Effects of arbuscular mycorrhiza (AM) on health ofLinum usitatissimum L. infected by fungal pathogens

Abstract

Effects of arbuscular mycorrhizal (AM) symbiosis on health of Linum usitatissimum infected by fungal pathogens were investigated exemplarily. Physiological and biochemical analyses were done to explain the mechanisms underlying the AM effects. AM plants showed increased resistance against the wilt pathogen (Fusarium oxysporum f. sp. lini), the level of this effects depended on the plant cultivars which all showed the same level of root colonization by arbuscular mycorrhizal fungi (AMF). In contrary to that, AM plants were highly susceptible against the shoot pathogen Oidium lini, but they suffered less than non-AM plants in terms of shoot fresh weight, CO2 assimilation and content of sucrose in shoot apex. This indicates that AM not only activates resistance mechanisms but also can induce tolerance against pathogens. The concentration of phytohormones such as auxin-and gibberellin-like substances were increased in shoots of AM plants. In roots the ethylene production was increased, too. Furthermore the content and composition of free sterols were highly altered in leaves of AM plants. Root infection by AMF caused an increased respiratory activity and a reduced degree of DNA methylation, but both modifications only occurred in infected root parts indicating an increasing gene activity. The presented results suggest that nearly all parts of a plant are influenced by AM but not in the same manner. In the case of mildewed linseed the effect of AM on plant health was impressing, it indicates that AM has an ability to induce tolerance.

Effect of Arbuscular Mycorrhizal Fungi on Growth and Development of Potato (Solanum tuberosum) Plant

“…Beneficial effects of AMF inoculation on potato growth, yield which were observed in this study were despite relatively low level of root colonisation. This is validly explainable on the basis of the observations of Dugassa et al (1996) who have said that the influence of AMF symbiosis on plant health depends more on host plant than on AMF fungal colonisation level.…”

Les mycorhizes : un outil de protection des plantes mais non une panacée

“…La colonisation mycorhizienne prédispose les plantes à réagir rapidement aux attaques de parasites (Dugassa et al 1996;Singh et al 2000). Cette protection indirecte se traduit au niveau cellulaire par des réac-tions anatomiques, métaboliques et physiologiques, ainsi que par l'induction ou la suppression de divers mécanismes de défense liés aux phytoalexines, phénols, peroxydases, chitinases, ß-glucanases, lignification, déposition de callose et diverses autres protéines liées à la pathogenèse.…”

A model for the development of the rhizobial and arbuscular mycorrhizal symbioses in legumes and its use to understand the roles of ethylene in the establishment of these two symbioses

“…The findings of Dugassa et al (1996) further complicate the issue; these authors reported nearly double the ethylene production in roots of Linum usitatissimum (flax) colonized by G. intraradices. It should also be noted that in well-irrigated roots, AM fungal colonization increased ethylene production despite no difference in ACC levels between AM and non-AM roots (Cruz et al 2000).…”