بررسي همبستگي اسپورزايي روي كوتيلدون و برگ ها به عنوان مهم ترين صفت آلودگي به بيماري سفيدك كركي آفتابگردان با ديگر صفات آن

Correlation of Sporulation on Cotyledons and Leaves as the Main Infection Characteristics of Sunflower Downy Mildew with its other Characteristics

In the present study eight symptoms of Plasmopara ha/stet/if (Far]) Berl and de Toni including damping-off, sporulation on cotyledons and true leaves, sporulation on cotyledons. stunting, leaf mosaic or chlorosis, deformation, hypocotyl lesions and root reduction on the inoculated plants were compared as disease infection characteristics for assessment of resistance and suceptibility of sunflower cultivars and hybrids. Three days-old seedlings were inoculated with spore suspension of P. halstedii using whole seedling immersion method (WSI). Reactions of cultivars were recorded 15 days later. A strong correlation between the above symptoms, and sporulation on cotyledons and true leaves (SCL) as the main infection characteristic of the disease was determined. The most suitable regressional model for resistance determination was calculated based on mosaic (M), stunting (S), hypocotyle lesions (HL) and root reduction (RR) symptoms. Among other regressional models tested for resistance determination, another model with high R2 value was also determined using only mosaic symptom.