“MANAGEMENT OF TURCICUM BLIGHT (Exserohilum turcicum (Pass.) Leonard and Suggs) OF MAIZE BY PHYLLOSPHERE MICROFLORA”
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Date
2019
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PROFESSOR JAYASHANKAR TELANGANA STATE AGRICULTURAL UNIVERSITY
Abstract
Maize (Zea mays L.) is one of the important cereal crops of the world and world’s
third leading cereal crop, after wheat and rice. Maize crop is prone to several foliar and
stalk rot diseases. Among the foliar diseases, turcicum leaf blight incited by the fungus
Exserohilum turcicum (Pass.) Leonard and Suggs has become a major threat and results
in severe reduction in grain yield to an extent of 28 to 91 per cent.
Keeping in view of importance of this disease, studies were conducted on survey
for the disease incidence of E. turcicum in major maize growing areas of Telangana;
cultural and morphological variability among the isolates; isolation and characterization
of phyllosphere microflora; screening of phyllosphere microflora against E. turcicum in
vitro; compatibility of fungicides with phyllosphere microflora and screening of potential
antagonists for their growth promoting activities in vitro.
A roving survey was conducted during Kharif, 2018 in major maize growing areas
of Telangana to assess the status of turcicum blight incidence of maize. The mean
maximum turcicum blight incidence was recorded in Karimnagar district 31.5 per cent
followed by Mahaboobnagar 28.6 per cent and Ranga Reddy 20.1 per cent. The highest
disease incidence of 45.0 per cent was recorded in Chinthakuntla village of Karimnagar
district and least disease incidence of 9.0 per cent was recorded in Dandumailaram village
of Ranga Reddy district.
Cultural and morphological variability among the twelve isolates were studied
by growing isolates on different media i.e., Maize leaf extract agar, Potato dextrose
agar, Potato carrot agar and Yeast + PDA. Among the media tested, maize leaf extract
agar supported good growth of the fungus with excellent radial growth
and high sporulation followed by potato dextrose agar and potato carrot agar,
while sporulation was not observed on Yeast + PDA medium.
Twenty-two bacterial cultures (P1 to P22) and six fungal cultures were isolated
from the phyllosphere by leaf imprint method and dilution method. The colony characters
of isolates of bacteria and fungi pertaining to their shape, size, elevation, margin, texture,
appearance and pigmentation were recorded. Gram’s staining and endospore staining
revealed that P1, P4, P6, P7, P12, P14 and P16 were Gram positive, endospores and rod
shaped.
Biochemical tests revealed that all the twenty-two isolates were positive for the
catalase and oxidase test. Isolates P1, P6, P7, P14, P16, P17 and P22 showed positive results
to Voges proskauer test. Isolates of phyllosphere bacteria P2, P3, P5, P8, P10, P11, P13, P15
and P21 revealed positive results to Indole test. Whereas, isolates P1, P4, P6, P7 and P22
showed negative reaction to methyl red test. The phyllosphere bacterial isolates P8, P15,
P17, P18, P19, P21 and P22 recorded negative reaction to gelatin liquefaction.
Screening of phyllosphere microflora against E. turcicum was conducted
following dual culture technique for all the isolates. Phyllosphere bacterial isolate P9
recorded maximum growth inhibition of 24.09 per cent radial growth of the test pathogen.
Fungal isolate Aspergillus niger showed highest inhibition 60.6 per cent compared to
other isolates.
Compatibility of six fungicides with potential bacteria and fungi were tested by
turbidometry and poisoned food technique. The growth of phyllosphere bacterial isolate
of P9 and isolate P16 was highest in carbendazim + mancozeb showing OD value of 3.14
and 2.54 respectively, indicating that carbendazim + mancozeb was compatible with the
phyllosphere bacterial isolates. Propiconozole was compatible with Aspergillus niger
fungal isolate.
The potential phyllosphere isolate P9 and isolate P16 along with compatible
fungicide were tested for their growth promoting activities under laboratory conditions.
Seed treatment with (carbendazim + mancozeb) + isolate P9 + isolate P16 not only
increased germination by 95.22 per cent but also enhanced seedling vigour (2394.78).
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D10,395