Investigating the role of rain as source of the tomato leaf microbiome.
M. MECHAN LLONTOP (1), L. Tian (1), V. Bernal Galeano (1), B. Vinatzer (1) (1) Virginia Tech, U.S.A.

Bacteria represent a major portion of organic aerosols and are not present in rain but may actually be a driving force behind the water cycle. Plants are colonized by a wide diversity of microorganisms whereby the phyllosphere harbors an average of 106 to 107 bacteria/cm2 of leaf. Where this microbial diversity originates from, how microbes interact with each other, and how microbes interact with the plants on which they live is poorly understood. In this study, we have started testing the hypothesis that rain is an important contributor to the tomato leaf microbiome. We characterized the rain microbiome and used bacteria isolated from rain to inoculate lab-grown tomato plants. The plant-associated bacterial communities on leaves were separated from leaves by sonication, DNA was extracted, and 16S rRNA was sequenced. We then compared the microbial population structure of the microbiome of tomatoes inoculated with bacteria from rain, inoculated with filter-sterilized rain, and treated with sterile water at zero and seven days post-inoculation. Our results revealed that some bacterial families present in rain colonize tomato efficiently while other families are present in rain but are absent from tomato leaves 7 days after inoculation. Therefore, rain is one likely source of the tomato leaf microbiome. We further postulate that the tomato immune system not has a strong effect on which bacteria colonize its leaves but that also the bacteria that succeed at colonizing tomato leaves affect the status of the tomato immune system and, lastly, affect the outcome of plant-pathogen interactions. To test these hypotheses, we are comparing tomato defense gene expression between tomatoes that have been treated with rain bacteria and sterile tomatoes and their susceptibility to pathogen infection.    

Abstract Number: P4-108
Session Type: Poster