Induction of defence responses in zucchini (Cucurbita pepo) by Anabaena sp. water extract

•BEA0300B (Anabaena sp.) water extract reduced P. xanthii symptoms on zucchini.•The extract induced systemic defence responses on plants.•Chitinases, β-1,3-glucanase and peroxidases accumulated in leaves after treatment.•Constitutive acidic isoenzymes were increased upon treatment.•The extract showed a direct antifungal activity reducing pathogen sporulation.

The induction of systemic defence responses in zucchini leaves treated by a water extract of Anabaena sp. BEA0300B strain was studied firstly through a bioassay under Podosphaera xanthii (Castagne) U. Braun and Shishkoff challenge. In a second experiment, enzyme activities correlated to induced systemic resistance were assayed 1, 2 and 3 days after treatment (DAT) with BEA0300B on untreated cotyledonar leaves. Endochitinase, β-N-acetylhexosaminidase, chitin 1,4-β-chitobiosidase, β-1,3-glucanase and peroxidases were spectrophotometrically determined. Enzyme isoforms were detected after isoelectric focusing. The extract reduced P. xanthii symptoms by 25%, similarly to chitosan, the positive control. BEA0300B treatment caused systemic accumulation of all the enzymes. In particular, the treatment provoked an early increase of total chitinase activity (15–38%) and of the expression of two constitutive chitinase isoforms, pI 4.4 (159%) and pI 4.6 (433%). The total β-1,3-glucanase and peroxidase activities were transiently increased. The expression of two constitutive isoforms of these enzyme increased, particularly pI 5.0 glucanase (148%, 1 DAT) and pI 4.9 peroxidase (181%, 2 DAT). BEA0300B water extract also showed a direct antifungal activity on pathogen sporulation.

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