Bacterial Wilt (Ralstonia (Pseudomonas) Solanacearum) Of Potato in South and Central Ethiopia: Distribution, Latency and Pathogen Characterization
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Date
1999-06
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Addis Ababa University
Abstract
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.
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Biology