Rhizoctonia Solani Strains Research Articles

Metabologenomics analysis of Pseudomonas sp. So3.2b, an Antarctic strain with bioactivity against Rhizoctonia solani.

Phytopathogenic fungi are a considerable concern for agriculture, as they can threaten the productivity of several crops worldwide. Meanwhile, natural microbial products are acknowledged to play an important role in modern agriculture as they comprehend a safer alternative to synthetic pesticides. Bacterial strains from underexplored environments are a promising source of bioactive metabolites. We applied the OSMAC (One Strain, Many Compounds) cultivation approach, in vitro bioassays, and metabolo-genomics analyses to investigate the biochemical potential of Pseudomonas sp. So3.2b, a strain isolated from Antarctica. Crude extracts from OSMAC were analyzed through HPLC-QTOF-MS/MS, molecular networking, and annotation. The antifungal potential of the extracts was confirmed against Rhizoctonia solani strains. Moreover, the whole-genome sequence was studied for biosynthetic gene clusters (BGCs) identification and phylogenetic comparison. Molecular networking revealed that metabolite synthesis has growth media specificity, and it was reflected in bioassays results against R. solani. Bananamides, rhamnolipids, and butenolides-like molecules were annotated from the metabolome, and chemical novelty was also suggested by several unidentified compounds. Additionally, genome mining confirmed a wide variety of BGCs present in this strain, with low to no similarity with known molecules. An NRPS-encoding BGC was identified as responsible for producing the banamides-like molecules, while phylogenetic analysis demonstrated a close relationship with other rhizosphere bacteria. Therefore, by combining -omics approaches and in vitro bioassays, our study demonstrates that Pseudomonas sp. So3.2b has potential application to agriculture as a source of bioactive metabolites.

Two Novel Rhabdoviruses Related to Hypervirulence in a Phytopathogenic Fungus.

Rhabdoviruses are ubiquitous and diverse viruses that propagate owing to bidirectional interactions with their vertebrate, arthropod, and plant hosts, and some of them could pose global health or agricultural threats. However, rhabdoviruses have rarely been reported in fungi. Here, two newly identified fungal rhabdoviruses, Rhizoctonia solani rhabdovirus 1 (RsRhV1) and RsRhV2, were discovered and molecularly characterized from the phytopathogenic fungus Rhizoctonia solani. The genomic organizations of RsRhV1 and RsRhV2 are 11,716 and 11,496 nucleotides (nt) in length, respectively, and consist of five open reading frames (ORFs) (ORFs I to V). ORF I, ORF IV, and ORF V encode the viral nucleocapsid (N), glycoprotein (G), and RNA polymerase (L), respectively. The putative protein encoded by ORF III has a lower level of identity with the matrix protein of rhabdoviruses. ORF II encodes a hypothetical protein with unknown function. Phylogenetic trees based on multiple alignments of N, L, and G proteins revealed that RsRhV1 and RsRhV2 are new members of the family Rhabdoviridae, but they form an independent evolutionary branch significantly distinct from other known nonfungal rhabdoviruses, suggesting that they represent a novel viral evolutionary lineage within Rhabdoviridae. Compared to strains lacking rhabdoviruses, strains harboring RsRhV2 and RsRhV1 showed hypervirulence, suggesting that RsRhV1 and RsRhV2 might be associated with the virulence of R. solani. Taken together, this study enriches our understanding of the diversity and host range of rhabdoviruses. IMPORTANCE Mycoviruses have been attracting an increasing amount of attention due to their impact on important medical, agricultural, and industrial fungi. Rhabdoviruses are prevalent across a wide spectrum of hosts, from plants to invertebrates and vertebrates. This study molecularly characterized two novel rhabdoviruses from four Rhizoctonia solani strains, based on their genomic structures, transcription strategy, phylogenetic relationships, and biological impact on their host. Our study makes a significant contribution to the literature because it not only enriches the mycovirus database but also expands the known host range of rhabdoviruses. It also offers insight into the evolutionary linkage between animal viruses and mycoviruses and the transmission of viruses from one host to another. Our study will also help expand the contemporary knowledge of the classification of rhabdoviruses, as well as providing a new model to study rhabdovirus-host interactions, which will benefit the agriculture and medical areas of human welfare.

