Production of Glomus intraradices propagules, an arbuscular mycorrhizal fungus, in an airlift bioreactor

Abstract

This work addresses the symbiotic culture of the arbuscular mycorrhizal (AM) fungus Glomus intraradices with Daucus carota hairy roots transformed by Agrobacterium rhizogenes, in two submerged culture systems: Petri dish and airlift bioreactor. AM fungi play an active role in plant nutrition and protection against plant pathogens. These fungi are obligate biotrophs as they depend on a host plant for their needs in carbohydrates. The effect of the mycorrhizal roots inoculum-tomedium volume ratio on the growth of both symbionts was studied. A critical inoculating condition was observed at ∼0.6 g dry biomass (DW) и L −1 medium, above which root growth was significantly reduced when using a low-salt minimal (M) liquid medium previously developed for hairy root-AM fungi co-culture. Below critical inoculum conditions the maximum specific root growth and specific G. intraradices spore production rates of 0.021 and 0.035 d −1 , respectively, were observed for Petri dish cultures. Maximum spore production in the airlift bioreactor was ten times lower than that of Petri dish cultures and obtained with the lowest inoculum assessed (0.13 g DW и L −1 medium) with 1.82 × 10 5 ± 4.05 × 10 4 (SEM) spores (g DW inoculum) −1 (L medium) −1 in 107 d. This work proposes a second-generation bioprocess for AM fungi propagule production in bioreactors.

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.…”

Nitrogen transfer and assimilation between the arbuscular mycorrhizal fungus Glomus intraradices Schenck & Smith and Ri T-DNA roots of Daucus carota L. in an in vitro compartmented system

“…Knowing that AM carrot roots were limited in the C source after 8 weeks might indicate a relationship to the enhanced GDH activity found in the present study. Jolicoeur et al (1999) showed that carrot roots under in vitro conditions hydrolyzed all the sucrose contained in the medium after 25 days but that glucose and fructose then became available to the roots without being limiting even at low concentrations. It is then reasonable to assume that the highest GDH activities in AM roots might be related to a requirement for C skeletons, which would have led to a greater uptake of NH 4 + .…”

Increased spore production by Glomus intraradices in the split-plate monoxenic culture system by repeated harvest, gel replacement, and resupply of glucose to the mycorrhiza

“…Diop et al (1994) used sheared roots as starter inoculum and produced 893 spores per plate in 3 months. The airlift bioreactor studied by Jolicoeur et al (1999) produced 12,400 spores per liter (approximately 375 spores in the equivalent volume of a split-plate compartment). This places in perspective the efficiency of the method of St-Arnaud et al (1996), which produced an average of 15,000 spores per distal side of a 9-cm-diameter split Petri dish (30 cm 3 ) 3-4 months after the fungus crossed the divider, 4-5 months total elapsed time.…”