What are a blackleg disease and its reasons?
This hemibiotrophic fungal pathogen is the causal agent of blackleg disease in B. napus (canola, oilseed rape), which causes a significant global yield loss. B. napus are the second-highest produced oilseed crop worldwide and is under constant threat of the blackleg disease. This underscores the economic effects of L. maculans.
According to Hiruma, IGSLs is required for resistance against hemibiotrophic fungi. However, their role in the B. napus – L. maculans pathosystem was unclear at the time. Considering that IGSLs promote the production of callose that likely prevents L. maculans colonization and reproduction in apoplastic spaces within cotyledons thereby conferring resistance on B. napus. This agrees with Aist and Bushnell, who proposed that callose deposition is a conserved defense response in plants that is controlled by GSL metabolism through acting as a physical barrier in the cell wall. Data from Becker also showed activation of the complete IGSL biosynthetic pathway in resistant B. napus cotyledons inoculated with L. maculans. This confirms the previous study by Clay et al. who stated that in resistant hosts, every gene of the IGSL biosynthetic pathway was upregulated following L. maculans infection, whereas in the susceptible genotype, several genes required for IGSL production were downregulated during infection. Future investigation may be directed at exposing specific interactions within the callose of major brassica that act under stress conditions from L. maculans to promote defense.