Studies on Variability and Management of Sclerotium rolfsii Sacc. Causing Wilt of Stevia
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Date
2011
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Publisher
UAS, Dharwad
Abstract
Stevia rebaudiana is a perennial herbaceous medicinal plant belonging to
family Asteraceae .Wilt caused by Sclerotium rolfsii is major constraint in stevia
production. Ten pathogenic isolates of Sclerotium rolfsii were obtained during survey
from different locations of Karnataka and per cent disease incidence varied from 8-
40%.
The study on variability indicated that all isolates showed marked differences
in their growth rate and time taken for sclerotial initiation, colour, size and weight of
sclerotial body.
Cultural studies on different media revealed that potato dextrose agar and
potato dextrose broth were best for growth of all the isolates. The isolates varied in
their growth in all temperature and pH. Maximum growth rate of all isolates was
observed at 300-350C while, no growth at 400C and optimum pH for isolates varied
from 4-5.
Present study clearly indicated that the virulence was correlated with many
aspects like isolates with small sized sclerotia, high virulence index, more oxalic acid
production and least vigour index (SrKAl, SrNID and SrSAI) were highly virulent
while, isolates with big sized sclerotia, low virulence index, less oxalic acid
production and high vigour index were less virulent viz., SrBEN, SrGAN, SrRIP and
SrSIR.
Host range studies revealed that coleus, tulsi, shatavari, brahmi, rose mary,
patchouli and aloe were collateral host. Aswagandha, lemon grass and basmati were
non host. Investigation on sensitivity of isolates to hexaconazole revealed that all
isolates except SrSAI, SrNID and SrKAL found sensitive to hexaconazole upto 100
ppb. In chemical studies except carbendazim all were effective. In biological
management trial, duranta, eupatorium, cow urine, panchagavya, Trichoderma
harzianum and T. viride were effective under in vitro condition.
In vivo studies revealed that soil drenching with 0.1 per cent hexaconazole or
propiconazole, 10% Eupatorium odoratum and Duranta repens, T. harzianum,
T. viride helped to manage the sclerotium wilt successfully.