Host range and banana cultivars’ susceptibility to Xanthomonas campestris pv. musacearum in Rwanda

Abstract

Xanthomonas campestris pv. musacearum (Xcm), a bacterium causing banana xanthomonas wilt (BXW) disease, is widely spread in the East and Central Africa and infects all cultivated bananas. The first objective of this study was to identify plant species produced in banana cropping systems of Rwanda that may act as host of Xcm, and to evaluate the susceptibility of different banana cultivars in Rwanda. Eighteen plant species including banana, banana-intercrop species and plant species closely related to banana were used to study the host range of Xcm. Similarly, five banana cultivars (Fhia-17, Fhia-25, Injagi, Mpologoma and Nkazikamwa) were used to assess their susceptibility level to Xcm. Tested plant species and banana cultivars were inoculated with Xcm isolate in a controlled environment. Only banana and its relatives (enset, blood banana, achira, African arrowroot, and Indian shot) developed xanthomonas wilt symptoms. Time to first symptoms expression and to complete wilting varied significantly (P < 0.0001) between susceptible plant species. Longer survival times (P < 0.0001) were observed in wild (blood) banana, Canna species and enset compared to cultivated banana. Since these susceptible plant species could host the bacteria, they should be avoided in farms or gardens neighbouring banana fields. All the five banana cultivars tested were susceptible to Xcm. Among the cultivars, Mpologoma was first to express disease symptoms and to wilt completely; while the longest incubation period and time to complete wilting were recorded in cultivar Fhia-17. Due to the broad host range and high susceptibility of banana cultivars to Xcm, information about how to limit the spread of the bacteria is crucial for disease control.

Key words: Disease progress, Musa spp., Xanthomonas wilt