Studies on macrophomina root rot of groundnut (Arachis hypogaea L.)
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Date
2014
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Department of Plant Pathology, BAU, Sabour
Abstract
Macrophomina root rot of groundnut (Arachis hypogaea L.) is an emerging problem in Bihar, where groundnut is extensively grow in large area as a major Kharif and spring oilseed crop. Its incidence varies from 0-32 percent in two seasons. On isolation from diseased plants, the associated pathogen was identified as Macrophomina phaseolina (Tassi.) Goid and its pathogencity was confirmed on Groundnut variety R-20 under artificially inoculated conditions. The typical symptoms of the disease may appear on roots, collar region, stem and branches of infected plants. The affected portions rotted, shriveled become darker or blakish in colour and plant collapsed and broke down from the rotted portion. Gradually affected plants showed general yellowing, drooping of leaves and ultimately death of plants before maturity. During cultural studies of the causal pathogen, M. phaseolina, Glucose asparagines agar medium supported maximum radial growth among nine different media tested fallowed by Czapek’s (dox) agar, potato dextrose agar and carrot extract. Among five tested liquid media Richard’s broth was found superior to other, in case biomass production which yielded 724.8 mg/flask after 21 days of inoculation, which was followed by Glucose asparagines, Czapek’s (dox) medium, Potato dextrose and Asthana and Howker’s agar medium.
During varietal screening, out of 20 entries of Groundnut, the cultivar, DH 86 (32.49 %) showed maximum root rot incidence percent during Kharif followed by CHICO (19.01 %). Minimum and no disease root rot percent was recorded in ICGV07214 (0.00 %). The cultivar, ICGV00338 (8.08%) showed maximum root rot incidence during Spring followed by ICGV02005 (5.71%). Minimum root rot disease incidence percent was recorded in the cultivar ICGV07210 (1.97%). Among the four fungicides namely Carbendazim, Mancozeb, Tricyclazole and Hexaconazole tested in vitro at four different concentration viz., 1ppm, 5ppm, 10 ppm, 20 ppm, 30ppm,40ppm, 50 ppm, 100 ppm, 100 ppm and 200ppm, The systemic fungicide, Carbendazim was highly effective in inhibiting the growth of the fungus at all the concentrations followed by Hexaconazole, Mancozeb and Tricyclazole. Seed treatment with different fungicides and one biological agent, maximum germination percentage 66% were observed in seed treated with Carbendazim (12%) + Mancozeb (63%) followed by thiram (30%). Minimum germination percentage observed in seed treated with Trichoderma (20%). Maximum disease incidence percent was recorded in seed treated with Trichoderma (90%) followed by thiram and Copper oxychloride. Minimum disease incidence (14%) recorded in seed treated with Carbendazim (12%) + Mancozeb (63%). Under in vitro condition the ability of Trichoderma isolates to inhibit the mycelial growth of M. phaseolina in dual culture was determined on PDA medium. A clear zone of inhibition was noted between the Macrophomina phaseolina and Trichoderma viride which near the pathogen. The inhibition growth of pathogen were recorded after 24 and48 hrs. upto 47. 61% and 35.18%, respectively in dual culture experiments.