STUDIES ON THE MANAGEMENT OF RICE GRAIN DISCOLORATION CAUSED BY FUNGI
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Date
2018
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Acharya N.G. Ranga Agricultural University
Abstract
The present investigation on “Studies on the management of rice
grain discoloration caused by fungi” was carried out in order to assess the
prevalence of rice grain discoloration in major rice growing mandals of
Nellore and Chittoor district of Andhra Pradesh, and to evaluate efificacy of
rice based fungicides plant extracts and natural preparations rice based
fungicides, plant extracts and natural preparations in vitro and field
conditions for its management.
Roving survey conducted during 2017-18 in Chittoor and Nellore
districts of Andhra Pradesh revealed that, In Nellore district, incidence of
rice grain discoloration was more in Vasili village (36.85 %) of Atmakur
mandal and least (20%) was observed in Kovur village of Nellore Rural
mandal. While in Chittoor district, the incidence of disease was more in
Yerpedu (32.26 %) village of Yerpedu mandal, least in Nagiri village
(19.79%) of Nagiri mandal.
A total of seven fungal genera using blotter method and twelve fungal
genera using agar plate method were isolated. Total 12 fungi viz; Alternaria
alternata, Aspergillus flavus, Aspergillus niger, Bipolaris oryzae,
Curvularia lunata, Curvularia clavata, Fusarium moniliforme, Fusarium
oxysporum, Sarocladium oryzae, Rhizopus stolonifer, Chetomium sp. and
Alternaria padwickii.
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Emphasis being laid to isolate the mycoflora associated, their
identification, and cultural and morphological characterization was carried
out.
Pathogenicity test was conducted using panicle detached method.
From the results, it was evident that the panicle dipped in F. moniliforme
spore suspension showed significantly higher disease incidence (26.27 %)
followed by C. lunata (21.80 %). Lowest disease incidence was observed
with A. padwickii (10.34%). Based on the results F. moniliforme and C.
lunata were selected as predominant and effective pathogens and used for
further studies.
To evaluate the bio-efficacy of rice based fungicides, Plant extracts
and Natural compounds against predominantly occurred pathogens viz; F.
moniliforme and C. lunata in vitro, poisoned food technique was used.
Among the six fungicides tested against F. moniliforme and C.
lunata, Trifloxystrobin (25%) + Tebuconazole (50%) WG and
Tebuconazole proved to be highly effective in inhibiting the mycelial
growth compared with other fungicides and control. Hence, these two
fungicides were selected for further field studies.
Among the six plant extracts tested against F. moniliforme and C.
lunata, garlic extract exhibited higher antifungal activity even at low
concentrations followed by neem extract. Hence, these two plant extracts
were considered as effective and used for further field studies.
However, among all the natural preparations tested against F.
moniliforme and C. lunata, Jeevamrutha proved to be highly effective in
inhibiting the mycelial growth followed by Modified panchagavya. Hence
these two natural products were selected for further field studies.
Bio-efficacy of effective fungicides, plant extracts and natural
preparations were tested under field conditions during Rabi 2017-18. The
experimental plot was laid at Agricultural Research Station, Nellore. During
flowering stage i.e., 60 DAS first spray was conducted. Number of panicles
pe hill, number of normal grains per panicle and number of discoloured
grains per panicle were measured after imposing treatments. Least per cent
disease incidence was recorded with treatment T1-nativo @ 0.4gm/lt (5.51
%) followed by T2-Tebuconazole @ 0.5 ml/lt (7.45 %). Among plant
extracts T3- Garlic extract @ 3 per cent (7.58 %) was found effective
followed by T4- Neem leaf extract @ 20 per cent (8.34 %). While among
natural preparations, T5– Modified panchagavya @ 4 per cent and T6-
Jeevamrutham @ 3 per cent had shown equal effect (9.11 %). There is
significant difference between treatments and at par each other. Similarly,
lowest number of discoloured grains was recorded with treatment T1 (8
grains/panicle) followed by treatment T2 and T3 (10 grains/panicle).
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Second spray was initiated after fortnight interval by imposing the
same treatments as done in the first spray. Data on Per cent disease
incidence (PDI), Number of of discoloured grains per panicle and yield
related parameters viz; Panicle weight, Grain yield, Straw yield and Test
weight of normal grains were recorded.
Among all the treatments tested, least per cent disease incidence was
observed in treatment T1 (5.03 %) followed by T2 (5.78 %), T3 (6.53 %) and
highest disease incidence was observed with control T7 (10.40 %) and there
is significant difference between treatments and at par with each other.
Similarly, lowest number of discoloured grains were recorded with
treatment T1 (7.0) and highest with control (T7) (10.40 %).
Higher panicle weight (2.96 g), grain yield per 5 m2 plot (3.23 kg),
straw yield (1.81 kg) and test weight of normal grains was highest (17.13 g)
was recorded in treatment (T1) over control.
To know the effect of effective fungicides, botanicals and natural
preparations on germination percentage (%), shoot length (cm), root length
(cm), shoot: root ratio and vigour index of rice seedlings, blotter method was
followed.
Maximum germination percentage (96.67 %) and shoot length (8.78
cm) was recorded in Treatment (T1), maximum root length (14.10 cm) and
shoot root ratio was observed with treatments T2 and T4 respectively over
control
Description
D5730
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