Pectobacterium carotovorum subsp. brasiliensis causing blackleg on potatoes in South Africa

摘要: In South Africa during the 2006/2007 potato growing season, outbreaks of blackleg occurred, causing severe economic losses in commercial production fields. Symptoms were initially observed on only one stem per plant, which top leaves rolled upwards, wilted and became necrotic. As symptoms progressed to lower with subsequent leaf desiccation, a light dark brown discolouration vascular system at base developed, followed by external darkening. Under prevailing wet humid conditions stems slimy pale. stems, pith necrotic hollow. These similar those described Brazil, where causal agent was identified as new subspecies, Pectobacterium carotovorum subsp. brasiliensis (Pbcb). Isolations from plants showing typical made CVP medium. Sequences phylogenetic analysis partial 16S–23S rDNA intergenic spacer region indicated that isolates Pbcb. Comparison PCR-RFLP patterns reference cultures confirmed identity African strains Pbcb, identical strain 8 isolated Brazil. This is first report Pbcb it appears be most important Africa. The disease poses major potential threat industry especially terms seed exports, tuber quality yield.