STUDIES ON FUNGAL PATHOGENS OF VANILLA WITH SPECIAL REFERENCE TO Colletotrichum gloeosporioides (Penz.) Penz. and Sacc.
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Date
2007-01-03
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University of Agricultural Sciences GKVK, Banglore
Abstract
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 Karnatalca, 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. ro//sn 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 diy mycelial weight of C. gloeosporioides. Temperature of 30"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 Trichoderma
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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