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Epidemiology and diversity of Alternaria brassicae (Berk.) Sacc the causal agent of black leaf spot in crucifers

KrishiKosh

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Title Epidemiology and diversity of Alternaria brassicae (Berk.) Sacc the causal agent of black leaf spot in crucifers
Ph.D.
 
Creator SELVAMANI, R.
 
Contributor Sharma, Pratibha
 
Subject diseases, fungi, biological phenomena, cauliflowers, enzymes, developmental stages, alternaria brassicae, cabbages, mustard, pathogens
 
Description Title of the thesis: Epidemiology and diversity of Alternaria brassicae (Berk.) Sacc the causal
agent of black leaf spot in crucifers.
Black leaf spot caused by Alternaria brassicae (Berk.) Sacc. is an important disease of
crucifers. The present study was undertaken to evaluate the epidemiology and diversity of
Alternaria brassicae in different varities of cabbage, cauliflower and mustard. Disease
progression studies under field conditions revealed that there was periodical increase in lesion
number and Per cent Disease Index (PDI). PDI progression was higher in mustard varieties
followed by cauliflower and cabbage varieties. The speed of progression of disease among the
crop cultivars was calculated by using Area Under Disease Progress Curve (AUDPC) and
apparent rate of infection (r-value). Highest AUDPC value was recorded on Pusa Bold variety of
mustard and the lowest was recorded on CJ-182 variety of cabbage. This may enable to select the
slow disease progressing varieties for the management of the disease. Relative humidity was
found negatively correlated with the development of disease. On the contrary, maximum and
minimum temperature was positively correlated with disease development. A total of forty
isolates were collected from different parts of the country and its cultural, morphological and
pathogenic variability were studied. All the isolates showed high level of variability in vitro in
respect to mycelia growth, growth pattern and sporulation. Higher growth rate and high number
of spore production were recorded on Cauliflower Leaf Extract Agar (CLEA) followed by Potato
Dextrose Agar (PDA) and Czepak Dox Agar (CDA). Substantial variation was found in spore
morphology in respect to conidial length, width and number of septa. Detached leaf technique
was carried out on fifteen varieties and it revealed that all these isolates behaved differently on
differentials. The Per Cent Disease Index (PDI) varied from 0-100 per cent. The studies,
therefore, indicated the existence of variability among isolates of Alternaria brassicae. High
level of variability was observed in respect to enzyme production and most of the isolates
produced more cellulase than lipase and pectinase. The pectinase production also has been
correlated with disease development. Brassinin hydrolase has played an important role in antifungal
activity which inhibits the spore germination, growth and development. Protein profiling
studies revealed that the isolates were grouped into three distinct groups. Among the two
techniques used to identify the polymorphism at molecular level, Randomly Amplified
Polymorphic DNA (RAPD) marker given more polymorphism than the Internal Transcribed
Spacer (ITS) region.
 
Date 2016-03-07T15:24:47Z
2016-03-07T15:24:47Z
2014
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/64886
 
Language en_US
 
Format application/pdf
 
Publisher IARI, Division of Plant Pathology, New Delhi