What pathogen is responsible for post-harvest damage of many crops?
Phytophthora brassicae is an economic and notorious oomycete pathogen. It has a narrow host range restricted to brassica plants such as Chinese cabbage (B. rapa subsp. pekinensis), Brussels sprouts (B. oleracea var. gemmifera) and rutabaga (B. napus var. napobrassica). P. brassicae is responsible for post-harvest damage that lowers the marketability of cabbage to around 90 % losses. P. brassicae is one of the few Phythophthora species that infect Arabidopsis plant both naturally and under laboratory conditions.
The susceptibility of the double mutant pen2-1 pad3-1, demonstrates that both camalexin and product of IGSL hydrolysis are important for P. brassicae disease resistance in brassica. Transcript analysis from Schlaeppi showed that genes encoding enzymes involved in tryptophan, camalexin and IGSL biosynthesis coordinate induced response to P. brassicae. On the other hand, the double mutant cyp79B2 cyp79B3 is highly susceptible to P. brassicae because it is unable to convert tryptophan into indole-3-acetaldoxime (IAOx), the precursor of camalexin and IGSLs. These authors also opined that the susceptibility of the double mutant cyp79b2cyp79b3 to Phytophthora capsici could be attributed to the deficiency of IGSLs and camalexin. Thus IGSLs confer resistance against P. brassicae. P. brassicae disease resistance may be established by the sequential activity of phytoanticipin IGSL and phytoalexin camalexin.