D.K. JhaManoj Kumar Barnwal2024-06-292024-06-291997https://krishikosh.egranth.ac.in/handle/1/5810211179Marigold (Tagetes spp.) suffers from Blight caused by Alternaria tenuissima (Kunze) Wiltshire. The incidence and intensity of disease varied from 24.67 to 57.33 and 27.13 to 52.47 per cent, respectively depending on the different localities. Leaves, stems and flowers were found to be infected and showed characteristic symptoms of the disease. The pathogen was isolated and purified by single spore method. Koch's postulate tests were done as also the pathogen has been described in detail. Which appears to be a new host record in Chotanagpur region of Bihar. In cultural studies, the best radial growth and good sporulation of the pathogen were observed on PDA among solid media and Richards media among liquid media. Fifteen plant species belonging to nine families were evaluated during host range studies of these, only three plants viz; Gram, Pigeonpea and Salvia were infected. The maximum disease intensity appeared on 21 days old Marigold plants sown on 6th October, 1995 and 12th October, 1996, respectively. Late sowing favoured disease development. 10.05 to 26.39°C temperature, 30.23 to 87.23 per cent relative humidity and 0.00 to 13.0 mm average total rainfall favoured maximum disease development of the crop in both the year.EnglishThesis