Sorgoleone concentration influences mycorrhizal colonization in sorghum

The association between arbuscular mycorrhizal fungi (AMF) and sorghum, the fifth most cultivated cereal in the world and a staple food for many countries, is relevant to improving phosphorus (P) absorption. The importance of root exudation as a signal for the symbiosis has been shown for several species, but a complete understanding of the signaling molecules involved in the mycorrhizal symbiosis signaling pathway has not yet been elucidated. In this context, we investigated the effect of sorgoleone, one of the most studied allelochemicals and a predominant compound of root exudates in sorghum, on AMF colonization and consequently P uptake and plant growth on a sorghum genotype. The sorghum genotype P9401 presents low endogenous sorgoleone content, and when it was inoculated with Rhizophagus clarus together with 5 and 10 µM sorgoleone, mycorrhizal colonization was enhanced. A significant enhancement of mycorrhizal colonization and an increase of P content and biomass were observed when R. clarus was inoculated together with 20 µM sorgoleone. Thus, our results indicate that sorgoleone influences mycorrhizal colonization, but the mechanisms by which it does so still need to be revealed.