Background
Rootstocks are the link between soil and scion in grapevine, and they can either provide tolerance to abiotic and biotic stresses, and regulate yield and grape quality. The vascular system of grapevine rootstocks is still an underexplored niche despite its potential for hosting beneficial and pathogenic microorganisms. The purpose of this study was to investigate the changes in the composition of fungal communities in 110 Richter and 41 Berlandieri rootstocks at different stages of the grapevine propagation process and to measure the absolute abundance and dynamic changes of Cadophora luteo-olivacea, a common pathogen associated with Petri disease of grapevine.
Results
Taxonomic analysis revealed that the fungal community predominantly consisted of phyla Ascomycota in all steps of the propagation process. The alpha-diversity of fungal communities differed among sampling moments for both rootstocks, with richness and fungal diversity in the vascular system decreasing throughout the propagation process. The core microbiome was composed by the genera Cadophora, Cladosporium, Penicillium and Alternaria in both rootstocks, while the pathogenic genus Neofusicoccum was identified as a persistent taxon throughout the propagation process. Fungal functionality analysis showed that the relative abundance of plant pathogens associated with trunk diseases increased towards the last stage in nurseries. Regarding C. luteo-olivacea, significant correlations between sequencing reads and droplet digital PCR (ddPCR) was observed.
Conclusions
Fungal communities in the vascular system of grapevine rootstocks differed among the different stages of the propagation process in nurseries. Numerous genera associated with potential biocontrol activity and grapevine trunk diseases have been identified. Understanding the large diversity of fungi in the rootstock vascular tissue and the interactions between fungal microbiota and grapevine will help developing sustainable strategies for grapevine protection.