Molecular Variability, Host Range and Management of Rhizoctonia solani (Kühn) causing Root Rot of Fenugreek (Trigonella foenum-graecum)
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Date
2022
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Abstract
Root rot of fenugreek (Trigonella foenum-graecum L.) caused by
Rhizoctonia solani has become an important constraint to the growers of
fenugreek in Rajasthan. Disease incidence varied from 24.98 to 32.81 per cent
in five surveyed districts of Rajasthan. Maximum disease incidence was
recorded in Jaipur (32.81%) followed by Jhunjhunu (32.73%), Nagaur
(29.81%), Ajmer (27.98%) and it was lowest in district Bikaner (24.62%). In
Rajasthan, the overall average of disease incidence was 29.59 per cent in 150
fields of 30 villages of five districts.
Isolation from infected roots yielded Rhizoctonia solani and proved
pathogenic by soil inoculation technique. Significant morphological, cultural and
pathogenic variability were observed among twelve isolates of Rhizoctonia
solani collected from Jaipur, Jhunjhunu, Nagaur, Ajmer and Bikaner districts of
Rajasthan. Twelve isolates of the pathogen, were coded as JPR Rs-1, JPR Rs 2, BKN Rs-3, BKN Rs-4, AJM Rs-5, AJM Rs-6, JJN Rs-7, JJN Rs-8, NAG Rs 9, NAG Rs-10, LCL Rs-11 and LCL Rs-12. Isolate JPR Rs-1 (Jaipur isolate)
proved to be most virulent in causing root rot of fenugreek in comparison to
other isolates.
OPA markers were showed 81.81% (OPA5) to 100% (OPA2, OPA4,
OPA7, OPA11 and OPA12) polymorphism, Highest marker index (0.66),
heterozygosity index (0.66) and discriminating power (0.90) values were
exhibited by OPA3 markerUnder host range studies, Rhizoctonia solani cause root rot in chick pea,
chilli, coriander, fenugreek, cumin, wheat, barley, okra, field pea, tomato, fennel
and cabbage but spinach was not infected.
In all twenty five, genotypes / varieties of fenugreek were recorded
minimum disease incidence in UM-208 and UM-209 genotype.
Seven plant extract namely; mehndi, holy basil, clove, cinnamon, annise,
giloy and ginger were evaluated against Rhizoctonia solani. Clove treated petri plate gave the maximum inhibition of mycelial growth and clove @ 10 per cent
treated seed gave minimum disease incidence and highest yield of fenugreek.
Under the different biocontrol agents i.e., Trichoderma harzianum,
Trichoderma viride, Bacillus subtillis and Pseudomonas flurosence,
Trichoderma harzianum resulted that maximum inhibition mycelial growth. T.
harzianum @ 6 g kg-1 seed + Neem cake 250 kg ha-1 soil application showed
minimum disease incidence and highest yield of fenugreek.
All the tested seven fungicides namely; iprobenfos 48% EC,
tebuconazole 25.9% W/W, propiconazole 25% EC, difenoconazole 25% EC,
carboxin 37.5% + thiram 37.5% DS, hexaconazole 5% EC, and azoxystrobin
8.3% + mancozeb 66.7% WG were evaluated different concentration and
resulted that tebuconazole 25.9% recorded maximum inhibition mycelial growth
and tebuconazole @ 0.2% treated seed gave minimum disease incidence and
highest yield of fenugreek