Isolation, Characterization of Fungal Pathogens of Yam from Seka Chokersa Woreda, Jimma Zone and Its Controls Using Trichoderma Spp and Fungicides

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Addis Ababa Universty


In the present study, five different fungal isolates (AUF1, AUA1, AUA2, AUV1 and AUV2) were isolated from infected yam leaves and tubers grown in Seka Chokersa woreda, Jimma Zone, Ethiopia based on cultural and morphological. The ranges of conidia (length by width) of AUF1, AUA1, AUA2, AUV1 and AUV2 were 19.00-26.20×3.20-5.80 μm, 30.50-40.47×10.90-17.37 μm, 27.30-42.50×11.60-16.90 μm, 3.50-11.20×1.80-3.80 μm and 2.50-9.00×1.25-3.20 μm, respectively. The pathogenicity test showed that the most virulent isolates were AUF1, AUA1 and AUV1 with 100% tissues infection. Growth characteristics of the isolates showed that isolate AUF1 and AUV1were best grown on PDA medium with mycelial diameter of 90 mm followed by AUA1, AUV2 and AUA2, respectively. Similarly, the isolates grew best at 25oC, with the exception of AUA1 that displayed maximum growth at 30 oC. From the pH levels studied, maximum dry mycelial weight was attained from AUV2 (697.6±1.6 mg), AUA1 (693.9±3.3 mg) and AUF1 (624.5±4.0 mg), at pH 6.0; whereas, dry mycelial weight of 693.4±4.9 mg and 356.4±1.1 mg at pH 5.0 and 7.0 measured from AUV1 and AUA2, respectively. Dextrose was the most utilized carbon source by AUF1 and AUV1; while maltose was the best carbon source for AUA1, AUA2 and AUV2. Potassium nitrate was the best nitrogen source for all fungal isolates with the exception of AUA2 that utilized ammonium nitrate best. In vitro evaluation of dual culture test with Trichoderma spp against the fungal pathogens revealed that both of them showed effective with 66.75 to 82.59% of mycelial growth inhibition. Similarly, curzate (43.93% WP) and sancozeb (80% WP) were effective at high concentrations of (400-1000 ppm), where sancozeb was more effective than curzate in terms of percent growth inhibition. From the study of combined treatment of the pathogens with fungicides and Trichoderma isolates, the highest percent of inhibition of mycelial growth of 85.6%, 79.7%, 87.5%, 89.3% and 80.2% were detected when AUT2 was combined with sancozeb against AUF1, AUA1, AUA2, AUV1 and AUV2, respectively. So, combination of Trichoderma spp (AUT1 and AUT2) with chemical fungicides (curzate and sancozeb) at lower concentration offers a promising control of fungal pathogens. Key words: Biocontrol agents, Dioscorea spp, Fungal isolates, In vitro



Biocontrol agents, Dioscorea spp, Fungal isolates, In vitro