Awasthi, R.P.Joshi, Pooja2018-10-232018-10-232013-06http://krishikosh.egranth.ac.in/handle/1/5810081949The Oilseed Brassica is the second largest oilseed crop after groundnut in terms of area and production in India. These crops have been known to be attacked by a variety of pathogens culminating in huge losses in seed yield. Peronospora parasitica (Pers.ex.Fr.) Fr. (new name Hyaloperonospora parasitica), Albugo candida (Pers. Ex. Lev.) Kuntze and Sclerotinia sclerotiorum (Lib) causing downy mildew, white rust and Sclerotinia rot, along with Alternaria brassicae (Berk) Sacc. Causing Alternaria Blight, respectively are the major pathogens which can cause major yield losses. A field experiment was conducted during rabi season of 2011-12 and 2012-13 at N. E. Borlaug Crop Research Centre of Govind Ballabh Pant University of Agriculture & Technology, Pantnagar (Uttarakhand) in augmented block design to study the evaluation of 480 B. juncea accessions for resistance/tolerance against major diseases to search resistant/tolerant sources or improved materials as such which have high yielding potential, taking 240 germplasms each year and was found that accession no. 491572 with 13 other accessions were highly resistant against downy mildew during 2011-12 crop season. Accession no. 491546 gave moderately resistant reaction against white rust (44.78%). None of the accession showed resistant reaction towards Alternaria blight on leaves during 2011-12 and 2012-13 crop seasons. Accession no. 491314 showed highly resistant reaction with minimum disease index on pod (12.45%) during 2011-12 crop season. Maximum plant height was attained by 113099 (170.03 cm) while maximum number of primary and secondary branches were produced by 399854 (9.42) and 426398 (17.70) respectively for 2012-13 crop season. Accession no. 426372 showed resistant reaction to Alternaria blight at pod and give high seed yield per plant with significantly higher test weight (4.90 g). During 2012-13, accession no 385673 was found to be highly resistant while 41 accessions were found to be resistant for downy mildew. Accession no. 491471 and 491326 were moderately resistant to white rust and downy mildew both during 2011-12 crop season. Accession no. 491604 was found highly resistant and moderately susceptible to downy mildew and Alternaria blight respectively as well as give higher yield and test weight during 2011-12 which could be used as donor for multiple disease resistance for the development of varieties.ennullThesis