Fosfito de potássio na ativação de respostas de defesa em genótipos de Coffea arabica

Abstract

The coffee culture is among the main commodities in Brazil. Plant diseases are one of the main factors that directly affect the productivity of the coffee tree, causing important losses, among which the coffee tree rust stands out. The main method of controlling this disease is chemical treatment, however, there is a demand for coffee free from residues of molecules that are harmful to man and the environment. One option for these products is the use of resistance inducers, a disease management measure that involves activating the plant's latent defense mechanisms. The present work aimed to evaluate the effect of potassium phosphite (K-Phi) on coffee cultivars with contrasting genotypes for rust. In order to elucidate the mechanism by which K-Phi activates defense responses in coffee plants, we studied the gene expression and enzymatic activity of components involved in the defense pathway of salicylic acid (SA), compared to the standard inducer acibenzolar-S-methyl (ASM). The quantification of metabolites was also performed. It was observed that a foliar application of K-Phi increased the transcription of genes related to the defense response pathway of the SA and the biosynthesis of secondary metabolites (PAL, EDS1, NPR1, GLU and POX), in addition, it increased the activity of defense enzymes related to oxidative explosion and the formation of secondary metabolites (SOD, APX and PPO). All these variables, quantified after treatment with K-Phi, presented results similar to the standard ASM inducer in several situations evaluated (cultivars and collection times). So, possibly, the mechanism of action of K-Phi in inducing resistance in coffee plants involves the same pathway induced by ASM. The results obtained demonstrate that K-Phi can be considered a potent coffee plant resistance inducer, as the previous treatment of plants with this inducer was able to induce an increase in defense responses in resistant and rust-susceptible coffee cultivars, even in the absence of the pathogen.