Endophytes: the effect of sustainable management in an olive grove under semi-arid conditions

Higher biodiversity in ecosystems leads to greater stability and multifunctionality. In bacteria-plant interactions, both the bacteria and the plant profit from each other. These interactions play an important role in agriculture, positively affecting plant status and improving product quality. Bacterial endophytes colonizing plants do not cause apparent damage and contribute to host plant’s protection and survival. This study was aimed at identifying bacterial endophytes in xylem sap and leaves of olive trees managed under sustainable practices for 17 years (i.e., no-tillage, drip irrigation with urban wastewater and recycling of polygenic carbon sources like cover crops and pruning material) compared to conventional one (i.e., soil tillage, burning of pruning residues, mineral fertilization, empirical irrigation) in a mature olive grove located in Southern Italy. During two different periods of the year, samples of soil, xylem sap and leaves were collected in both treatments for DNA extraction and metagenomic analysis of the endophytic bacterial communities. Results revealed that endophytes responded positively to sustainable orchard management, showing a higher complexity and abundance, compared to the conventional one. The abundance of nitrogen-fixing bacteria in the samples of the sustainable treatment was also discussed. A deeper understanding of endophytic microbiota of olive trees grown in different agronomic systems could be useful to promote plant growth and crop quality, also improving plant protection against pathogens.