Abstract
AbstractThe root holoparasitic angiosperm sunflower broomrape (Orobanche cumana) specifically affects sunflower (Helianthus annuus) growth and causes severe damage all over the world. This investigation was designed to examine the protective effects of salicylic acid (SA) treatment to the seeds of anO. cumana‐susceptible cultivar of sunflower (TK0409). Sunflower seeds were pretreated with different concentrations (0, 0.5 and 1 mM) ofSAand inoculated withO. cumanafor 4 weeks.O. cumanainfection resulted in reduction in plant biomass, endogenousSAlevel, and the expression ofSA‐related genes includingpal,chsandNPR1. By contrast,O. cumanainfection enhanced the production of reactive oxygen species, activities of antioxidant enzymes as well as contents of phenolics and lignin. Seed treatment with 1 mMSAincreased sunflower biomass in terms of plant height, fresh weight and dry weight by 10%, 13% and 26%, respectively, via reducing the number and biomass of establishedO. cumana. The increase of hydrogen peroxide contents by 14% in the 1 mMSAtreated sunflower plants appeared to be because of the inhibition of ascorbate peroxidase and catalase by exogenousSA. The enhanced expression of pathogenesis‐related genes (PR3andPR12, encoding chitinase and defensin, respectively) after 4 weeks of inoculation indicated that systemic acquired resistance was induced in theSAtreated sunflower in which the level of endogenousSAwas also elevated in a dose‐dependent manner. The increased expression of a hypersensitive‐responsive (HR) genehsrindicated that the resistance of sunflowers might be associated with a hypersensitive reaction which was activated by exogenousSAtreatment.
Published Version
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