Eelgrass slabs, a soilless culture substrate that inhibits adhesion of fungi and oomycetes and enhances antioxidant activity in tomato

Composed of a marine plant, Zostera sp., eelgrass slabs are a novel organic substrate for soilless cultures used in tomato production. The benefit of using eelgrass slabs for growing tomatoes was assessed by comparing it with coconut fiber slabs in regard to contamination by Pythium spp. and to the antioxidant properties of tomato fruits. First, tomato root contamination by Pythium spp. was studied by direct plate counting, and a molecular comparison of fungal and oomycete communities was conducted using PCR-DHPLC. Second, the antioxidant properties of tomato fruits were analyzed by measuring total phenol and carotenoid contents and by evaluating radical scavenging activity. Compared to plants grown on coconut fiber slabs, those on eelgrass slabs presented a lower rate of Pythium spp. root contamination. Moreover, culture on eelgrass slabs produced fruits with better radical scavenging activity and higher total phenol content compared to controls. Carotenoid content was not affected by the type of substrate. This study highlights the value of detrital leaves of Zostera sp. as a substrate for soilless culture that reduces root contamination and also promotes the production of tomato fruits with better nutritional value.