News: News, Research, WA

Stopping stem rot

The most cost-effective means to control plant pathogens in economically important crops is to develop resistance within the plants.

An understanding of how crops become naturally resistant to Australia’s important fungal and viral pathogens is fundamental to improving the management of crop diseases. However, little is actually known about the processes involved. The Plant Pathology Group at the University of Western Australia (UWA) has been working with the AMMRF at UWA to define key host resistances of Brassicas to important pathogens. Important Brassica crops include canola, mustard, cabbages, cauliflower and broccoli.

Stem cross section of canola showing strong autoflourescence surrounding a lesion and in the endodermis, demonstrating lignin barriers formed against the fungal pathogen Sclerotinia.

In a Linkage Project with the Department of Agriculture and Food Western Australia, A/Prof. Peta Clode used confocal microscopy in the AMMRF (now Microscopy Australia) at UWA to show that the pathogen, Sclerotinia sclerotiorum invades the vascular system of highly susceptible types of Brassica causing rapid rotting of the stems. However, in contrast, resistant Brassicas restrict growth of the fungus by impeding its progress towards stem vascular tissues. They do this by producing more cell layers in the outer part of the stem and rapid lignification of the surrounding tissue. This initiates the rapid death of cells around the infected area.

Lignin is the tough structural molecule of wood and lignification is a common part of the resistance puzzle in Brassicas, protecting vascular tissue from invasion. The resistance mechanisms identified in these studies will be highly valuable for targeted breeding programs to develop new disease-resistant cultivars. They will also enable new, more effective strategies to be developed for managing crop diseases in Australia.

M. Uloth et al., Annals of Botany, doi:10.1093/aob/mcv1502015, 2015