Studies on variability and management of rhizoctonia spp. inciting root rot disease of cotton
Abstract
The present study entitled, “Studies on Variability and Management of Rhizoctonia spp.
Inciting Root Rot Disease of Cotton” was carried out in Department of Plant Pathology, CCS Haryana
Agricultural University, Hisar and RRS, Bawal. The study was aimed to know the occurrence and
incidence of cotton root rot disease in Haryana, morphological, molecular and pathogenic variability
among R. bataticola and R. solani isolates and and management of Rhizoctonia spp. through
fungicides, botanicals and native Trichoderma isolates. The maximum cotton root rot disease incidence
was recoded in Fatehabad district followed by Sirsa district, whereas; minimum was in Charkhi Dadri
district during both the year 2021 and 2022. Among all the isolates the maximum radial growth 69.33
mm was recorded in isolate RB5 followed by RS2 (59.00 mm) and RB8 (52.00 mm) whereas, the
minimum radial growth of 32.33 mm was recorded in RB3 isolate (32.33). Maximum mycelial width
was recorded in isolate RS2 (7.29 μm) followed by RB6 (7.23 μm) and RB13 (6.93 μm) whereas, the
minimum radial growth of 32.33 mm was recorded in RS1 isolate (3.58 μm). All the isolates showed
high level of polymorphism. The cluster analysis of R. bataticola isolates based on RAPD primers,
isolate RB4, RB5 and RB8 were most diverse and cluster analysis of isolates based on ISSR primers
isolate RB16 was most diverse among all the isolates. The cluster analysis of R. solani isolates based
on RAPD primers, isolate RS3 was most diverse. Among the fungicides evaluated under in vitro
conditions against RB5 and RS2, carbendazim showed maximum inhibition of the mycelial growth
(98.27% and 97.04%) of RB5 and RS2 at 200 ppm concentration which was statistically significant
than other treatments. Among the botanicals evaluated under in vitro conditions against RB5 and RS2,
Lantana camara showed maximum inhibition of the mycelial growth (77.14% and 75.67%) of RB5
and RS2 at 20 per cent concentration, where it was statistically significant than all other treatments
followed by Parthenium hysterophorus (72.11% and 71.55%) and least was showed by ginger (24.61%
and 22.75%) respectively. Evaluation of native Trichoderma isolates against Rhizoctonia spp. under in
vitro conditions revealed that HST2 showed maximum antifungal activity with 72.78, 72.50 per cent
growth inhibtion against RB5 and RS2 respectively and statistical significant than other native isolates.
As far as biocontrol activities are concerned, HST2 showed positive results for HCN production, IAA
production, siderophore production, cellulase activity, pectoloytic avtivity, ammonia production, Zn
solubilisation and phosphate solubilization. In vivo evaluation of fungicides, botanicals and bio-agents,
it was observed that they significantly reduced the disease incidence of root rot during Kharif, 2021 and
Kharif 2022 and maximum disease control was achieved by carbendazim and significantly higher with
other fungicides in both Desi and American cotton. Among botanicals under study during Kharif 2021
and Kharif, 2022, maximum disease control was recorded by Lantana camara which significantly
differed with other botanicals in both Desi and American cotton. Different Trichoderma isolates
showed the wide range of antagonistic activity against R. bataticola and R. solani. Maximum disease
control was showed by native Trichoderma isolates i.e., HST2 followed by HMT2 during both the
years of experiments.