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Evaluation of Taro Genotypes against the Most Virulent Isolate of Phytophthora colocasiae in Wolaita and Kembata Tembaro Zones of Southern Ethiopia

Zerhun Tomas*, Elfinesh Shikur, Alemar Said

Taro leaf blight disease, caused by Phytophthora colocasiae is a major limiting factor in Taro production worldwide. Knowledge of resistance of Taro genotypes against the pathogen is very important for effective management of Taro leaf blight disease. Taro leaf blight disease was surveyed in 27 Taro growing farmers’ fields of Wolaita and Kembata Tembaro Zones of Southern Ethiopia during 2017. A total of 15 representative Phytophthora colocasiae isolates were isolated at Areka Pathology Laboratory. This isolates virulence test was carried out by using detached leaf disc method. From the 15 P. colocasiae, isolate A, collected from Sodo Zuria produced extensive necrotic lesions on the leaf and the pathogen was found to be most virulent when compared with the other fourteen isolates. Then after most aggressive P. colocasiae isolate (A) identified by virulent test was adjusted at the concentration of 3 × 10⁴ sporangia/ml and inoculated at green house on five Taro cultivars. Finally three days after inoculation mean lesion diameter was measured at 24 hr interval for six consecutive days. The result of the study indicated that more or less all the cultivars tested were infected by the pathogen and none of them were found to be immune to P. colocasiae. Bolloso-I was resistant with MLD of 22 mm, whereas two cultivars, Yeda (MLD of 35 mm) and Dolka (MLD of 30 mm) showed moderately resistant (MR) reaction. Cultivars Molia (MLD of 50 mm) and Yiteria (MLD of 65 mm) showed susceptible and highly susceptible reactions, respectively. The result of the present study demonstrates the role host resistance may play in integrated management of the disease. Future research should be directed towards evaluating additional taro genotypes against P. colocasiae.