Evaluation of disease incidence and severity and yield loss of finger millet varieties and mycelial growth inhibition of <i>Pyricularia grisea</i> isolates using biological antagonists and fungicides in vitro condition.

Abstract

Objective: The aim of this study was to conduct a survey on the disease incidence and severity at 5 agroecological zones of Ethiopia. Moreover, the study was also designed to carry out pathogenicity test, estimate yield losses caused by test pathogen and in vitro evaluation of fungicides and biocontrol agents against finger millet blast isolates. 
Methodology and Results: The incidence of finger millet blast was assessed as the percentage of plants with visible symptoms in a field and greenhouse. Blast severity was also evaluated as the percentage of leaf area with symptoms. From the surveyed areas, maximum disease incidence and severity were recorded in west Wollega zone with 63.03 and 34.60%, and lowest disease incidence and severity was recorded in Awi zone with 46.7 and 15.7%, respectively. A total of 42 isolates of P. grisea were collected and isolated from infected finger millet plants and wild relatives from five agro-ecological zones of Ethiopia. The pathogenicity test conducted in greenhouse on three finger millet varieties also indicated that among P. grisea isolates, Pg.11, Pg.41 and Pg.40 showed the highest disease incidence on all the three varieties with 74.8, 69.5 and 66.5%, respectively. Moreover, the highest disease severity with 27.7 and 27.8% were observed by isolates Pg.11 and Pg.41, respectively. In vitro evaluation and testing of Trichoderma viride have showed maximum mycelial growth inhibition with 77.1% and 74.1% by isolates Pg.41 and Pg.22, respectively; while Pseudomonas fluorescens showed maximum mycelial growth inhibition by isolates Pg.40 (57.2%), followed by Pg.26 (56.1%). The efficacy tests of four fungicides evaluated for their antifungal activity showed Sancozeb (85.50- 88.40%) as the most effective fungicide to inhibit mycelial growth of P. grisea.
Conclusion and application of findings: The highest percent of mycelial growth inhibition of P. grisea isolates was observed by T.harzianum and T. viride and followed by Pseudomonas fluorescens. Sancozeb was the most effective fungicide and also showed the highest mycelial growth inhibition on the isolate of P. grisea and followed by ridomil, bayleton, and curzate. From in vitro evaluation of the effectiveness of biological agents and fungicides against the mycelia growth of P.grisea isolates, fungicides were most effective for the control of blast disease of finger millet than biological agents.

Keywords: Biocontrol, Blast disease, Eleusine coracana, Fungicide, Pyricularia grisea.