322,877 research outputs found
Time-course of appressorium formation on host plants by arbuscular mycorrhzal fungi
No full textAppressorium formation in arbuscular mycorrhizal fungi was monitored on the roots of three host plants over periods up to 156 h. The first appressoria were formed by Glomus mosseae within 36 h after the beginning of the interaction with Ocimum basilicum and Helianthus annuus. The first arbuscules were formed by G. mosseae and Glomus A6 within 42 and 48 h respectively, after their inoculation on H. annuus. The importance of the present data for the study both of the early events of recognition in arbuscular mycorrhizal symbioses and of infectivity of the different endophytes is discussed
Anastomosis formation and nuclear and protoplasmic exchange in arbuscular mycorrhizal fungi
No full textWe observed anastomosis between hyphae originating from the same spore and from different spores of the same isolate of the arbuscular mycorrhizal fungi Glomus mosseae, Glomus caledonium, and Glomus intraradices. The percentage of contacts leading to anastomosis ranged from 35 to 69% in hyphae from the same germling and from 34 to 90% in hyphae from different germlings. The number of anastomoses ranged from 0.6 to 1.3 per cm (length) of hyphae in mycelia originating from the same spore. No anastomoses were observed between hyphae from the same or different germlings of Gigaspora rosea and Scutellospora castanea; no interspecific or intergeneric hyphal fusions were observed. We monitored anastomosis formation with time-lapse and video- enhanced light microscopy. We observed complete fusion of hyphal walls and the migration of a mass of particles in both directions within the hyphal bridges. In hyphal bridges of G. caledonium, light-opaque particles moved at the speed of 1.8 ± 0.06 μm/s. We observed nuclear migration between hyphae of the same germling and between hyphae belonging to different germlings of the same isolate of three Glomus species. Our work suggests that genetic exchange may occur through intermingling of nuclei during anastomosis formation and opens the way to studies of vegetative compatibility in natural populations of arbuscular mycorrhizal fungi
Plant growth and root system morphology of Olea europea L. rooted cuttings as influenced by arbuscular mycorrhizas
No full textThe effects of arbuscular mycorrhizal (AM) fungi on plant development and root system morphology of different cultivars of Olea europaea were investigated. Rooted cuttings of olive cvs Frantoio, Moraiolo and Leccino at the beginning of the rooting phase, were inoculated with the AM endophyte Glomus mosseae. After six monthly growth increments, the percentage of root colonization and the root system morphology of the rooted cuttings were evaluated. AM inoculation enhanced growth of olive plants compared with the controls, inducing a different behaviour of the three olive cultivars colonized by G. mosseae. The fungal symbiont mainly increased the growth of the rooted cuttings of 'Moraiolo' and 'Frantoio', whereas 'Leccino' plants showed no significant differences from the controls. Staining of root samples of the cuttings indicated differences in the percentage of AM root colonization depending on cultivar. 'Moraiolo' root systems showed significantly less root length infected by Glomus mosseae compared with the other two cultivars. The morphometric analysis of olive roots demonstrated that colonization by AM fungi can significantly alter root system morphology. Colonization increased the intensity of branching on lateral orders in all cultivars and greatly increased the proportion of higher order laterals in the root system. The overall effect of mycorrhizas was, consequently, to increase lateral root frequency; giving rise to a more branched root system. Moreover the results show that such an increase in branching could be due in part to a better nutrition of mycorrhizal plants whereas mycorrhizal colonization and cultivar type greatly influenced the rooting pattern. These results show that mycorrhizal symbiosis can not only result in a significant increase in plant growth but can also alter olive root system morphology, positively affecting the establishment of plantlets
Infectivity and effectieness of different species of arbuscular mycorrhizal fungi in micropropagated plants of Mr S 2/5 plum rootstock
No full textMicropropagated plum plants (Prunus cerasifera Ehrh clone MrS 2 5) were inoculated with 4 different species of arbuscular mycorrhizal fungi (Glomus mosseas, G caledonium, G coronatum and Glomus strain A6) after transfer from an in vitro to an in vivo system. The most and the least infective fungi, G mosseae and G coronatum respectively, were tested for their growth-promoting abilities with respect to the micropropagated plum plants. Both fungi improved plant growth in comparison with uninoculated plants. G coronatum showed a prolonged lag phase during the early stage of mycorrhizal infection and affected growth less than G mosseae at the first harvest (4 wk). At the second harvest (14 wk), when mycorrhizal infection by both fungi was high, G coronatum was as effective as G mosseae in promoting plant growth of P cerasifera. The importance of a rapid mycorrhizal infection during the acclimatization phase of micropropagated plants is discussed in this paper
