LAUSR

Certain chemical pesticides control plant diseases through induction of systemic resistance mechanisms. In this study, orysastrobin, a “quinone outside inhibitor” (QoI)-type commercial fungicide, decreased disease severity in the leaves of A. thaliana resulting from inoculation with P. syringae pv. tomato DC3000; protection from the orysastrobin treatment correlated with lowered bacterial populations in the plant tissue. The fungicide-induced cross protection to a bacterial pathogen was at the same level as that given by foliar treatment with beta-aminobutyric acid (BABA), an inducer of salicylic acid (SA) - defense pathway, leading to induced resistance for this pathogen. Although another chemical inducer of the SA-pathway, benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), induced the marker gene for the salicylic acid (SA) pathway PR1a, there was no induction with orysastrobin or methyl jasmonate treatments. However, orysastrobin induced AtVSP1.2, in the JA-pathway and PDF1.2 in the ET defense pathway. These findings suggested that the fungicide, orysastrobin, induced resistance to the pathogenic pseudomonad. Because orysastrobin induced the JA/ET defense pathways, applications of this strobilurin-type fungicide have the potential to protect plants from a large array of pathogens and abiotic stresses.