Variability among Corynespora cassiicola isolates causing target leaf spot disease collected from soybean growing area of Chhattisgarh

Abstract

Target leaf spot disease of soybean caused by Corynespora cassiicola. The disease affects leaves, stems, pods and seeds. Leaf lesions are rounded to irregular and reddish brown they vary from speck to big mature spot. Lesions are frequently surrounded by a dull green or yellowish green halo. Eleven isolates were isolated from different soybean growing areas and used for variability studies. Maximum radial growth was observed in two isolates CC-8 and CC-1 (90 mm) and minimum radial growth was observed in two isolate CC-2 and CC-9 (82 mm). There were great variability was observed in colony pigmentation especially on top of the culture viz. black, pale brown, brown, dark brown, pale green and gray. There were two patterns were observed on colour of bottom of the colony (dark brown and black), texture (thin and thick) and shape of the colony viz. round and polygon.There were enormous variations were observed in conidial morphology of all the isolates. Variations were observed in shape (oval, obclavate, cylindrical or Y, curved or straight), size (10.3–168.8μm long; and 1.3–12.4μm wide) and the number of pseudosepta (0–16).