@article{hanson_burton_1994, title={CONTROL FOR RATE OF SEED DEVELOPMENT AND SEED YIELD POTENTIAL IN SOYBEAN}, volume={34}, ISSN={["0011-183X"]}, DOI={10.2135/cropsci1994.0011183X003400010023x}, abstractNote={Selecting for increased weight per seed among male‐sterile soybean plants [Glycine max (L.) Merr.] increased seed weight and seed yield for male‐fertile progeny but had minimal effects on seed number per ha. Assimilate availability to the seed during selection was essentially nonlimiting for an extended period, since male‐sterile plants have few seeds per plant. For the observed range, seed weight has shown no association with seed yield potential. This study tested two alternate hypotheses to explain the increased seed yield potential: (i) selection identified genotypes with increased seed sink activity per plant or (ii) selection identified genotypes with reduced seed maturation rates. Dry matter accumulation rate (DMAR) per unit seed dry weight, DMAR per unit seed coat area, and rate of increase in seed density were determined for greenhouse‐grown plants using a 7‐d period during mid‐seed development. The following observations led to the acceptance of the reduced seed maturation rate hypothesis: (i) When assimilates were made essentially nonlimiting to the seed by partial pod removal, selected and nonselected populations had similar DMAR per unit seed coat area and per unit seed dry weight, (ii) Selection for seed weight on male‐sterile plants reduced the rate of increase in seed density. (iii) DMAR per unit seed coat area did not increase with selection. Selected and nonselected populations, had similar DMAR per unit seed dry weight. Apparently, selection had occurred against the reduction in rate of dry matter uptake by the seed. This reduction is normally associated with reduced seed maturation rate. Selection for seed weight on male‐sterile plants can be completed during the early generations of a breeding program and used to identify genotypes that have longer seed‐filling durations and more efficient systems for assimilate utilization.}, number={1}, journal={CROP SCIENCE}, author={HANSON, WD and BURTON, JW}, year={1994}, pages={131–134} }
 @article{hanson_1994, title={DISTANCE STATISTICS AND INTERPRETATION OF SOUTHERN STATES REGIONAL SOYBEAN TESTS}, volume={34}, ISSN={["0011-183X"]}, DOI={10.2135/cropsci1994.0011183X003400060016x}, abstractNote={The failure of genotypes to respond similarly to different environmental conditions, genotype environment (GXE) interaction, is an important aspect of genotypic stability. The objectives of this paper were to develop distances based on concepts of genotypic stability and to interpret regional soybean [Glycine max (L.) Merr.] tests based on these distances. Distances increased in relation to differential responses among sites for two genotypes or among genotypes for two sites. They were designed to evaluate the importance of region of origin in determining genotypic responses, the similarity of selections arising from different breeding programs, and the comparability of sites in regional testing. Seed yields for the Uniform Soybean Trials, Southern States, Maturity Groups V and VI, 1981–1991, were evaluated. Region of origin for genotypes did not have a major impact upon the nature of genotypic responses; however, genotypes from all regions showed less differential responses when tested at sites in the East Coast Region. The Group V selections from the North Carolina, Maryland, and Virginia breeding programs were more similar than selections from other breeding programs. Group VI selections from the Missouri program responded differently to environments than Group VI selections from other programs. The Plymouth, NC, Clemson, SC, and Athens, GA, test sites had similar relative seed yields among genotypes. A central belt of comparable sites extended from Virginia, North Carolina, South Carolina, and northeast Georgia to the mid and upper Delta Region. A northern belt of comparable sites covered Delaware, Maryland, western Virginia, Kentucky, upper Delta, and southeastern Kansas. The Tennessee sites were intermediate to these two belts. Sites in northwestern Georgia and northern Alabama and the remaining sites in the southern tier of states gave heterogeneous genotypic responses. Comparable sites that represent areas within this region were not found. Genotypes with unique local adaptations would be required.}, number={6}, journal={CROP SCIENCE}, author={HANSON, WD}, year={1994}, pages={1498–1504} }
