Morphological, Physiological and cultural variability in Alternaria brassicae isolates of Indian mustard, Brassica juncea L. Czern & Coss. collected from different agro-climatic regions of India
Mahesh Singh, H.K. Singh, Shiwangi, Madan Maurya
Indian mustard (B. juncea) is a crop of tropical as well as temperate zone, which is grown during rabi. Alternaria blight disease caused by A. brassicae (Berk.) Sacc. is one of the most important diseases of Indian mustard. Ten isolates of A. brassicae were collected from different geographical region in India for studied the morphological, physiological and cultural variation. All the isolates showed high level of variability in vitro in respect of size and septation of conidiophores and conidia, conidial beak length, effect of temperature and relative humidity on redial growth and different liquid medium on mycelia fresh weight. The length and width of conidiophores ranged from 36.82 to 63.45µm and 4.73 to 6.58 µm respectively. The average conidiophores septation ranged from 4.53 to 6.25 in different isolates of A. brassicae. The conidial length ranged from 104.0 to 142.47 µm, width 11.62 to 16.95 µm and beak length of conidia ranged from 43.35 µm to 70.57 µm in different isolates of A. brassicae. Number of transverse and longitudinal septa ranged from 6.0 to 8.3 and 0.25 to 2.75 respectively. The effect of different temperature on growth of ten isolates of A. brassicae indicates that maximum growth among all the isolates was noted at 25 0C followed by 30 0Cand 20 0C. Each isolates of A. brassicae, grown on Potato dextrose broth, Oatmeal broth, Host leaf broth, Czapek’s broth and Carrot broth. Maximum fresh mycelial weight in the present study was obtained on 20 days of inoculation on potato dextrose broth, which is indicative of the optimum growth of the fungus. The fresh weight of mycelium ranged between 469.67 to 656.67 mg in Potato dextrose broth, 615.67 to 436.33 mg in Oatmeal broth, 441.67 to 628.67 mg in Host leaf extract broth, 389.33 to 571.33 mg in Czapek-dox broth and in Carrot broth, the fresh weight ranged from 425.00 to 611.33 mg in different isolates of A. brassicae.