Effects of carbohydrates and organic acids on the mycelial growth of the endomycorrhizal fungus Gigaspora gigantea In vitro

Abstract

The effects of organic compounds on the mycelial growth of G. gigantea in vitro were studied. Surface desinfested spores were germinated in water-agar and transferred to a liquid medium suplemented with 0,0; 0,5; 1,0; 2,0 and 4,0 g/l of fructose, arabinose, sucrose, trehalose, mannitol on starch, and 0,0; 0,156; 0,313; 0,625 and 1,25 g/l of pectin or of pyruvic, citric, oxalic and tartaric acids. The effects of 0, 10 and 20 day pre-growth periods on the response of the fungus to the addition of sucrose (4 g/l) were also studied. For the carbohydrates, significant stimulatory effects were only obtained with low concentrations of pectin. Trehalose was inhibitory to growth in all concentrations studied, while the remaining carbohydrates had no significant effects on growth. Stimulatory effects for sucrose (4 g/l) were obtained when it was added after 10 or 20 days incubation of the pre-germinated spores. For the organic acids, stimulatory effects were obtained with the tartaric and citric acids, and inhibition, with the piruvic and oxalic acids.