Bacterial wilt, caused by Xanthomonas vasicola pv. musacearum (Xvm), formerly X. campestris pv. musacearum, is the most threatening and economically important disease of enset (Ensete ventricosum), the multipurpose food security crop orphan to south and southwestern Ethiopia. Xvm has also had a major impact on banana and plantain production in East Africa following its detection in Uganda in 2001 and subsequent spread. Effective control of this disease currently relies on integrated disease management (IDM) strategies including minimization of field pathogen inoculum and deployment of wilt resistant enset landraces. Identifying landraces with stable and durable Xvm resistance will greatly accelerate breeding of varieties that can be included as a component of IDM. In this study, 20 enset landraces previously reported to exhibit lower susceptibility to Xvm were grown in pots under open field conditions and inoculated with an aggressive Xvm inoculum isolated from a disease hotspot area. Longitudinal and survival analyses were applied to each landrace, based on disease units representing a combination of area-under-disease progress stairs, disease index and apparent infection rate. Considerable variation was observed among the 20 landraces; however, none exhibited full immunity to Xvm infection. Three landraces, viz. Hae’la, Mazia and Lemat (HML), showed lowest susceptibility to Xvm as evidenced by lower disease units and higher survival rates. Landraces Kuro, Gezewet, Bededet, and Alagena showed similar levels of Xvm infection as did HML, but with lower survival rates. By contrast, landrace Arkia showed the highest infection level and lowest survival rate, suggesting a high degree of susceptibility to Xvm. This study identifies new material that can be used in future breeding programmes to develop Xvm-resistant enset varieties.
Thirty six accessions of Plectranthus edulis were evaluated to estimate the nature and magnitude of variability and associations among tuber yield and related characteristics. Analysis of variance for each characters indicated highly significant (p<0.01) variation among the accessions for all characters except tuber length. Relatively high phenotypic (43.17, 37.85, and 24.25 %) and genotypic coefficients of variation (42.42, 36.47 and 18.40%) were observed for tuber weight per hill, number of tuber per hill and stem number per hill in the order of magnitudes. High heritability (96.50 and 92.84%) coupled with high genetic advance as percent of mean (86.85 and 72.38%) were recorded for tuber weight per hill and number of tubers per hill respectively. Analysis of phenotypic correlation indicated that tuber yield per hill was significantly and positively associated with number of branches (r =0.366), tuber diameter (r = 0.435), and number of tuber per hill (r =0.567). Path coefficient analysis at genotypic level also revealed that number of tubers per hill (p=0.982) exerted a high magnitude of positive direct effect on tuber weight per hill. Nevertheless, the need for confirmation of genotypic-environment interaction and widening of the genetic base for P. edulis improvements are suggested.
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