Management of Faba Bean Rust by Some Antagonistic Bioagents and Induced Resistance Chemicals

Eight bacterial and fungal isolates as well as four induced resistance chemicals (IRCs) were assessed in vitro and in vivo against Uromyces viciae –fabae (Pers.) Schroet, the causal of faba bean rust. The inhibitory effect of Bacillus spp. was ranged between 35.2-50.4%, Trichoderma spp. between 39.0-59.0%. and IRCs between 34.3- 57.7%. In addition, the highest inhibitory effect on the germinated urediospores of the causal fungus was obtained by B. subtilis, T. viride and bion (BTH). Under greenhouse conditions, spraying faba bean plants with any of the tested bioagents significantly reduced disease severity and increased the produced pod yield compared with the control treatment. Also, spraying plants grown from soaked seeds for 12 hrs before sowing in any of the IRCs or soaking in water only with any of these inducers significantly reduced disease severity and increased the produced pod yield compared with the control treatment. Field experiments during two successive seasons under the natural infection by faba bean rust at Behera governorate revealed that spraying B. subtilis and T. viride, each alone or in combination, on plants grown from soaked seeds in BTH at beginning of the incidence of the disease significantly reduced disease severity and increased the produced seed yield compared with the control. On the other hand, plants sprayed with the mixture of both bioagents were of the lowest infection and produced the highest dry seeds/plot compared with the other treatments and the control. However, the fungicide Topas was the superior treatment for lowering disease severity and increasing the produced seeds yield. Considerable increase in the activity of three oxidative- reductive enzymes, i.e phenyl alanine ammonia lyase (PAL), peroxidase (PO) and polyphenoloxidase (PPO) in the leaves of all treatments compared with both control treatments. Furthermore, plants grown from seeds soaked in BTH showed the highest activity of the three enzymes followed by those sprayed with B.subtilis then with T.viride.