The relationship between ureide N and N
2
fixation was evaluated in greenhouse-grown soybean (
Glycine max
L. Merr.) and lima bean (
Phaseolus lunatus
L.) and in field studies with soybean. In the ...greenhouse, plant N accumulation from N
2
fixation in soybean and lima bean correlated with ureide N. In soybean, N
2
fixation, ureide N, acetylene reduction, and nodule mass were correlated when N
2
fixation was inhibited by applying KNO
3
solutions to the plants. The ureide-N concentrations of different plant tissues and of total plant ureide N varied according to the effectiveness of the strain of
Bradyrhizobium japonicum
used to inoculate plants. The ureide-N concentrations in the different plant tissues correlated with N
2
fixation. Ureide N determinations in field studies with soybean correlated with N
2
fixation, aboveground N accumulation, nodule weight, and acetylene reduction. N
2
fixation was estimated by
15
N isotope dilution with nine and ten soybean genotypes in 1979 and 1980, respectively, at the V9, R2, and R5 growth stages. In 1981, we investigated the relationship between ureide N, aboveground N accumulation, acetylene reduction, and nodule mass using four soybean genotypes harvested at the V4, V6, R2, R4, R5, and R6 growth stages. Ureide N concentrations of young stem tissues or plants or aboveground ureide N content of the four soybean genotypes varied throughout growth correlating with acetylene reduction, nodule mass, and aboveground N accumulation. The ureide-N concentrations of young stem tissues or plants or aboveground ureide-N content in three soybean genotypes varied across inoculation treatments of 14 and 13 strains of
Bradyrhizobium japonicum
in 1981 and 1982, respectively, and correlated with nodule mass and acetylene reduction. In the greenhouse, results correlating nodule mass with N
2
fixation and ureide N across strains were variable. Acetylene reduction in soybean across host-strain combinations did not correlate with N
2
fixation and ureide N. N
2
fixation, ureide N, acetylene reduction, and nodule mass correlated across inoculation treatments with strains of
Bradyrhizobium
spp. varying in effectiveness on lima beans. Our data indicate that ureide-N determinations may be used as an additional method to acetylene reduction in studies of the physiology of N
2
fixation in soybean. Ureide-N measurements also may be useful to rank strains of
B. japonicum
for effectiveness of N
2
fixation.
Soybean (Glycine max) is one of the most important crop plants for seed protein and oil content, and for its capacity to fix atmospheric nitrogen through symbioses with soil-borne microorganisms. We ...sequenced the 1.1-gigabase genome by a whole-genome shotgun approach and integrated it with physical and high-density genetic maps to create a chromosome-scale draft sequence assembly. We predict 46,430 protein-coding genes, 70percent more than Arabidopsis and similar to the poplar genome which, like soybean, is an ancient polyploid (palaeopolyploid). About 78percent of the predicted genes occur in chromosome ends, which comprise less than one-half of the genome but account for nearly all of the genetic recombination. Genome duplications occurred at approximately 59 and 13 million years ago, resulting in a highly duplicated genome with nearly 75percent of the genes present in multiple copies. The two duplication events were followed by gene diversification and loss, and numerous chromosome rearrangements. An accurate soybean genome sequence will facilitate the identification of the genetic basis of many soybean traits, and accelerate the creation of improved soybean varieties.
Scrutinizing soybeans' secrets Hyten, David L; Cregan, Perry B
Agricultural research (Washington),
07/2008, Letnik:
56, Številka:
6
Magazine Article
Soon, soybean breeders will have access to an invaluable new tool for improving this key oilseed crop's yield and pest resistance, the quantity and quality of its protein and oil, and other desirable ...traits. That's because scientists are at work cataloging roughly 50,000 single nucleotide polymorphisms, or SNPs-the variations in DNA that make soybean varieties different from each other- occurring in over 19,000 unique lines, or accessions, that make up the extensive USDA soybean germplasm collection. Maintained by ARS on the University of Illinois campus at Urbana-Champaign, the collection comprises accessions gathered from sites all over the world and includes wild soybeans, soybeans grown by ancient farmers, and modern cultivars.
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