Host plants directly determine the α diversity of rhizosphere arbuscular mycorrhizal fungal communities in the National Tropical Fruit Tree Field Genebank

Abstract

Arbuscular mycorrhizal fungi (AMF) typically exhibit reduced diversity in nutrient-rich soils. However, whether the influence of host plants on AMF within the rhizosphere is direct or indirect through the alteration of soil nutrient levels has yet to be determined. This study explored the diversity and colonization of AMF in the National Tropical Fruit Tree Genebank, where chemical fertilizers are used to preserve minor tropical fruit germplasms. We aimed to understand the direct and indirect effects of host plants on AMF community dynamics, sporulation, and colonization. By analyzing fine roots and rhizosphere soil from 12 tropical fruit trees, we assessed mycorrhizal colonization indices, soil nutrients, AMF spore density, and community structure. Despite their low colonization density and arbuscular abundance, all the tree roots harbored AMF, with spore densities ranging from 24.00 to 204.80 spores/100 g of dry soil. High-throughput sequencing identified 207 AMF virtual taxa (VTs) from 60 soil samples, with dominant taxa, including early-evolved Paraglomus fungi and ruderal AMF, being minimally affected by soil nutrient levels. Interestingly, there was no correlation between α diversity and spore density. Structural equation modeling (SEM) indicated that host plant evolutionary divergence time (ET) directly influenced AMF α diversity indices and indirectly impacted spore density via soil nutrients. However, neither ETs nor soil nutrients significantly affected the AMF community structure, with only arbuscular abundance showing a negative correlation with ET. This research underscores the intricate relationship between host plants and AMF in genebanks, offering insights for effective AMF resource management and informed conservation practices. Graphical Abstract