STUDIES ON VARIABILITY AND MANAGEMENT OF TURCICUM LEAF BLIGHT (Exserohilum turcicum (Pass.) Leonard and Suggs) IN MAIZE
KrishiKosh
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Title |
STUDIES ON VARIABILITY AND MANAGEMENT OF TURCICUM LEAF BLIGHT (Exserohilum turcicum (Pass.) Leonard and Suggs) IN MAIZE
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Creator |
RAJESHWAR REDDY, V
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Contributor |
RANGA REDDY, R
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Subject |
VARIABILITY, MANAGEMENT, TURCICUM, LEAF, BLIGHT, MAIZE
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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. |
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Date |
2016-06-29T10:24:52Z
2016-06-29T10:24:52Z 2012 |
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Type |
Thesis
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Identifier |
http://krishikosh.egranth.ac.in/handle/1/68189
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Language |
en
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Relation |
D9169;
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Format |
application/pdf
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Publisher |
ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY RAJENDRANAGAR, HYDERABAD
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