Imbibitional chilling sensitivity and soluble carbohydrate composition of low raffinose, low stachyose soybean seed

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-[alpha]-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 [alpha]-galactosides in embryos (cotyledons) of LRS seed (90% cotyledons, 2% axis, 8% seed coat) may have contributed to imbibitional chilling tolerance.