Presence of banana xanthomonas wilt (Xanthomonas campestris pv. musacearum) in the Democratic Republic of Congo (DRC)

In May 2004, following reports from local farmers of a devastating new banana disease, the first three authors visited Masisi District, 72 km north-west from Goma in North Kivu Province (altitude 1700 m above sea level) and diagnosed banana bacterial wilt caused by Xanthomonas campestris pv. musacearum (Xcm).]

Symptoms were similar to those in Uganda (Tushemereirwe et al., 2003) and included: progressive yellowing, wilting and blackening of leaves (Fig. 1); yellow or brown vascular streaks throughout the plant; pockets of pale yellow bacterial ooze in airspaces within leaf bases (Fig. 2); premature ripening and internal discoloration of fruits; and shrivelling of male inflorescence buds (Fig. 3). Inflorescence symptoms probably result from transmission of bacteria by insects and were uncommon. This may explain the limited spread in DRC of only about 10km from the original focus at Bashali Mokoto village since 2001, compared with more than 400km in Uganda over the same time period (see www.banana.go.ug). As in Uganda, ABB banana genotypes (especially Pisang Awak) seem to be the first, and matooke clones (Musa AAA-EA group) the last, to be infected. Affected stools do not always die; new suckers emerge and these initially appear healthy but usually become infected from the mother plant, rarely surviving to flowering stage. The epicentre of the outbreak in Masisi was devastated (Fig. 4), with total loss of yield and an alarming impact on food security.

Using methods described by Tushemereirwe et al. (2004), yellow pigmented bacteria were isolated as almost pure cultures from samples of diseased inflorescence stalks sent to the Global Plant Clinic at CABI Bioscience. Biochemical and molecular characteristics of two isolates were indistinguishable from Xcm from Uganda. Both caused rapid wilting within 7-10 days of inoculation into young banana plants from which the same organism was reisolated.

It may be feasible to eradicate this outbreak by destroying affected plants and cleaning up affected fields, combined with removing male flower buds in surrounding healthy plants to prevent insect transmission. However, the first author has recently observed a new disease focus about 20km from the first one, so continued vigilance and control action will be needed. The origin of these outbreaks is unknown. Until 2001, Xcm was known only from Ethiopia, where it causes disease in enset (Ensete ventricosum) and cultivated banana (Yirgou & Bradbury, 1968, 1974). It is possible that the disease has spread from wild or semi-cultivated enset plants, which can be found throughout the Masisi region.