Potential Functional Role of Carrot Endophyte Communities.

Endophytic microbial communities are expected to be critical for plant growth and health, however knowledge of their functional role in crops with long-lived storage roots like carrot remains unexplored. In this study, we quantified the potential for individual endophyte isolates to promote growth and protect plants against a key carrot pathogen (Alternaria dauci). For this purpose, we treated A. dauci and carrot plants (Napoli F1 & Chantenay Red Cored) in in vitro and greenhouse trials respectively, with a broad group of endophytes isolated from roots of field grown carrot plants. Many of the microbial taxa isolated from carrot roots increased carrot biomass and had antagonistic activity toward A. dauci, indicating that carrot endophytes play an important role in promoting carrot productivity and reducing susceptibility to plant pathogens. Moreover, the plant growth promoting benefits of these isolates differed among carrot genotypes, further demonstrating the potential implications of these studies for varietal selection. The Pseudomonas isolates had the greatest activity on carrot growth and A. dauci suppression, indicating these isolates may hold promise for use as microbial inoculants to improve carrot productivity. However, given the wide diversity of endophytes found to inhabit carrot roots, further studies investigating potential synergistic or antagonistic interactions among individual microbial taxa are needed to develop the most effective microbial inoculant formulations. Our data provides novel insights about the functional role of microbial endophytes in carrot roots and has potential to help growers improve carrot productivity, while reducing reliance on pesticides for disease control.