Systemic biochemical changes in pepper (Capsicum annuum L.) against Rhizoctonia solani by kale (Brassica oleracea var. acephala L.) green manure application

Background: In the search for new alternatives to avoid the problems associated with the use of chemical fungicides in agriculture, the use of green manure (GrM) could help to combat fungal diseases of crops, such as those produced by the necrotrophic pathogen Rhizoctonia solani . In the case of the use of brassica-tissues as GrM, could have an elicitor capacity of systemic plant resistance. Results We used kale-leaves as GrM and applied to pepper plants infected with R. solani . Application of freeze-dried kale-tissues to roots of pepper plants produced a systemic activation of foliar defenses via the salicylic acid (SA) and ethylene (ET) pathways, significantly reducing pathogen damage. In addition, this systemic response led to the accumulation of secondary defense metabolites in leaves, such as pipecolic acid, hydroxycoumarin or gluconic acid, among others. Remarkably, pepper plants treated with lyophilized kale-GrM accumulate glucosinolates when infected with R. solani . We also confirm that autoclaving removed part of the glucobrassicin (GBS) (85%) and sinigrin (19%) content of the kale-tissues. Conclusions GrM kale-tissues are able to activate systemic defenses in bell pepper against foliar pathogens through SA/ET hormonal pathways, accumulating secondary defense metabolites.