Jornal de Patologia Vegetal e Microbiologia

Abstrato

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

Ararsa Leta and Thangavel Selvaraj

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