Efficiency of Using Some Biological Organisms as Biological Catalysts to Reduce the Incidence of Cantaloupe Downy Mildew Disease Under Greenhouse Conditions

Abstract

Infection of cantaloupe plant with Downy mildew caused by the fungus <i>Pseudoperonospora cubensis</i> leads to significant losses in the amount of the crop, in addition to, reducing its marketing value in many countries around the world, therefore, the efficacy of each of the organisms (<i>Trichoderma harzianum</i>, <i>Trichoderma viride</i>, <i>Bacillus subtilis</i>, <i>Bacillus megaterium</i> and <i>Pseudomonas fluorescens</i>), and the fungicide Ridomil gold plus 71.5 WP for the control of cantaloupe downy mildew under laboratory and greenhouse conditions was studied, initially, under laboratory conditions, the results obtained showed that, when using bio filters, in addition to, the recommended concentration of the fungicide to inhibit the germination of <i>P. cubensis</i> sporangia, a significant reduction in the germination rate of the pathogenic fungus sporangia was observed, also, under greenhouse conditions, treatment of cantaloupe with the tested organisms and with the fungicide significantly reduced the severity of downy mildew, compared to the control treatment, where, the best of these treatments in reducing the severity of the disease was the use of the fungicide, while, the organisms were arranged according to their efficiency in reducing the severity of the disease in the following descending order: <i>B. subtilis</i>, <i>Ba. megaterium</i>, <i>P. fluorescens</i>, <i>T. viride</i> and <i>T. harzianum</i>, In addition, cantaloupe plants showed a significant increase in plant growth parameters, for example, (number of leaves, leaf area and total chlorophyll content), also, an increase in yield components, For example, (number of fruits/plant and fruit weight /plant), the above treatments also increased the activity of defense-related enzymes, for example, peroxidase and polyphenol oxidase enzymes, as well as, total phenol content compared to the control treatment.