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Host Plant Nodule Enzymes Associated with Selection for Increased N 2 Fixation in Alfalfa 1
Author(s) -
Groat R. G.,
Vance C. P.,
Barnes D. K.
Publication year - 1984
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1984.0011183x002400050016x
Subject(s) - biology , germplasm , phosphoenolpyruvate carboxylase , nitrogenase , glutamate synthase , glutamate dehydrogenase , glutamine synthetase , nitrogen fixation , nitrogen assimilation , asparagine synthetase , cultivar , agronomy , botany , horticulture , biochemistry , enzyme , photosynthesis , glutamine , amino acid , asparagine , glutamate receptor , genetics , receptor , bacteria
In legumes symbiotically fixed N 2 is assimilated into C skeletons to form amino acids as a prerequisite for enhancing plant growth. No attempts have been made to determine which nodule enzymes of ammonia and C assimilation are related to N 2 fixation in alfalfa ( Medicago sativa L.). The objective of this study was to assess if nodule enzymes of ammonia and C assimilation were associated with acetylene reduction acitivity in alfalfa genotypes previously selected for various traits associated with N 2 fixation. Nodules from eight subpopulations derived by bi‐directional selection within each of two alfalfa germplasm sources, an intercross between the two germplasm sources and three alfalfa cultivars were used to measure nodule soluble protein, and in vitro specific activities of the plant enzymes glutamine synthetase (GS), glutamate synthase (GOGAT) glutamate dehydrogenase (GDH), and phosphoenolpyruvate carboxylase (PEPC). Acetylene reduction rate was measured as an indicator of nitrogenase activity. Significant genotypic differences were observed among subpopulations for all variables tested. The GOGAT and PEPC activities were correlated with acetylene reduction activity in one germplasm source but not the other. Phenotypic correlation coefficients among variables showed that GOGAT and PEPC activities were frequently coupled. Germplasm differences in nodule enzyme activity suggest that nodule carbon and N assimilation may be more closely associated with N2 fixation potential in one germplasm than the other. The GOGAT and PEPC activity may be useful traits to include in breeding programs to enhance N 2 fixation in alfalfa.