BIOCHEMICAL CHARACTERIZATION OF WHEAT GENOTYPES WITH RESPECT TO NITROGEN USE EFFICIECNY
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Date
2012
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PAU Ludhiana
Abstract
Increased use of nitrogen (N) fertilizer has raised concerns because N surplus causes environmental contamination and also high cost associated with its production. Thus, improving nitrogen use efficiency (NUE) through identification of efficient genotypes is becoming a necessity. In this two years study (2009-10 and 2010-11), 18 wheat genotypes (PBW 621, PBW 636, PBW 590, DBW 17, HD 2967, PBW 509, BW 9178, BW 9183, BW 8989, BW 9022, PBW 343, PBW 550, GLU 1101, GLU 1356, GLU 2001, GLU 700, PH132-4836, PH132-4840) selected on the basis of their commercial relevance or distinct genetic background were used for studying N metabolism at four N doses including the presently recommended N dose (RDN) (120 Kg N/ha), suboptimal N doses [RDN-50% (60 Kg N/ha) and RDN-25% (90 Kg N/ha)] and supraoptimal N dose [RDN+25% (150 Kg N/ha)]. Enzymes involved in N assimilation [nitrate reductase (NR), nitrite reductase (NIR), glutamine synthetase (GS), glutamate synthase (GOGAT) and glutamate dehydrogenase (GDH)] in relation to deposition of amino acids and proteins were studied at tillering (30 days after sowing; DAS), anthesis (about 90-100 DAS) and post-anthesis (15 days post anthesis) stages. PBW 621 showed higher activities of NR, NIR and GS at RDN-25%. At RDN-50%, PBW 636 and GLU 1356 showed highest GS activity. HD 2967 and PBW 590 revealed maximum activities of these enzymes at RDN and RDN+25%. Widely grown cultivar PBW 343 and advanced breeding lines BW 9178, BW 9183, BW 8989 and BW 9022 showed low efficiency for N assimilating enzymes. GLU 1356 showed high grain protein content indicating higher translocation of assimilates from flag leaf to sink. Sugar and starch content was higher in the PBW 343, BW 9178, BW 8989 and BW 9022 genotypes in which amino acid and protein content was less. PBW 621 showed higher NUE and yield compared to other genotypes. NR and GS enzymes were positively correlated with NUE and yield indicating that these might be the rate limiting steps in N metabolism. Biochemical similarity between PBW 621, PBW 636 and GLU 1356 was authenticated from cluster analysis. Tiller culture technique did not reveal much difference with respect to PBW 621 and PBW 343 in N metabolism. However, hydroponically raised seedlings showed complementary results with field studies in identifying genotypes with maximum NUE. Due to stable performance of PBW 621, PBW 636 and GLU 356 at suboptimal doses over two years, these genotypes hold future potential for developing new cultivars with improved NUE.
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