Changes in Inositol Phosphates in Low Phytic Acid Field Pea ( Pisum sativum L.) Lines during Germination and in Response to Fertilization

Abstract

Inositol phosphates are the main form of phosphorous (P) storage in legume seeds. Mutants low in inositol hexaphosphate (IP6), also known as phytic acid (PA), have been developed to increase iron (Fe) bioavailability and reduce P waste to the environment. The objectives of this study were to determine 1) inositol-P form changes during germination, and 2) the effect of P fertilizer application on seed PA, total P, and Fe concentration of three field pea (Pisum sativum L.) cultivars and two low-PA lines grown under greenhouse conditions. Low-PA field pea lines clearly had lower PA (1.3 - 1.4 mg·g-1) than cultivars (3.1 - 3.7 mg·g-1). Phytic acid concentration in both cultivars and low-PA lines decreased during germination, but tended to increase seven days after germination. Levels of inositol-3-phosphate-phosphate (IP3-P; 0.6 mg·g-1) and inorganic P (1.8 - 2.0 mg·g-1) were higher in low-PA lines than in the field pea cultivars. Reduction of PA in low-PA line seeds may reduce seed Fe and total P concentrations, as levels in the low-PA lines (37 - 42 mg·kg-1 Fe; 4003 - 4473 mg·kg-1 total P) were typically less than in field pea cultivars (37 - 55 mg·kg-1 Fe; 3208 - 4985 mg·kg-1 total P) at different P fertilizer rates. Overall, IP3 is the major form of P present in low-PA field pea lines during germination; however IP6 is the major form of P present in field pea cultivars. Therefore, low-PA field pea lines could be a potential solution to increase Fe bioavailability, feed P utilization, and reduce P waste to the environment.