Cultural and morphological variability in Alternaria brassicae isolates of Indian mustard, Brassica juncea L. Czern & Coss.

Alternaria brassicae is the most virulent on all brassicaceous plants and cause adverse effect on both quality and quantity of the crop. The present investigation was carried out to know the cultural and morphological variability in Alternaria brassicae causing alternaria blight of oilseeds Brassica. One hundred and five disease samples were collected from 18 districts of Haryana (India) at 20 to 25 km intervals. The spot/lesion size on leaves of the collected samples ranged from 3.0 to 11.5 mm. These samples were isolated and purified by single spore technique to study the morphological, cultural and radial growth behavior at 20 and 25°C. The radial growth varied from 34.6–81.1 mm with creamish, light brown to dark brown in colour and compressed to fluffy mycelial growth. The average conidial length ranged from 117.0 to192.0 pm and breadth from 14.0 to 24.0 pm. The conidial beak length varied from 42.0 to 116.0 pm, number of horizontal/longitudinal septa ranged from 6 to 9 and vertical/transverse septa ranged from 1 to 3 and average distance between two septa have also been determined.