Compost Tea Induces Growth and Resistance against Rhizoctonia solani and Phytophthora capsici in Pepper

Compost teas (CTs) are organic solutions that constitute an interesting option for sustainable agriculture. Those that come from garden waste have been applied in vitro and in vivo on pepper plants to determine its suppressive effect against both Phytophthora capsici and Rhizoctonia solani. The studied CT showed relevant content in NO3-, K2O, humic acids, and microorganisms such as aerobic bacteria, N-fixing bacteria, and actinobacteria, which play a role in plant growth and resistance. This rich abundance of microbiota in the CT induced a reduction in the relative growth rate of both P. capsici and R. solani (31.7% and 38.0%, respectively) in in vitro assays compared to control. In addition, CT-irrigated plants displayed increased growth parameters and showed the first open flower one week before those treatments without CTs, which suggests that its application advanced the crop cycle. Concerning pathogen infection, damage caused by both pathogens became more apparent with a one-week inoculation compared to a four-week inoculation, which may indicate that a microbiological and chemical balance had been reached to cope with biotic stresses. Based on these results, we conclude that CT application induces plant growth and defense in pepper plants against P. capsici and R. solani because of its relevant soluble nutrient content and microbiota richness, which provides a novel point for plant nutrition and protection in horticultural crops.