Valorization of pelagic Sargassum into a biostimulant (OJA1) for improved tomato yields and protection against bacterial and fungal phytopathogens
TL;DR
The evaluation of a Sargassum biostimulant formulation (OJA1) and its effect on tomato demonstrates the valorisation potential of Sargassum and could contribute to sustainable agriculture and propels economic development in coastal communities.
Abstract
Several environmental and economic issues have been brought about by mass accumulations of Sargassum seaweed along the coastlines in Trinidad and Tobago, and the wider Caribbean region. Though there are many issues associated with this seaweed biomass, there remains opportunities to transform this problem into a solution. The current study presents the evaluation of a Sargassum biostimulant formulation (OJA1) and its effect on tomato. Tomato plants were foliar (0.5% v/v) treated with the OJA1 biostimulant under both greenhouse and field conditions. OJA1 significantly improved plant performance (p < 0.05) by means of increased chlorophyll (22.7%), plant height (29.3%), root biomass (34.4%), shoot biomass (49.6%), and yield (54.8%), while reducing disease severity by 37.8% for bacterial spot and 37.5% for early blight under greenhouse conditions. In field trials, OJA1 significantly increased yield and reduced disease severity across both growing seasons. Yield increases ranged from 75.6–103.2% with OJA1 alone and 114.6–154.8% when alternated with fungicides. Similarly, bacterial leaf spot and early blight severity were reduced by up to 50.6% and 61.8%, respectively, relative to the Control. Molecular mechanistic testing revealed that OJA1-treated tomato plants had more than a two-fold increase in gene transcripts responsible for abiotic/biotic stress tolerance and biosynthesis of growth hormones. Additionally, OJA1-treated plants had significantly lower DNA levels of both pathogens. Additional analysis further showed that OJA1-treated plants had significantly higher hormonal content (auxin, cytokinin, and gibberellin), and fruits had significantly higher mineral content (N, P, K, Na, and Zn) than Control plants. The results exemplify the valorisation potential of Sargassum and could contribute to sustainable agriculture and propels economic development in coastal communities.