Author(s):

Meghchand Dewangan, Anupama Jain, Vishakha Tiwari and Kamlesh Kumar Mohle

Abstract: Myrothecium leaf spot of soybean caused by Myrothecium roridum. Myrothecium leaf spot of soybean is occurring in almost all the major soybean growing areas of India causing about 30 per cent yield loss. Initial symptoms of the disease appear as small round or oval, brown spots with dark brown margin on leaves in the infected plant. In cultural and morphological variability studies of 20 isolates of Myrothecium roridum. The maximum radial growth (38.9mm) was observed in isolate Mr9 at 5 DAI and minimum radial growth (25.9mm) was observed in isolate Mr14. Maximum mean mycelial growth (88.5mm) was observed in isolate Mr9 and minimum mean mycelia growth (43.9mm) was observed in isolate Mr14. Sporulation color of M. roridum were recorded PDA. Seven isolates were found black in color, two isolates brownish black color, three isolate light green color, five isolates dark green color and three isolates produced white color sporulation. Mycelial growth pattern of all the isolates were observed on PDA out of which eleven isolates categorized in circular margin with smooth surface and nine isolates were categorized in irregular with rough surface. Thirteen isolates showed concentric ring and remaining seven isolates were without concentric ring. The highest conidia size (6.24×1.45μm, length × width) was recorded in isolate Mr5 and lowest conidia size (2.48× 0.61μm, length × width) was recorded in isolate Mr2.Conidia of nine isolates were cylindrical with round end shape, eight isolates were rod shaped with round end and three isolates were narrowly ellipsoid with round end shape.

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