Synthetic microbial communities for sustainable hydroponic tomato production
Tomato (Solanum lycopersicum) is a widely cultivated crop. In cooler climates, such as Northern Europe, commercial tomato is predominantly cultivated hydroponically under glass.  While these hydroponic systems enable high yields, they also enhance disease susceptibility and accelerate pathogen spread through the inter-connected nutrient supply, increasing the risk of devastating yield losses. In this study, we have examined whether synthetic communities of plant-beneficial microbes (SynComs) offer a sustainable crop protection solution. We identified individual microbes and small SynComs that induce systemic disease resistance during the more vulnerable early stages of development. The two most effective SynComs were evaluated further in a commercial scale greenhouse trial. Although each SynComs slightly reduced early growth, they had no adverse effects on final yield or fruit quality. Strikingly, while only one SynCom strain consistently persisted in the hydroponic stonewool substrate throughout the six-month trial, the introduction of the disease-suppressive SynComs at sowing had significant and highly similar impacts on the bacterial community structures six months later. Our findings demonstrate that microbial SynComs can reduce disease susceptibility of hydroponically grown tomato without compromising yield, offering a viable and sustainable strategy for crop protection in controlled environment agriculture.