Pathogenic variability and management of fusarium wilt of chilli (Capsicum annuum L.)
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Date
2016
Authors
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Publisher
CCSHAU
Abstract
The Fusarium wilt disease caused by Fusarium spp. has emerged as a serious problem in most of the
chilli growing irrigated tracts of India, leading to considerable yield losses in chilli (Capsicum annuum L.). The
present investigation on cultural, morphological, pathogenic and genetic variability was carried out with twentythree isolates of Fusarium spp. collected from chilli growing areas of the country. The isolates identified belonged
to F. oxysporum and F. solani based on their morpho-cultural characteristics. The average radial growth of
different isolates evaluated on different media, Czapek’s Dox agar and potato dextrose agar were the most
effective media supporting the mycelial growth (>75.0 mm). All the isolates exhibited variations in their colony
colour, type of growth and mycelial growth. Mycelia colour among the F. oxysporum isolates varied from white to
pale yellow, whereas, in F. solani the mycelial colour varied from white, cream to pale yellow. Fusarium
oxysporum isolates showed undulate fluffy, concentric fluffy, filamentous fluffy, filamentous suppressed,
filamentous scanty fibrous, undulate fluffy to entire fluffy type of growth, however, the F. solani isolates formed
only undulate fluffy and entire fluffy type of growth. Significant variations were observed in mean size of macroconidia and micro-conidia, where the F. oxysporum isolates formed larger size conidia compared to F. solani. The
average septa in F. oxysporum isolates varied from 1-3 and 1-5, whereas, F. solani isolates formed 1-5 septa.
Temporal and symptomatic wilt expression starting from 1
st
to 4
th
week on susceptible cultivars Pusa Jwala and
Arka Meghana indicated the isolates Fo5, Fo7, Fo8 and Fo10 in F. oxysporum and Fs8 in F. solani were highly
pathogenic. Amplification with genera and/or species specific internal transcribed spacer (ITS) primers clearly
differentiated all the isolates into F. oxysporum and/or F. solani isolates based on amplification and size of
amplicons in different isolates. The diversity analyses using universal rice primers (URPs) exhibited the genetic
relatedness among the twenty-three isolates varied from 0.53-0.88, i.e., 53-88 per cent with an average similarity
of 71 per cent. The URP analyses differentiated Fusarium isolates into two major clusters at similarity coefficient
of 0.53, i.e., 53 per cent similarity, where all the F. oxysporum isolates were clustered into major cluster A and all
the F. solani isolates into major cluster B. The isolates Fo5 & Fo10 in F. oxysporum and Fs8 & Fs3 in F. solani
isolates were distantly related with 48 per cent and 50 per cent genetic similarity, respectively. The in vitro and in
vivo management study involving chemicals, botanicals or antagonists as well as their integration indicated that
chemicals (carbendazim + mancozeb @ 0.1% or carbendazim @ 0.1%) applied as seed treatment + seedling root
dip + soil application were the most effective treatments and the chilli cultivar CO-4 found effective after
extensive evaluation in screen house and field, will be highly useful for the effective management of the Fusarium
wilt disease in chilli.
Description
Keywords
Fungi, Diseases, Biological development, Planting, Chillies, Pathogens, Biological phenomena, Developmental stages, Fusarium oxysporum, Fruits