Long-term P fertilization significantly altered the diversity, composition and mycorrhizal traits of arbuscular mycorrhizal fungal communities in a wheat-maize rotation

Abstract

Phosphorus (P) fertilization rates have been dramatically increasing in intensive agro-ecosystems. However, the impact of such long-term P fertilization in intensive agro-ecosystems on the diversity, composition mycorrhizal traits of arbuscular mycorrhizal fungi (AMF) communities and the relationship between them remains poorly understood. By conducting a long-term field experiment (10 years) in north China in a typical calcareous soil with a wheat-maize rotation, we investigated the effects of six P fertilization rates on AMF community properties. We found that AMF alpha diversity (including OTU number and Shannon index) was positively correlated with both AMF root colonization of maize, hyphal density in soil and expression of the phosphate transporter gene ZmPht1;6 for maize. AMF community structure was significantly correlated with AMF colonization of maize roots, hyphal density and P concentrations in maize shoots. The relative abundance of the most dominant taxon Funneliformis caledonium OTU1 decreased while that of the second dominant taxon Claroideoglomus lamellosum OTU55 increased as the P fertilizer rate increased. AMF colonization of roots and hyphal density was positively correlated with the relative abundances of Glomus sp. (including OUT 29, OTU32, and OTU37) in soil but was negatively correlated with the relative abundances of Septoglomus viscosum OTU14. The relative abundances of Glomus sp. (OTU 5, OTU 25, OTU27, OTU23, and OTU29) were positively correlated with AMF colonization of roots, hyphal density and ZmPht1;6 expression under low rates of P fertilization (P0 and P12.5 treatments), while the relative abundance of Glomus sp. OTU20 was positively correlated with AMF colonization of roots, hyphal density and ZmPht1;6 expression under high rates of P fertilization (P100 and P200 treatments). Long-term P fertilization significantly altered the alpha diversity, structure, and composition of AM communities, which affected AMF colonization of maize roots and expression of a phosphate transporter gene. Our results indicate that different members of AMF communities differentially modulated their mycorrhizal traits with maize under different P fertilization rates. An improved understanding of how AMF taxa and functions are altered by P fertilization and the mycorrhizal traits impact on plant nutrition could help guide P fertilization practices in agro-ecosystems.