Evaluation of Arbuscular Mycorrhizal Fungi and Trichoderma Species for the Control of Onion White Rot (Sclerotium cepivorum Berk)

Abstract

The present study was carried out to evaluate the indigenous Arbuscular Mycorrhizal Fungi (AMF) and\rTrichoderma species isolated from rhizosphere soils of onion cultivated fields at Ambo and Toke Kutaye districts\rof West Showa, Ethiopia, and their effect on plant growth, and their biocontrol against onion white rot caused by\rSclerotium cepivorum Berk. Five species with twenty isolates of Trichoderma were isolated and screened in vitro\rfor the inhibition of S. cepivorum. Out of these, four isolates of Trichoderma spp viz. T. harzianum (ATh1), T. viride\r(ATv1), T. hamatum (NThm3), and T. koningii (QTk2), were found potent antagonists with mean percent inhibition\rof the pathogen, 65.4, 64.8, 54.3 and 53.5, respectively. Altogether, 10 AMF species representing four genera viz.\rAcaulospora, Gigaspora, Glomus, and Scutellospora, were isolated and identified. Six dominant species of AMF were\rselected and mass multiplied by using Sorghum vulgare Pers. as the compatible host plant. Among six AMF species,\rthe potential efficient strain, Glomus aggregatum (Awaro isolate), was selected for using as bio control agent. The\rbio-control potential of these bio-agents against white rot pathogen was carried out under pot culture condition,\rusing G. aggregatum alone or in combination with four isolates of Trichoderma spp. Incidence of S. cepivorum was\rsignificantly reduced in bulbs of onion (66.19%), and also improved plant growth was observed in plants inoculated\rwith combined inoculation of G. aggregatun and T. harzianum (ATh1 isolate), followed by the combined inoculation\rof G. aggregatum and T. viride (ATv1) with pathogen (59.75%). Plants inoculated with S. cepivorum alone showed\rpronounced disease symptoms with mean disease incidence of 90.5%. The overall reduction in the incidence of\rwhite rot was 56.22% in the treatment of T. harzianum ATh1 isolate with pathogen, followed by 53.72% for G.\raggregatum with pathogen. These results clearly pointed out that G. aggregatum and T. harzianum ATh1 isolate can\rblock the severity of disease caused by S. cepivorum in onion. Use of these bio-control agents could be promoted\ras an active component of bio-intensive Integrated Disease Management Program (IDMP), under organic mode.