The compound BTH controls plant diseases activating a plant disease resistance response, which can be characterised by identifying genes or enzymes activated during this reaction. Some genes or enzymes can be activated during plant reaction to colonization pathways by microsymbionts. Therefore, the application of products that activate protection mechanisms like BTH, could also inhibit mutualistic symbioses. An experiment was carried out to establish the effect of BTH on soybean colonization by Bradyrhizobium elkanii and Glomus intraradices. Control plants or plants inoculated with rhizobium or mycorrhizal fungus were treated with BTH (20 mL of a 25 mg L-1 solution) via seeds, roots or leaves. BTH reduced plant growth when applied to roots. Roots were colonized at a lower rate by B. elkanii in plants to which BTH was applied via roots, when compared to control plants or plants treated via leaves. BTH treatment had no effect on the colonization of soybean roots by Glomus intraradices. It is suggested to avoid BTH application to soybean roots, although there is no restriction to the foliar treatment.
mycorrhiza; rhizobium; systemic acquired resistance
