MANAGEMENT OF COLLAR ROT DISEASE OF CROSSANDRA [Crossandra infundibuliformis (L.) Nees.] INCITED BY Sclerotium rolfsii Sacc.
Loading...
Files
Date
2003
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ACHARYA N. G. RANGA AGRICULTURAL UNIVERSITY RAJENDRANAGAR, HYDERABAD
Abstract
Crossandra [Crossandra infundibuliformis (L) Nees.] is an
economically important ornamental flower plant in Andhra Pradesh. It is
gaining more importance in Chittoor district. Recently, crossandra has
become prone to collar rot disease incited by Sclerotium rolfsii Sacc. S.
rolfsii is a polyphagous soil borne pathogen with a wide host range of 500
plant species. The pathogen was isolated from field infected plant showing
typical collar rot symptoms viz., drying of leaves, white mycelial growth at
collar region and brownish discoloured roots.
Among 8 native antagonistic mycoflora of rhizosphere of
crossandra, Trichoderma isolate-1 (T1) inhibited S. rolfsii to maximum
69.76% (mycelial growth) and 90.86% (sclerotial population). Among 3
bacterial isolates isolated from the rhizosphere of crossandra, Pseudomonas
sp. (B1) was found to be effective which inhibited 43.1% of mycelial
growth and 71% of sclerotial population of S. rolfsii. Trichoderma isolate-1
(T1) and Pseudomonas sp. (B1) were found compatible in in vitro tests.
In vitro efficacy of four fungicides viz., captan, propiconazole,
thiophanate - methyl and thiram was evaluated against S. rolfsii at 50, 100,
250, 500 and 1000 ppm concentrations. Propiconazole was found to be
effective which resulted in complete inhibition of vegetative growth and
sclerotial population of the pathogen followed by thiram.
In in vitro compatibility tests between antagonists and the fungicides
thiram was found to be compatible with both Trichoderma isolate-1
(inhibition was 31.99%) and Pseudomonas sp. (inhibition was 2.22%).
The efficacy of effective antagonists (Trichoderma isolate-1 (T1) and
Pseudomonas sp. (B1)) and fungicide (Thiram @ 0.1%) was tested in pot
culture against collar rot pathogen and found that treatment T7 involving
seedling root dip in thiram @0.1% + seedling root dip in effective
antagonists + soil application of effective antagonists was found to be
superior which recorded least PDI (6.66%). This treatment also recorded
maximum plant height (16.17 cm) and maximum dry weight of shoot
(113.67 mg) and root (53 mg) of crossandra when compared to all other
treatments.
Description
Keywords
MANAGEMENT, COLLAR, ROT, DISEASE, CROSSANDRA, Crossandra infundibuliformis , Nees INCITED, Sclerotium rolfsii Sacc