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STUDIES ON VARIABILITY AND MANAGEMENT OF TURCICUM LEAF BLIGHT (Exserohilum turcicum (Pass.) Leonard and Suggs) IN MAIZE

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Title STUDIES ON VARIABILITY AND MANAGEMENT OF TURCICUM LEAF BLIGHT (Exserohilum turcicum (Pass.) Leonard and Suggs) IN MAIZE
 
Creator RAJESHWAR REDDY, V
 
Contributor RANGA REDDY, R
 
Subject VARIABILITY, MANAGEMENT, TURCICUM, LEAF, BLIGHT, MAIZE
 
Description Maize is one of the important cereal crops and it is 3rd major crop in India
after rice and wheat. The crop is affected by number of fungal diseases of which leaf
blight or northern corn leaf blight or turcicum leaf blight is one of the important
diseases affecting photosynthesis with severe reduction in grain yield to an extent of
28 to 91%. Disease symptoms first appear on the leaves at any stage of plant growth,
but usually at or after anthesis. Studies were conducted on the survey, variability and
management of turcicum leaf blight of maize caused by Exserohilum turcicum.
The studies on survey reveals that high intensity of the disease was noted in
the district where mean maximum temperature was below 320C and relative humidity
was above 85 percent during the cropping season (June-October). The maximum PDI
of 51 percent was recorded in Khammam district where the maximum temperature of
31.820C and the relative humidity of 87.5 percent was recorded whereas minimum
(33 percent) PDI was recorded in Guntur district and it was due to high maximum
temperature of 35.220C and low relative humidity of 76 percent.
A total of seven isolates of E. turcicum from maize and one isolate of E.
turcicum from sorghum were chosen for variability studies. All the eight isolates of
E. turcicum showed variability in respect to cultural and morphological characters.
Based on the colony colour all the eight isolates were grouped in to 5 categories i.e
gray, dark grey, very dark gray, very darkish brown and black. Based on the
pigmentation E. turcicum isolates were grouped into 3 groups i.e black, bluish black,
greenish black. All the eight E. turcicum isolates were classified into three groups
based on the sporulation. Based on the growth eight E. turcicum isolates are
classified in to 3 groups viz., profuse growth, moderate growth and poor restricted
growth. All E. turcicum isolates were classified in to 2 groups based on colony
margin viz., regular margin and irregular margin
The Eight isolates were grown on four different solid media viz., PDA, MLE,
PCA and PDA + Yeast medium and incubated separately at three different
temperatures (200C, 250C and 300C) to study their effect on the growth of the E.
turcicum. Among the media tested, potato dextrose agar supported good growth of
the fungus followed by maize leaf extract and potato carrot agar, while least growth
was observed on Yeast + PDA medium with some exceptions. As the temperature
increases from 20 to 250C and 25 to 300C there was increase in the colony diameter
of all the isolates on four tested media.
All the isolates of E. turcicum have shown variation with respect to conidial
size and septation. Conidial size varied from1757.00 μm2 (Et5) to 3352.13 μm2 (Et1)
and the number of septa varied from 5.46 (Et8) to 9.20 (Et5). The toxin extracted
from all the eight isolates of E. turcicum was tested at three different concentration of
100 ppm, 200 ppm and 500 ppm. The results reveal that at 100ppm concentration no
symptoms were observed on detached maize leaves. While at 200 ppm the toxin
from only one isolate Et4 showed necrotic symptoms. At 500 ppm concentration all
the isolates exhibited necrotic lesion except the sorghum isolate Et8.
Pathogenicity of all the isolates was tested by spray inoculation technique on
both maize and sorghum cultivars. Considerable variation was observed among the
isolates for PDI, virulence index, lesion length and latent period. Among all the eight
isolates, on maize, the isolate Et4 (Warangal) recorded the maximum PDI (36.00),
virulence index (9.22), lesion length(13.43 cm) and shortest latent period (4.00 days)
while the minimum PDI (13.33), virulence index (1.70) and longest latent period
(8.00 days) was noticed by the sorghum isolate and isolate Et5 from Khammam
district produced minimum (4.23 cm) lesion length. Whereas on sorghum the
maximum PDI (21.33), virulence index (3.06), lesion length (11.00 cm) and shortest
latent period (7.00 days) was observed in the isolate Et6 from Mahaboobnagar
district followed by the sorghum isolate while the minimum PDI (9.33), virulence
index (0.86), lesion length (5.93 cm) and longest latent period (11.00 days) was
recorded by the isolate Et3 from Guntur district followed by the isolate Et5 from
Khammam district. The remaining isolates i.e., Et1, Et2 and Et7 recorded similar
type of reaction on both maize and sorghum.
Genetic variability of isolates was studied with Randomly Amplified
Polymorphic DNA with 20 oligonucleotide operon primers and constructed the
dendrogram using NTSys-PC package. Data generated in this study, differentiated
the test isolates into 2 major clusters A and B. Cluster A was divided into sub-
clusters A1 and A2 . A1 was further classified in to A3 and A4; A3 was differentiated
into A5 and A6. A5 was further divided into A7 and A8. cluster A2 includes
Mahaboobnagar and RangaReddy isolates, A4 includes Almora isolate, A6 includes
sorghum isolate, A7 includes Karimnagar isolate, A8 includes Guntur and Warangal
isolates; cluster B includes Khammam isolate.
The management studies showed that (mancozeb 0.25%) and (carbendazim +
mancozeb 0.25%) was significantly superior over other treatments and can be
recommended for the control of disease under field conditions.
 
Date 2016-06-29T10:24:52Z
2016-06-29T10:24:52Z
2012
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/68189
 
Language en
 
Relation D9169;
 
Format application/pdf
 
Publisher ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY RAJENDRANAGAR, HYDERABAD