EVALUATION OF THE ANTIBIOTIC ACTIVITY OF EXTRACELLULAR COMPOUNDS OF PSEUDOMONAS SP. IN THE CONTROL OF XANTHOMONAS ARBORICOLA PV. PRUNI.

Fernanda Corrêa da Silva Vasconcellos (UEL); Admilton Gonçalves Oliveira Junior (UEL); Lucilene de Paula Lopes (UEL); Jamile Priscila Oliveira Beranger (UEL); Flávia Regina Spago (UEL); Cintia Greice Matsuoca Góis (UEL); Galdino Andrade (UEL); Marco Antonio Nogueira (UEL); Suzana Sosa Coimbra (UEL); João Carlos Palazzo Mello (UEM)

The control disease in the peaches orchards in Brazil is still very dependent of pesticides. The high economic cost of these and the problems caused, like that, bacterial resistance and contamination of the environment is increasing the search of new products which is eco-friend and more efficient. The bacterial spot of peach trees (Prunus persica) caused by Xanthomonas arboricola pv. pruni (Xap) is considered an important disease, that causes economic losses. The symptom is early defoliation which results in plant weakening and consequently its death. Therefore the objective of this study was evaluate the antimicrobial properties of extracellular compounds (fraction F3) of Pseudomonas sp. in the control of bacterial spot caused by Xap. For extraction of extracellular compounds was cultivated Pseudomonas sp. in the nutrient broth plus CuCl₂ (15 days, 28ºC, 150 rpm), after was realized the centrifugation (20 min, 4ºC, 9000 rpm), the supernatant free cells was washed with dichloromethane obtaining dichloromethane phase (DP), the DP was concentrated in rotator evaporator, freezed in a liquid nitrogen and lyophilized, the DP was fractionated by vacuum liquid chromatography (VLC) using three organic solvents with crescent polarity. The fraction F3 obtained from VLC was tested against Xap. After the extraction of extracellular compounds were realized two experiments in greenhouse with peach trees. The first, plants were kept in moist chamber clear with 100 % humidity and 30ºC for 24 hours and spraying cells of Xap (10⁸ mL^-1); suspension in abaxial leaves surface where the largest numbers of stomata; and after 24 hours spraying the suspension fraction F3 in peach trees. The second experiment with other peach trees was first spray the fraction F3 and after 24 hours sprays Xap suspension. For the negative control was used sterile distilled water and for positive control was used a suspension of Xap. The results showed that both experiments were satisfactory to reduce the Xap, then fraction F3 has effective antibiotic activity against Xap and can be used as an alternative in controlling bacterial spot of peach trees.