Biological control of Fusarium nelsonii causing Root Rot disease of pear using the bacteria Pseudomonas fluorescens and Azotobacter chroococcum

Abstract

The presence isolation results resets of isolation from roots of pear trees and diagnosing indicated of the fungi Fusarium nelsonii from 10 orchard in the province of Babylon. This was considered as the first records of the Fungi F.nelsonii on pear trees in Iraq .The preliminary tests of pathogenicity for isolates were pathogenic showed as maintested by percentage of seed germination 2%-30%. Lathhouse conditions Pathogenicity test of 8 isloates of F.nelsonii (F.n8, F.n1, F.n4, F.n3, F.n7, F.n6, F.n5 and F.n2) . Using 90 days old pear seedling as host plant showed that all isolated significant increased increment in disease severity which ranged between 40% t0 86% . Under lathhouse conditions pathogenicity test of three isolates of F.nelsonii (F.n2 , F.n5 and F.n6) using one year old pear seedling showed that all isolated increased significantly in disease severity which ranged between 80% , 78.5% and 75% compared to control non-contaminated though the disease severity was zero% . Under the lathhouse condition the result of test for the effect of two biocontrol agent Azotobacter chroococcum 5×108 and Pseudomonas fluorescens 5×107 colonies forming unit/ml using pear seedling 90 days and one year old and presence of isolate pathogen (F.n2,F.n5) showed that all treatment caused significant reduction in percentage of infection severity on 90 days and one year old pear seedling . As it ranged 15%, 14%, 22.5% , 20% and 16%,18% , 18% , 20% respectively compared to the control treatment pathogen(fungus alone ) which ranged in severity of disease86.5%, 80.75%, 82% and 75.25% . All elements caused significant increased in the criteria such as pear seedling height and fresh and dry weights of shoots and roots