STUDIES ON POWDERY MILDEW (Erysiphe polygoni D C) OF URDBEAN [Vigna mungo (L.) Hepper] IN RELATION TO WEATHER, HOST PLANT RESISTANCE AND MANAGEMENT
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Date
2016
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Acharya N.G. Ranga Agricultural University
Abstract
Powdery mildew disease caused by Erysiphe polygoni D C is one of the serious
constraints that afflict cultivation of blackgram in India and other countries. In view of
the significance of the disease, investigation was carried out to study the severity of
powdery mildew on urdbean (Vigna mungo (L.) Hepper) in relation to weather, host
plant resistance and management. Observations were made on different aspects like
incidence, severity (PDI), morphological characters and biochemical changes and
growth and yield parameters.
A roving survey was conducted during rabi 2015-16 in Guntur district of
Andhra Pradesh. Disease incidence and severity were recorded in the surveyed villages
of Tadikonda, Veticherukuru, Pedanandipadu and Kakumanu mandals of Guntur
district. Incidence was ranged from of 13.69% (Pedanandipadu mandal) to 87.01%
(Tadikonda mandal) and severity were ranged from 11.61% (Kakumanu mandal) to
88.08% (Tadikonda mandal), respectively.
Symptoms first appeared on shaded lower leaves. These white, powdery
colonies grew in size and cover both sides of the leaf, petioles and young stems. When
disease progressed leaves became smaller and chlorotic with stunting, distortion and
premature leaf fall due to infection of E. polygoni. The pathogen was observed to
produce amphigenous dirty white hyaline mycelium and barrel shaped conidia
measuring 1.089 μm × 0.7131 μm at 40X magnification.
Correlation studies with weather parameters and crop age on powdery mildew
disease severity revealed that significant positive correlation of disease was recorded
with crop age (r=0.984) and maximum temperature (r=0.657). Regression analyses for
per cent severity of diseases with weather factors revealed that maximum temperature
and wind speed and minimum temperature would influence powdery mildew disease in
urdbean up to 86.6 per cent.
During kharif, out of 47 genotypes evaluated, KUP-1 was immune, two
genotypes were highly resistant, and ten were moderately resistant to powdery mildew,
whereas, twenty moderately susceptible and ten were susceptible and four highly
susceptible. In rabi, out of eleven genotypes, two were highly resistant against powdery
mildew disease, one moderately resistant, one moderately susceptible, other seven
genotypes were highly susceptible.
Among selected blackgram genotypes, significantly highest leaf thickness was
observed in highly resistant genotypes KUP-34 (201.4 μm), KUP-40 (191.3 μm).
Significantly lowest stomatal frequency was observed in highly resistant genotypes
KUP-34 (88.64/mm2), KUP-40 (99.24/mm2). Higher trichome density was observed in
highly resistant genotypes KUP-34 (62.33), KUP-40 (59.11).
Significantly higher phenol content was observed in highly resistant genotypes
KUP-34 (0.912 mg/100 mg) and KUP-40 (0.861 mg/100 mg) and one moderately
resistant genotype KUP-12 (0.678 mg/100 mg). Highly susceptible genotype LBG-623
recorded the lowest total phenol content (0.299 mg/100 mg).
Significantly lowest total sugars, reducing sugars and non reducing sugars were
recorded in highly resistant genotypes KUP 34 and KUP 40.
In field evaluation of different chemicals, two sprays of Myclobutanil @ 0.2 W.P
(31.23%), Wettable sulphur @ 0.3 W.P (32.81%) were found superior as they recorded
the lowest per cent disease index. Significant increase in shoot length, number of
primary branches per plant, number of pods per plant, 100 seed weight, seed yield was
recorded with Myclobutanil spraying at 35 and 45 DAS followed by Wettable sulphur.
Highest benefit cost ratio was observed in Wettable sulphur (1.82) followed by
Myclobutanil (1.17).
Description
D5292
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