Browsing by Author "Glover, Natasha M."

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    The Genetic Basis of Phytate, Oligosaccharide Content, and Emergence in Soybean
    Glover, Natasha M. (Virginia Tech, 2011-06-27)
    Soybean [Glycine max (L.) Merr] is one of the U.S.'s most economically important crops due to the protein and oil content of seeds. The major storage form of phosphorus in soybean seeds is found in the form of phytate, but because of its negative nutritional and environmental impacts, seed phytate and raffinosaccharide content have been a recent focus of breeders and molecular geneticists. The soybean line CX1834 is a low phytate mutant known to have two low phytate QTLs on linkage groups (LGs) L and N. The first objective of this research was to determine the genetic basis of the low phytate trait in CX1834. By using the whole genome sequence, we identified two candidate multidrug resistance-associated (MRP) ABC transporter genes. Sequencing the genes from CX1834 and comparing them to the reference genome sequence revealed a single nucleotide polymorphism (SNP) in the MRP gene located on LG N (causing a stop codon), and a SNP mutation in the MRP gene located on LG L (causing an amino acid change from arginine to lysine). One major concern with low phytate soybeans is the low seedling emergence. The second objective was to undertake a population-wide study of emergence in the recombinant inbred population CX1834 x V99-3337, over two years and two locations. We found a positive correlation between phytate level and emergence, and that variation among year, location, genotypic class, year x genotypic class, and year x location interactions were significantly affecting emergence. V99-5089, in addition to being low phytate, has high sucrose and low raffinosaccharide content. This phenotype of V99-5089 has been previously determined to be due to a SNP mutation in its myo-inositol phosphate synthase (MIPS) gene located on LG B1. The third objective was to use the recombinant inbred population derived from CX1834 x V99-5089 to observe the combinations of all three mutations to see how the different alleles impact phytate and raffinosaccharide content. The individuals with all three mutations, as well as those with the two MRP mutations together had lower phytate than the other genotypic classes. However, these lines (all three mutations) had unexpectedly high stachyose.
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    Genetic interactions regulating seed phytate and oligosaccharides in soybean (Glycine max L.)
    Redekar, Neelam R.; Glover, Natasha M.; Biyashev, Ruslan M.; Ha, Bo-Keun; Raboy, Victor; Saghai-Maroof, Mohammad A. (2020-06-25)
    Two low-phytate soybean (Glycine max(L.) Merr.) mutant lines- V99-5089 (mipsmutation on chromosome 11) and CX-1834 (mrp-landmrp-nmutations on chromosomes 19 and 3, respectively) have proven to be valuable resources for breeding of low-phytate, high-sucrose, and low-raffinosaccharide soybeans, traits that are highly desirable from a nutritional and environmental standpoint. A recombinant inbred population derived from the cross CX1834 x V99-5089 provides an opportunity to study the effect of different combinations of these three mutations on soybean phytate and oligosaccharides levels. Of the 173 recombinant inbred lines tested, 163 lines were homozygous for various combinations of MIPS and two MRP loci alleles. These individuals were grouped into eight genotypic classes based on the combination of SNP alleles at the three mutant loci. The two genotypic classes that were homozygousmrp-l/mrp-nand either homozygous wild-type or mutant at themipslocus (MIPS/mrp-l/mrp-normips/mrp-l/mrp-n) displayed relatively similar similar to 55% reductions in seed phytate, 6.94 mg g(-1)and 6.70 mg g(-1)respectively, as compared with 15.2 mg g(-1)in the wild-type MIPS/MRP-L/MRP-N seed. Therefore, in the presence of the double mutantmrp-l/mrp-n, themipsmutation did not cause a substantially greater decrease in seed phytate level. However, the nutritionally-desirable high-sucrose/low-stachyose/low-raffinose seed phenotype originally observed in soybeans homozygous for themipsallele was reversed in the presence ofmrp-l/mrp-nmutations: homozygousmips/mrp-l/mrp-nseed displayed low-sucrose (7.70%), high-stachyose (4.18%), and the highest observed raffinose (0.94%) contents per gram of dry seed. Perhaps the block in phytic acid transport from its cytoplasmic synthesis site to its storage site, conditioned bymrp-l/mrp-n, alters myo-inositol flux inmipsseeds in a way that restores to wild-type levels themipsconditioned reductions in raffinosaccharides. Overall this study determined the combinatorial effects of three low phytic acid causing mutations on regulation of seed phytate and oligosaccharides in soybean.