A single, recessive mutation in soybean (Glycine max L. Merr.), which confers a seed phenotype of increased inorganic phosphate, decreased phytic acid, and a decrease in total raffinosaccharides, has been previously disclosed (S.A. Sebastian, P.S. Kerr, R.W. Pearlstein, W.D. Hitz [2000] Soy in Animal Nutrition, pp 56-74). The genetic lesion causing the multiple changes in seed phenotype is a single base change in the third base of the codon for what is amino acid residue 396 of the mature peptide encoding a seed-expressed myo-inositol 1-phospate synthase gene. The base change causes residue 396 to change from lysine to asparagine. That amino acid change decreases the specific activity of the seed-expressed myo-inositol 1-phosphate synthase by about 90%. Radio tracer experiments indicate that the supply of myo-inositol to the reaction, which converts UDP-galactose and myo-inositol to galactinol is a controlling factor in the conversion of total carbohydrate into the raffinosaccharides in both wild-type and mutant lines. That same decrease in myo-inositol 1-phosphate synthetic capacity leads to a decreased capacity for the synthesis of myo-inositol hexaphosphate (phytic acid) and a concomitant increase in inorganic phosphate.

A soybean [Glycine max (L.) Merr. I mutation conferring resistance to a wide range of sulfonylurea (SU) herbicides would greatly enhance the weed control options available to soybean farmers. This report describes the selection, characterization, and potential utility of such mutants. Seed mutagenesis (using N‐nitroso‐N‐methylurea and ethyl methanesulfonate) followed by selection for resistance to chlorsulfuron [2‐chloro‐N‐[(4‐methoxy‐6‐methyl‐l,3,5‐triazin‐2‐yl)aminocarbonyl] benzenesulfonamide] yielded a soybean mutant with a high degree of resistance to both postemergence and pre‐emergence applications of a variety of SU herbicides. Resistance was monogenic, semidominant, and not allelic to any of the previously identified recessive genes hs1, hs2, or hs3 that confer tolerance to SU herbicides. Biochemical tests indicate that the mechanism of resistance is reduced sensitivity of acetolactate synthase to SU inhibition. The SU resistance afforded by this mutation (designated Alsl) can be used to enhance soybean weed control options and can serve as a selectable marker for seed purification.

BACKGROUNDSulfonylurea (SU) herbicides are effective because they inhibit acetolactate synthase (ALS), a key enzyme in branched-chain amino acid synthesis required for plant growth. A soybean line known as W4-4 was developed through rounds of seed mutagenesis and was demonstrated to have a high degree of ALS-based resistance to both post-emergence and pre-emergence applications of a variety of SU herbicides. This report describes the molecular and phenotypic characterization of the Als1 and Als2 mutations that confer herbicide resistance to SUs and other ALS inhibitors.RESULTSThe mutations are shown to occur in two different ALS genes that reside on different chromosomes: Als1 (P178S) on chromosome 4 and Als2 (W560L) on chromosome 6 (P197S and W574L in Arabidopsis thaliana).CONCLUSIONAlthough the Als1 and Als2 genes are unlinked, the combination of these two mutations is synergistic for improved tolerance of soybeans to ALS-inhibiting herbicides. © 2014 DuPont Pioneer. Pest Management Science published by JohnWiley & Sons Ltd on behalf of Society of Chemical Industry.

Despite the importance of grain yield potential to plant breeders and society in general, it has been difficult to identify grain yield quantitative trait loci (QTL) effective for marker‐assisted selection (MAS) across a wide range of genetic and/or environmental contexts. However, as genotyping becomes more cost effective, it might be feasible to use preliminary yield trials to model a target genotype within each context and immediately select the progeny that approach that target genotype in real time. In the present study, elite soybean cultivars with residual heterogeneity were leveraged as populations (the genetic context) to detect yield QTL within a limited set of environments (the environmental context), to model a target genotype, and to select subline haplotypes that comprised the target genotype. The yield potential of the selected subline haplotypes were then compared to their respective mother lines in highly replicated yield trials across multiple environments and years. Statistically significant yield gains of up to 5.8% were confirmed in some of the selected sublines, and two of the improved sublines were released as improved cultivars. This context‐specific MAS (CSM) approach might also be applicable to the more typical biparental and backcross populations commonly used in plant breeding programs. Factors that can affect the efficiency and applicability of CSM are discussed.

Genetic improvement for yield in soybean [Glycine max (L.) Merrill] has beenaccomplished by breeding within a narrow elite gene pool. Plant introductions (Pis) may be useful for obtaining additional increases in yield if unique and desirable alleles at quantitative trait loci (QTL) can be identified. The objectives of the study were to identify QTL for yield in elite and PI germplasm and to determine if the Pis possessed favorable alleles for yield.Allele frequencies were measured with simple sequence repeat (SSR) markers in three populations that differed in their percentage of PI parentage. AP10 had 40 PI parents, API 2 had 40 PI and 40 elite parents, and API 4 had 40 elite parents. Four cycles of recurrent selection for yield had been conducted in the three populations. Nei's genetic distance indicated that AP10, AP12, and AP14 remained distinct through cycle 4 (C4), but that the genetic diversity narrowed within each population. Less gametic phase disequilibrium (GPD) was observed in the parents used to form the cycle 0 (CO) populations than in C4 of AP12 and AP14. Allele frequencies of the highest-yielding C4 lines in the three populations were compared with the parents used to form the populations of the initial cycles. Allele flow was simulated to account for genetic drift. Ninety-two SSRs were associated with 56 yield QTL. Nine of the QTL had been identified in previous research. Thirty-three favorable marker alleles were unique to the PI parents. The restriction of alleles from the 40 CO parents to the 20 cycle 1 (CI) parents of AP10 was reflected in the number of alleles that had frequency changes and could explain the reduced genetic variance for yield in the C4 of AP10. Genetic asymmetry may account for the different genetic gain for yield that had been observed between AP10 and AP14.