Sharma, AchlaMohd. Shamshad2019-12-152019-12-152019http://krishikosh.egranth.ac.in/handle/1/5810137744Nitrogen (N) plays the crucial role for plant growth, and plant canopy photosynthesis drives grain yield and grain quality. However, excessive input of nitrogen ultimately increases the production cost and pollutes the environment. For combating these environmental and health issues, breeders need to improve the nitrogen uptake and utilization efficiency in elite agronomic backgrounds. Therefore, the present investigation was planned to assess genetic and physiological basis of nitrogen uptake and utilization efficiency in structured mapping population derived from the cross between PBW677 and PBW 703. The study also dissected the location of genes/QTLs governing nitrogen uptake and utilization efficiency in the wheat genome using high through-put sequencing (35K Axome® Breeder array) methods. A total of 296 wheat genotypes were sown under full nitrogen (Nf), half nitrogen (Nh) and zero nitrogen (Nz) conditions in alpha lattice design in the experimental area of wheat section, Department of Plant Breeding and Genetics, PAU, Ludhiana during rabi season of 2016-17 and 2017-18. Analysis of variance indicated a larger amount of genetic variability for components traits i.e., morpho-physiological traits, nitrogen uptake (NUpE), utilization efficiency (NUtE), grain protein content, biological yield and grain yield. The spikelets per spike and tiller number were found to have the highest heritability and genetic advance whereas straw N percentage in above ground parts was found to be least heritable. Half N regime in comparison to full nitrogen regime was more effective in discriminating the genotypes for various nitrogen uptake and utilization efficiency component traits. Grain yield, biological yield, grain N yield, total N yield, straw N yield, NUpE, NUtE and NHI has strong correlation with NUE whereas N percentage in shoot has no impact, thereby identifying the selection of traits to be used for screening genotypes. Principal component analysis revealed that the PCs contribution were more for grain yield, tiller number, total N yield, biological yield, straw yield, harvest index, NHI, NUtE grain protein content and GNC, So selection for these traits can be helpful for selecting N use efficient physiology. PCA also showed that the NUE, NHI and NUtE were markedly higher when there was no nitrogen apply (Nz regime). Further investigation on roots revealed the importance of root length, root diameter and root shoot ratio for NUpE, indicating the improvement for NUE. Few lines having most consistent performance under low N conditions were also identified and tested under local trials for preliminary yield evaluation. Four lines viz. BWL 6289, BWL 6838, BWL 6300 and BWL 6293 had high yield in local yield trials. These lines may be exploited for improving nitrogen use efficiency in wheat breeding programs. Inclusive composite interval mapping based on 35K SNPs array detected a total of 294 QTLs of which 105 QTL under full N, 93 under half N and 96 under zero N for nitrogen uptake, utilization efficiency and others agronomic traits were identified. The highest QTLs were found on D genome, with 90 QTLs (30.6%); 100 QTLs (34%) and 104 QTLs (35.4%) on A, B and D genomes respectively. The proportion of phenotypic variance ranged from 3.02 to 19.31 percent with LOD score 2.5 to 21.24. The number of QTLs ranged from 2 to 24 for the studied traits. These QTLs were mapped on different clusters. The identified QTLs will be further validated in other populations for their use in marker assisted selection for wheat improvement.ennullThesis