compound analysis showed that 2-methylpropanoic acid was the main VOCs produced by M. musae, M. suthepensis and M. equiseti. The mixed volatiles from each fungus showed in vitro antimicrobial activity. Muscodor suthepensis had the highest antifungal activity.     

Endophytic fungal entomopathogens with activity against plant pathogens: ecology and evolution

Dual biological control, of both insect pests and plant pathogens, has been reported for the fungal entomopathogens, Beauveria bassiana (Bals.-Criv.) Vuill. (Ascomycota: Hypocreales) and Lecanicillium spp. (Ascomycota: Hypocreales). However, the primary mechanisms of plant disease suppression are different for these fungi. Beauveria spp. produce an array of bioactive metabolites, and have been reported to limit growth of fungal plant pathogens in vitro. In plant assays, B. bassiana has been reported to reduce diseases caused by soilborne plant pathogens, such as Pythium, Rhizoctonia, and Fusarium. Evidence has accumulated that B. bassiana can endophytically colonize a wide array of plant species, both monocots and dicots. B. bassiana also induced systemic resistance when endophytically colonized cotton seedlings were challenged with a bacterial plant pathogen on foliage. Species of Lecanicillium are known to reduce disease caused by powdery mildew as well as various rust fungi. Endophytic colonization has been reported for Lecanicillium spp., and it has been suggested that induced systemic resistance may be active against powdery mildew. However, mycoparasitism is the primary mechanism employed by Lecanicillium spp. against plant pathogens. Comparisons of Beauveria and Lecanicillium are made with Trichoderma, a fungus used for biological control of plant pathogens and insects. For T. harzianum Rifai (Ascomycota: Hypocreales), it has been shown that some fungal traits that are important for insect pathogenicity are also involved in biocontrol of phytopathogens.     

Antimicrobial volatile organic compounds affect morphogenesis-related enzymes in Guignardia citricarpa,causal agent of citrus black spot

Although non-volatile substances toxic to plant pathogenic microorganisms have been extensively studied over the years, few studies have focused on microbial volatile organic compounds (VOCs). The VOCs produced by the yeast Saccharomyces cerevisiae strain CR-1, used in fermentative processes for fuel ethanol production, are able to inhibit the vegetative development of the fungus Guignardia citricarpa, causal agent of the disease citrus black spot. How microbial VOCs affect the development of fungi is not known. Thus, the objective of the present work was to study the effect of the artificial mixture of VOCs identified from S. cerevisiae on intracellular enzymes involved in the mycelial morphogenesis in G. citricarpa. The phytopathogenic fungus was exposed to artificial mixture of VOCs constituted by alcohols (ethanol, 3-methyl-1-butanol, 2-methyl-1-butanol and phenylethyl alcohol) and esters (ethyl acetate and ethyl octanoate) in the proportions naturally found in the atmosphere produced by the yeast. The VOCs inhibited considerably the mycelial development and interfered negatively with the production of the morphogenesis-related enzymes. After 72 h of exposure to the VOCs the laccase and tyrosinase activities decreased 46 and 32%, respectively, however, the effect on the chitinase and β-1,3-glucanase activities was lower, 17 and 13% of inhibition, respectively. Therefore, the exposure of the fungus to the antimicrobial volatiles can influence both fungal mycelial growth rate and activity of enzymes implicated in morphogenesis. This knowledge is important to understand the microbial interactions mediated by VOCs in nature and to develop new strategies to control plant pathogens as G. citricarpa in postharvest.     

撕裂蜡孔菌(Emmia lacerata)SR5抑菌特性及生防潜力评价

【背景】撕裂蜡孔菌(Emmia lacerata)是一种在世界范围内广泛分布的白腐真菌,对植物病原真菌有较好的抑制作用,可作为生防真菌进行开发和利用。【目的】对撕裂蜡孔菌SR5的抑菌能力和胞外产铁载体能力进行测定,挖掘其生防潜力。【方法】采用平板对峙法检测SR5对9种植物病原真菌的抑菌能力,并通过不同浓度的发酵原液测定真菌胞外代谢物的抑菌效果;结合铬天青S(chrome azurol S, CAS)检测法测定真菌产铁载体能力,明确SR5抑菌特性。【结果】SR5以过度生长的方式快速竞争营养和生存空间,拮抗9种植物病原真菌,抑菌率为23.7%–62.7%,对可可毛色二孢(Lasiodiplodia theobromae)的拮抗等级为Ⅳ级,而对其余8种病原真菌的拮抗等级为Ⅲ级,其中对香港丽赤壳(Calonectria hongkongensis)和间座壳(Diaporthe sp.)抑菌效果最佳;CAS检测法表明SR5能产生分泌型铁载体,产铁载体能力中等,最高铁载体活性单位(siderophore unit, SU)为44.1%。【结论】SR5以过度生长方式快速竞争营养和生存空间,而且以分泌...     

