STUDIES ON BIOLOGICAL CONTROL OF FUSARIAL WILT OF CHILLIES
Loading...
Files
Date
2006
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY, RAJENDRANAGAR, HYDERABAD
Abstract
Wilt of chilli (Capsicum annuum) caused by F. solani is an important
and destructive soil borne disease causing yield losses in most popular cultivars
of chilli especially in Northern Telangana zone of Andhra Pradesh during both
kharif and rabi seasons during recent years. Detailed investigations were carried
out on biological control of this disease by developing mutants of Trichoderma
viride, T. harzianum and Pseudomonas fluorescens and studying the role of
mutants on the antagonistic activity against the pathogen. The studies also
included testing of the mutant biocontrol agents against commonly used
fungicides, insecticides and herbicides. An attempt has also been made to
develop disease management strategy using biocontrol agents and
agrochemicals.
Symptoms of the disease was as pale yellowing of the leaves of
seedlings followed by withering and chlorosis of leaves, subsequently, the
affected plants gradually wilt and die with vascular discoloration and marked
reduction in root system. The fungus associated with the disease was isolated
and identified as Fusarium solani (Mart.) Sacc. and pathogenicity was proved
under glasshouse conditions.
Of the four dosages of gamma radiation 50, 75, 100 and 125 K rad to
which wild slant cultures of T. viride, T. harzianum and P. fluorescens exposed,
exposure at 125 K rad produced eight and three each of T. viride and
T. harzianum, carbendazim tolerant mutants. Wherein, the mutants tolerated
higher concentrations of carbendazim as indicated by their growth on fungicide
amended medium. While, gamma irradiation did not induce any distinguishable
mutants of P. fluorescens. The mutants of T. viride and T. harzianum differed
from their wild types in colony morphology, growth habit and rates,
sporulation, antagonism against F. solani and tolerance to carbendazim.
Among the eight and three mutants of each of T. viride and
T. harzianum, mutants TvM1 and ThM1 recorded a faster growth rate of 82 mm
within 72 h and could antagonize the test pathogen F. solani by forming zone of
inhibition within 96 h, with 90.85 and 90.24 per cent inhibitions respectively
compared to the rest of the mutants and wild types. While the bacterial
biocontrol agent P. fluorescens (commercial isolate) inhibited the growth of
F. solani to an extent of 65.9 per cent.
Scanning electron microscopic studies revealed a perfect phenomenon of
mycoparasitism involving chemotrophic stimulus, coiling, secretion of extra
cellular enzymes and lysis of the pathogen’s mycelium / hyphae.
Of the different pesticides tested against the mutants, carbendazim,
fipronil and fluchloralin were found to be compatible with the mutants of
T.viride, T. harzianum and P. fluorescens at their recommended and half the
recommended dosages.
An IDM strategy was developed for fusarial wilt of chilli based on
glasshouse experiments. Results obtained in pot culture experiments revealed
that, seed and soil application of TvM1 + ThM1 + P. fluorescens combined with
soil drenching with carbendazim + fipronil + fluchloralin recorded significantly
highest germination of chilli seedlings with no wilt incidence coupled with
maximum shoot and root lengths and fresh and dry weights of chilli seedlings.
The treatment not only controlled wilting but also enhanced the growth of chilli
seedlings.
Description
Keywords
STUDIES, BIOLOGICAL, CONTROL, FUSARIAL, WILT, CHILLIES