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PATHOGENIC AND MOLECULAR CHARACTERIZATION OF Alternaria helianthi (Hansf.) Tubaki and Nishihara, THE INCITANT OF SUNFLOWER LEAF BLIGHT

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Title PATHOGENIC AND MOLECULAR CHARACTERIZATION OF Alternaria helianthi (Hansf.) Tubaki and Nishihara, THE INCITANT OF SUNFLOWER LEAF BLIGHT
 
Creator RAJENDER, J
 
Contributor PUSHPAVATHI, B
 
Subject PATHOGENIC,MOLECULAR, Tubaki, Nishihara, INCITANT, SUNFLOWER, LEAF, BLIGHT
 
Description A study on characterization of Alternaria helianthi populations with reference
to cultural, morphological, biochemical and amplification patterns of genomic DNA
has been taken up to ascertain the pathogenic and molecular variability in
A. helianthi isolates. A total of 25 isolates of A. helianthi representing four important
sunflower growing states in India were collected in pure form from DOR,
Rajendranagar, Hyderabad for this purpose.
Pathogenicity of all the isolates were proved on Morden, a blight susceptible
sunflower cultivar by adopting spray inoculation method. Among the 25 isolates, the
per cent disease index ranged from 15.53 % (Ah-8) to 61.43 % (Ah-21). Isolate
Ah-21 was found most virulent and recorded highest virulence index (23.81) with
shortest latent period (2.66 days), while the isolate Ah-8 recorded the lowest
virulence index (3.07) with longest latent period (5 days). Based on per cent disease
index on Morden, the 25 isolates were grouped into three pathogenicity groups viz.,
low ( 50 % PDI) pathogenicity
groups.
The isolates varied significantly for cultural and morphological
characteristics. Among the 25 isolates, six isolates (Ah-2, Ah-5, Ah-7, Ah-18, Ah-23
and Ah-25) showed circular growth pattern and the remaining isolates recorded
irregular growth with wavy margin. Based on variation in pigmentation and colour of
aerial mycelium, 25 isolates were categorized into five types viz., yellowish brown to
dark brown pigmentation with grey to brown aerial mycelium, yellowish brown
to dark brown pigmentation with whitish grey to white aerial mycelium, light brown
to dark grey pigmentation with grey to brown aerial mycelium, dark grey
pigmentation with whitish grey aerial mycelium and light grey pigmentation with
brown to whitish grey aerial mycelium. Variation in colony diameter varied from
21.00 mm (Ah-19) to 42.00 mm (Ah-24). With regard to sporulation the isolates
Ah-2, Ah-12, Ah-21, Ah-24 and Ah-25 had recorded abundant sporulation
(>12 × 104 spores ml-1), while the isolates Ah-3, Ah-14 and Ah-18 showed scanty
sporulation (< 4× 104 spores ml-1) and the remaining fell inbetween.
Among the isolates studied, the range of average conidial length and width
varied from 124.23 ± 4.58 (Ah-23) to 158.42 ± 3.88 μm (Ah-12) and from 30.66 ±
5.7 (Ah-9) to 40.09 ± 3.76 μm (Ah-25) respectively. The average septation was
highest in isolate Ah-7 (8.9 ± 1.04), while that was least in Ah-3 (6.04 ± 1.07). Based
on similarity in morphological and colony growth characters, the 25 isolates were
categorized into seven groups and from each group one representative member were
evaluated for variability in pathogenicity by using of five selected differential
cultivars (DRSH-1, DRSF108, KBSH-44, KBSH-1, and NDSH-1) along with one
susceptible genotype (Morden). Though all seven isolates induced symptoms on all
the differentials, their level of virulence varied greatly across the host cultivars. The
isolate Ah-21 was found highly virulent with highest mean virulence index (15.22)
and Ah-18 was found least virulent with lowest mean virulence index (4.56).
Among the isolates tested significant variation was observed in bio-chemical
composition. Maximum total sugars were found with the isolate Ah-25 (13.28 mg)
while the minimum was noticed in Ah-13 (3.10 mg). Similarly, the highest total
proteins content were found with the isolate Ah-25 (21.43 mg) and the lowest with
isolate Ah-15 (9.53 mg). Across the isolates, the total free amino acids were ranged
between 5.67 mg (Ah-15) to 21.24 mg (Ah-21).
The phytotoxicity of toxin isolated from 25 isolates of A. helianthi was tested
at 50, 100, 200 and 500 ppm concentrations on sunflower leaves by using detached
leaf technique. Isolates Ah-1, Ah-2, Ah-4, Ah-7, Ah-12, Ah-17, Ah-21, Ah-24 and
Ah-25 showed necrotic lesions at a toxin concentration of 100 ppm. At 200 ppm
concentration of toxin, the isolate Ah-3, Ah-5, Ah-6, Ah-9, Ah-10, Ah-11, Ah-16,
Ah-18 and Ah-23 exhibited symptoms, while same lesions were observed with the
isolates Ah-8, Ah-13, Ah-14, Ah-15, Ah-19, Ah-20 and Ah-22 at 500 ppm.
The isolates of A. helianthi when subjected to ISSR analysis showed high
degree of polymorphism at DNA level. Among the 30 Inter Simple Sequence Repeat
primers used for amplification, only twelve able to amplify the DNA of the fungal
isolates. Of these, the polymorphisms were higher for the primers UBC-819,
UBC-831, UBC-879 and UBC-888 followed by UBC-849. Least polymorphisms
were observed with UBC 834. Based on similarity index, the 25 isolates were
clustered into seven groups. The cluster composition varied for ISSR analysis and
morphological analysis, and these two were found independent.
 
Date 2016-06-29T10:31:11Z
2016-06-29T10:31:11Z
2012
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/68191
 
Language en
 
Relation D9170;
 
Format application/pdf
 
Publisher ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY RAJENDRANAGAR, HYDERABAD