Sekhon, P.S.Astha2017-09-292017-09-292017http://krishikosh.egranth.ac.in/handle/1/5810031982Oomycetes pathogens; Phytophthora infestans causing late blight of potato and Pseudoperonospora cubensis causing downy mildew in muskmelon are most important foliar diseases, causing significant yield losses. The present study was conducted to reduce fungicide load and work out alternate method for control of these two diseases. Different SAR compounds were tested and exogenous foliar sprays of different conc. of Salicylic acid, Jasmonic acid and Bion (Benzothiadiazole-BTH) @ 50µM, 250µM,500µM, 1000µM and of Beta amino butyric acid of 20 mM, 30mM, 50 mM, 100mM were given for inducing resistance in potato against late blight and in muskmelon against downy mildew. Twenty germplasm lines/varieties of potato and thirtythree germplasm lines/varieties of muskmelon were tested with these four compounds in year 2014, 2015 and 2016. Five lines of potato and eleven lines of muskmelon showed moderate resistance along with better response to SAR elicitors against oomycete pathogens. Concentration of Salicylic acid, Jasmonic acid and Bion @ 500 µM, and Beta amino butyric acid @ 50 mM gave good control of disease. Salicylic acid gave best results with 81.28 per cent disease control followed by Jasmonic acid with 76.23%; whereas Bion and Beta amino butyric acid were almost at par with each other and gave 74 % disease control as compared to control plants. Recommended spray schedule of fungicides gave 93 % disease control, which was at par with disease control given by Salicylic acid and BABA spray schedules in combination with contact fungicides. Protein content of treated muskmelon plant varied from 10.5 to 13.1 mg/g fresh weight compared to 5.4 mg/g fresh weight in control. Similarly, treated potato plants showed 6.4 to 7.7 mg/g fresh weight total protein as compared to 4.0 mg/g fresh weight in control. Induction of proteins and defense enzymes was systemic in nature in response to all the four elicitors. Electrophoretic protein profiling of treated potato and muskmelon plants also confirmed the induction of pathogenesis-related proteins ranging from 15- 75 kDa along with some other proteins. The inducers also stimulated enzymatic activities i.e. β-1,3 glucanase, Peroxidase (POD), Polyphenol oxidase (PPO), Phenylalanine ammonia lyase (PAL) from 26 to 99 % indicating induced resistance in treated potato and muskmelon plants as compared to control. Total chlorophyll and carotenoids also showed spike of 2% to 91 % in response to elicitors. Thus integration of disease tolerance and SA spray schedule resulted in effective and economical control in potato against late blight and in muskmelon against downy mildew.ennullThesis