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Fungal root‐endophytes isolated from rooted cuttings of various cranberry cultivars. (a) Principal component analysis (PCA) plot of the Hellinger‐transformed root‐endophyte abundance data. Symbols filled blue, cuttings from conventional fields; symbols filled red, cuttings from fields without use of fungicides. According to the equilibrium circle method (red circle), the magnitude and the direction of the red lines indicate the scores of the contribution of operational taxonomic units (OTUs) to the separation of the cultivars. The fungal pathogens Colletotrichum sp. and Diaporthe sp. dominate conventionally rooted cuttings (the rooting substrate contains fungicides), whereas relatives of the mycorrhizal fungus Rhizoscyphus ericae dominate in “organic” cuttings rooted without fungicides. Data points close to the center of the graph are not shown. (b) Functional classification of fungal OTUs isolated from roots of the cultivars Mullica queen (MullQ), scarlet knight (ScarK), and Stevens; blue, conventional cuttings; orange, “organic” cuttings. OTUs were assigned to functional groups based on their affiliation to genera, members of which were designated in the literature as ericoid mycorrhizal fungi (Rhizoscyphus ericae and Pezicula ericae), dark septate endophytes (DSE) (Phialocephala fortinii and Phialocephala sp.), or pathogens (Colletotrichum sp., Alternaria alternata, Diaporthe sp., Physalospora vaccinii, Guignardia vaccinii, Godronia sp., Leptosphaeria sp., Didymella sp., Paraphoma sp., and Pleotrichocladium sp.). Pathogenic OTUs dominate in roots from conventionally produced cuttings (which includes fungicide treatments). Mycorrhizal and DSE OTUs were only observed in plants from organically managed fields.
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This investigation addresses the diversity of microbial endosymbionts in cranberry, which are among the least understood and ill‐defined ericoid symbionts. There is excellent potential for Ericaceous plants, such as cranberry and blueberry, to be farmed more sustainably once the properties and functioning of their associat...
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... Similarly, an endophytic strain of Codinaea sp. significantly affected the elongation of rooted cuttings from different cranberry cultivars [87]. ...
Biotic stress in cotton plants caused by the phytopathogenic fungus Colletotrichum gossypii var. cephalosporioides triggers symptoms of ramulosis, a disease characterized by necrotic spots on young leaves, followed by death of the affected branch’s apical meristem, plant growth paralysis, and stimulation of lateral bud production. Severe cases of ramulosis can cause up to 85% yield losses in cotton plantations. Currently, this disease is controlled exclusively by using fungicides. However, few studies have focused on biological alternatives for mitigating the effects of contamination by C. gossypii var. cephalosporioides on cotton plants. Thus, the hypothesis raised is that endophytic fungi isolated from an Arecaceae species (Butia purpurascens), endemic to the Cerrado biome, have the potential to reduce physiological damage caused by ramulosis, decreasing its severity in these plants. This hypothesis was tested using plants grown from seeds contaminated with the pathogen and inoculated with strains of Gibberella moniliformis (BP10EF), Hamigera insecticola (BP33EF), Codinaeopsis sp. (BP328EF), G. moniliformis (BP335EF), and Aspergillus sp. (BP340EF). C. gossypii var. cephalosporioides is a leaf pathogen; thus, the evaluations were focused on leaf parameters: gas exchange, chlorophyll a fluorescence, and oxidative metabolism. The hypothesis that inoculation with endophytic strains can mitigate physiological and photochemical damage caused by ramulosis in cotton was confirmed, as the fungi improved plant growth and stomatal index and density, increased net photosynthetic rate (A) and carboxylation efficiency (A/Ci), and decreased photochemical stress (ABS/RC and DI0/RC) and oxidative stress by reducing enzyme activity (CAT, SOD, and APX) and the synthesis of malondialdehyde (MDA). Control plants developed leaves with a low adaxial stomatal index and density to reduce colonization of leaf tissues by C. gossypii var. cephalosporioides due to the absence of fungal antagonism. The Codinaeopsis sp. strain BP328EF can efficiently inhibit C. gossypii var. cephalosporioides in vitro (81.11% relative inhibition), improve gas exchange parameters, reduce photochemical stress of chlorophyll-a, and decrease lipid peroxidation in attacked leaves. Thus, BP328EF should be further evaluated for its potential effect as a biological alternative for enhancing the resistance of G. hirsutum plants and minimizing yield losses caused by C. gossypii var. cephalosporioides.
... Recently, we isolated and characterized a large number of bacterial and fungal endosymbionts of cranberry plants and measured their biofertilizing and biocontrol ability (Salhi et al., 2022). The Codinaeella sp. ...
... The Codinaeella sp. isolate EC4 proved to promote cranberry-plant growth (Thimmappa et al., 2023) and, in addition, to inhibit the growth of two cranberry-plant pathogens, Godronia sp. and Cytospora chrysosperma (Salhi et al., 2022). Here, we aim to unravel the biocontrol mechanism of EC4. ...
... 3.1 EC4 inhibits the growth of a broad range of plant pathogens Codinaeella sp. isolate EC4 is a phytostimulating fungal endosymbiont of cranberry, which was shown in on-plate assays to inhibit the growth of two fungal pathogens, Cytospora chrysosperma and Godronia cassandrae (Salhi et al., 2022;Thimmappa et al., 2023). Here, we examined which other pathogens are suppressed by EC4 and validated their pathogenicity in cranberry plants. ...
