Use of Root Organ Cultures To Investigate the Interaction between Glomus intraradices and Pratylenchus coffeae

Abstract

The interaction between Glomus intraradices and Pratylenchus coffeae on transformed carrot roots was studied in root organ culture. G. intraradices provided the roots with increased protection against P. coffeae by suppressing nematode reproduction in the roots. The internal and external mycorrhizal development was not influenced by the presence of the nematodes.The effects of arbuscular mycorrhizal fungi (AMF) on damage caused by root nematodes have been widely addressed (2, 21, 23). However, most research so far has been conducted under greenhouse conditions, with potentially misleading results due, in part, to the presence of undesirable contaminants (3). In recent years, the development of the root organ culture (ROC) system has opened new avenues to study various aspects of the symbiosis (for a review, see reference 13). Numerous studies have been dedicated to interactions between AMF and bacteria and fungi (3,4,12,18), while interactions with nematodes were seldom considered. One recent study reported the effect of AMF on the reproduction and root infestation of the nematode Radopholus similis by using this ROC system (10), but no data reported the impact of this nematode on the fungus development within and outside the host root. Since both organisms are obligatorily dependent on the root for the completion of their life cycle and occupy the same ecological root niche, each may impact the development of the other, either directly or indirectly. This communication reports, for the first time, the development and interaction of the obligatory parasitic nematode, Pratylenchus coffeae, and the obligatory AMF symbiont, Glomus intraradices, under ROC conditions.Transformed carrot roots (Daucus carota L.) colonized with G. intraradices Schenck and Smith (MUCL 41833) and nonmycorrhizal transformed carrot roots were purchased from GINCO (Louvain-la-Neuve, Belgium). Both materials were provided in petri dishes on the modified Strullu-Romand (MSR) medium (reference 7, modified from the description in reference 25). The petri dishes were maintained in an inverted position in the dark at 27°C. To obtain enough transformed carrot roots for the experiment, the root cultures were multiplied by transferring individual 70-mm-long root tips to new petri dishes containing MSR medium every 3 weeks. The AMF cultures were incubated for 5 months in order to obtain enough AMF spores for the inoculation. Several thousand spores were produced within this period and isolated by solubilization of the MSR medium (8), previous to the experiment.A P. coffeae population from Ghana (originally isolated from Musa spp.) was maintained on Medicago sativa L. callus, grown on modified White's medium (11). Nematodes were extracted from the callus with a modified Baermann funnel (15).At the beginning of the experiment, 48 90-mm-diameter petri dishes were filled with 40 ml of MSR medium. In each petri dish, one 70-mm-long transformed carrot root was transferred on the medium. Subsequently, they were separated in two homogenous groups (i.e., two g...

Development of an autotrophic culture system for the in vitro mycorrhization of potato plantlets

“…Such observation confirmed previous results obtained with in vitro cultures of various AM fungi [36,26]. Specifically focusing on G. intraradices , coefficients of variation calculated from different experiments ranked from 11%[37] to 22%[31], 38%[38] and even 61%[33]. The high variability observed in our experiment could be attributed to the host–fungus interaction and to both the fungal and plant physiology.…”

“…The length of extraradical hyphae measured in our study was similar to the values recorded in experiments conducted on excised transformed carrot roots with three different strains of G. intraradices [31,33]. Identically, the intraradical root colonization values estimated in our system were equivalent with the ones obtained on excised transformed carrot roots associated with G. intraradices , using the same method of estimation [33].…”

“…The autotrophic culture system developed in the present study allowed the AM fungus to develop, under in vitro conditions, typical colonization structures and to produce an abundant extraradical mycelium with spores morphologically similar to those observed in the classical monoxenic culture systems on excised root organs [20] and in pot cultures. Spore production, extraradical hyphal length and intraradical root colonization were close to the values recorded with the same strain or different strains of the same species cultured in association with excised transformed carrot roots [31–33]. The newly produced spores were capable to form associations with a new host in vitro, following sub‐cultivation, indicating that the AM fungus is able to complete its life cycle through successive generations.…”

Selecting Native Arbuscular Mycorrhizal Fungi to Promote Cassava Growth and Increase Yield under Field Conditions

“…For example, it was shown that Radopholus similis and Pratylencus coffeae affected the frequency of Funneliformis mosseae colonization in banana, but not the intensity (Elsen et al, 2003a,b). In contrast, root colonization by R. irregularis in vitro banana plantlets was not affected either by R. similis (Koffi et al, 2013) or by P. coffeae in transformed carrot roots (Elsen et al, 2003c). …”

Use of the arbuscular mycorrhizal fungus Glomus intraradices as biological control agent of the nematode Nacobbus aberrans parasitizing tomato

“…In addition, AMF affects the nematodes by altering root exudates (Graham and Menge 1982) or by producing phytoalexins in the root, such as glyceollin, which could have nematicidal effects (Morandi 1996). Although possible mechanisms have been proposed to explain the reduction of harmful nematodes in the presence of AMF, they remain a matter of speculation (Elsen et al 2001;Elsen et al 2003). The interaction between the AMF and Meloidogyne spp.…”