Chaudhary, Dharam PaulVeena Devi2022-12-042022-12-042022Veena Devi (2022). Biochemical studies on methionine accumulation in maize grains (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.https://krishikosh.egranth.ac.in/handle/1/5810190354Present study was designed to understand the accumulation pattern of essential amino acids (methionine, lysine and tryptophan), methionine synthesis associated key enzymes activities and responsible genes expression in maize grains. For this purpose diverse panel of 300 inbred lines, procured from ICAR-IIMR and CIMMYT were screened for methionine content and a set of 22 experimental lines (12 high methionine and 10 low methionine) was selected for further study. Field parameters viz., Plant height, cob height, stem and root logging, no. of cobs, no. of rows/cob, no. of seeds/row, germination rate, anthesis and silking intervals, 100 kernel weight, specific gravity, moisture content were recorded. None of the field parameter showed any positive significant correlation with methionine content. The lines E7-24-3, E711-1, E19-14-1, E4-5-2, E2-52-1, E2-7 and E19-22-2 showed better field performance whereas the lines 174705 (3.293%) and 194010 (2.275%) showed highest methionine content thus can be used as acceptor and donors in breeding high methionine maize, respectively. Kernel colour showed correlation with methionine content. Lysine and tryptophan showed declining trend during kernel development and their accumulation was higher in low methionine lines. Aspartate kinase showed similar activity in both high and low methionine lines whereas cystathionine-gamma-synthase does not showed any fixed trend. Serine acetyltransferase enzyme activity was observed to be higher in high methionine than low methionine lines. Higher activity in high methionione lines indicated higher rate of cysteine synthesis, and its flow towards the synthesis of methionine. Its activity showed significant correlation (r = 0.87) with methionine content at 45th DAP. During kernel development zein (prolamin and prolamin-like) accumulated at higher rate in comparison to non-zeins (albumin, globulin and glutelins) in total protein. Methionine showed significant positive correlation with prolamins (r = 0.65) and proteins (r = 0.47). In SDS-PAGE 10-kDa δ-zein was more prominent in high methionine lines, whereas other zeins did not showed any change in high and low methionine lines. Lastly, the mRNA was quantified to study the expression profile of genes responsible for methionine accumulation. It was observed that 10-kDa δ-zein showed enhanced expression in high methionine lines, so its expression affects the accumulation of methionine in developing maize kernel.EnglishThesis