Sharma, PushpMamta Pal2023-12-112023-12-112023Mamta Pal (2023). Physiological and biochemical variability in Brassicas under conservation tillage (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.https://krishikosh.egranth.ac.in/handle/1/5810202469Drought is a multifarious stress affecting almost all the growth stages and yield in Brassicas. Present investigation was carried out to assess germination and tolerance to moisture stress induced by different concentration of PEG in laboratory. Comparative germination studies for drought tolerance using distilled water as control and six osmotic potentials (-0.2, -0.4, -0.6, -0.8, 1.0 and -1.2 MPa) induced by PEG 6000 were carried out under controlled condition. All the germination traits suffered a decline over control with increased stress levels except to mean germination time. The three varieties GSC-7 (B.napus), Giriraj (B. juncea) and PC-6 (B. carinata) exhibited better performance for germination and related traits in the induced six stress levels over the control which was further endorsed by PCA and HCA. Field trials were conducted for 2 years to study the morpho-physiological and biochemical variability in Brassicas under conservation tillage. Twelve varieties/strains of the three Brassica species: B.napus (GSC-7, GSC-6, GSC-21, GSC-22 and I-75), B. juncea (JC-210-325, CJRD-1261, PBR-357, Giriraj and RLC-3) and B. carianata (PC-5 and PC-6) were selected for field evaluation under split-split plot design with 3 irrigation regimes: moisture stress, restricted stress and normal irrigation along with two tillage treatment: conventional (CT) and zero tillage (ZT). ZT delayed the phenophases over CT irrespective of irrigation regimes. Flowering duration, siliquing duration and reproductive phase were longer under ZT over CT. At studied 3 crop stages physiological parameters, i.e. SPAD, NDVI, photosynthetic pigments, hill reaction activity increased with ZT. Similar increased trend was noticed in RWC, LWR however RSD and WSD declined. Membrane stability in the varieties/ strains was higher under ZT with lowered membrane injury. Antioxdative enzymes and biomolecules were upregulated under stress, but were more in CT relative to ZT. Total carbohydrate were more under ZT and reached maximum at flowering stage whereas proteins under CT and were highest at siliquing stage. Assimilation improved with irrigation regimes. ZT was also beneficial in improving oil content (≤1%), seed N content and N in stem and chaff. Overall, GSC-7, a canola variety of B.napus, non-canola varieties (PBR-357 and Giriraj), canola variety (RLC-3) of B. juncea and non-canola determinate variety PC-6 of B. carianata registered more siliqua length, seed/siliqua, more developed and lesser shriveled seed/siliqua with ZT. The elite varieties possessed higher tolerance indices viz. DTI≥ 0.8, YSI≥0.79 and DTE≥ 70% under both the tillage treatments.EnglishThesis