Studies on variability in Rhizoctonia solani (Kuhn) causing root rot on cotton
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Date
2021-09
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CCSHAU, Hisar
Abstract
The present investigations entitled “ Studies on variability in Rhizoctonia solani
(Kuhn) causing root rot on Cotton.” was conducted for morphological, chemo-sensitivity and
molecular variability was carried out with twelve isolates of R. solani collected from northern
region of India. The isolates were identified on the basis of their morpho-cultural
characteristics. All the isolates of R. solani exhibited variation in their colony colour, colony
growth and pattern of sclerotia. In cultural and morphological variability maximum radial
growth after 74 hours was observed in FTB Rs10 (84.3mm) and was fastest among all the
isolates. Mycelial width varied significantly from 4.92 μm (BWN Rs5) to 7.33 μm (PWL Rs
2). Significant variation was observed in mean size of sclerotia, where the size varied between
1.16mm to 1.97mm and sclerotia colour varied significantly viz. olive brown, light and dark
brown. A significant positive Karl Pearson‘s Correlation coefficient of 0.604 was found
between sclerotia initiation and full growth of petri plate. No significant correlation was found
between other cultural and morphological characters. In molecular variability, isolates FTB
Rs10 and PWL Rs2 varied significantly. The Internal transcribed spacer ITS primers were used
for the identification of R. solani and SSR primers exhibited the genetic variability among the
isolates and generated a wide range of amplicons from 0.25 kb to 3 kb bp. Carbendazim 50%
was found significantly effective even at lower concentrations (50 ppm), Thiophanate methyl
70% was not found much effective up to 100 ppm whereas, captan 50% was least effective at
all the concentrations. The inhibition of mycelial growth noticed in T. harzianum (85.55%) that
was significantly superior to T. viride (79.25%). In future, it is likely these two isolates of
Rhizoctonia solani can be used in the breeding programme of cotton