Abstract:
Enset (Ensete ventricosum) bacterial wilt (EBW) incited by Xanthomonas
campestris pv. musacearum (Xcm) is threatening enset production in southwestern
Ethiopia. The objectives of this study were to determine the pathogenicity of Xcm
isolates and select enset clones resistant to pathogenic Xcm isolates in the study areas.
A total of 30 Xcm isolates were subjected to pathogenicity tests on a susceptible enset
clone Yeko and all were found pathogenic. Out of 30 pathogenic isolates, three isolates
representing three altitude groups [lowland (1470 m.a.s.l), midland (1938 m.a.s.l) and
highland (2360 m.a.s.l)] were used for enset clonal evaluation trials. In the clone
evaluation trial, 15 enset clones (13 local and a tolerant and susceptible check) were
evaluated for 2 years (2017 and 2018) under screen house conditions at Tepi National
Spice Research Center, southwestern Ethiopia. The experiments were factorially
arranged in a completely randomized design with three replications. An aliquot of
10 ml of the bacterial cell suspension with a concentration of 1 × 108 cfu/ml was
inoculated into the second innermost leaf petiole of enset using a sterile hypodermic
syringe. Starting from 15 days after inoculation (DAI), data were collected onincubation period (IP), disease incidence (DI), percentage severity index (PSI), days to
complete wilting/death (DD), area under disease progress curve (AUDPC) and disease
progress rate. Analysis of variance for IP, DI, DD and AUDPC revealed significant
differences (P < 0.05) among tested enset clones, while for PSI significant differences
(P < 0.05) existed among the interaction effect of enset clones x bacterial isolates.
Disease incidence recorded ranges from 0% to 90% and IP ranges from 0 to 23 days.
Similarly, the days to complete wilting of susceptible clone reaches up to 63 days, while
the calculated AUDPC values ranged from 0 (Gudiro, Maziya and Nobo) to 3190%-days
(Arkia, Ataro, Yeko, Chikaro and Ogisso). Disease progress rates also ranged from
−0.00165 to 0.04398 units day−1. Clones Gudiro, Maziya and Nobo showed a resistant/
tolerant reaction to EBW, while clones Arkia, Ataro, Yeko, Chikaro and Ogisso were the
most susceptible enset clones. Based on the results, it is recommended that more
clones be evaluated across different agro-ecological areas to select enset clones with
stable resistance against the disease. In addition, clone selection should also be given
due attention to adaptability as well as quantitative and qualitative yield traits to
improve adoption.
