Bacterial Wilt (Ralstonia (Pseudomonas) Solanacearum) Of Potato in South and Central Ethiopia: Distribution, Latency and Pathogen Characterization

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Addis Ababa University


Survey of potato bacterial wilt caused by Rats/ollia sotallacearum was conducted in south and central zones of Ethiopia during 1996/97 cropping seasons and incidence, prevalence, latency and characteristics of strains were detennined. Mean percentage wilt incidence of the disease was found to be relatively high in the irrigated areas of Bako (27.8%) and Ambo (18.2%) and in Shashemene district in both Meher (19.8%) and Belg (22.3%) produced potato crops. The percentage wilt incidence was low at Wondo Genet(7.2%), Jeldu (2.3%) and Inchini (1.3%). Mean percentage wilt prevalence of the disease was also high in Bako (87.5%), Shashemene (Belg, 75%; Meher, 70%), Ambo (70%) and Wondo Genet (62.5 %) and low in Jeldu (17.5%) and Inchini (7.5%). Assessment of preceding crop on bacterial wilt development showed that successive potato . cropping resulted in more disease development than preceded by non-host crop(s) and mean wilt incidences of, respectively, 35.3, and 19.1 % were recorded. Cultural, biochemical, carbohydrate utilization, hypersensitivity reaction and pathogenicity tests indicated that isolates belong to biovar 2 and race 3 of R. sotallacearllm. Relative virulence study showed that isolates from Bako and Ambo are more virulent while virulence of isolates from Jeldu and Inchini are least. Mean percentage latent tuber infection was found to be relatively high in tubers harvested from infested crops at Jeldu (77.7%) and Shashemene (Meher 65.3%) followed by Wondo Genet (52.6%), Shashemene (Belg 53.7%), Ambo (51.2%) and Bako (45.7%), and least in tubers from Inchini (18.6%). In market bought tubers, high percentage infection was also recorded at Jeldu (53.5), Wondo Genet (50.0) and Shashemene (Meher ,48.5) and least was at Inchini (6.0) On investigation of weed host plants as carriers of the pathogen, the pathogen was isolated from a common weed, Galillsoga parviflora. The bacterium was found pathogenic to potato and tomato., but not to G. parviflora. Hence, the weed is a latent carrier of R. soiallacearlllll. Generally, the disease is widespread and is a serious problem to potato production in the major growing areas of south and central zones of Ethiopia.