Medicago truncatula in Interaction with Fusarium and Rhizoctonia Phytopathogenic Fungi: Fungal Aggressiveness, Plant Response Biodiversity and Character Heritability Indices.

Fusarium and Rhizoctonia genera are important pathogens of many field crops worldwide. They are constantly evolving and expanding their host range. Selecting resistant cultivars is an effective strategy to break their infection cycles. To this end, we screened a collection of Medicago truncatula accessions against Fusarium oxysporum, Fusarium solani, and Rhizoctonia solani strains isolated from different plant species. Despite the small collection, a biodiversity in the disease response of M. truncatula accessions ranging from resistant phenotypes to highly susceptible ones was observed. A17 showed relative resistance to all fungal strains with the lowest disease incidence and ratings while TN1.11 was among the susceptible accessions. As an initiation of the characterization of resistance mechanisms, the antioxidant enzymes’ activities, at the early stages of infections, were compared between these contrasting accessions. Our results showed an increment of the antioxidant activities within A17 plants in leaves and roots. We also analyzed the responses of a population of recombinant inbred lines derived from the crossing of A17 and TN1.11 to the infection with the same fungal strains. The broad-sense heritability of measured traits ranged from 0.87 to 0.95, from 0.72 to 0.96, and from 0.14 to 0.85 under control, F. oxysporum, and R. solani conditions, respectively. This high estimated heritability underlines the importance of further molecular analysis of the observed resistance to identify selection markers that could be incorporated into a breeding program and thus improving soil-borne pathogens resistance in crops.

Characterization of three novel betapartitiviruses co-infecting the phytopathogenic fungus Rhizoctonia solani

In this study, we isolated and characterized seven dsRNA elements, designed as dsRNA-1 to 7, from a Rhizoctonia solani strain. Sequence analysis indicated that there were at least three novel mycoviruses co-infected in this fungal strain, termed Rhizoctonia solani partitivirus 6 (RsPV6), Rhizoctonia solani partitivirus 7 (RsPV7), and Rhizoctonia solani partitivirus 8 (RsPV8), respectively. RsPV6 contained three dsRNA segments, dsRNA-1, 6 and 7. DsRNA-1 encoded a RNA-dependent RNA polymerase (RdRp), whereas the proteins encoded by dsRNA-6 and 7 showed no detectable sequence similarity with any known viral proteins in the database. RsPV7 had the genome segments of dsRNA-2 and 5, encoding proteins of RdRp and capsid protein, respectively. RsPV8 containing the genomes of dsRNA-3 and 4 also encoded a RdRp and a protein with unknown function. RdRp-based phylogenetic analysis revealed that all the three viruses were phylogenetically related to members of the genus Betapartitivirus in the family Partitiviridae. In addition, the three viruses could be horizontal co-transmitted via hyphal contact between R. solani strains and cause no apparent phenotypic alteration to their fungal host. These findings provided new insights into the virus taxonomy of the family Partitiviridae and expanded our understanding of viral diversity in R. solani fungus.

Pectin induced transcriptome of a Rhizoctonia solani strain causing sheath blight disease in rice reveals insights on key genes and RNAi machinery for development of pathogen derived resistance.

RNAi mediated silencing of pectin degrading enzyme of R. solani gives a high level of resistance against sheath blight disease of rice. Rice sheath blight disease caused by Rhizoctonia solani Kuhn (telemorph; Thanatephorus cucumeris) is one of the most devastating fungal diseases which cause severe loss to rice grain production. In the absence of resistant cultivars, the disease is currently managed through fungicides which add to environmental pollution. To explore the potential of utilizing RNA interference (RNAi)-mediated resistance against sheath blight disease, we identified genes encoding proteins and enzymes involved in the RNAi pathway in this fungal pathogen. The RNAi target genes were deciphered by RNAseq analysis of a highly virulent strain of the R. solani grown in pectin medium. Additionally, pectin metabolism associated genes of R. solani were analyzed through transcriptome sequencing of infected rice tissues obtained from six diverse rice cultivars. One of the key candidate gene AG1IA_04727 encoding polygalacturonase (PG), which was observed to be significantly upregulated during infection, was targeted through RNAi to develop disease resistance. Stable expression of PG-RNAi construct in rice showed efficient silencing of AG1IA_04727 and suppression of sheath blight disease. This study highlights important information about the existence of RNAi machinery and key genes of R. solani which can be targeted through RNAi to develop pathogen-derived resistance, thus opening an alternative strategy for developing sheath blight-resistant rice cultivars.