 @article{hanson_1992, title={MODIFIED SEED MATURATION RATES AND SEED YIELD POTENTIALS IN SOYBEAN}, volume={32}, ISSN={["0011-183X"]}, DOI={10.2135/cropsci1992.0011183X003200040028x}, abstractNote={Seed embryos of soybean [Glycine max (L.) Men‐.] genotypes can have different levels of specific dry matter accumulation rate (SDMAR) and specific seed density (SSD) under greenhouse growing conditions, but the relevance of these measures for field‐grown plants is not known. The objectives of this research were to interrelate these measures as they reflect characteristics of the developing soybean seed and to determine their association with seed‐yield potential. As the seed matured, SSD increased ⊄0.01 g cm−3 d−1. Differences in this rate of change were positively associated with SDMAR. Genotypes selected for increased, as compared with decreased, seed‐filling duration had lower SDMAR and lower rate of change in SSD (decreased seed maturation rate) and greater seed yield under favorable field conditions. However, the yield advantage was lost under environments having drought stress during the reproductive period. Selections for high seed protein content exhibited an apparent increased seed‐maturation rate and a reduced seed yield. Divergent selection for SSD produced major shifts in SSD at the 55% seed‐filling stage. In contrast, the modified reproductive period selections and the seed protein selections had only secondary differences for SSD at that seed‐filling stage, indicating that the low SSD selections initiated delayed seed maturation at an earlier stage of seed development. While the low SSD selections had the reduced seed‐maturation rates, they did not express the expected yield advantage. Under drought stress, they exhibited lower seed number and seed yield than the modified reproductive period and high SSD selections. The stage of maturity for initiating delayed maturation appeared important. The proposed desirable genotype maintained specific dry matter accumulation rate during early seed fill but shifted to reduced seed maturation rate at a later stage of seed development.}, number={4}, journal={CROP SCIENCE}, author={HANSON, WD}, year={1992}, pages={972–976} }
 @article{hanson_1992, title={PHENOTYPIC RECURRENT SELECTION FOR MODIFIED REPRODUCTIVE PERIOD IN SOYBEAN}, volume={32}, ISSN={["0011-183X"]}, DOI={10.2135/cropsci1992.0011183X003200040027x}, abstractNote={Seed‐filling duration has generally shown a positive association with seed yield in soybean [Glyelne max (L.) Merr.], but results have been inconsistent among studies. Four phenoWpic recurrent selection programs were completed, increased flowering.period duration (FPD) vs. increased seed‐filling duration (SFD) and long vs. short reproductive period duration (RPD), with the objective of investigating the effects of these modifications on seed development and seed yield. Selection for average physiological maturity (RT) maintained R7 maturities among populations. Selection for increased RPD through FPD or SFD increased genetic correlations between reproductive stages. The major responses to selection occurred in the first cycle due in part to the 3‐yr evaluation, but high correlations between stages also restricted progress. Manipulating RPD modified primarily FPD. The SFD seemed to have a minimum threshold, but responded to selection pressure. Divergent selection for RPD created a 10‐d difference in RPD, but the selection had minimal effects on seed yield potential. The soybean has the capacity to achieve seed yield independent of changes in duration of reproductive stage. Increasing RID through increased SFD within a broad‐base population had an associated increase in seed set and in seed yield for a set of favorable environments, but this yield advantage was not expressed for a set of environments with drought stress during the reproductive period. Increased SFD was associated with increasing potential number of seed set and, as has been shown, decreasing assimilate uptake rate. Selection for increased SFD would be important for populations where SFD could be limiting. The effects of modifying seed‐filling duration are not clear‐cut, but manipulating facets that affect it can create unacceptable responses.}, number={4}, journal={CROP SCIENCE}, author={HANSON, WD}, year={1992}, pages={968–972} }