Fungi colonizing plants are gaining attention because of their ability to promote plant growth and suppress pathogens. While most studies focus on endosymbionts from grasses and legumes, the large and diverse group of ericaceous plants has been much neglected. We recently described one of the very few fungal endophytes promoting the growth of the Ericaceae Vaccinium macrocarpon (American cranberry), notably the Codinaeella isolate EC4. Here, we show that EC4 also suppresses fungal pathogens, which makes it a promising endophyte for sustainable cranberry cultivation. By dual-culture assays on agar plates, we tested the potential growth suppression (or biocontrol) of EC4 on other microbes, notably 12 pathogenic fungi and one oomycete reported to infect not only cranberry but also blueberry, strawberry, tomato plants, rose bushes and olive trees. Under greenhouse conditions, EC4 protects cranberry plantlets infected with one of the most notorious cranberry-plant pathogens, Diaporthe vaccinii, known to cause upright dieback and berry rot. The nuclear genome sequence of EC4 revealed a large arsenal of genes potentially involved in biocontrol. About ∼60 distinct clusters of genes are homologs of secondary metabolite gene clusters, some of which were shown in other fungi to synthesize nonribosomal peptides and polyketides, but in most cases, the exact compounds these clusters may produce are unknown. The EC4 genome also encodes numerous homologs of hydrolytic enzymes known to degrade fungal cell walls. About half of the nearly 250 distinct glucanases and chitinases are likely involved in biocontrol because they are predicted to be secreted outside the cell. Transcriptome analysis shows that the expression of about a quarter of the predicted secondary-metabolite gene clusters and glucan and chitin-degrading genes of EC4 is stimulated when it is co-cultured with D. vaccinii. Some of the differentially expressed EC4 genes are alternatively spliced exclusively in the presence of the pathogen, altering the proteins’ domain content and subcellular localization signal, thus adding a second level of proteome adaptation in response to habitat competition. To our knowledge, this is the first report of Diaporthe-induced alternative splicing of biocontrol genes.
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... Some authors use the term for all the endomycorrhizal fungi of Ericaceae [19], whereas others restrict this definition to those that form dense, coiled hyphae of a given shape within the epidermal root cells, and optionally, sheath-like structures in the rhizosphere surrounding the roots of the host [20]. In stark contrast to AMF, ErMF are the most diverse assortment of fungi belonging to the Ascomycota and Basidiomycota [19], suggesting either convergent evolution or horizontal gene transfer in creating the 'typical' ericoid mycorrhizal phenotype [21]. Therefore, fungal endophytes described in the literature as ErMF have little in common with each other except that they colonize ericacean plants and are unrelated to AMF. ...
... A more recent study of our laboratory explored ErMF systematically by surveying the microbiome of Vaccinium macrocarpon Aiton (American cranberry) [29]. Nearly 60 different endophytic fungi were isolated and classified by ribotyping as members of at least ten distinct classes of Leotiomyceta (Ascomycota) [21]. In-plantae tests showed that certain endosymbiont isolates promote the growth of their host (bio-fertilizers), while others suppress the growth of cranberry plant pathogens (biocontrol agents) or have no notable impact on the plant. ...
... The fungal endophyte EC4 was initially isolated from the roots of V. macrocarpon (cultivar Stevens) [21]. To investigate if EC4 also colonizes other plant tissues, endophytefree cranberry seedlings were inoculated with the fungus and subsequently examined by light and fluorescence microscopy. ...
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Ericaceous plants (Ericaceae, the heath family) establish complex symbioses with soil-borne microorganisms that facilitate their survival in challenging environments such as nutrient-impoverished heathlands, heavy metal-polluted soils, and inert volcanic rock substrates. While the symbiosis with the ericoid mycorrhizal (ErM) fungi has attracted significant attention, little is known about the endophytic bacteria and how they affect fitness of their ericaceous hosts. In this study, we isolated and identified endophytic bacteria from hair roots of Gaultheria poeppigii colonizing volcanic deposits at a site in the Chilean southern Andes. In addition, their in vitro capacity to solubilize phosphate, produce exopolysaccharides, siderophores, ammonia, indole acetic acid (IAA), and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity was evaluated. In total, 74 isolates were obtained, belonging to the phyla Proteobacteria, Firmicutes, and Actinobacteria and the genera Paraburkholderia, Paenibacillus, Variovorax, Bacillus, Leifsonia, and Arthrobacter. Only two Paraburkholderia sp. isolates showed phosphate solubilization. Siderophore production was detected in six isolates, with the highest production detected in the Variovorax paradoxus. All strains produced ammonia and IAA in different amounts and six displayed ACC deaminase activity, the highest being detected in V. paradoxus GC55. The results of our biocontrol assay showed that V. paradoxus GC51 had the highest percentages of inhibition of common phytopathogens with values ranging from 65 to 100%. To our best knowledge, this is the first report on the cultivable bacteria colonizing the hair roots of ericaceous plants growing in volcanic deposits and our results suggest that at least some of them might promote the host growth and confer protection against pathogens. We suggest that not only the ErM fungi but also the root-symbiotic bacteria contribute to the remarkable resilience of ericaceous plants in challenging environments such as volcanic deposits.
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