Two alphapartitiviruses co-infecting a single isolate of the plant pathogenic fungus Rhizoctonia solani.

Seven dsRNA segments were detected from a single Rhizoctonia solani strain HG81. From the full-length cDNA sequences of four smaller dsRNA segments, the genomes of two related partitiviruses, designated as Rhizoctonia solani partitivirus 3 (RsPV3) and RsPV4, were determined. The genomes of RsPV3 and RsPV4 are both composed of two separate dsRNA segments, with each segment possessing a single open reading frame (ORF). ORF1 from RsPV3 and RsPV4 encodes a putative RNA-dependent RNA polymerase, while ORF2 of RsPV3 and RsPV4 encodes a putative capsid protein. RsPV3 and RsPV4 share high sequence identity with viruses classified within the genus Alphapartitivirus, family Partitiviridae.

The Effect of Alcoholic Extract of Silybum Marianum Leaves Against Some of Rhizoctonia Solani Strains

The Effect of Alcoholic Extract of Silybum Marianum Leaves Against Some of Rhizoctonia Solani Strains

The Effect of Alcoholic Extract of Silybum Marianum Leaves Against Some of Rhizoctonia Solani Strains

The Effect of Alcoholic Extract of Silybum Marianum Leaves Against Some of Rhizoctonia Solani Strains

Phytopatological properties of symbiotic Rhizoctonia solani strains associated to orchids

The mycobiota of the Orchidarium of ELTE Botanical Garden (Budapest) has been studied applying aerobiological methods and isolating of tissue samples taken from 92 individuals of sixty orchid species. Among isolated basidiomycetaceous fungi 13 strains of Rhizoctonia solani were surviving in axenic culture. These symbiotic R. solani strains proved to be pathogenic on 24 cultivated plant species at varying degree. The symptoms of disease caused by R. solani strains isolated from orchids did not differ from that caused by reference strains. Three groups of strains could be separated regardless of their source or aggressivity. The host plants clustered into two groups, and their taxonomic position had no role in this respect. In general, we can assume that orchid associated Rhizoctonia strains are potential plant pathogens, and removed or withdrawn orchid stools should be treated as hazardous waste.

Cuevaenes C–E: Three new triene carboxylic derivatives from Streptomyces sp. LZ35ΔgdmAI

Two pairs of geometrical isomers – cuevaenes A (1) and C (3) as well as cuevaenes D (4) and E (5) – and cuevaene B (2) were isolated from gdmAI-disrupted Streptomyces sp. LZ35. The constitution of cuevaene C (3) was found to be identical to cuevaene A (1) by means of NMR spectroscopy and high resolution mass spectrometry. However, the relative configurations of the triene side chain moieties were determined to be different. It was established on the basis of spectroscopic data that cuevaenes D (4) and E (5) are amides and geometrical isomers. Cuevaenes A–C (1–3) displayed moderate activity against Gram-positive bacteria (e.g., Bacillus subtilis strain ATCC 11060) and modest activity against fungi (e.g., Fusarium verticillioides strain S68 and Rhizoctonia solani strain GXE4). However, cuevaenes D (4) and E (5) showed no inhibitory activity against any of the tested microbes.

Efficacy of selected Pseudomonas strains for biocontrol of Rhizoctonia solani in potato.

Thirty seven bacterial isolates from faba bean (Vicia faba L.) root-nodules were screened for their antagonistic activity against eight Rhizoctonia solani strains isolated from infected potato (Solanum tuberosum L.) tubers. Two bacterial strains (designated as Kl.Fb14 and S8.Fb11) gave 50% in vitro inhibition of R. solani mycelial growth. 16S rDNA sequence analysis indicated that strain Kl.Fb14 exhibited 99.5% identity with Pseudomonas moraviensis, and that S8.Fb11 exhibited 99.8% identity with Pseudomonas reinekei. Greenhouse trials in soil showed that strain S8.Fb11 reduced the percentage of sclerotia on potato tubers and amounts of tuber infection for the potato cultivars Spunta and Nicola. In a field trial conducted in South Tunisia, infection with R. solani reduced potato yield by approximately 40% for ‘Spunta’ and 17% for ‘Nicola’; about 20% of the total tuber production was severely infected. However, when potato tubers were treated with strain S8.Fb11 prior to sowing, disease incidence was reduced to 6% of total production with low infection levels; potato yield was enhanced by about 6 kg per 10 m row in comparison to R. solani infected plants. The second selected Pseudomonas sp. (strain Kl.Fb14) did not affect either the levels of sclerotia on tubers or potato yield.

