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Studies on cultural and molecular variability among the isolates of Sclerotium rolfsii Sacc.

Sclerotium wilt/ rot of potato caused by Sclerotium rolfsii Sacc. is one of the major soil borne diseases of potato causing heavy losses every year. Ten isolates varied with respect to morphological characters. The colour of mycelium was light buff to cottony white. The sclerotial initiation started between 5th and 9 th day in different isolates. The growth rate was excellent in DSr1, DSr2 and DSr3 isolates. The colour of sclerotia was dark brown in DSr1 and DSr3; brown in DSr2, DSr4, BSr1 and HSr1 while it was light brown in BSr3, HSr2 and HSr3. The shape of the sclerotia was spherical in all the isolates except DSr1 and BSr2 wherein ellipsoidal and subspherical shapes were noticed respectively. Highest dry mycelial weight and mean colony diameter was observed in isolate DSr3. Isolate DSr1 (2.10 mm and 98.38 mg) recorded highest sclerotial diameter and test weight. RAPD data distinguished the ten isolates into two major clusters A and B. Cluster A was classified in to A1 and A2 further A2 was sub grouped in to A3 and A4 comprising of isolates DSr1 (UAS, Dharwad), DSr2 (Kurubagatti) and DSr3 (Hangarki) belong in to Dharwad district. A major cluster B was classified up to sub-sub cluster B6. Cluster B1 comprising of isolates of Hassan district and cluster B2 comprising of isolates of Belgaum district. In the present investigation, the results revealed that geographical locations of isolates were closely related. | Studies on cultural and molecular variability among the isolates of Sclerotium rolfsii Sacc.