INVESTIGATION ON GANODERMA WILT OF COCONUT AND ARECANUT WITH RESPECT TO PATHOGEN VARIABILITY AND DISEASE MANAGEMENT
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Date
2016-10-23
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK, BENGALURU
Abstract
The incidence of Ganoderma wilt of coconut and arecanut was maximum (19.32
%) in Tumkur district followed by Chitradurga and Hassan in southern Karnataka.
Diseased root bits and sporocarp were good source(s) for isolation of Ganoderma with
Potato Dextrose Agar and Oat Meal Agar that supported highest radial growth and
biomass production. Of the nine Ganoderma isolates, CG11 recorded maximum disease
severity index (62.50 DSI) in coconut. However, Arecanut isolate AG9 recorded
maximum DSI (75) and designated as most virulent isolates. The pileus shape, pileus
thicknes, stipe length, stipe attachment and colour of pore surface of sporocarps varied
greatly in coconut and arecanut. The molecular characterization of Ganoderma through
DNA amplification resulted in 650bp in all isolates tested. The phylogenetic analysis of
TIS sequence with other known species of Ganoderma through NCBI web proved that
the isolates were related to Ganoderma sp. with 80-100 per cent identity and shown close
relationship with India, China and Sri lanka Ganoderma species. Bengalgram, redgram
and bhendi were found indicator plants for early detection of disease. Cent per cent
inhibition of mycelial growth of Ganoderma was recorded in Tebuconazole,
Propiconazole, Hexaconazole, Kitazin, Propineb and combi-products viz., Hexaconazole
+ Zineb, Hexaconazole + Captan, Fenmidone + Mancozeb, Tebuconazole +
Trifloxystrobin WG at >250ppm. Urea recorded 67.34 and 46.89 per cent inhibition
against CG14 and AG7 respectively. However, chemical fertilizers supported the
development of T viride at lower concentration (250 ppm). ZnSo4 and Gypsum recorded
52.53 and 7.42 per cent inhibition of biocontrol agent at 1000 ppm; MgSo4 supported the
growth and sporulation of biocontrol agent. Tebuconazole root feeding in coconut @1.5
ml in 100 ml water/palm at quarterly interval + Soil application of 5 kg neemcake
enriched with T. viride/ palm/ half yearly + Pseudomonas fluorescens (talc formulated)
@ 50 g/palm/ half yearly + Soil drenching with half yearly 1per cent Bordeaux mixture
@ 20 l/palm reduced disease index and which accounted 76.41per cent reduction over in
control with maximum nut yield. Similarly, the treatment in arecanut recorded the least
increase of 7.39 disease index, which accounted 55.22 per cent reduction over control
with maximum nut yield.
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