Systemicity of X anthomonas campestris pv. musacearum and time to disease expression after inflorescence infection in E ast A frican highland and P isang A wak bananas in U ganda

Banana xanthomonas wilt ( XW ) caused by X anthomonas campestris pv. musacearum ( X cm) attacks all banana cultivars. Xcm in inflorescence‐infected P isang A wak plants with wilting male bud bracts is restricted to the upper parts of the true stem; therefore, cutting these plants at the pseudostem base has been recommended to prevent further X cm spread. In order to fine‐tune existing control strategies, this study examined the movement of X cm into plants and mats, in relation to disease incubation period. M ature P isang A wak and E ast A frican highland ( AAA ‐ EA ) plants were inoculated with X cm through abscission wounds of female bracts, male bud bracts, male flowers, a combination of male bud bracts and flowers, and by cutting male buds with a contaminated machete. Thirty plants per genotype and treatment were monitored for 24 months for disease symptoms. An additional 68 AAA ‐ EA and 33 P isang A wak plants were sampled weekly to assess the rate of X cm spread within the plants. All floral entry points resulted in disease, with the highest incidence in combined male bract and male flower abscission wound inoculations. The study confirmed the systemicity of X cm, with the pathogen able to live within the mat for long periods (5–16 months) without causing disease. Reliance on disease symptom expression to manage XW is therefore not sufficient. The long incubation period in lateral shoots may explain the current resurgence of the disease in locations where the disease was thought to have been successfully eradicated.