Bacillus pumilus, a new pathogen on potato tubers in storage in Mali

Abstract

Soft rot occurred severely in potato tubers stored in traditional and ameliored storehouses at Sikasso, Mali. 17 infective bacterial isolates were isolated from potato rot tissues (Solanum tuberosum L var. Odessa). Out of all, the isolate Od23 was found pathogenic and was characterized as rod-shaped, Gram positive, endo-spore formers and yellow pigment producers. This isolate which was found to be the principal organism responsible for potato rot in storage in Sikasso, grew at a temperature range from 5 to 45°C, with optimum temperature of 30 - 35°C. However, it showed strong pathogenicity to potato tubers at 30°C at 3 days. Furthermore, the 16S DNA analysis confirmed that the obtained isolate was Bacillus pumilus. All Potato varieties cultivated in Mali responded to infection with B. pumilus. Potato var. Sahel was the most susceptible, while Pamina appeared the most resistant potato variety from Mali. According to literature review, this is the first report on the occurrence of B. pumilus as a causal agent of potato soft rot in storage in the region of Sikasso, Mali. Key words: Potato, storage, Bacillus pumilus, soft rot, Mali.