Manjeet SinghJanvi2024-05-162024-05-162023-05https://krishikosh.egranth.ac.in/handle/1/5810209068The grey leaf spot disease of sorghum (Sorghum bicolor L. Moench.) caused by Cercospora sorghi has emerged as a seriousprobleminmost ofthe sorghumgrowingplaces of India,leadingtoconsiderableyieldlosses. The present investigation on epidemiology, management and biochemical analysis were carried out during Kharif 2022-23. Epidemiology of the pathogen was studied under field condition in two varieties (HC 136 and CSV32F) of sorghumby sowing the cropatthreedifferentdates. Outofthethree datesof sowingof sorghum,higherdisease severity,AUDPC andAIR was observed on early sown crop (15thJune) followed by normal sown crop (30th June) and least in late sown crop (15th July) on both the varieties. Disease severity,AUDPC andAIR was higher in HC 136 as compared to CSV32F in all three dates of sowingduring Kharif 2022.Temporal increasewas maximumin 30th to 31st standard meteorological week (SMW) followed by 38th to 39th SMW in both the varieties. The inhibitory effect of chemical inducers was evaluated against Cercospora sorghi under in vitro conditions and maximum mycelial growth inhibition was recorded in salicylic acid followed by indole butyric acid. Among the biorational components evaluated against C. sorghi, neem leaves extract at 20 per cent concentration and Trichodermaharzianumandwerefoundthemost effectiveinmyceliumgrowthinhibitionofthepathogenunder in vitro conditions. Out of eight fungicides evaluated against C. sorghi, under in vitro conditions, Carbendazim 50% WP and Propiconazole 25% EC at 50 µg/ml were found most effective. Under screen house conditions, salicylic acid showed maximum per cent disease control at 100 µg/ml concentration in both the variety i.e., HC 136 (susceptible) and SH 1951 (moderately resistant). The analysis of biochemical parameters like determination of total phenol content and different enzyme activities i.e., Polyphenol Oxidase (PPO), Phenylalanine AmmoniaLyase(PAL)andTyrosineAmmoniaLyase(TAL)revealedsignificantresults.Totalphenolswerefoundmaximum in plants inoculated with conidial suspension of Cercospora sorghi and increase from 0 to 96 HAI. But in other treatments it increased upto 72 HAI and then decreased in both the varieties and being higher in SH 1951. The enzyme activities were higher in plants sprayed with salicylic acid. Polyphenol Oxidase (PPO) activity continuously increased from 0 to 96 HAI in all treatments. Phenylalanine Ammonia Lyase (PAL) and Tyrosine AmmoniaLyase(TAL)activitiesincreased upto48HAIand thendecreased from48 to96HAIin alltreatmentsof both varieties. Among the best promising non conventional chemicals, botanicals, bioagents and fungicides, carbendazim 50% WP and Propiconazole 25% EC at 50 µg/ml were found under field conditions. Out of eighty five varieties of sorghum screened against grey leaf spot, twenty three and twelve varieties were highly resistant and resistant respectively. For sorghum, which is grown as fodder crop, fungicides are often not advised due to their residual impact, therefore use of chemical inducers to induce systemic resistance in plants and integrated approaches for management of grey leaf spot is, therefore, a high-priority research area.EnglishThesis