Isolation and Identification of Fugi Associated with Root Rot Disease in Broad Bean Caused by Rhizoctonia solani (Kuhn) and Select The Disease Repressor Species as Biological Control Agents 1. Induced Resistance Marker by Isolated Fungi and Their Relationship With The Disease

Abstract

Sixteen isolates of various fungal species associated with root rot disease in broad bean Vicia faba were isolated and identified from several regions in Salah Al-din governorate , in addition to 4 isolates of pathogen Rhizoctonia solani, the most severe isolate R.s.4 was selected after application of koch hypothesis on it, for study of induced resistance marker in broad bean by the isolated fungi. These markers include Pathogen Related Proteins (PRP); Peroxidase, β-1,3glucanase, Chitinase, Poly phenol oxidase and Phenyl alanine ammonia lyase. The results showed the activity of all these enzymes increased in broad bean treated with all isolated fungi in present and absence of pathogenic fungus R. solani along with three stages of plant growth, the first was after 2 weeks of seeds germination,second and third were after 2 and 4 weeks from the first stage.The maximum specific activity of peroxidase was 7.86 unit/mg protein which recorded in the third stage of plant growth that treated with Trichoderma harzianum in absence of the pathogen R.solani , while the maximum specific activity was 7.61 unit/mg protein which recorded in plants treated with A.oryzae in present of the pathogen. T.harzianum showed the maximum specific activity of β-1,3glucanase with and without the pathogen resulting in 0.881 and 0.852unit/mg protein,respectively. T.harzianum also showed the maximum specific activity of Chitinase with and without the pathogen resulting in 6.867 and 6.584unit/mg protein,respectively.the higher specific activity of Poly phenol oxidase in present of the pathogen was 1.71 unit/mg protein by plants treated with T.harzianum, in addition to the maximum specific activities of Phenyl alanine ammonia lyase were 0.191 and 0.161 unit/mg protein by plants treated with T. viride in present and absence of pathogenic fungus R. solani respectively.the results also showed that all isolated fungi reduce of infection percentage and disease severity, the significant reduction of infection and disease severity were 13.12% and 0,06 by T. harzianum .the fungi T. viride,T. harzianum,and A. oryzae in present of the pathogen lead to increase in shoot dry weight (resulting in 8.14,8.11 and 8.04g,compared to 3.68g in the pathogen alone) and root dry weight (resulting in 6.71,5.66 and 5.13g,compared to 2.02g in the pathogenR.solani alone).