LEAF BLIGHT (Alternaria triticina) OF WHEAT AND ITS MANAGEMENT 2807
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Date
2019-06
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JAU, JUNAGADH
Abstract
The present research work entitled “Leaf blight (Alternaria triticina) of
wheat and its management” was under taken at the Department of Plant Pathology,
Junagadh Agricultural University, Junagadh during 2017-18 to 2018-19.
Wheat suffers from many fungal diseases, among which Alternaria leaf
blight disease caused by Alternaria triticina is one of the important disease and
intensity of disease has also increased in the recent years in North India. Hence, with
a view to generate scientific information under agro climatic conditions of South
Saurashtra region of Gujarat conditions, present investigation was carried out during
2017-18 to 2018-19.
The typical symptoms of leaf blight appeared on leaves of the infected wheat
plants. The disease initially appeared in the field as small, oval, chlorotic lesions they
were irregularly scattered on the leaves. These enlarge, become irregular in shape and
develop into dark brown or grey sunken lesions. Some lesions showed bright-yellow
marginal zone and minute black powdery conidia inside the lesions. At the dough
stage of wheat development infected fields appear dull and bronzed with a burnt
appearance when seen from a distance. The fungal pathogen was isolated from
diseased plant on PDA and pathogenicity was proved successfully by spray
inoculation method. Based on cultural and morphological characters viz., dirty white
mycelium with black colour discolouration with mycelium initially hyaline, later on
turn olive buff to deep olive buff colour, branched, septate at irregular interval and conidia were acrogenous borne singly or in chain of 2-7 with beak, smooth obclavate,
conical, elongated, cylindrical and both ends rounded gradually tapering in to beak.
Based on the size, shape and colour of conidia, the fungus was identified as
Alternaria triticina.
Out of 10 varieties screened under artificial condition, none of the entries
were free from leaf blight. However, GW 366, GW 322, GW 496, GW 173, Raj 4238,
GW 11 and Lok 1 were found resistant. The remaining three entries were moderately
resistant.
In laboratory screening, non-systemic fungicides viz., mancozeb 75 % WP
and propineb 70 % WP were found most effective with 89.41 and 88.70 per cent
fungal growth inhibition, respectively. While systemic fungicides viz., propiconazole
25 % EC and hexaconazole 5 % EC proved most effective with 96.00 and 90.33 per
cent fungal growth inhibition, respectively. But in combination fungicides viz.,
azoxystrobin 11 % + tebuconazole 18.30 % WP, hexaconazole 4 % + zineb 68 % WP
and carboxin 37.5 % + thiram 37.5 % WS were found most effective with cent per
cent growth inhibition of fungus.
In phytoextracts studies, Azardirachtha indica (Neem leaves extracts) was
found effective with 40.06 per cent mean mycelial growth inhibition. While
biological control point of view under in vitro condition Trichoderma viride gave
70.56 per cent mean mycelial growth inhibition of test pathogen.
Among the different fungicides tested as foliar spray under field conditions,
the lower disease intensity (15.79 %) was recorded in foliar application of
propiconazole 25 % EC (500 ppm) followed by hexaconazole 4 % + zineb 68 % WP
(18.44 %) at 1000 ppm. The maximum grain yield (3831 kg/ha) was also recorded in
foliar spray of propiconazole 25 % EC which was at par with hexaconazole 4 % +
zineb 68 % WP and hexaconazole 5 % SC.