Sharma, SanjulaGoyal, Sakshi2020-07-162020-07-162020http://krishikosh.egranth.ac.in/handle/1/5810149210The present situation urgently demands the crop plants with increased nitrogen (N) uptake and assimilation efficiencies in order to reduce damage caused to the ecosystem due to nitrate leaching. With this objective, the variation and correlation of N uptake and assimilatory enzymes with non-enzymatic metabolites and yield parameters was studied at three developmental stages viz., pre-anthesis, anthesis and post-anthesis in a DArT-genotyped association panel of 195 Brassica rapa diversity set grown at a recommended dose of 100 kg N/ha. Among all the growth stages, N-metabolism enzymes were maximally active during anthesis stage. Correlation study depicted a significant positive relationship between all the N-metabolism enzymes and biochemical parameters. Out of 195 genotypes, seven promising genotypes viz., DRBS-56-A5, DRP-31-A5-P5, DRT-80-A5, DRT-59-A1, DRT-66-A2, LTE- 16 and CN107774 recorded highest enzyme activities and nitrogen use efficiency (NUE). Of these, DRT-59-A1, LTE-16, CN107774 and DRP-31-A5-P5 were higher yielding as well. The genome wide association study (GWAS) revealed 21 significant SNP’s associated with N metabolism traits on all the chromosome from A01-A10 except chromosome 4. SNPs that include A02_1906734 and A03_20450126 individually co-localized with two functional gene groups that were associated with QTLs for glutamate dehydrogenase, glutamine synthetase and glutamate synthase. The study helped in identification of genotypes with favorable combination of traits that could be of interest in Brassica breeding programs. Also, the identified significant SNPs on further validation could be used for marker assisted selection and trait introgression in Brassica for raising N uptake and assimilation rates.ennullThesis