Background and Aims: Laboratory and greenhouse experiments have shown that root-associated bacteria have beneficial effects on grapevine growth; however, these effects have not been tested in the field. Here, we aimed to demonstrate whether bacteria of different geographical origins derived from different crop plants can colonize grapevine to gain a beneficial outcome for the plant leading to promote growth at the field scale. Methods: To link the ecological functions of bacteria to the promotion of plant growth, we sorted fifteen bacterial strains from a larger isolate collection to study in vitro Plant Growth Promoting (PGP) traits. We analysed the ability of these strains to colonise the root tissues of grapevine and Arabidopsis using green-fluorescent-protein-labelled strain derivatives and a cultivation independent approach. We assessed the ability of two subsets randomly chosen from the 15 selected strains to promote grapevine growth in two field-scale experiments in north and central Italy over two years. Parameters of plant vigour were measured during the vegetative season in de novo grafted vine cuttings and adult productive plants inoculated with the bacterial strains. Results: Beneficial bacteria rapidly and intimately colonized the rhizoplane and the root system of grapevine. In the field, plants inoculated with bacteria isolated from grapevine roots out-performed untreated plants. In both the tested vineyards, bacteria-promotion effects largely rely in the formation of an extended epigeal system endowed of longer shoots with larger diameters and more nodes than non-inoculated plants. Conclusions: PGP bacteria isolated in the laboratory can be successfully used to promote growth of grapevines in the field. The resulting larger canopy potentially increased the photosynthetic surface of the grapevine, promoting growth.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This research was supported by the EU project BIODESERT (European Community’s Seventh Framework Programme CSA-SA REGPOT-2008-2 under grant agreement no. 245746) and King Abdullah University of Science and Technology (KAUST). ER and FM acknowledge support by Università degli Studi di Milano, DeFENS, the European Social Fund (FSE) and Regione Lombardia (contract ‘Dote Ricerca’). The authors would like to thank the “Arnaldo Caprai” and “Castello Bonomi” farms for their kind availability and interest in performing the field trials in their vineyards. The authors would like to thank Usama A. El-Behairy and Ayman F. Abou-Hadid (Ain Shams University, Cairo, Egypt) and Roberto Gerbino (Fondazione Bussolera Branca, Casteggio, Italy) for support in grapevine sampling, Umberto Fascio (CIMA, Centro Interdipartimentale di Microscopia Avanzata, University of Milan, Milan, Italy) for technical support with the confocal microscope and the “Vitis Rauscedo” grapevine nursery for kindly providing the grapevine plantlets. The authors dedicate this work to Nicola Rubaga.