Xanthomonas manihotis(Arthaud-Berthet) Starr, Causal Agent of Bacterial Wilt, Blight and Leaf Spots of Cassava in Zaire

Abstract

Bacterial wilt of cassava has been causing a severe reduction of tuber yield in the savanna of the southern part of Zaire since 1970. Infection of young shoots often takes place through insect punctures made mainly by Pseudorheraprus devastans Distant. Systemic colonisation of the stem leads to vascular browning, formation of bacterial pockets in the'bark which extrude a yellowwhite exudate and sudden drying of the leaves and necrosis of the stem tips. Angular leaf spots, accompanied by small droplets of exudate on the lower surface of the lesion, rapid blight of large areas of the lamina and defoliation, are endemic in Zaire. Epidemics develop under conditions of heavy rainfall. The cultural appearance, the morphological and biochemical characters as well as the cross-inoculation tests demonstrate that the bacteria causing wilt, leaf spotting and blight are identical. Thev are identified as Xanthomonas manihotis (Arthaud-Berthet) Starr and can be distinguished from a Brazilian isolate of X. manihotis only by a lower amylolytic activity. A critical analyskof the literature suggests a worldwide distribution of the disease. The recent epidemic development of bacterial wilt in Zaire and the control by resistant cultivars are discussed. PANS 21: 27-37,1975.

Characterization of Congolese Strains of <i>Xanthomonas axonopodis</i> pv. <i>manihotis</i> Associated with Cassava Bacterial Blight

“…manihotis strains, suggesting variations in aggressiveness. The variation in aggressiveness of strains was reported in other studies [2] [8]. Grousson et al [29] confirm the existence of such variability in aggressiveness of Xanthomonas axonopodis pv.…”

“…Variation in virulence has also been found among X. axonopodis pv. manihotis strains from Brazil [6] [28], from Africa [2] [29] [30], and from Asia and South America [5]. X. axonopodis pv.…”

“…manihotis is the most important bacterial disease of cassava, a major root crop widely grown in the tropics. Typical symptoms of CBB include watersoaked angular leaf spots, blighting, wilting, defoliation, vascular necrosis of the stem, production of exudates on leaves, petioles or stems, and stem dieback [1] [2].…”

“…Defoliation caused by CBB resulted in starvation during epidemic periods in the 1970s [2] [3]. The upsurge in the disease in Africa has been attributed to the introduction of susceptible cassava varieties from Brazil and Colombia, where the disease was highly virulent and destructive [4].…”

Survival of Xanthomonas Axonopodis Pv. Manihotis in Weed Species and in Cassava Debris : Implication in the Epidemiology of Cassava Bacterial Blight.

“…manihotis (Xam) (Vauterin et al, 1995), is a seedborne pathogen (Persley, 1979;Daniel and Boher, 1981;1985b;Elango and Lozano, 1980). Infected cuttings as planting materials (Maraite and Meyer, 1975;Daniel and Boher,1985b;Bani, 1990;Fanou, 1999) are also dispersion means of the pathogen. In all cassava production areas, weeds are a serious problem reducing cassava yield (65%) and marketable value of cassava roots (Akobundu, 1990).…”