 @article{hanson_1991, title={ROOT CHARACTERISTICS ASSOCIATED WITH DIVERGENT SELECTION FOR SEEDLING ALUMINUM TOLERANCE IN SOYBEAN}, volume={31}, ISSN={["0011-183X"]}, DOI={10.2135/cropsci1991.0011183X003100010030x}, abstractNote={Soybean (Glycine max [L.] Merr.) roots are susceptible to A1 toxicity. This study tested the hypothesis that seedling characteristics could serve as selection criteria for plant tolerance to A1. Phenotypic‐recurrent, divergent selection programs for seedling tolerance to A1 were completed within two broad‐base soybean populations based on a laboratory screen. Genotypes differing in seedling tolerance to A1, rate of electron release (and, H+ release) from the root surface, and root thickness (g cm‒1) were identified. Root penetration from a soil horizon with low A1 into soils with high A1 was selected to measure A1 tolerance for greenhouse‐grown plants. Selection pressure for seedling root growth under A1 within these two populations evolved a number of apparent mechanisms affecting seedling root growth in solutions containing A1. Selecting genotypes for differences in A1 seedling tolerance gave inconsistent associated responses for root penetration into soils with high A1. High electron release rates and small roots (and seeds) were associated with selection for low A1 seedling tolerance. Selecting genotypes for differences in electron release rate or for differences in root thickness did not create an associated response in root penetration into soils with high A1. Preconditioning of seedling roots to A1 increased tolerance to A1 proportionately in tolerant and nontolerant selections, when tolerant and nontolerant selections were grown in different A1 concentrations selected to yield ≈75% reduction in root growth. Genetic variability available was not such as has been associated with the inducible A1‐binding proteins proposed for wheat (Triticum aestium L.). New genetic sources for A1 tolerance and information on the nature of this tolerance are needed to develop selection criteria for A1 tolerance.}, number={1}, journal={CROP SCIENCE}, author={HANSON, WD}, year={1991}, pages={125–129} }
 @article{hanson_1991, title={SEED PROTEIN-CONTENT AND DELIVERY OF ASSIMILATES TO SOYBEAN SEED EMBRYOS}, volume={31}, ISSN={["0011-183X"]}, DOI={10.2135/cropsci1991.0011183X003100060044x}, abstractNote={Increasing seed protein content in soybean [Glycine max (L.) Merr.] is associated with reduced seed yields. The objectives Of this study were to investigate the effects of seed protein content on the capacity to deliver dry matter and amino acids to the seed embryo and to identify possible yield‐limiting factors. Fifteen soybean genotypes representing 0.42 to 0.51 g g‐1 seed protein content were grown in the greenhouse during the winter season. High seed‐protein content did not limit specific dry matter accumulation rates. Removing side leaflets to reduce assimilate availability reduced assimilate uptake rates 21%. The reduced uptake rates were not associated with seed protein content. The modified seed structure associated with increased seed protein content did not limit rate of assimilate uptake by the seed. Thus, high seed protein content did not reduce sink activity. Genotypes with high seed protein content had higher rates of increase in seed density than the cultivar Ransom, indicating possible increased seed maturation rates for these genotypes. Rates of amino acid unloading from opened seed coats into a collection medium were associated With the seed protein content. The ratio of rate of amino acid unloading from opened seed coats to rate of dry matter delivery to the embryo was similar to the seed protein content. On the average, selecting for high seed protein content increased the capacity for amino acid production and transport and for amino acid unloading from the seed coat; however, additional factors were involved in the control, of seed protein content. A possible yield‐limiting factor, which is supported by the data on changes in seed density, is the capacity for amino acid unloading from the seed coat.}, number={6}, journal={CROP SCIENCE}, author={HANSON, WD}, year={1991}, pages={1600–1604} }
 @article{hanson_1989, title={STANDARD ERRORS FOR HERITABILITY AND EXPECTED SELECTION RESPONSE}, volume={29}, ISSN={["1435-0653"]}, DOI={10.2135/cropsci1989.0011183X002900060051x}, abstractNote={Confidence statements for response expected from selection are needed. The first order approximation in Taylor's expansion was used to develop standard errors for heritability and expected progress. Both standard errors contain adjustments for level of heritability. They offer criteria for establishing approximate confidence intervals for these two estimated parameters.}, number={6}, journal={CROP SCIENCE}, author={HANSON, WD}, year={1989}, pages={1561–1562} }