Factors affecting appressorium development in the vesicular-arbuscular mycorrhizal fungus Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe
No full textInvestigations on the lack of appressorium formation in the roots of the non-host plant Lupinus albus L. showed that root exudates do not inhibit mycelial growth of the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, but that they hinder hyphal attachment and fungal recognition of roots. Exudates do not stimulate hyphal proliferation in the rhizosphere. G. mosseae hyphae were able to recognize and attach to excised roots of both lupin and host plants, forming swellings resembling appressoria. No growth of G. mosseae hyphae was observed around simulated roots consisting of nylon, silk, polyamide and glass threads, whereas appressoria were formed on heterologous hyphae of VAM fungal species. The hypothesis that a purely thigmotropic stimulus could trigger hyphal attachment and the further differentiation of appressoria was excluded
Differential hyphal morphogenesis in arbuscular mycorrhizal fungi during pre-infection stages-
No full textRoots of host plants elicit a local change in morphology in the hyphae of arbuscular mycorrhizal fungi, prior to the formation of appressoria. The elicited hyphae switch from their original branching pattern and apical dominance to differentiate in a new irregular, septate branching pattern with reduced inter-hyphal spacing. The extensive hyphal development associated with roots of host plants was shown to be due to the differential growth pattern described, and to precede the further cascade of events leading to appressorium formation and the development of a functional symbiosis
Analysis of factors involved in fungal recognition responses to host-derived signals by arbuscular mycorrhizal fungi
No full textAn experimental model for the study of recognition responses by arbuscular mycorrhizal symbionts to host roots was validated by analysing the main factors which might affect such responses. Results showed that fungal responses to host-derived signals were unaffected by the degree of sterility of the system, host age and mycorrhizal status, symbiont age, or different chemical and physical characteristics of hydrophilic membranes. Use of dialysis membranes showed that the molecules putatively eliciting fungal responses weigh less than 500 Da. Utilization of the model for studies of developmental expression of proteins and genes in arbuscular mycorrhizal symbionts is examined
Effects of the antimycotic molecule Iturin A2, secreted by Bacillus subtilis strain M51, on arbuscular mycorrhizal fungi.
No full textThe saprophytic growth of the fungus Glomus mossae was inhibited by Iturin A2 concentrations higher than 100 mug/g of sand; whereas, in the presence of the tomato host plant, both, pre-infection events and intraradical growth were not negatively influenced by the antifungal compound; furthermore, the development of arbuscular mycorrhizal symbiosis was not impeded by the biocontrol agent in field conditions, while Fusarium oxysporum f. sp. lycopersici infection was hindered
Ultrastructural spatial distribution of bacteria associated with sporocarps of Glomus mosseae
No full textTransmission electron microscopy studies showed many bacteria associated with the sporocarps of Glomus mosseae, occurring not only on the hyphal surface, but also on the surface of spores within the sporocarps and in microniches formed by peridial hyphae. Sequential cuts of the sporocarps showed the spatial distribution of the bacteria, and evidenced bacterial cells embedded in spore walls by means of tunnels mined within the electron-dense spore wall layers. Quantitative determinations of microorganisms associated with G. mosseae sporocarps showed the occurrence of large numbers of bacteria, fungi and actinomycetes on the sporocarp surface and in the sporocarp homogenate. Moreover, chitinolytic microbes were detected in the sporocarps
Formulation and characterization of native and crosslinked hyaluronic acid microspheres for dermal delivery of sodium ascorbyl phosphate: A comparative study
No full textThe present work evaluates for the first time the use of urea-crosslinked hyaluronic acid (HA-CL), a novel derivative of native hyaluronic acid (HA), to produce microspheres (MS) by emulsification-solvent evaporation, for dermal delivery of sodium ascorbyl phosphate (SAP). As the term of comparison, HA MS were prepared. A pre-formulation study—investigation of the effects of polymers solutions properties (pH, viscosity) and working conditions—led to the production of optimized HA-CL MS and HA-CL—SAP MS with: almost unimodal size distributions; mean diameter of 13.0 ± 0.7 and 9.9 ± 0.8 μm, respectively; spherical shape and rough surface; high yield, similar to HA MS and HA–SAP MS (≈ 85%). SAP was more efficiently encapsulated into HA-CL MS (78.8 ± 2.6%) compared to HA MS (69.7 ± 4.6%). Physical state, thermal properties, relative moisture stability of HA-CL MS and HA-CL–SAP MS were comparable to those of HA MS and HA–SAP MS. However, HA-CL–SAP MS exhibited an extended drug release compared to HA–SAP MS, despite the same kinetic mechanism—contemporaneous drug diffusion and polymer swelling/dissolution. Therefore, HA-CL formulation showed a greater potential as microcarrier (for encapsulation efficiency and release kinetic), that could be improved, in future, using suitable excipients
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