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INTEGRATED MANAGEMENT OF STEM AND POD ROT OF GROUNDNUT CAUSED BY Sclerotium rolfsii Sacc.

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Title INTEGRATED MANAGEMENT OF STEM AND POD ROT OF GROUNDNUT CAUSED BY Sclerotium rolfsii Sacc.
 
Creator RAKHOLIYA KALUBHAI BALUBHAI
 
Contributor Jadeja K. B.
 
Subject GROUNDNUT
PLANT PATHOLOGY
 
Description Groundnut (Arachis hypogaea L.) is an important leguminous edible oilseed crop. Stem and pod rot of groundnut caused by Sclerotium rolfsii is an economically important disease of groundnut. Looking to the high disease incidence in Kharif season and economic damage due to stem and pod rot some basic and applied research studies were carried out.
The initial symptoms expressed yellowing and wilting of branches. Under high humidity and moist soil surface this fungus produced white mycelium around affected plants at or near the soil surface. Abandant sclerotia were produced on the mycelial mat on the affected plant parts adjacent to soil surface. The sclerotia were initially white later turned brown to dark brown when mature. Shredded stems and peg tissue were noticed as typical symptom.
The affected branches or whole plant died. Peg and pods were also affected and seeds of severely affected pods were discolored.
The fungal pathogen was isolated from diseased plant on PDA. The Koch’s postulates were successfully proved on groundnut cv. GG-20 and GG-7.
Thirty isolates of pathogen collected from different locations of Saurashtra region and IARI, New Delhi differed in morphological characters viz. mycelial growth, colony colour, mycelial appearance, sclerotial colour, size, shape, weight and arrangement. Basidiospores were not observed in any of the isolates when tested on C-PDA medium.
During the survey stem rot incidence ranged from 2 to 40 per cent in 76 locations of Saurashtra. The highest incidence was observed in Keshod and Vanthali talukas of Junagadh district followed by Amreli, Rajkot, Jamnagar, Bhavnagar and Porbandar districts. The avoidable pod yield loss due to stem and pod rot was 40.89 per cent which was equivalent to loss of 856 kg/ha or Rs. 17120 /ha.
The plant species viz. castor, sorghum, wheat, cumin, bottle gourd, and bitter gourd remained disease free from S. rolfsii infection during host ranged study. Two weed plants viz. Sickle pod (Cassia tora L.) and beggar (Desmodium triquetrum L.) were recorded as new hosts of S. rolfsii in the present investigation.
Total phenol content decreased in infected tissues of highly susceptible and susceptible varieties of groundnut as compared to healthy tissues. However phenol content was higher in infected tissues of moderately resistant varieties of groundnut than healthy.
Total sugars and oxalic acid were higher in infected stem tissues of groundnut as compared to healthy tissues.
Maximum oxalic acid was recorded in the isolate CTRI-2754 (1.60mg/5ml filtrate) followed by Keshod isolate (1.44mg/5ml). Maximum dry mycelium weight (896.67mg) was recorded in the Dhoraji isolate.
The cellulase and PG activity in the culture medium decreased under the growth inhibition of test pathogen due to Trichoderma isolates.
The activity of -1,3-glucanase was recorded maximum in T. harzianum-4J v/s S. rolfsii (4.21 μM glucose/min/ml CF). The -1,3-glucanase activity in the culture increased with increase in growth inhibition of the pathogen by respective antagonists. Chitinase activity also increased during antagonism and its highest activity was recorded in the culture medium of T. viride (Bang.) v/s S. rolfsii followed by T. viride (Local) v/s S. rolfsii.
Laboratory screening of fungicides, insecticides, weedicides and fertilizers were carried out against the pathogen. Among the fungicides, vitavax, propiconazole, hexaconazole, mancozeb and carbendazim 50 wp + mancozeb 75 wp, (1:2 manual mixture) exhibited cent per cent growth inhibition at all the concentrations. Similarly the insecticides viz. chlorphyriphos and endosulfan also inhibited cent per cent growth at 750, 1000 and 1500 ppm. The herbicides viz. quizalofop-ethyl and metsulfuran were also highly effective and showed cent per cent growth inhibition of S. rolfsii at all concentrations tried. Complete growth
inhibition was also recorded in IFFCO-NPK at 4000 ppm concentration. Sclerotial formation was hampered in CAN, NPK 12:32:16 (IFFCO), SSP and DAP at 3000 and 4000 ppm concentrations.
Ten selective chemicals were tested for germination of sclerotia of S. rolfsii under in vitro conditions and cent per cent sclerotial germination inhibition was reported in hexaconazole and vitavax.
Cent per cent growth inhibition of all the isolates of S. rolfsii was found in propiconazole (500 ppm) and tebuconazole (500 ppm) and vitavax power (2000 ppm), while sensitivity of mancozeb (2500 ppm) varied against different isolates.
Ten selective isolates of Trichoderma were tested against the S. rolfsii under in vitro condition and highest inhibition of S. rolfsii (77.41%) was observed in the presence of T. harzianum–4J followed by T. viride (68.52%)) and T. harzianum-2J (64.44%). Looking to the overgrowing of Trichoderma on S. rolfsii, T. viride (Local) and T. viride (Bang.) completely overgrew the pathogen and categorized into R1 as per modified Bell’s scale. Trichoderma viride (Local) was also tested against 23 isolates of the pathogen. The growth inhibition of the isolates ranged from 44.44 to 74.93 per cent.
Different seed treatments were evaluated under field condition for stem and pod rot management. Minimum disease incidence was recorded in the seed treatment of Trichoderma
harzianum 10.00g/kg seed followed by vitavax power (vitavax + thiram) 3.0 g/kg seed and tebuconazole 1.25 g/kg seed.
Efficacy of different soil amendments with Trichoderma harzianum on disease incidence was conducted in field conditions for two Kharif seasons. Minimum stem and pod rot incidence was recorded in the treatment of caster cake @500 kg/ha amended with T. harzianum@1.5kg/ha followed by FYM @ 500kg/ha amended with T. harzianum @ 1.5kg/ha.
An experiment on integrated management of stem and pod rot of groundnut was conducted under field condition. Highest pod yield (2176 kg/ha) and minimum disease incidence (23.09%) was recorded in preemergence spraying of fluchloraline @1.5kg a.i./ha + seed treatment with vitavax power (vitavax + thiram) 3.0 gm/kg seed + furrow application of T. harzianum @1.5 kg/ha mixed in 300 kg FYM at sowing time + three sprayings of hexaconazole (0.005%) at 35, 55 and 75 days after sowing.
None of the varieties was resistant against stem and pod rot disease, when 14 groundnut cultivars screened under artificially inoculated micro plots. Two varieties viz. GG-11 and GG-13 were found moderately resistant, eight varieties viz. J-11, GG-4, GG-6, JL-24, TG-26, TAG-24, BAU-13 and ICGV-86564 were susceptible and rest four varieties viz. GG-2, GG-5, GG-7 and GG-20 were highly susceptible. Under natural conditions three groundnut lines viz. JB-113, JB-1140 and JB-1155 were moderately resistant to S. rolfsii.
 
Date 2016-09-21T09:25:53Z
2016-09-21T09:25:53Z
2009-10
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/77873
 
Language en
 
Format application/pdf