Food attraction and population growth of fungivorous nematodes with different fungi

AbstractFood attraction of the fungivorous nematodes Aphelenchus avenae and Aphelenchoides spp. to seven fungal species (Pyrenochaeta lycopersici, Botrytis cinerea, Rhizoctonia solani strains AG 3 and AG 2‐1, Verticillium dahliae, Pochonia bulbillosa, Mortierella hyalina and Trichoderma harzianum) was determined on agar plates by counting the number of test nematodes present on the mycelium of each fungus 24 h after inoculation. Population growth of A. avenae and Aphelenchoides spp. on five of the seven fungi included in the attraction test (P. lycopersici, R. solani strain AG 3, V. dahliae, P. bulbillosa and T. harzianum) was also determined on agar plates by counting nematode numbers every week during a 6‐week period. A. avenae and Aphelenchoides spp. were attracted to all the fungi tested. A. avenae was preferentially attracted to V. dahliae (P < 0.0001), and Aphelenchoides spp. did not show any preference except for low attraction to R. solani. A. avenae and Aphelenchoides spp. reproduced on all fungal species tested. After 6 weeks of incubation, the highest number of nematodes was found on P. lycopersici and P. bulbillosa, while the lowest number occurred on R. solani for A. avenae and on T. harzianum for Aphelenchoides spp. The suitability of a fungus as a host was not clearly related to the attraction to that fungus.

Growth Promotion and Induction of Systemic Resistance in Rice Cultivar Co-47 (Oryza sativa L.) by Methylobacterium spp.

Pink-pigmented facultatively methylotrophic bacteria (PPFMs), persistent colonizers of plant leaf surfaces, belong to the genus Methrlobacterium and are mostly transmitted through seeds. Plant growth-promoting activity of methylotrophic bacteria and their effects on disease suppression were evaluated on rice under greenhouse conditions. Rice seeds were inoculated with Methylobacterium sp. strain PPFM-Os-07 and seed germination was evaluated in terms of morphometric measurements, seedling growth, rate of germination (R(subscript G)), and seedling vigour index (SVI). Another experiment was carried out to study the induction of pathogenesis-related proteins (PR-proteins) in rice plants that were inoculated with methylotrophic bacteria by seed imbibition or foliar spray. In the third experiment, sixty-day-old rice plants grown in pots were challenge inoculated with Rhizoctonia solani strain TNAU-01. Methylobacterium inoculation promoted seed germination and plant growth. Increased plant height, number of tillers, plant biomass, and grain yield were observed. The average yield increases for seed imbibition and phyllosphere spray were, respectively, 22.1% and 24.3% greater than control. The bacteria also significantly reduced the sheath blight incidence when applied as either bacterial culture through seed imbibition and or phyllosphere spray. The percent disease reduction recorded for seed imbibition alone and for combined applications of seed imbibition and phyllosphere spray were 17.8% and 23.5%. Rice plants sprayed with PPFM-Os-07 strain showed increased presence of PR-proteins and phenolic contents on day 1 after application. Maximum phenylalanine ammonia lyase (PAL) and peroxidase activity on day 4 and β-1,3-glucanase and chitinase activity on day 5 were recorded. The results suggest that Methylobacterium inoculation may alter rice susceptibility to R. solani. This work emphasizes the importance of evaluating induced systemic resistance while studying plant-associated growth promoting bacteria.

Characterization of antimicrobial peptides against a US strain of the rice pathogen Rhizoctonia solani.

