Isolation and Pathogenic diversity among Fusarium oxysporium f.sp. capsici isolates in southern Ethiopia and evaluation of Biocontrol agents against the pathogenic isolates

Abstract

Fusarium wilt is one of the major biotic factors affecting hot pepper production in Ethiopia. Therefore, this study was designed with the objectives to analyze the pathogenic diversity of Fusarium oxysporium f.sp. capsici isolates and to evaluate the biocontrol potential of some antagonists for the management of the disease. For this purpose, twenty nine isolates of Fusarium oxysporium f.sp. capsici were identified from visibly diseased plant samples collected from the 80 surveyed fields based on macroscopic and microscopic characteristics. Pathogenicity test was analyzed within 29 Fusarium oxysporium f.sp. capsici isolates and based on diseases severity index value, isolates were classified as highly pathogenic, moderately pathogenic, and weak. Isolate LWS7 was found to be as the most pathogenic isolate that induced disease and used as a master isolate for the studies involving biocontrol agents. The difference in virulence may be due to differences in genes responsible for pathogenicity and virulence and/or genetic makeup of host plants that could differentiate pathogenic isolates from non-pathogenic isolates. The in vitro and in vivo efficacy of six Trichoderma spp. and Bacillus subtilis was investigated under dual culture assays and in a greenhouse, respectively. The highest (81.8%) and lowest (48%) mycelial growth inhibition were estimated from Trichoderma harzianum and Trichoderma hamatum, respectively. Lower wilt incidence (31%) was recorded on pepper plants following seedling root dip inoculation by Trichoderma viride. In addition to their significant effect on mycelia growth in-vitro, the bioagents evaluated in the current experiment also found to result in significant reduction of the disease and promotion of the growth of hot pepper in soil application and seedling root dip tests. This indicates bioagents are an important development direction for their role in the sustainable development of agriculture. The efficacy and economic feasibility of hot pepper management through biocontrol agents may need additional investigation to come up with conclusive results.