What effect pathogens have on plants?
Pathogens have significant effects on plant fitness and may regulate plant population and in turn lead to considerable economic damage. After successful penetration, pathogens may directly benefit from the active metabolism of their host to complete their life cycle by either keeping the host cells alive during colonization (biotrophic strategy) or induce host cell disintegration after infection (necrotrophic strategy). Some pathogenic fungus utilizes hemibiotrophic strategy whereby they undergo a biotrophic phase and later switch to a necrotrophic phase. Williamson posited that necrotrophic pathogens pose the signiﬁcant economic challenge on brassica crops because of their ability to cause lesions on nearly all harvestable parts of the plant. No completely resistant brassica germplasm have been recorded for most of this necrotrophic fungus.
As a group of thioglucosides, including tryptophan-derived indole glucosinolates (IGSLs) and methionine, derived aliphatic glucosinolates (AGSLs), glucosinolates (GSLs) are important secondary metabolites in Brassica species. This health-promoting, sulfur, and nitrogen containing a group of phytochemicals can be found in several brassica species including cauliflower, rapeseed, cabbage, broccoli, radish, rutabaga, baemuchae, kohlrabi, turnip, black mustard, Chinese cabbage, leaf mustard, and kale. They are present in different concentrations in the different parts of the plant. Brassica species have also been implicated in phytoremediation and biofumigation. Myrosinases coexist with GSLs but are stored separately in adjacent cells but mix upon sensing a pathogen attack. The result is hydrolysis of thioglucosides GSLs bond to produce unstable aglycones, which decompose to various bioactive compounds, including isothiocyanates and thiocyanate with toxic effects on microorganisms, nematodes, insects and other pathogens.