To identify antimicrobial peptides with high lytic activity against Rhizoctonia solani strain LR172, causal agent of rice sheath blight and aerial blight of soyabeans in the US. Among 12 natural and synthetic antimicrobial peptides tested in vitro, the wheat-seed peptide, purothionin, showed the strongest inhibitory activity that was similar to the antifungal antibiotics, nystatin and nikkomycin Z. Cecropin B, a natural peptide from cecropia moth, and synthetic peptide D4E1 produced the highest inhibitory activity against R. solani among linear peptides. Membrane permeabilization levels strongly correlated with antifungal activity of the peptides. Noticeable changes in membrane integrity were observed at concentrations of >/=0.5 micromol l(-1) for purothionin, 2 micromol l(-1) for cecropin B, D4E1, D2A21, melittin, and phor21, and 8 micromol l(-1) for magainin II and phor14. An increase of nuclear membrane permeabilization was observed in fungal cells treated with cecropin B, but not with purothionin. Diffusion of nuclear content was observed by fluorescent microscopy 10 min after adding a lethal concentration of cecropin B. Evaluation by electron microscopy confirmed severe cytoplasmic degradation and plasma membrane vesiculation. Purothionin and cecropin B were the most stable against proteolytic degradation when added to liquid cultures of R. solani. Purothionin, cecropin B, D4E1 and phor21 were shown to exhibit high in vitro lytic activity against R. solani strain LR172 for rice and soyabean. These peptides are greater than 16 amino acids long and rapidly increase fungal membrane permeabilization. Resistance to proteolysis is important for sufficient antifungal activity of antimicrobial peptides. Selected antimicrobial peptides offer an attractive alternative to traditional chemicals that could be utilized in molecular breeding to develop crops resistant to rice sheath blight and aerial blight of soyabean.

Efficacy of cultural methods in the control of rhizoctonia solani strains causing tomato damping off in Kenya

Rhizoctonia damping off of tomato caused by Rhizoctonia solani can be a serious problem in most intensive production environments. Recent increase in smallholder vegetable production of 0.5- 3.0 ha in Kenya has resulted in build up of the pathogen to above economic threshold levels. There is no effective chemical control or resistant varieties. Use of soil fumigants such as methyl bromide in the control of Rhizoctonia and other soil borne pathogens is not sustainable due to their high costs, and toxicity to ma n and environment. Cultural methods such as soil amendments, mode of planting and influencing soil moisture levels either alone or in combination with other methods are among the most likely substitute s to use of toxic fumigants for control of soil borne pathogens in agriculture. This study was undertaken to evaluate the effect s of cow manure application, transplanting , planting on raised beds and varying watering interval on Rhizoctonia damping off of tomato as measured by percent seedling survival at 5 -30 days after planting (DAP), disease severity at 30 DAP, percent crop stand at 60 DAP and fruit yield at maturity . The study was conducted in a field artificially inoculated with pathogenic strains of Rhizoctonia solani isolated from infected tomato plants and Rhizosphere soil sampled from the major production regions of Kenya. The efficacy of the various cultural strategies both singly and in combination on the Rhizoctonia damping off management was compared with the conventional disease control involving chemical fumigation with metham sodium and two chemical seed dressers (pencycuron, thiram, imidacloprid) and ( captafol) as the standard . Cow manure application and shorter watering interval when used singly or in combination with other cultural methods produced lower disease control and yield. Transplanting, planting on raised beds and medium irrigation interval when used singly or in combination with other cultural strategies produced good disease control resulting in higher yield that compared favorably with the conventional disease control involving soil fumigation and seed dressing. The various cultural disease control methods documented in this study can be used alone and in integration with other compatible Rhizoctonia damping off of tomato control strategies. Furthermore the promising non- chemical strategies may form part of the urgently sought for alternative to use of hazardous fumigants in agriculture and since they are not specific, there is low risk of resistant development over time.

ISOLATION, CHARACTERIZATION AND INOCULATION OF ORCHID ENDOMYCORRHIZAS IN SPECIES OF ORCHIDS

Orchids are found in may tropical places. Their production has a double importance: as an ornament and as an important economic resource. The purpose of this study was to characterize the fungal population in orchid roots and study the ex vitro plant mycorrhiza-tion. Of the isolations we selected 25 strains of Catleya sp., Encyclia belizensis, and Oncidium sphacelatum from roots. Fusarium was found to be the most common genera present. Inoculation with orchid mycorrhizal fungi (Rhizoctonia solani strain C96/45 and C96/48) produced a positive effect on the establishment and development of plantlets with 19.44 and 97.82% dry leaf mass and 52.61 and 57.5% dry root mass, respectively. The strain C96/48 was the best.

