Carbohydrate composition of mature and immature faba bean seeds

• Glucose, fructose, and sucrose of immature and mature faba bean seeds were measured.
• Raffinose, stachyose, verbascose of immature and mature faba bean seeds were measured.
• Germplasm with high sucrose and low raffinose contents were identified.

Faba bean is a valuable pulse crop for human consumption. The low molecular weight carbohydrates (LMWC): glucose, fructose, sucrose (GFS), raffinose, stachyose, and verbascose (RFO- raffinose family oligosaccharides) in faba bean seeds contribute to the flavor and prebiotic nature of this edible bean. Understanding the variation of these compounds across the species would aid plant breeders in their selection efforts to release improved varieties. Therefore, this study was conducted to quantify LMWCs from a diverse collection of faba bean germplasm. The LMWCs of mature and immature seed from 40 faba bean populations across a range of seed sizes (26.2–172.0 g 100 seed−1) were quantified with an Agilent 1260 Infinity LC (size exclusion chromatography/gel permeation chromatography) system with refractive index detection. Sucrose was the predominant constituent LMWC of immature seeds ranging from 5.9 to 22.6% DW for cotyledons and 6.7 to 16.7% DW for seed coats, while total RFO averaged <1% DW across populations. The sucrose content of mature seeds was relatively stable across population with a mean of 2.4% DW, while RFO content ranged from 2.5 to 7.5% DW. The apparent positive relationship between seed size and GFS of immature seed and sucrose and RFO of mature seed indicates that selection for seed size may also affect LMWC concentration.