Compost tea reduces the susceptibility of Pinus radiata to Fusarium circinatum in nursery production

Nutrition is one of the factors that most limits forestry plant growth; thus, current production in nurseries is based on conventional fertilization focused on enhancing vigor. However, an excessive intake of mineral nitrogen can cause morphological imbalances and the formation of more succulent tissues which, consequently, increase susceptibility to plant pathogens. Fusarium circinatum is the causal agent of pitch canker in plants of the Pinus genus, with Pinus radiata being the species most susceptible to this disease. This study compares the response of P. radiata seedlings to infection by F. circinatum as influenced by two fertilizers-conventional and aerated compost tea (ACT)-applied during the nursery phase. The potential of ACT against F. circinatum was first tested in vitro, where it was found to inhibit the pathogen's mycelial growth and conidial germination. In the greenhouse, infected plants fertilized with ACT exhibited less severe internal and external symptoms of pitch canker and lower levels of pathogen colonization of both stems and needles than with conventional fertilizer. An analysis of the hormone content and defense-related gene expression shows greater salicylic acid production and phenylalanine ammonium-lyase and chalcone synthase expression in ACT-fertilized pine. All of the parameters assessed are consistent in showing that biofertilization with ACT reduces the susceptibility of pine seedlings to the disease compared with conventional fertilization.