Phytochemical profiles and antifungal activity of extracts from Prunus persica leaves inoculated with Taphrina deformans

BUTASSI, ESTEFANÍA; CASTELLI, MARÍA VICTORIA; LOPEZ, SILVIA; VALENTINI, GABRIEL; DRINCOVICH, MARÍA FABIANA; LARA, MARÍA VALERIA

Congreso; Reunión conjunta SAIB-SAMIGE 2020; 2020

Taphrina deformans is a dimorphic fungus that causes the ?leaf curl disease? in peach trees (Prunus persica) around the world. This fungus is responsible for premature leaf drop, and a severe defoliation leads to lower fruit production, higher vulnerability to frost and opportunistic pathogens, leading to very important economic problems. In order to understand the plant metabolic changes upon fungal infection, the secondary metabolite profile of different P. persica extracts obtained from leaves of susceptible and resistant genotypes before and after fungal infection was studied. For this purpose, leaves of P. persica susceptible (DS and FL) and resistant (DR) genotypes were inoculated with the fungus and collected at 0 (control) and 96 hpi (hours post inoculation). Then, dried leaves were extracted by maceration using hexane, chloroform, ethyl acetate and methanol (MeOH). Solutions were filtered and evaporated in vacuum, obtaining the control (FL0, DS0 and DR0) and inoculated (FL96, DS96, and DR96) extracts. After that, extracts were analyzed using Thin Layer Chromatography (TLC) in automated equipment CAMAG. Plates were revealed with UV light (254 and 366 nm) and 10 % (v/v) H2SO4. Flavonoids were detected using NP-PEG reagent (Natural Products-polyethylenglycol). TLC analysis of extracts shows that there is no difference in the chromatographic profiles neither among genotypes nor inoculation status. However, some compounds were observed as more intense bands in the DR96 MeOH extract. This is interesting since, although the induction of new metabolites is not observed upon infection, an increase in the synthesis of some of them could be involved in the tolerance of the resistant genotype DR against the attack of the pathogen. In addition, chlorogenic acid was detected in all MeOH extracts, and flavonoids analysis allowed to detect rutin and quercitrin in MeOH extracts, and quercetin and kaempferol in hydrolyzed MeOH extracts. The antifungal activity of extracts against T. deformans was studied using the broth microdilution technique in 96-well microplates. Results show that MeOH extracts were active, reaching an inhibition between 75-80% of the fungal growth at 500 µg/ml. The antifungal activity was the same for the inoculated and un-inoculated extracts within the same genotype, and the same among the different genotypes studied. In addition, different flavonoids identified in the extracts and chlorogenic were also tested for their antifungal activity. Besides these metabolites showed activity against the pathogen, the mixtures of chlorogenic acid with rutin, quercitrin or kaempferol were more active than individual components. Therefore, in vivo antifungal activity would rely on the combination of different metabolites which act additively to fight the fungus. Even though the same metabolite profile was detected at 0 and 96 hpi by this technique, the further induction of new compounds at later times cannot be ruled out and should be tested.