Sunflower, Helianthus annuus L. is a major oilseed crop widely cultivated across the globe. White mold, caused by the necrotrophic pathogen Sclerotinia sclerotiorum (Lib.) de Bary, is a common and widespread pathogen of sunflower. Changes in a partially resistant and a susceptible sunflower line infected with Sclerotinia sclerotiorum were studied 12, 24 and 48 h after inoculation. Electrophoretic patterns and quantitative changes in soluble proteins were determined in the basal stem region. Soluble proteins were accumulated post infection in the partially resistant line. A rapid accumulation of stress-related, low molecular weight proteins was induced in both lines by different pathways. By 12 and 24 h post inoculation, stress proteins with molecular masses of 27 kDa had accumulated in infected stems of the partially resistant line. SDS-PAGE results showed the accumulation of proteins with a molecular mass of 55 kDa in the susceptible line and the absence of this band in the resistant line. This relatively faster response to Sclerotinia sclerotiorum invasion could be partially responsible for the resistance or susceptibility to this pathogen. The differences between lines may also indicate further avenues worth exploring in host-pathogen relations which could ultimately lead to selection and production of new lines with higher levels of resistance to Sclerotinia sclerotiorum.
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