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STUDIES ON BLIGHT OF TOMATO INCITED BY Rhizoctonia solani

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Title STUDIES ON BLIGHT OF TOMATO INCITED BY Rhizoctonia solani
 
Creator SUMALATHA NALLABEEMA
 
Contributor PUSHPAVATHI, B
 
Subject BLIGHT, TOMATO, INCITED, Rhizoctonia solani,
 
Description Tomato is one of the most important vegetable crop cultivated for its fleshy fruits.
Rhizoctonia solani is the most important soilborne pathogen of tomato crop and in recent
past it is known to cause blight symptoms on stems of tomato plants which has become a
serious threat to tomato cultivation in Ranga Reddy district of Andhra pradesh.
The pathogen was isolated on PDA from blight effected tomato plants collected
from farmers’ fields and was identified as Rhizoctonia solani based on its cultural and
morphological characteristics. The culture of the fungus was greyish white in the
beginning which later turned to black in color with cottony aerial mycelial growth. The
hyphae produced branches mostly at right angles with constriction at the origin of branch
and often formed a septum near the branch origin. The fungus produced microsclerotia of
0.8 - 1.0 mm in size in sixty days old cultures.
Of the three inoculation methods, root dip inoculation was found to be the best as it
resulted in maximum per cent disease incidence (96.67) in a short period of incubation
(two days). Symptoms produced due to soil infestation and root dip inoculation appeared
as typical damping off symptoms with dark brown leasions at the collar region and
yellowing of leaves which lead to death of seedlings. Whereas, in case of stem application
the intial sympyoms appeared as water soaked lesions on stems which later became oval to
irregular light brown necrotic spots. Mature spots on stems appeared as large brown
blighted portion with typical cracks on the bark. In advanced stages plant collapsed at
infected portion leading to death of the plant.
Of the eleven tomato cultivars screened in vitro and glass house condition, Arka
abha and PKM-1 were found significantly superior over other cultivars in terms of
incidence of Rhizoctonia solani. Cultivar Arka vikas showed maximum susceptibility
towards Rhizoctonia incidence and also poor growth parameters.
Among the sources of rhizosphere soil collected, significantly highest mean cfu
count of mycoflora (27.70) and fluorescent pseudomonads (40.75) was observed in case of
samples collected from weed plants followed by healthy tomato plants. The least mean cfu
count of mycoflora (20.20) and fluorescent pseudomonads (21.31) was observed in
samples collected from diseased plants. All the antagonistic isolates were tested for their
efficacy against R. solani under in vitro condition. Among the mycoflora, the isolate M10
was found to be the potential antagonist and was identified as Trichoderma viride,
whereas the effective pseudomonad isolate P1 was identified as Pseudomonas fluorescens.
Of the eight fungicides tested propiconazole, hexaconazole, tebuconazole, captan +
hexaconazole and trifloxystrobin + tebuconazole showed cent per cent inhibition of the
growth of the pathogen over control at all the dosages tested (recommended, 75% of
recommended, 50% of the recommended, 25% of recommended dosage). Of these
chemicals, pyroclostrobin+metiram was found compatible with Trichoderma viride.
Among the IDM components tested, the treatment with potential antagonist +
effective fungicide + tolerant cultivar showed lowest per cent disease incidenc (18.67)
when compared to all other treatments tried and found to be the most effective IDM
strategy in reducing the incidence of R. solani on tomato.
 
Date 2016-09-06T11:36:59Z
2016-09-06T11:36:59Z
2014
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/75562
 
Language en
 
Relation D9551;
 
Format application/pdf
 
Publisher ACHARYA N. G. RANGA AGRICULTURAL UNIVERSITY. RAJENDRANAGAR, HYDERABAD