Trehalose, a Biostimulant to Reduce Bacterial Wilt Disease on Tomato

Farmers suffer large losses to bacterial wilt, a widespread crop disease caused by soilborne Ralstonia species. There is no good control for bacterial wilt, which affects many economically important crops, including tomato. Trehalose is an environmentally benign non-reducing disaccharide that is present in all kingdoms of life. Previous studies suggested that trehalose has potential as a biostimulant to reduce bacterial wilt of tomatoes and also to increase plant drought tolerance. We sought to define optimal strategies to apply this biostimulant for tomato plant protection. Imbibing seeds with a 30 mM trehalose solution before planting slightly increased drought tolerance but did not increase bacterial wilt resistance. However, exogenous application of 30 mM trehalose solutions substantially reduced wilt disease severity on tomato plants inoculated with high doses of Ralstonia pseudosolanacearum strain GMI1000. Trehalose was protective when applied either by soaking bare-root seedlings at the time of transplant or as a soil drench to older plants. Three or more trehalose soil drenches rendered tomato plants highly resistant to Ralstonia but also decreased their biomass and leaf chlorophyll content. Reducing the number of soil drenches to two resulted in good protection from bacterial wilt with minimal phytotoxicity. Soaking bare-root seedlings in trehalose also increased bacterial wilt resistance without major effects on plant health. Together, these experiments identified an environmentally sustainable solution for a common and destructive plant disease.