Studies on cultural variability of Exserohilum turcicum (Pass.) Leonard and Suggs. causing turcicum leaf blight of sorghum

Abstract

Eight solid and liquid media were tested for growth and sporulation of E. turcicum (Et-8). Among the solid media, potato dextrose agar supported the maximum radial growth (87.67mm) and excellent sporulation. The least growth was recorded on host leaf extract agar and Richard's agar media which are on par with each other by supporting the radial growth of 39.67 mm. whereas no sporulation was observed in Malt extract agar and czapeck’s dox agar. With respect to cultural characteristics, the colony colour varied from grey to black. Mycelial growth varied from fluffy to slightly raised colony. Among the liquid media, highest dry mycelial weight with excellent sporulation was recorded in potato dextrose broth (689.67 mg). The least growth with no sporulation was observed in malt extract broth (239.67 mg). Among the eight isolates (Et1-Et8) tested for cultural variability Et4 and Et6 recorded maximum colony diameter of 90.00 mm. The poor growth was observed in Et1 isolate (70.00mm) after 12 days of incubation. Shape of conidia in all the isolates revealed that the conidia were straight, ellipsoidal, oblong or oval shape, round at one end and another end protruding, brownish to dark brown in colour and symmetrical in shape, pale to slight brownish in appearance. Pigmentations varied from greyish, greyish black, whitish gray, blackish and dark blackish colours. Excellent sporulation was exhibited by the isolates Et7 and Et8. However poor sporulation was noticed in the isolate Et3.