Evaluation of Different Culture Media for Alternaria Helianthi Causing Blight in Sunflower

Symptoms of Alternaria leaf spot/blight were observed in the form of small scattered brown spots on the leaf surface. Further, these spots covered larger leaf area with dark brown margin and yellow halo with indistinct zonations. Linear necrotic lesions were observed on the stem, petioles, capitulum, sepals, and petals at different stages of plant growth. Isolation of the fungus from the infected leaf sample collected from the field yielded Alternaria helianthi and pathogenicity was proved on KBSH 44 which expressed the symptoms in 8-9 days after inoculation under laboratory condition. The pathogenicity studies showed the external symptoms as small scattered brown spots on the leaf surface. Later, these spots increased in size covering larger area with dark brown margin and yellow halo with indistinct zonations. Linear necrotic lesions also appeared on stems, petioles and sepals. Cultural studies revealed that potato dextrose agar (82.80 mm) was the best followed by Sunflower leaf extract agar (71.54 mm) and Richard's agar (63.64 mm) for growth of fungus. Whereas, the growth of A. helianthi was not observed in water agar. In case of liquid media, potato dextrose broth yielded maximum dry mycelial weight (282.79 mg) followed by sunflower leaf extract broth (241.51 mg).