STUDIES ON FUNGAL PATHOGENS OF VANILLA WITH SPECIAL REFERENCE TO Colletotrichum gloeosporioides

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Date
2007-01-03
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University of Agricultural Sciences GKVK, Banglore
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STUDIES ON FUNGAL PATHOGENS OF VANILLA WITH SPECIAL REFERENCE TO Colletotrichum gloeosporioides (Penz.) Penz. and Sacc. ASHOKA, S. 2005 ABSTRACT YASHODA R. HEGDE MAJOR ADVISOR Vanilla {Vanilla planifolia Andrews] is herbaceous, spice crop mainly grown in Karnataka, Kerala and Tamil Nadu. Vanilla crop is affected by many pathogens in Karnataka. Pathogens were isolated from infected parts of vanilla and were identified as Colletotrichum gloeosporioides (Penz) Penz. and Sacc., Fusarium oxysporum Schlecht, Rhizoctonia sp. and Sclerotium rolfsii Sacc. Incidence of C. gloeosporioides and F. oxysporum was observed in all four districts viz., Shimoga, Uttar Kannada, Dharwad and Belgaum whereas Rhizoctonia sp. and S. rolfsii incidence was observed in Shimoga and Uttara Kannada districts respectively. Lower incidence of C. gloeosporioides and F. oxysporum and absence of S. rolfsii and Rhizoctonia sp. was observed under shade net conditions. Partial and discontinuous wilting was observed in few places of Sagar taluk of Shimoga district which was due to mixed infection of C. gloeosporioides and F. oxysporum. In the host pathogen interaction C. gloeosporioides caused rotting of stem upto 15 cm from soil level in 45 days, F. oxysporum caused rapid wilting, Rhizoctonia sp. caused shredding of stem and S. rolfsii caused girdling of stem. Conidia of C. gloeosporioides were single celled, hyaline, straight, cylindrical or oval, measuring 15 x 3.50 pm. Potato dextrose agar and Richards' agar supported maximum growth. Richards' broth supported maximum dry mycelial weight of C. gloeosporioides. Temperature of SC^C, 12 h light and 12 h darkness and pH 6.0 were found to be best for the fungal growth. Under in vitro conditions, 10% neem leaf extract and Trichodenna harzianum were able to reduce the growth of pathogen. Systemic fungicides viz., triadimefon, benomyl, prochloraz and combiproduct, Carbendazim 12% + Mancozeb 63% completely inhibited growth of pathogen at concentration of 0.1, 0.05 and 0.025%. Non-systemic fungicides viz., mancozeb and copper sulphate at 0.30% were found effective in inhibiting growth of pathogen.
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