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a Pioneer Hi-Bred, International, Inc., P.O. Box 184, Johnston, IA 50131-0184
b Dep. of Agronomy, Iowa State Univ., Ames, IA 50011-1010
c Pioneer Hi-Bred, International, Inc., P.O. Box 177, Johnston, IA 50131-0177
* Corresponding author (wfehr{at}iastate.edu)
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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-galactosidase, which is necessary to break down raffinose and stachyose into sucrose and galactose, which monogastric animals can readily digest (Gitzelmann and Auricchio, 1965). The inability to digest raffinose saccharides results in a reduction in metabolizable energy and an increase in flatulents and diarrhea (Kuriyama and Mendel, 1917; Coon et al., 1990; Hata et al., 1991). Suarez et al. (1999) found that less flatulents were formed in humans after consuming soybean products derived from lines with reduced raffinose saccharides than from conventional lines. Adult roosters that consumed soybean meal in which raffinose saccharides were chemically extracted produced less excreta than when they consumed soybean meal derived from conventional lines (Leske et al., 1993). A plant introduction with reduced raffinose and stachyose and increased sucrose was identified by Kerr and Sebastian (2000). They found that the reduction in the raffinose saccharides and the increase in sucrose in PI200508 was controlled by the recessive allele stc1a. When soybean meal derived from lines with the Stc1a Stc1a genotype (Stc1a lines) and from lines with the stc1a stc1a genotype (stc1a lines) were fed to roosters, dry matter digestion and metabolizable energy were significantly higher for the meal obtained from the stc1a lines (Parsons et al., 2000).
The stc1a allele has been incorporated into commercial cultivars. These cultivars are used as a source of protein for food and feed use. At present, the stc1a cultivars yield less than conventional Stc1a cultivars. This may be due to a negative influence of the stc1a allele or to a lack of sufficient breeding to incorporate the allele into the most elite cultivars. The purpose of our study was to determine the influence of the stc1a allele on agronomic and seed traits by comparing the agronomic and seed characteristics of stc1a and Stc1a lines derived from the same single-cross populations.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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The F1 seeds of the single crosses were planted in November 1999 at the Pioneer nursery at Tapachula, Nayarit, Mexico. The F1 plants were confirmed as hybrids by pubescence color. The F2 seed of each population was harvested in bulk and planted in February 2000 at the Pioneer nursery in Tapachula. The F3 seed of each population was harvested in bulk and planted in May 2000 at the Pioneer Research Center in Johnston. The F3 plants of each population were harvested and threshed individually. In May 2001, 360 F3:4 lines of each population were planted at the Pioneer Research Center at Johnston for maturity classification and seed increase in single-row plots 1.5 m long with a row spacing of 0.9 m. Each line was considered mature when 95% of its pods had reached their mature color. Each line was harvested individually with a self-propelled plot combine.
Each line was evaluated for the content of raffinose and stachyose to differentiate between those with the stc1a and Stc1a alleles. Raffinose and stachyose usually are measured by high-performance liquid chromatography (HPLC). For the initial evaluation of the large number of lines harvested in 2001, HPLC was considered too time consuming and expensive. A more rapid method of testing was developed as a modification of a protocol from the Biotechnology Outreach Education Center of the Office of Biotechnology at Iowa State University (Zeller, 2001). The modified protocol was used to discriminate between stc1a lines with high sucrose and Stc1a lines with normal sucrose. A random sample of 25 seed from each line was ground for 5 s in an SM2 coffee grinder (Braun, Boston, MA). The coffee grinder was cleaned between samples by blowing it out with compressed air. A 0.17-g sample of the resulting seed powder was placed in individual wells of a 12-well tissue culture tray (Costar 3513, Corning Incorporated, Corning, NY). A 1-mL aliquot of deionized water was added to each well. After 1 h, 0.05 mL of a 10% (w/v) invertase (Number I-9253, Sigma Chemical Company, St. Louis, MO) solution was added to each well. The solution was allowed to react for 30 min. A new transfer pipette (Number 251 SEDI-PET, Samco Scientific Corp., San Fernando, CA) was used to transfer one drop of the solution to the test strip of an electronic diabetic blood test kit (ReliOn blood glucose monitor, Solartek Products, Incorporated, Bedford, MA). The amount of glucose in the solution was recorded in milligrams per deciliter.
Lines with a glucose content equal to or greater than the stc1a control sample were considered to have the stc1a stcla genotype and those with a glucose content equal to or less than the Stc1a control sample to have the Stc1a Stcla genotype. Homozygous F3:4 lines with similar maturity were selected for further evaluation of raffinose, stachyose, and sucrose content with the HPLC procedure described by Hitz et al. (2002). The Dionex HPLC system (Sunnyvale, CA) was used with a Dionex PA1 column eluted at 1.5 mL min–1 with 180 mM NaOH. The parents of each population were used as controls in the evaluation.