Complementarity effects through dietary mixing enhance the performance of a generalist insect herbivore

The ontogenetic niche concept predicts that resource use depends on an organism’s developmental stage. This concept has been investigated primarily in animals that show differing resource use strategies as juveniles and as adults, such as amphibians. We studied resource use and performance in the grasshopper Chorthippus parallelus (Orthoptera, Acrididae) provided with food plant mixtures of either one, three or eight plant species throughout their development. C. parallelus survival and fecundity was highest in the food plant mixture with eight plant species and lowest in the treatments where only one single plant species was offered as food. C. parallelus’ consumption throughout its ontogeny depended on sex, and feeding on different plant species was dependent on a grasshopper’s developmental stage. To depict grasshopper foraging in food plant mixtures compared to foraging on single plant species, we introduce the term “relative forage total” (RFT) based on an approach used in biodiversity research by Loreau and Hector (Nature 413:548–274, 2001). RFT of grasshoppers in food plant mixtures was always higher than what would have been expected from foraging in monocultures. The increase in food consumption was due to an overall increase in feeding on plant species in mixtures compared to consumption of the same species offered as a single diet. Thus we argue that grasshopper foraging exhibits complementarity effects. Our results reinforce the necessity to consider development-related changes in insect herbivore feeding. Thorough information on the feeding ontogeny of insect herbivores could not only elucidate their nutritional ecology but also help to shed light on their functional role in plant communities. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Biological activity of secondary metabolites produced by a strain of<Emphasis Type="Italic">Pseudomonas fluorescens</Emphasis>

Biological activity of secondary metabolites produced by a plant-growth-promotingPseudomonas fluorescens was evaluated. The strain produced antibiotics phenazine (PHE), 2,4-diacetylphloroglucinol (PHL) and siderophore pyoverdin (PYO) in standard King’s B and succinic acid media, respectively. After extraction, PYO was identified by comparing the UV-spectra and moss-green color development after ‘diazotized sulfanilic acid’ (DSA) spray in TLC. PHE and PHL were identified by comparing standard compounds on TLC and orange-color development immediately after DSA spray.In vitro antibiosis study of the metabolites revealed their antibacterial and antifungal activity against bacterial test organismsCorynebacterium sp.,Mycobacterium phlei andM. smegmatis and test fungiFusarium moniliforme, F. oxysporum, F. semitectum, F. solani andRhizoctonia solani. A statistically significantly higher plant growth was recorded in siderophore-amended plantlets under gnotobiotic conditions whereas PHE and PHL did not show any plant-growth-promoting activity. These results support the importance of the secondary metabolites produced by the strainP. fluorescens in enhancing plant growth and in controling fungal and bacterial pathogens.     

Mycorrhiza status of Gnetum spp. in Cameroon: evaluating diversity with a view to ameliorating domestication efforts

A field survey was carried out to investigate the diversity of mycorrhizal fungi associated with Gnetum spp. in Cameroon. The extent and variation of ectomycorrhizal colonisation as well as the degree of host specificity were evaluated. Gnetum spp. were found to be almost always ectomycorrhizal in all sites visited. There were just two ectomycorrhizal morphotypes (‘yellow’ and ‘white’) associated with this plant. Such low diversity is unusual for an ectomycorrhizal plant. The yellow morphotype was the most widespread and prevalent and was identified by morphological and molecular methods to have been formed with Scleroderma sinnamariense. Propagules of this fungus were present in soil collected from farm lands, cocoa plantations, Chromolaena and bush fallows, as well as in a relatively undisturbed forest harbouring ectomycorrhizal legumes. The fungus responsible for the white morphotype was identified as also belonging to the genus Scleroderma by ITS sequence similarity. Arbuscular mycorrhizal structures were absent in cleared and stained portions of the roots.     

