Hanieh Abedinpour - Sari Agriculture Science and Natural Resource University (SANRU), Sari, Iran.Genetics and Agricultural Biotechnology Institute of Tabarestan (GABIT), Sari, Iran.
Nadali Babaeain Jeloudar - Sari Agriculture Science and Natural Resource University (SANRU), Sari, Iran
Ali Dehestani - Genetics and Agricultural Biotechnology Institute of Tabarestan (GABIT), Sari, Iran.
Ghorbanali Nematzadeh - Sari Agriculture Science and Natural Resource University (SANRU), Sari, Iran.Genetics and Agricultural Biotechnology Institute of Tabarestan (GABIT), Sari, Iran.

Cucumber is an important crop of economic importance and its performance is affected by biotic and abiotic stresses. Cucumber Downey mildew, caused by Pseudoperonospora cubensis, is an important disease that can remarkably reduce its production. Pathogenesis-related proteins (PRs) are a major factor during the period of plant-pathogen interaction, and any group of PR proteins may be part of the first line of defense against the pathogen. β-۱,۳- glucanase is a pathogenesis-related protein that degrades β-۱,۳- -glucan, a main structural component of the fungal cell wall, and prevents pathogen growth. For this purpose, β-۱,۳- glucanase enzyme has been measured in cucumber plants treated with ۱ mM salicylic acid (SA) and ۱ mM azelaic acid (Aza) at ۶, ۱۲, ۲۴ and ۷۲ hours after inoculation with Downy mildew. Results indicated that β-۱,۳- glucanase content was decreased in SA and Aza-treated plants compared with control . However, the highest amount of enzyme was observed at ۱۲ h post-inoculation with the pathogen. The enzyme content was increased in SA-treated plants at ۶h post-inoculation with pathogen and there was no significant difference with the untreated control at ۲۴ and ۷۲ h post-inoculation. Enzyme content was recorded higher in plants treated with Aza at ۶ and ۲۴ hours post inoculation with the pathogen than in the control. These results suggest that an increase in the glucanase activity as one of the pathogenesis-related proteins may have significantly contributed to the resistance of cucumber plants against downy mildew.

Pathogen, Salicylic acid, Azelaic acid, Pathogenesis-related (PR) proteins