This invention provides novel methods for improving plant quality and yield inthe presence of pathogens. The method increases the levels of pathogenesis-related proteins, such as PR1, phenylalanine ammonia lyase, or plant cell wallproteins such as hydroxyproline-rich glycoproteins, in a plant by contactingthe plant with a plant systemic inducer and a reactive oxygen species whereinthe amount of the reactive oxygen species is sufficient to increase the amountof the pathogenesis-related protein above the level induced by the plantsystemic inducer in the absence of the reactive oxygen species. A preferredreactive oxygen species is peracetic acid； a preferred plant systemic induceris salicylic acid.
