Exposure in vitro to an environmentally isolated strain TC09 of Cladosporium sphaerospermum triggers plant growth promotion, early flowering and fruit yield increase

Authors: LI, ZHIJIAN - OAK RIDGE INSTITUTE FOR SCIENCE AND EDUCATION (ORISE); JANISIEWICZ, WOJCIECH; Liu, Zongrang; CALLAHAN, ANN; Evans, Breyn; Jurick, Wayne; Dardick, Christopher - Chris

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2018
Publication Date: 2/1/2019
Citation: Li, Z., Janisiewicz, W.J., Liu, Z., Callahan, A.M., Evans, B.E., Jurick II, W.M., Dardick, C.D. 2019. Exposure in vitro to an environmentally isolated strain TC09 of Cladosporium sphaerospermum triggers plant growth promotion, early flowering and fruit yield increase. Frontiers in Plant Science. https://doi.org/10.3389/fpls.2018.01959.
DOI: https://doi.org/10.3389/fpls.2018.01959

Interpretive Summary: Over the past decade, researchers have identified a number of microbes that can promote the growth of plants. In some cases, this has been shown to occur through the release of airborne chemicals by both bacteria and fungi that, for largely unknown reasons, cause plants to grow faster. Microbes that have been tested so far have shown relatively modest growth promoting effects which have not been evaluated beyond the laboratory. Here we describe a common, harmless fungal strain that we isolated from the environment (dubbed TC09) that dramatically increases plant growth. When plants were grown alongside TC09 cultures in enclosed containers for 10-20 days, plant growth was 10 to 25 fold faster than untreated plants. Pepper plants that were pre-treated with TC09 before being transferred to the greenhouse flowered nearly 3 weeks faster and yield over 200% more peppers than control plants harvested at the same time. The discovery of TC09 potentially provides a safe and sustainable method for reducing the time-to-harvest and increasing yields of crop plants.

Technical Abstract: A growing number of bacteria and fungi have been found to produce microbial volatile organic compounds (MVOCs) that can promote plant growth. The magnitude of such growth enhancement by currently known microorganisms, however, remains relatively small thus limiting their practical application. Here we report the identification of an environmentally isolated strain of Cladosporium sphaerospermum (herein named TC09), that is able to dramatically enhance plant growth via VOCs. When cultured on Murashige and Skoog (MS) medium under in vitro conditions, tobacco seedlings (Nicotiana tabacum) exposed to physically separated TC09 cultures for 20 days increased stem elongation and whole plant biomass by up to 25 and 15 fold, respectively, over controls without exposure. TC09-mediated growth promotion required >5 g/L sucrose in the plant culture medium and was influenced by the duration of exposure ranging from one to ten days, beyond which no differences were detected. When transplanted to soil under greenhouse conditions, TC09-exposed tobacco plants retained higher rates of growth. Comparative transcriptome analyses using tobacco seedlings exposed to TC09 for 10 days uncovered a large number of differentially expressed genes (DEGs) associated with diverse biological processes including cell expansion and cell cycle, photosynthesis, phytohormone homeostasis and defense responses. To test the potential efficacy of TC09-mediated growth promotion on agricultural productivity, pepper plants (Capsicum annuum) of two different varieties, cayenne and minisweet, were pre-exposed to TC09 and planted to the greenhouse to monitor growth, flowering, and fruit production. Results showed that treated pepper plants flowered 20 days earlier and gave up to 212% yield increase over untreated controls. Altogether the data suggest that exposure of young plants to TC09 produced VOCs may provide a useful tool to improve crop productivity