Effect of the Combination Between Bioagents and Benzothiadiazole (BTH) on Management of Uromyces Pisi the Causal of Pea Rust

Abstract

Antagonistic bioagents naturally occurring on pea leaves free from rust infection were isolated and evaluated for their antagonism against Uromyces pisi, the causal of rust. Isolates of both Bacillus spp., i.e. Bacillus chitinosporus, B. megaterium, B. thuringiensis and B. subtilis and Trichoderma spp., i.e. Trichoderma album, T. hamatum, T. harzianum and T. viride were selected, purified and identified The inhibitory effect of these isolates was assessed in vitro on the germination of the urediospores of the causal fungus. The inhibitory effect of Bacillus spp. ranged between 31.9-42.4% and Trichoderma spp. between 34.9-53.5%. In addition, B. thuringiensis recorded the highest inhibition to the urediospores of the causal fungus followed by B. megaterium then B. subtilis and B. chitinosporus. Meanwhile, T. viride gave the highest inhibition followed by T. harzianum then T. hamatum and T. album. The tested antioxidant, i.e. bion (BTH), chitosan and salicylic acid caused significant reduction to the germinated urediospores of U. pisi compared with the control. This reduction was gradually increased by increasing the concentration. In addition, BTH was the most efficient one in this regard. Under greenhouse conditions spraying of pea plants with any of Bacillus spp. and Trichoderma spp., 48 h. before inoculation with U. pisi on the grown plants from seeds soaked or not in 20 mM of BTH significantly reduced the severity of the disease in the range of 4.0 – 5.4, 12.0-15.8%, respectively compared with the control (48.7%). Soaking pea seeds in BTH before sowing was best method than un-soaked seeds in BTH for managing the disease. The fungicide Topas was the superior treatment followed by B. thuringiensis then T. viride in reducing rust severity and increasing the number of the produced green pods and their weight / plant compared with control. All the tested bioagents, BTH and the fungicide Topas resulted in considerable increase to sugars and phenol contents of pea leaves compared with the control., BTH was always more effective more than the tested bioagents and the fungicide Topas in this regard. Total nitrogen, the concentration of the total free amino acids and the percentages of crude protein in the seeds of Master B pea cv. were greatly increased due to spraying the tested bioagents, BTH and the fungicide Topas compared with the control. BTH was the superior treatment in increasing these components followed by the tested bioagents then the fungicide Topas. In addition, B. thuringiensis and T. viride were the best bioagents in increasing of these components.