Rootstock genetic background in almond cultivation influences the composition of root-associated microbial communities and enrichment of taxa associated with plant defense and nutrient availability.

backgroundBeneficial root microorganisms play a crucial role in influencing key agronomic traits in rootstocks. However, little is known about the microbial communities naturally associated with almond rootstocks in Spain. To address this gap, we sampled roots of six commercial Prunus rootstocks in a 15-year-old almond orchard representing two different genetic backgrounds: P. cerasifera background (PCB) with Rootpac

resultsBacterial and fungal communities differed according to the genetic background of the rootstocks. Roots of PCB rootstocks were significantly enriched with amplicon sequence variants (ASVs) identified as Streptomyces, which contain bacterial species known as biocontrol agents. In contrast, PPB rootstocks were significantly enriched with ASVs identified as Hyalorbilia, Rhizoglomus, and Entrophospora, the first one being an ascomycete known for its nematophagous activity, and the two latter for their role as mycorrhizal fungi. Interestingly, taxa including known fungal plant pathogens were significantly enriched in PCB rootstocks, namely ASVs included in Venturiales and Nectriaceae (Hypocreales). Moreover, in PCB rootstocks we identified bacterial and fungal ASVs that were positively correlated with N and P soil concentrations, respectively, thus suggesting their potential role in enhancing nutrient availability for plants. Similarly, a number of bacterial and fungal ASVs were positively and highly correlated with soil Na concentration among PPB rootstocks.

conclusionThese results suggest that the genetic background of the rootstock may influence bacterial and fungal taxa recruitment in field conditions, thus potentially influencing nutrient cycling and plant defense.