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|Title:||Studies on Epidemiology of False Smut (Ustilaginoidea virens) of Rice and Its Sustainable Management|
|Publisher:||Department of Plant Pathology, BAU, Sabour|
|Abstract:||False smut of rice caused Ustilaginoidea virens is considered as one of the emerging disease. The reasons for emergence of this disease are mainly attributed to climate change and intensive rice cultivation. There is little information available with respect to biology and epidemiology if the disease in Bihar. Present study was conducted to understand the biology and epidemiology of false smut of the pathogen. The fungus was isolated by ‘standard ball isolation technique’ of Ustilaginoidea virens and incubated at 27±1°C. Fungus was initially isolated based on the characters described viz., fluffy white growth on PDA and moniliform mycelium with oval or round in shaped conidia. Further, the identity of the fungi was confirmed by the taxonomist’s examination at ‘Indian type culture collection’, New Delhi. Maximum mycelial growth of was U. virens observed on potato sucrose agar medium (32.64 mm) and at pH 6.0 (68.82 mm). Under in vitro evaluation of fungicides against the false smut fungus, all the treatments were found inhibiting the fungal growth at all the concentrations (10, 25, 50, 100 ppm). Among six fungicides, propiconazole was found to be best at all the concentration with cent per cent inhibition at 50 and 100 ppm followed by Azoxystrobin and hexaconazole having cent per cent inhibition at 100 ppm concentration and the least inhibition was observed at in Copper oxy chloride at all concentrations. Among four nano particles, Silver nanoparticles (67.11% inhibition) were highly effective in controlling the fungus at 100 ppm followed by silicon carbide (60.17%) and minimum achieved by aluminium nanoparticles (55.92%) at 100 ppm concentration. Disease severity and disease incidence were observed highest in Sabour ardhajal (19.54% and 52.83% severity and incidence respectively) followed by Sushak samrat (16.66% and 35.56%) and lowest in Sahbhagi (14.72% and 17.41%). Disease severity and disease incidence were maximum in crop sown during 25th June (17.23% and 43.37%) and minimum disease severity and disease incidence was observed in 15th July (15.62% and 23.77%). There was no significant interaction observed between varieties and date of sowing. Epidemiology of pathogen revealed that the maximum disease severity (52.83%) and disease incidence (19.54%) occurred at temperature range between 23.14-31.36ºC, relative humidity (73.50-88.85%), rainfall (6.66 mm) and sunshine hrs (6.20 hrs) in Sabour ardhajal which were flowered during 25th Sept to 20th Oct than other varieties whereas, minimum disease incidence (14.72%) and disease severity (17.41%) occurred in Sahbhagi when flowered during 10th Sept to 5th Oct at same range of temperature and relative humidity but at low sunshine hrs (4.81 hrs) and high rainfall (7.27 mm). Among different date of sowing disease incidence and severity were highest in 25th June sown crop which flowered during 15th Sept to 5th Oct, when temperature, relative humidity, rainfall and sunshine hours occurred between 23.17-31.44ºC, 74.00-87.48%, 6.67 mm and 6.29 hrs. Lowest disease incidence (15.62%) and disease severity (23.77%) were found during 15th July sowing which flowered during 5th Oct to 25th Oct, when rainfall was lower than 0.2 mm besides temperature, relative humidity and sunshine hrs which was relatively similar as 25th June sown crop. In Crop flowered during 7th Sep to 30th Sep and 25th Sept to 15th Oct the disease incidence and severity was lower than crop flowered during during15th Sept to 5th Oct. Among the growth character of different varieties on different date of sowing revealed that germination percentage, days to 50 per cent flowering and days to maturity was highest in Sabour Ardhajal and least in IR-64. 15th July sowing had highest days to 50% flowering and 25th June had least days to 50% flowering. The days to maturity were vice versa to days to 50 per cent flowering for date of sowing. Grain yield and chaffy grain/panicle were found to be highest in Sushak samrat. Lowest grain yield was observed in Sahbhagi and chaffy grains/panicle was in Sabour ardhajal. During 25th June sowing highest yield (41.20 q/ha) and chaffy grains/panicle (22.40 grains/ panicle) were found whereas lowest was found during 15th July (36.93 q/ha) in case of yield and during 5th July (18.40 grains/panicle) in case of chaffy grains/panicle.|
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