Stimulation of defense reactions in potato against Pectobacterium sp.

The pesticides used to tackle potato pathogens, including bacteria, are environmentally damaging, so more sustainable treatments are needed. Because plant defense-related hormones such as methyl jasmonate and salicylic acid and the elicitor chitosan can stimulate plant defense systems, the effect of these compounds was tested by adding them to a watering solution 2 days before inoculating two S. tuberosum cultivars with either Pectobacterium carotovorum strain 5890 or P. atrosepticum strain 889. Growth and the production of several defense phenolic compounds were determined in treated and untreated plants, inoculated or not. P. carotovorum 5890 was more virulent than P. atrosepticum 5889 as reflected by higher levels of phenolic compounds in the plants. The defense-related hormone salicylic acid offered the most protection against the bacteria without interfering with plant growth. Because plants produce and accumulate secondary metabolites for protection against infection, higher production was accompanied by less pathogen damage and higher resistance.