Control by arbuscular endomycorrhizae of Pratylenchus brachyurus in pineapple microplants

Pratylenchus brachyurus (Godfrey) Filip & Schurr-Steekh. has been reported in association with pineapple roots and is considered as an important pathogen on pineapple. Microplants of Queen Tahiti, Smooth Cayenne and Spanish varieties were inoculated with Glomus sp. (LPA21) and/or P. brachyurus at transplanting from axenic conditions or one month later. The presence of the nematode did not affect shoot growth of endomycorrhizal plants. Late P. brachyurus inoculation did not influence growth of nonmycorrhizal plants while early pathogen application caused reductions in nonmycorrhizal plant growth. Nematode number per g of root was significantly decreased for endomycorrhizal plants when pathogen was introduced at outplanting or one month later. Nematode inoculation affected endomycorrhizal colonization estimated by non vital staining for the Queen Tahiti and Spanish varieties but did not alter development of metabolically active arbuscules in roots of the three varieties. P concentration of endomycorrhizal shoots was higher for all treatments and P. brachyurus tended to decrease mineral concentration of nonmycorrhizal plants with early nematode application

Mycorrhization of micropropagated mature wild cherry (Prunus avium L.) and common ash (Fraxinus excelsior L.)

Micropropagated plants of common ash and wild cherry were inoculated with arbuscular mycorrhizal fungi during a 20-day weaning period, after which they were transferred to two different substrata supplemented with slow-release fertilizer. After a 13-week growth period, the stem height and diameter of the ash plants which had been inoculated with Glomus intraradices were three times greater than those of uninoculated control plants. Increasing the peat content of the substratum improved growth of ash. Four weeks after being transferred to pots, shoots of wild cherry inoculated with G. intraradices or G. deserticola were taller and stems thicker than those of control plants, whereas those inoculated with Gigaspora rosea had shorter shoots and thinner stems than the controls. These beneficial effects of fungal inoculation on plant development disappeared after 13 weeks. Increasing the peat content, but not the level of fertiliser of the substratum, improved growth of both inoculated and uninoculated wild cherry

Pathogenesis-related proteins in roots: a role in plant resistance or an epiphenomenon?

International audienceAlthough Pathogenesis-Related (PR) proteins have been identified in numerous monocotyledons and dicotyledons across different genera and in relation to very different physiological situations, relatively few studies have been conducted on roots which are the site of multimicrobial interactions. PR proteins are considered to be inducible proteins elicited by many environmental and developmental stimuli, but an increasing body of data points to their occurrence as constitutive components in different plant organs (Edreva 2005), including roots. This is the case, for example, of a Nicotiana glutinosa x Nicotiana debney hybrid which over-expresses PR protein genes and shows constitutive resistance to root fungal pathogens, but susceptibility to root colonisation by symbiotic fungi. However, successful root colonisation by beneficial microbes must imply a permanent control over microbial development. This could result from defence mechanisms being modulated in their intensity by the beneficial microbe (Gianinazzi 1981). In mycorrhizal interactions this phenomenon is associated with the weak and localized expression of several PR protein genes, and it could be responsible for priming the localized and systemic resistance against subsequent attack by microbial pathogens that is induced in mycorrhizal root systems. The induction of resistance by mycorrhiza formation requires a yet undefined systemic signal in roots, the activity of which in the above-ground part of the plant is not clear. Moreover, PRprotein synthesis induced by fungal pathogens in roots is associated with the development of root disease which raises the question of the role of PR proteins in root control over microbial invasion (Dumas-Gaudot et al. 2000). Edreva A, 2005, Gen.Plant Physiology, 31,105-124 Gianinazzi S, 1981, Agric.Ecosys.Environ.35, 105-112 Dumas-Gaudot E et al., 2000, Arbuscular mycorrhizas: physiology and function, 173-200

Mycorrhizal biotechnology in plant management

International audienc

Mycorrhizal inocula for agricultural systems and forestry: achievements and perspectives

International audienc

La biotechnologie des mycorhizes à arbuscules en horticulture

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