SHARMA, J.N.ARJUN, SINGH2017-01-042017-01-04201247718http://krishikosh.egranth.ac.in/handle/1/94372ABSTRACT The present investigation entitled “Studies on sensitivity and monitoring for resistance to fungicides in Marssonina coronaria causing premature leaf fall of apple” was undertaken to study the baseline sensitivity and sensitivity of different isolates of Marssonina coronaria causing premature leaf fall of apple in Shimla district of Himachal Pradesh against systemic and non-systemic fungicides, in terms of their EC50, Minimum Inhibitory Concentration (MIC) and Resistance Factor (RF). Baseline sensitivity of wild isolate of Marssonina coronaria after 24 hours of incubation it ranged from 0.704μg/ml in copper oxychloride to 0.966 μg/ml in Propineb. Similarly, after 48 hours of incubation it ranged from 0.712 μg/ml in carbendazim to 0.980 μg/ml in mancozeb. Minimum Inhibitory Concentration of wild isolate ranged from 80 to 160 ppm in non-systemic and 80 ppm in systemic fungicides, which showed different levels of sensitivity to different fungicides. Ten different fungicides, viz. mancozeb, zineb, propineb, captan, dodine, metiram, chlorothalonil, copper oxychloride, carbendazim and thiophanate methyl were evaluated at different concentrations (5 to 160 ppm) for their sensitivity against five different isolates collected from Shimla district of Himachal Pradesh. All fungicides tested against different isolates were moderate to highly sensitive in respect of premature leaf fall of apple. Resistance Factor shown by fungicides increased 1 to 2 times from the baseline value, however, it did not reveal development of resistance against commonly used fungicides, which means that the isolates were still sensitive to these fungicides. On the basis of sensitivity and MIC shown by different fungicides, it concluded that dodine followed by carbendazim, metiram, chlorothalonil, propineb, mancozeb, thiophanate methyl and zineb were highly effective in controlling Marssonina coronaria causing premature leaf fall of apple while, copper oxychloride and captan were less effective against different isolates collected from Shimla district of Himachal Pradesh.enThesis