Respostas bioquímicas, metabólicas e moleculares de genótipos de pimenta (Capsicum baccatum) com níveis distintos de pungência cultivados sob déficit hídrico

Abstract

The pungency in Capsicum peppers is due to capsaicinoid compounds, whose content varies depending on genetic and environmental factors. The effect of drought stress (SD) on peppers, their metabolic responses and the involvement in capsaicinoid biosynthesis in this response are not well established. Based on this, the objective was to characterize the molecular, biochemical and metabolic responses of three genotypes of pepper (Capsicum baccatum), with different potential for capsaicinoid accumulation, in the face of drought stress. Genotypes with medium pungency (P232), low pungency (P337) and non-pungent (P323) were grown under DS and under ideal conditions of irrigation in two harvest. The medium pungency genotype did not show significant losses of fresh weight of the fruits due to the DS, being an indication that this genotype tolerated this condition better. This genotype also differed from other genotypes regarding the effect of DS on the levels of amino acids, phenolic acids and capsaicinoids. The accumulation of active osmolytes, observed by the reduction of the osmotic potential in response to the DS occurred only in the pungent genotypes (P232 and P337). This result, associated with the accumulation of amino acids and sugars under DS exclusively in these genotypes indicates the involvement of these osmoprotectors as a response mechanism to drought in pungent peppers. The fact that this performance is not observed in the non-pungent genotype leads us to believe that somehow capsaicinoids may be involved in the mechanism of response to the condition of DS via osmoprotection. However, the expression of PUN1 (capsaicin synthase enzyme) and the capsaicinoid content were generally reduced depending on the condition of DS. The transcriptional expression of genes putatively involved in the response to stressful conditions was also affected by DS. The application of the DS led to a reduction in the accumulation of DREB1A transcripts (type of transcription factor element-ligand responsive to dehydration) and an increase in the accumulation of ERF5 transcripts (type of transcription factor responsive to ethylene).