Based on the HPLC test, the 20 lines with the lowest total raffinose and stachyose content and the 20 lines with the highest total raffinose and stachyose content were selected from each population for evaluation in 2002.
The 40 F3:5 lines from each population were grown in separate experiments at Johnston, Dallas Center, and Stuart, IA, in 2002. The soil type at Johnston is a Wiota silty clay loam (fine silty, mixed, mesic Typic Argiudolls), at Dallas Center is a Nicollet loam (fine-loamy, mixed, mesic Aquic Hapludolls), and at Stuart is a Winterset silty clay loam (fine, montmorillonitic, mesic Typic Argiaquolls). Each experiment was a randomized complete-block design with two replications at each location. The plots were two rows 3.7 m long spaced 0.76 m apart within the plot and between adjacent plots. The seeding rate was 31 seeds m–1 of row.
Emergence percentage was determined by counting the number of plants in each plot at V2 (Fehr and Caviness, 1977), dividing by the 230 seeds planted, and multiplying by 100. Maturity was recorded as days after 31 August when 95% of the pods reached their mature color. Plant height was measured at maturity in centimeters from the soil surface to the terminal node. Lodging was scored at maturity on a scale of 1 (all plants erect) to 5 (all plants prostrate). The plots were harvested with a two-row self-propelled combine. The yield of the seed was expressed in kilograms per hectare at 130 g kg–1 moisture. The raffinose, stachyose, and sucrose content of one replication at each location was determined by HPLC on a dry-weight basis as previously described. The fatty ester composition of each plot was determined on a dry-weight basis by the procedure described by Reske et al. (1997). The protein and oil content of each plot was determined on a dry-weight basis with a random sample of about 450 seeds by a Perten DA-7000 near-infrared analyzer (Perten Instruments AB, Huddinge, Sweden).
The HPLC analysis indicated that some lines were segregating for the stc1a allele. These lines were excluded from the final analysis. This resulted in 17 stc1a lines and 13 Stc1a lines in Population 1 and 18 stc1a lines and 19 Stc1a lines in Population 2 that were included in the data analysis.
The data were analyzed as a randomized complete-block design by the general linear model procedure of the SAS statistical software package (release 8.02) (SAS Institute, 2001). Environments and replications were considered random effects. The two types of lines and the lines within each type were considered fixed effects. F tests were used to evaluate the significance of main effects and interactions. The environment x main effect interactions were used to evaluate the significance of the main effects for all traits. Phenotypic correlations among the traits measured in the study were computed on the basis of the line means averaged across environments with the CORR procedure of the SAS statistical software package (release 8.02) (SAS Institute, 2001).
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RESULTS AND DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
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The mean seed yields of stc1a and Stc1a lines were not significantly different in both populations (Table 1). The highest yielding line in both populations was a stc1a line. The phenotypic correlation coefficients of raffinose, stachyose, and sucrose with seed yield were not significant (Table 2). The lack of a negative association between the reduced raffinose saccharides and seed yield indicated that the stc1a allele is not the cause of the yield difference between current stc1a cultivars and conventional Stc1a cultivars. It should be possible to develop stc1a cultivars in the future that yield as well as conventional Stc1a cultivars.
Maturity, lodging, and height of the stc1a and Stc1a lines were not significantly different (Table 1). There were no significant correlation coefficients of raffinose, stachyose, and sucrose with lodging or height (Table 2). Significant correlation coefficients were obtained for sucrose with maturity in Population 1 and raffinose with maturity in Population 2.
Significant difference between the stc1a and Stc1a lines was observed for protein in Population 1 (Table 1). Mean oil content was not significantly different for the stc1a and Stc1a lines in either population. Only the phenotypic correlation coefficient of raffinose with protein was significant in one of the populations (Table 2). The only significant differences between stc1a lines and Stc1a lines for fatty ester composition were palmitate and linoleate in Population 1 (Table 1). The phenotypic correlation coefficients of raffinose, stachyose, and sucrose with the fatty esters were 0.3 or less in the two populations (Table 2).
There were no negative associations of the stc1a allele with agronomic and seed traits that should hinder the development of stc1a cultivars comparable to Stc1a cultivars. The soybean was able to accommodate the reduction in raffinose and stachyose and increase in sucrose with no detrimental effects on the traits measured.
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ACKNOWLEDGMENTS |
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Received for publication August 2, 2003.
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  M. S. Cicek, P. Chen, M. A. Saghai Maroof, and G. R. Buss Interrelationships among Agronomic and Seed Quality Traits in an Interspecific Soybean Recombinant Inbred Population Crop Sci., April 25, 2006; 46(3): 1253 - 1259. [Abstract] [Full Text] [PDF]
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