Vol. 19 No. 1
Morphological and physiological characteristics of Sclerotium rolfsii causing stem rot or rhizome rot disease in tuberose (Polianthes tuberosa)
Author(s): P. BOOPATHI
Abstract: Tuberose is the most popular ornamental bulbous perennial plant cultivated throughout the world especially in India for the cut and loose flower trade. But this tuberose is most affected by stem rot (Sclerotium rolfsii Sacc.), one of the most destructive and widespread soil-borne diseases. In Tamil Nadu, tuberose cultivation is highly interrupted by this pathogen. The survey was conducted in different tuberose growing districts of Tamil Nadu and eight different isolates of pathogenic fungi were obtained viz., SR1 to SR8. Among them, SR1 produced the white cottony mycelium (9.0cm), reddish-brown colour sclerotia with maximum sclerotial size (1.69mm) and weight (180 mg100-1 sclerotial bodies).Under pot culture conditions, the various isolates show classic stem rot symptoms. Based on the different degrees of virulence, SR1 was identified as the most virulent isolate (88.00 %). The PDA medium showed maximum radial growth of the fungus (9.00cm) and a similar result was also obtained in potato dextrose broth (7.30g). Among the seven different carbon sources, starch was recorded as the best source (8.29cm) followed by dextrose (8.18cm). Among the six different nitrogen sources tested, sodium nitrate (8.77cm) recorded maximum growth followed by potassium nitrate (5.38cm). The maximum growth of the pathogen was recorded at 300C (9.00cm) and pH 7.0 (8.92cm).
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