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

Abstract

In South Africa during the 2006/2007 potato growing season, outbreaks of blackleg occurred, causing severe economic losses in commercial potato production fields. Symptoms were initially observed on only one stem per plant, on which the top leaves rolled upwards, wilted and became necrotic. As symptoms progressed to the lower leaves with subsequent leaf desiccation, a light to dark brown discolouration of the vascular system at the stem base developed, followed by external darkening. Under prevailing wet and humid conditions stems became slimy and pale. In

Cardinal temperature differences, determined in vitro, between closely related species and subspecies of pectinolytic bacteria responsible for blackleg and soft rot on potatoes

“…Comparing the results from this study with survey data from a previous study (van der Merwe et al 2010), there do not appear to be any correlations between cardinal temperatures obtained in this experiment and species prevalence in different climatic regions. This raises the question of why Pcc and Pcb are not equally prevalent in diseased potatoes in SA.…”

“…brasiliense was first reported in SA in 2010 and has been identified as the most prevalent species in South African potato growing regions (Van der Merwe et al 2010, Ngadze et al 2012). The South African Pcb isolates showed no significant differences in their optimal growth temperatures (31°C to 32°C) or temperature ranges (20°C to 39°C).…”

“…Pectobacterium carotovorum subsp. brasiliense prefers humid subtropical conditions, making it extremely virulent at both cool and warm temperatures and unlike Pba, Pcb has the ability to grow at temperatures above 37°C (Duarte et al 2004;van der Merwe et al 2010). On the other hand Dickeya spp.…”

Pectinolytic bacteria associated with potato soft rot and blackleg in South Africa and Zimbabwe

“…brasiliensis (Pcb) was recently described in Brazil and South Africa. The pathogen causes severe soft rotting of tubers and blackleg of the stems (Duarte et al 2004, van der Merwe et al 2010.…”

“…This was the first report of the pathogen affecting potato in both of these countries (van der Merwe et al 2010). As Zimbabwe has been importing potato seed from South Africa for almost a decade, it is of great interest to examine the genetic diversity of Pcb isolates from these two countries.…”