Imbibitional Chilling Sensitivity and Soluble Carbohydrate Composition of Low Raffinose, Low Stachyose Soybean Seed

Abstract

Soybean [Glycine max (L.) Merrill] seed with low raffinose, stachyose, and phytin is desired for feeding nonruminant animals to improve feed efficiency, increase mineral uptake, and reduce flatulence, but may have reduced agronomic quality. Composition of soluble carbohydrates in seed parts and sensitivity of mature seed to imbibitional chilling were determined for low raffinose and stachyose (LRS) seed; low raffinose, stachyose, and phytin (LRSP1, LRSP2) seed; and normal raffinose, stachyose, and phytin (CHECK) seed. Cotyledons and axes of seed from the three modified lines had low raffinose, stachyose, and verbascose compared to the CHECK. Cotyledons from LRS seed had significantly higher concentrations of galactinol and the di‐ and tri‐α‐galactoside derivatives of myo‐inositol, d‐pinitol, and d‐chiro‐inositol than cotyledons from LRSP1 and LRSP2 seed. Seed coats of all four lines were similar in soluble carbohydrate composition indicating the modifications were expressed in embryo tissues. Mature seed of LRS and CHECK was tolerant to imbibitional chilling, but LRSP1 and LRSP2 seed were sensitive to imbibitional chilling. The higher accumulation of cyclitol α‐galactosides in embryos (cotyledons) of LRS seed (90% cotyledons, 2% axis, 8% seed coat) may have contributed to imbibitional chilling tolerance.

Soluble Carbohydrates in Soybean

“…The low raffinose and stachyose (LRS) phenotype is associated with a novel raffinose synthase allele, RS2 (Dierking & Bilyeu, 2008). LRS seeds expressing the mutant stc1 phenotype have increased accumulation of galactosyl cyclitols (fagopyritols and galactopintitols) (Obendorf et al, 2008b and are tolerant to imbibitional chilling (Obendorf et al, 2008b) (Table 2). Seeds with low raffinose, stachyose and phytin (LRSP phenotype with 50% less phytin than the normal Mips phenotype) expressing a mutant mips gene conferring reduced myo-inositol-phosphate synthase (MIPS) activity (Sebastian et al, 2000;Hitz et al, 2002) have decreased field emergence, especially when seeds are produced in subtropical environments (Meis et al, 2003), and also are sensitive to imbibitional chilling (Obendorf et al, 2008b) (Table 2).…”

“…LRS seeds expressing the mutant stc1 phenotype have increased accumulation of galactosyl cyclitols (fagopyritols and galactopintitols) (Obendorf et al, 2008b and are tolerant to imbibitional chilling (Obendorf et al, 2008b) (Table 2). Seeds with low raffinose, stachyose and phytin (LRSP phenotype with 50% less phytin than the normal Mips phenotype) expressing a mutant mips gene conferring reduced myo-inositol-phosphate synthase (MIPS) activity (Sebastian et al, 2000;Hitz et al, 2002) have decreased field emergence, especially when seeds are produced in subtropical environments (Meis et al, 2003), and also are sensitive to imbibitional chilling (Obendorf et al, 2008b) (Table 2). Seeds expressing the mutant mips phenotype (wild-type Mips sequence designation GM mI 1-PS-1A, AY038802; Hitz et al, 2002) with low stachyose and phytin (LRSP1, LRSP2) accumulate very small amounts of galactosyl cyclitols (galactinol, galactopinitols, fagopyritol B2, fagopyritol B3) (Obendorf et al, 2008b), but these seeds can accumulate galactinol, raffinose and stachyose after incubation with myo-inositol (Hitz et al, 2002) (Table 2).…”

“…Seeds with low raffinose, stachyose and phytin (LRSP phenotype with 50% less phytin than the normal Mips phenotype) expressing a mutant mips gene conferring reduced myo-inositol-phosphate synthase (MIPS) activity (Sebastian et al, 2000;Hitz et al, 2002) have decreased field emergence, especially when seeds are produced in subtropical environments (Meis et al, 2003), and also are sensitive to imbibitional chilling (Obendorf et al, 2008b) (Table 2). Seeds expressing the mutant mips phenotype (wild-type Mips sequence designation GM mI 1-PS-1A, AY038802; Hitz et al, 2002) with low stachyose and phytin (LRSP1, LRSP2) accumulate very small amounts of galactosyl cyclitols (galactinol, galactopinitols, fagopyritol B2, fagopyritol B3) (Obendorf et al, 2008b), but these seeds can accumulate galactinol, raffinose and stachyose after incubation with myo-inositol (Hitz et al, 2002) (Table 2). Seeds and isolated embryos of all four lines accumulate fagopyritol B1 after incubation with D-chiro-inositol followed by slow drying (Obendorf et al, 2008a; Obendorf, R.L., Sensenig, E.M., Byrt, E.M., Owczarczyk, A.B., Ohashi, M., & Schnebly, S.R., unpublished).…”

“…LRS seeds also accumulate more diand tri-galactosyl cyclitols than CHECK seeds. LRS seeds are desiccation tolerant, tolerant to imbibitional chilling (Obendorf et al, 2008b), and have normal field emergence (Meis et al, 2003) (Table 2), perhaps because these seeds, that are low in RFO, accumulate more galactosyl cyclitols (Tables 1 & 2). Buckwheat seeds normally accumulate only very small amounts of raffinose and stachyose, but buckwheat seeds do accumulate fagopyritols and are desiccation tolerant with a high germination percentage (Horbowicz & Obendorf, 1994;Horbowicz et al, 1998).…”

“…Buckwheat seeds normally accumulate only very small amounts of raffinose and stachyose, but buckwheat seeds do accumulate fagopyritols and are desiccation tolerant with a high germination percentage (Horbowicz & Obendorf, 1994;Horbowicz et al, 1998). It is proposed that fagopyritols and other galactosyl cylitols can function in the same way as stachyose in conveying seed desiccation tolerance and seed performance (Horbowicz & Obendorf, 1994;Horbowicz et al, 1998) in LRS soybean seeds (Obendorf et al, 2008b).…”