STUDIES ON Alternaria solani CAUSING EARLY BLIGHT DISEASE IN TOMATO (Lycopersicon esculentum Mill.)

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Date
2017
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Indira Gandhi Krishi Vishwavidyalaya, Raipur (C.G.)
Abstract
The present investigation on “Studies on Alternaria solani causing early blight disease in tomato (Lycopersicon esculentum Mill) was carried out in the Department of Plant Pathology, S.K.College of Agriculture and research station (IGKV, Raipur), Kawardha, during 2016-17. Among the several disease of tomato, early blight of tomato is one of the most destructive diseases, which cause heavy losses in fruit yield on tomato. The symptoms of early blight of tomato were first observed as small brown water soaked lesion on the older leaf. Symptoms also reported on stem and petioles as brown to dark brown elongated target board type spots on leaf, stem and fruit. Survey carried out during Rabi 2016-17 revealed that severity of early blight of tomato was more in Mungeli district followed by Rajnandgaon and Kabirdham district. In case of village the highest PDI was noticed in Kalegondi village of Rajnandgaon district, while the lowest PDI was recorded in Arasnara village of Durg district. Maximum AUDPC was recorded in Rajnandgaon district followed by Mungeli. However, least AUDPC was found in Durg district. Alternaria solani was identified as the pathogen of early blight disease on the basis of morphological characters and pathogenicity test. The conidia were observed solitary straight and slightly flexuous oblong or muriform or ellipsoidal tapering to beak, pale or olivaceous brown colour, length 28-75μm and 15-20μm thick in the broadest part with 8- 10 transverse and 0-4 longitudinal septa. Among the isolates of A.solani, different culture media were exhibited variation in respect of colony colour, substrate colour, growth pattern, margin colour, topography, thickness of mycelium and sporulation. Alternaria solani produce grayish, dark brown, grayish black to olive green colony colour in different isolate on different medium. Growth pattern were also varied among the isolates from circular smooth to irregular rough. Margin colour of colony was varied from whitish to brown among the isolates. Isolates produce Aerial, submerge to merge topography. Margin colour of colony was varied from whitish to brown among the isolates of A. solani. Water agar media produce maximum sporulation in all seven isolates. Among the fourteen solid culture media, potato dextrose agar medium produce maximum mycelia growth followed by oat mea agar media, while water agar medium was produce minimum mycelium growth. However, in liquid media oatmeal broth gave higher biomass followed by potato dextrose agar media. Minimum biomass was obtained in mineral broth. The fungus preferred neutral pH level (6.0-7.0) for better growth and sporulation. The pathogen showed maximum growth and sporulation at 25-30°C temperature. Among the fungicides, most effective fungicide was found Hexaconazole 5%EC followed by Thiafluzamide 24% SC under in vitro condition. Among the plant extacts, Allium sativum gave maximum inhibition of mycelial growth followed by Crotalaria juncea and Azadirachta indica, while Euphorbia hirta was showed least mycelium inhibition. Out of the different bio-agents tested, P. fluorescens was found most effective followed by Trichoderma harzianum under in vitro condition. Under field conditions, integrated effect of fungicides, P. fluorescens and NSKE was studied to determine effectiveness of integrated management strategy. All the treated plots showed significantly less percent disease index than untreated plot.T5=Propineb @ 3g /kg (ST) + Trifloxystrobin 25% + tebuconazole 50% WG @ 0. 05% (FS) + NSKE @5% (FS) was found the most effective followed by T6=Propineb @ 3g /kg (ST) + Azoxystrobin 23%SC @ 0.1% + NSKE @5% (FS). While, treatment T7=Propineb @ 3g /kg (ST) + NSKE @ 5% (FS) + Pseudomonas florescence @ 1x 109 was found less effective over the control. The number of fruits per plant was found maximum in the plot which sprayed with T5=Propineb @ 3g /kg (ST) + Trifloxystrobin 25% + tebuconazole 50% WG @ 0.05% (FS) + NSKE @5% (FS). The field evaluation of integrated management indicate that the Propineb @ 3g /kg (ST) + Trifloxystrobin 25% + tebuconazole 50% WG @ 0. 05% (FS) + NSKE @5% (FS) found most effective for the management of early blight disease, produce maximum fruit yield and net return.
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