Mycorrhizal colonization and growth of soybean influenced by different fungal species and application of the isoflavonoid formononetin

Abstract

The effects of soil-applied synthetic formononetin (7-hydroxy 4'methoxi-isoflavone) on arbuscular mycorrhizal colonization, plant growth and nutrient content of soybean (Glycine max L. Merril) inoculated or not with different mycorrhizal fungi were studied. The experiment was conducted in plastic pots containing 1.6 kg of a Dusk-Yellow Latossol (Oxisol) with 2 mg/kg of P. Plants were submitted to inoculation with Acaulospora morrowiae Spain & Schenck, Gigaspora margarita Becker & Hall, Glomus clarum Nicol. & Schenck, Glomus etunicatum Becker & Gerdemann and Scutellospora heterogama Nicol. & Gerdemann Walker & Sanders) in the presence and absence of formononetin (5µg/mL) applied as solution form at the sowing time. Formononetin enhanced mycorrhizal formation by all fungal species. However, such effects were influenced by the growth period and parameter of colonization. Plant growth, nodulation and leaf nutrient content were stimulated by inoculation, but not by application of formononetin. G. etunicatum was the most effective species for soybean, independent of formononetin application.