CONTROL OF BACTERIAL BLIGHT (XANTHOMONAS AXONOPODIS PV. PHASEOLI) AND BIOCHEMICAL ANALYSES OF BEAN RESISTANCE TREATED WITH PYCNOPORUS SANGUINEUS EXTRACTS

ABSTRACT

The aim of this work was to verify the antimicrobial and resistance induction activities of Pycnoporus sanguineus extracts for the control of common bacterial blight caused by Xanthomonas axonopodis pv. phaseoli. In vitro assays were performed using aqueous extracts from basidiocarp, mycelium and culture filtrate of P. sanguineus in concentrations of 1, 5, 10, 15 and 20%, with water, acibenzolar-S-methyl (ASM - 125 mg a.i. L^-1) and antibiotic (oxytetracycline 22.5 mg L^-1 + streptomycin 225 mg L^-1) as control treatments. For the in vivo assays the disease severity and the activities of peroxidase, polyphenol oxidase, β-1,3 glucanase and phenylalanine ammonia-lyase were evaluated using extracts of mycelium, basidiocarp and culture filtrate of P. sanguineus at 5% and 10%. Antibacterial activity was verified only for culture filtrate in concentrations above 15% and for concentrations of 1% to 20% of basidiocarp extract. The results of the in vivo assays indicated the potential of basidiocarps extracts from P. sanguineus for the control of X. axonopodis pv. phaseoli in beans, with an average severity reduction of 56%, which may have been due either to direct antimicrobial activity or to resistance induction involving mainly the activation of the plant defense enzymes peroxidase and polyphenol oxidase.

KEY WORDS
Alternative control; resistance induction; pathogenesis related proteins; antimicrobial activity