Diversity and Community Composition of Arbuscular Mycorrhizal Fungi in Robusta Coffee in its Region of Origin, the Drc: Impact of Environmental Drivers and Coffee Production Systems

Abstract

Robusta coffee, grown by 25 million farmers across more than 50 countries, plays an important role in smallholder farmers' livelihoods and the economies of many low-income countries. Despite robusta coffee’s growing economic importance, currently accounting for 43% of global coffee production next to Arabica, its association with arbuscular mycorrhizal fungus (AMF) communities and how agricultural practices affect this association remains poorly understood. To address this, we characterised the AMF community composition of robusta coffee in part of its region of origin, the Democratic Republic of Congo, and we compared AMF diversity and community composition between coffee monoculture and agroforestry production systems, as well as with wild robusta in its native rainforest habitat. Using Illumina sequencing on 304 root samples, we identified 307 AMF operational taxonomic units (OTUs), dominated by the genera Glomus and Acaulospora. OTU richness did not vary across the three studied systems, yet large differences in community composition were found, with many unique OTUs only observed in the coffee in the rainforest. In general, lower available soil phosphorus (P) and lower soil bulk density increased AMF diversity, yet higher available soil P and pH increased AMF diversity in the wild forest coffee. Shifts in AMF community composition across coffee systems were driven by canopy closure, soil pH, available soil P and soil bulk density. Our study is the first to characterise mycorrhizal communities in wild robusta coffee in its region of origin and shows that even low-input agricultural practices result in major AMF community shifts as compared to a natural baseline.

Keywords: Next Generation Sequencing, Arbuscular mycorrhizal fungi, Biodiversity, Agroecology