Mixtures of plant growth-promoting rhizobacteria for induction of systemic resistance against multiple plant diseases

Studies of induced systemic resistance using strains of plant growth-promoting rhizobacteria (PGPR) have concentrated on the use of individual PGPR as inducers against multiple diseases of a single crop. To date, few reports have examined the potential of PGPR strain mixtures to induce systemic resistance against diseases of several different plant hosts. The objective of this study was to select mixtures of compatible PGPR strains with the capacity to elicit induced systemic resistance in four hosts. The specific diseases and hosts tested in this study included: bacterial wilt of tomato (Lycopersicon esculentum) caused by Ralstonia solanacearum, anthracnose of long cayenne pepper (Capsicum annuum var. acuminatum) caused by Colletotrichum gloeosporioides, damping off of green kuang futsoi (Brassica chinensis var. parachinensis) caused by Rhizoctonia solani, and cucumber mosaic virus (CMV) on cucumber (Cucumis sativus). To examine compatibility, seven selected PGPR strains were individually tested for in vitro antibiosis against all other PGPR strains and against three of the tested pathogens (R. solanacearum, C. gloeosporioides, and R. solani). No in vitro antibiosis was observed among PGPR strains or against pathogens. Twenty-one combinations of PGPR and seven individual PGPR were tested in the greenhouse for induced resistance activity. Results indicated that four mixtures of PGPR and one individual strain treatment significantly reduced the severity of all four diseases compared to the nonbacterized control: 11 mixtures reduced CMV of cucumber, 16 mixtures reduced bacterial wilt of tomato, 18 mixtures reduced anthracnose of long cayenne pepper, and 7 mixtures reduced damping off of green kuang futsoi. Most mixtures of PGPR provided a greater disease suppression than individual PGPR strains. These results suggest that mixtures of PGPR can elicit induced systemic resistance to fungal, bacterial, and viral diseases in the four hosts tested.     

Antifungal substances produced by Penicillium oxalicum strain PY-1—potential antibiotics against plant pathogenic fungi

This paper reports the isolation from soil of Penicillium strain PY-1 with strong antagonistic activity against plant pathogenic fungi. On the basis of its morphological characteristics and the sequence of the ITS region, strain PY-1 was identified as P. oxalicum. Strain PY-1 produces antifungal substances that suppress the mycelial growth of Sclerotinia sclerotiorum and many other plant pathogenic fungi tested; the highest antagonistic activity was detected at 72 h when cultured in a 250-ml flask containing 80 ml potato dextrose broth. Compared with carbendazim, the relative activity of the antifungal substances produced by strain PY-1 was approximately 4 μg active ingredient (a.i.) per milliliter. The antifungal substances were extracted with ethyl acetate and further separated by high-performance liquid chromatography (HPLC); at least two active components were discovered. The ability to control plant disease with strain PY-1 was confirmed with S. sclerotiorum, a widespread pathogenic fungus that attacks rapeseed (Brassica napus) and other plants. Spores (10⁶ or 10⁷ ml⁻¹) and filtrate (tenfold diluted or undiluted) of strain PY-1 could significantly suppress infection and/or the extent of infection by S. sclerotiorum of plants at seven-true-leaves stage. The potential of strain PY-1 for identifying new antibiotics to control fungal disease and for biological control of plant disease, for example oilseed rape stem rot, is discussed.     

Biocontrol of aerial plant diseases in agriculture and horticulture: current approaches and future prospects

Until recently, the majority of research on the biological control of aerial plant diseases was focused on control of bacterial pathogens. Such research led to the commercialization of the biocontrol agent Pseudomonas fluorescens A506, as BlightBan A506™, for control of fire blight of pear. In contrast, chemical fungicides typically have provided adequate control of most foliar fungal pathogens. However, fungicide resistance problems, concerns regarding pesticide residues and revocation of registration of certain widely used fungicides have led to increased activity in the development of biocontrol agents of foliar fungal pathogens. Much of this activity has centered around the use of Trichoderma spp and Gliocladium spp to control Botrytis cinerea on grape and strawberry. The biocontrol agent Trichoderma harzianum T39 is commercially available in Israel, as Trichodex ™, for control of grey mold in grapes and may soon be registered for use in the US. Also targeted primarily against a foliar disease of grapes, in this case powdery mildew caused by Uncinula necator, is the biocontrol agent Ampelomyces quisqualis AQ10, marketed as AQ^{10  TM} biofungicide. Another promising development in the area of foliar disease control, though one which is not yet commercialized, is the use of rhizobacteria as seed treatments to induce systemic resistance in the host plant, a strategy which can protect the plant against a range of bacterial and fungal pathogens. Received 06 February 1997/ Accepted in revised form 05 June 1997