Biological control of Pythium root rot of broccoli plants under greenhouse conditions.

Pythium ultimum, Rhizoctonia solani and Fusarium solani were the most isolated fungi from roots of broccoli (Brassica oleracea L. var. italica ) plants showing root rot disease symptoms collected from different governorates in Egypt . Pathogenicity test proved that Pythium ultimum is the main causal agent of root rot disease on broccoli plants .No significant difference between broccoli varieties (Atlantic F1 and southern star) in their susceptibility to Pythium ultimum infection. Trichoderma harzianum ,T. virdi , Bacillus subtilis and Pseudomans fluorescens isolated from the rhizospheric soil of healthy broccoli plants could completely inhibit the growth of Pythium ultimum on PDA medium in vitro .Under greenhouse trials, A combination of soil mixing plus root dipping method was generally more effective in reducing disease incidence than each method applied individually. Dipping roots of broccoli seedlings in water suspensions of each bio control agent i.e., Trichoderma harzianum , T. virdi (5x10 spore/ml) , Bacillus subtilis and Pseudomans fluorescens (8x10 spore/ml) and mixing soil with the same suspensions of bio control agents during transplanting ,gave the highest effect in reducing Pythium rot disease if compared with applying the two methods individually.The use of bio control agents as soil mixing or root dipping treatments as applicable safe and fungicides alternative might be used for controlling Pythium root rot on many crops especially under organic farming system.