Sharma, PushpHarmandeep Kaur2021-08-232021-08-232021Harmandeep Kaur (2021). Variations for traits associated with heat tolerance in Indian mustard (Brassica juncea L. Czern and Coss) germplasm (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.https://krishikosh.egranth.ac.in/handle/1/5810174271The present investigation was conducted to assess the variations for traits associated with heat tolerance in Indian mustard (Brassica juncea L. Czern and Coss) germplasm at seedling and terminal stages. Field experiment was conducted in rabi season (2017-18) at Punjab Agricultural University, Ludhiana at two dates of sowing i.e. timely sown and late sown conditions. Heat stress at early seedling stage lead to seedling mortality thus affecting plant population and seed yield Terminal heat stress caused by delayed sowing shortened the phenological durations to variable extent, significantly reduced the physiological traits like photosynthetic pigments, SPAD value (7.2%), RWC (8%), LWR (17.2%) while increased the RSD (23.9%), WSD (23.9%), LWL (30.4%), membrane injury (6.9%) and MDA (57.2%). Antioxidative enzymes like SOD (40.4%), CAT (69.3%) and POX (76.7%) were upregulated along with other biomolecules like ascorbic acid (65.4%) which increased significantly for the protection against the late sowing/ stressful environment. Total soluble sugars decreased by 36.8%, reducing sugars by 44.7% and non-reducing sugars by 32.4% with delayed planting. Growth parameters, yield attributes and seed yield were reduced significantly with late sowing as compared to optimum sowing date. However, variations existed within genotypes for different studied traits. Seed yield under late sown condition had positive and significant correlation with siliquing duration (r= 0.600*) and reproductive phase (r= 0.558*) whereas, negative with flowering completion (r= -0.573*) and siliqua initiation (r= -0.519*). Biological yield had significant association with seed yield under timely sown (r= 0.774**) and late sown (r= 0.841**) conditions. Similarly, biological yield had strong relationship with seed yield both under timely sown (R2= 0.5985) and late sown (R2= 0.7075) conditions. Genotype IAN was rated heat tolerant with seedling mortality ≤30%, seed yield reduction ≤30%, HTI (≥0.5), HSI (≤1.0), YSI (≥0.71), lesser decline in the physiological traits added with relatively higher antioxidative enzymes.EnglishThesis