Page 98 - University of Pretoria RESEARCH REVIEW 2016

PLANT PRODUCTION and food security
IDENTIFYING DEFENCE MECHANISMS
Professor Lucy Moleleki, in the Department of Microbiology and Plant Pathology, is the leader of the bacterial genomics and host pathogen group in FABI. One of the research group’s aims is to understand the threat posed by root knot nematodes (RKN) in the potato industry. Their focus is on Pectobaterium carotovorum subsp. brasiliense (Pcb), identified as the most important potato pathogen in South Africa and East Africa. Much of the current research focuses on the virulence mechanisms that Pcb uses to infect potato stems and tubers, as well as on defence responses in the host plant potato.
The research team has screened different potato cultivars against Pcb infection. While most commercially available cultivars tested were highly susceptible to Pcb, one of the cultivars appeared
to be highly tolerant to Pcb. A time-course ‘RNA- seq’ study has revealed key differences in the transcriptomes of the susceptible and tolerant cultivars – in simple terms, the ‘transcripts’ that influence cell structure and regulate genes. These results offer a new route to the development of new and highly-resistant commercial potato cultivars.
STAPLE FOOD CROPS AND PATHOGENS
The potato ranks fourth, after rice, wheat and maize, as the most important human food crop worldwide. However, cultivated potatoes, like many other plants, are exposed to diverse abiotic and biotic stresses.
Since the first description of the devastating Pectobacterium carotovorum subsp. brasiliense (Pcb) infection of potatoes in South Africa in 2010, Professor Jacquie van der Waals and her research team (the Potato Pathology Programme @ UP) have demonstrated that Pcb is the causal agent of soft rot, blackleg and aerial stem rot on potatoes, and can cause substantial yield losses. There is no chemical control available to manage this disease complex.
Van der Waals’ research has focused primarily on gaining a better understanding of the epidemiology of the disease, as well as investigating disease management options to reduce yield losses in
the potato industry. She collaborates with many researchers at universities in South Africa and at the
Agricultural Research Council, and with researchers in Scotland, The Netherlands, Israel, Poland and Zimbabwe. The Potato Pathology Programme @ UP also houses a diagnostic clinic for plant diseases, specifically potato diseases.
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