Characterization of the Crater Disease Strain of Rhizoctonia solani

ABSTRACT Crater disease (CD) of wheat is caused by a Rhizoctonia solani strain of ambiguous phylogeny. Anastomosis reactions confirmed placement of CD-causing R. solani in anastomosis group (AG) 6, with results indicating a closer affinity to AG-6 GV than to AG-6 HG. Cultures of CD isolates were initially white to cream, turning a yellowish light brown after 10 days. Concentric rings of dark and light mycelium were evident from an early stage. Mycelium generally was appressed to the agar surface, with sparse aerial growth. A few light-colored, irregularly shaped sclerotia could be discerned after 2 weeks. The mean hyphal diameter of CD-causing R. solani was 7.46 mum (ranging from 5.0 to 10.0 mum), and cells contained a mean number of four (ranging from two to eight) nuclei, compared to a mean hyphal diameter of 8.58 and 8.42 mum and a mean nuclear number of six and four for AG-6 HG and AG-6 GV, respectively. The CD isolates had a slower growth rate (15.3 mm/day) than AG-6 HG (29.1 mm/day) and AG-6 GV (22.6 mm/day) but, like AG-6, were thiamine prototrophic. Conspicuous nodulose swellings were produced by CD-causing R. solani on roots of wheat, and infection resulted in retarded shoot growth. Smaller nodules were evident on bean and soybean roots. Fingerprint patterns generated for the various isolates with four enzymes, HpaII, Sau3AI, TaqI, and CfoI, showed the presence of a unique 610-bp fragment in the pathogen. It is proposed that CD-causing R. solani isolates represent a distinct intersterility group within AG-6 that is more related to subgroup GV than to subgroup HG.

Characterization of a Rhizoctonia solani strain carrying plasmids.

A Rhizoctonia solani strain, RI-64, carrying DNA plasmids grew slowly, was weakly pathogenic, produced oxalic acid and was unable to form sclerotia on agar media. But 5 of 205 isolates regenerated from protoplasts of RI-64 grew rapidly and formed sclerotia, yet they carried plasmids and produced a small amount of oxalic acid. Sclerotia were formed in media containing pyruvate or glycerol, but were repressed in media containing large amounts of glucose. Growth and sclerotium formation were repressed in media adjusted to low pH and in media containing oxalic acid. These results suggest that slow growth and inability to form sclerotia in strain RI-64 result from low pH in the media around mycelia, caused by the production of oxalic acid.

THE RELATION BETWEEN HOST AND ENDOPHYTE IN ORCHID MYCORRHIZA

SummaryExtensive isolation of root endophytes from Orchis (Daciylorchis) purpurella and other British orchids yielded a variety of strains of Rhizoctonia and of other fungi. R. repens, a common orchid endophyte, occurred in several host species and habitats. R. solani was uncommon, being obtained only from Orchis purpurella and Coeloglossum viride in certain situations. Most Rhizoctonia strains were obtained from only one plant and one habitat and the evidence indicated that there was no specificity between host and endophyte.In symbiosis tests isolates from roots generally infected the protocorms but did not always stimulate the growth of the species from which they originated. Four strains of R. solani isolated from soil were stimulatory to Orchis purpurella protocorms. Of four Rhizoctonia solani strains pathogenic on crop hosts, two stimulated protocorm growth and one was parasitic. It is suggested that the occurrence of a strain as a root endophyte may largely be a reflection of its distribution and of the factors affecting its growth in the soil.

THE DEVELOPMENT OF ORCHIS PURPURELLA IN ASYMBIOTIC AND INOCULATED CULTURES

SummaryIn asymbiotic cultures Orchis (Dactylorchis) purpurella seed germinated freely on deionized water agar and on defined and undefined media. Germination was enhanced by prolonged sterilization periods and high temperatures but was inhibited by light. Asymbiotic protocorms never attained the photosynthetic stage except on undefined media.Several Rhizoctonia solani strains enhanced seed germination at low temperatures. The further development of the relationship between host and endophyte varied with the strain; two pathogenic isolates from tomato and rice were strongly symbiotic to protocorms while other strains although stimulating growth ultimately became parasitic.Symbiosis was most stable at low temperatures but with any one strain there was a general pattern of infection in which nutrient depletion in the protocorm was often followed by parasitism. Drip feeding with carbohydrate delayed parasitism but in some conditions led to intense growth of the fungus. It is suggested that a careful balance of nutrients is important in the maintenance of a stable relationship between host and endophyte. The significance of this is discussed in relation to conditions in nature.