DisplayTitle

Fusarium Wilt Disease Caused by Fusarium oxysporum f. sp. phaseoli on a Common Bean Cultivar, G 2333, in Rwanda and the Democratic Republic of Congo

The common bean (Phaseolus vulgaris L.) is an important source of dietary protein for poor resource families in Rwanda and the Kivu region of the Democratic Republic of Congo (DRC). During the second season of 1990, symptoms consisting of chlorosis, premature defoliation, stunting, wilting, and vascular discoloration were observed for the first time on an improved popular climbing bean cultivar, G 2333, in the prefectures of Butare and Gikongoro, in southwest Rwanda. Between 1991 and 1994, surveys to determine disease occurrence were conducted in the two prefectures and in Kigali North, Gitarama, Cyangugu, and Kibuye in Rwanda, and in the south Kivu region of the DRC. Aseptic isolation from diseased plant samples yielded the fungus Fusarium oxysporum f. sp. phaseoli. Pathogenicity tests on G 2333 seedlings by the root-dip inoculation method resulted in symptoms similar to those observed in the field, and recovery of the fungus, fulfilling Koch's postulate. Control seedlings gave no symptoms. Disease incidence was 44 and 53% in Butare and Gikongoro, respectively, during the first season of 1991 and 50 and 70% in the second season, while crop loss in some fields was as high as 100%. Between 1992 and 1994 the disease was also observed in the four other prefectures in Rwanda, and in south Kivu. Climbing bean cultivars Gisenyi-2-bis, G 865, Flora de Mayo, and Puebla 444 Criollo, and several bush local varietal mixtures grown where the disease occurred, were unaffected. CIAT bean Fusarium wilt differentials IPA 1, RIZ 30, A 211, Mortiño, Diacol Calima, BAT 477, HF 465-63-1, and Ecuador 650, and lines A 300 and XAN 112, were inoculated with three isolates (FOP-RW1, FOP-RW2, FOP-RW3) from Rwanda. Only IPA 1, RIZ 30, and A 211 were susceptible, indicating the isolates' likeness to the Brazilian race (1). This was the first report of Fusarium wilt disease on G 2333 in the two countries despite the cultivar having been grown for about 5 years.

Reference: (1) R. L. D. Ribeiro and D. J. Hagedorn. Phytopathology 69:272, 1979.