BIOLOGICAL CONTROL OF DAMPING OFF OF OKRA (Abelmoschus esculentus L.)
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Date
2019-06-28
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CSKHPKV, Palampur
Abstract
The investigation on the biological control of damping off of okra (Abelmoschus
esculentus L.) was undertaken during 2017-19 in the Department of Plant Pathology, CSK
HPKV, Palampur. Damping off pathogen (Rhizoctonia solani) was isolated from the disease
samples collected from different okra growing areas and pathogenicity proved. Twenty
isolates of Trichoderma spp. were isolated from different rhizosphere soil and five standard
isolates of Trichoderma spp. were evaluated for their antagonistic activity in vitro against R.
solani. The bioagent strains obtained from the department were statistically less effective than
Trichoderma strains isolated from okra rhizosphere soil such as isolate 2,6,9,11. Trichoderma
sp.-2 was the best performing strain among the bioagents tested in dual culture as well as its
volatile compounds activity in inhibiting maximum mycelial growth 67.8 and 42.4 per cent,
respectively. However, non-volatile compounds produced by Trichoderma sp.-6 in autoclaved
sterilized and filter sterilized culture filtrates inhibited mycelial growth upto 11.1 and 62.2 per
cent at 2:1 ratio, respectively. In morpho-cultural identification of four potential Trichoderma
isolates, Trichoderma sp.-6 and Trichoderma sp.-9 were identified as T. harzianum and T.
viride, respectively. In mycoparasitic interaction, bioagents hyphae coiled around R. solani
and after penetration lysed the pathogen hyphae. Among the eleven different solid media
evaluated for the linear mycelial growth and spore production of potential bioagents,
Trichoderma sp.-2 showed highest mycelial growth (171.0 mm) and population
(2.6×108spore/g) in sorghum grains. Agro-by products viz., paddy straw, cow dung and FYM
supplemented with different carbohydrates viz., glucose, sucrose and jaggery (at the rate 1.0%
and 5.0%) enhanced the growth of bioagents. Trichoderma sp.-2 showed highest linear
mycelial growth on paddy straw (170.7 mm) when amended with 5.0 per cent sucrose. Under
net house conditions, seed biopriming was found superior application method of bioagents for
management of damping off of okra than soil application, seed treatment and drenching while
Trichoderma sp. -2 was found most superior to other bioagents. Among Four fungicides
tested in vitro carbendazim was most effective against R. solani but incompatible with
bioagents while copper oxychloride was found compatible with bioagents.
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