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.
Highlights
Phytic acid (PA), myo-inositol 1,2,3,4,5,6-hexakis or phytate, is a naturally occurring phosphorous (P)-rich compound formed during seed maturation [1]
Poultry and swine feed grain P is in the phytic acid-P (PA-P) form and is excreted as phosphate complexed minerals; monogastric animal feeds must be supplemented with bioavailable P and minerals or phytase enzyme supplements for the animals to utilize P and mineral nutrients [2]
Our results indicate low-PA field pea lines suffer no significant effects with respect to germination percentage (99%), seed viability (99%), weight of total plant biomass (12 - 15 g of biomass per pot), and seed weight (5 8 g of seeds per pot) compared to field pea cultivars grown under the same greenhouse conditions
Summary
Phytic acid (PA), myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate) or phytate, is a naturally occurring phosphorous (P)-rich compound formed during seed maturation [1]. Poultry and swine feed grain P is in the phytic acid-P (PA-P) form and is excreted as phosphate complexed minerals; monogastric animal feeds must be supplemented with bioavailable P and minerals or phytase enzyme supplements for the animals to utilize P and mineral nutrients [2]. PA-derived P in animal waste is a major environment pollution issue in the United States, Europe, and elsewhere [3]. Optimizing the level of PA and other inositol phosphates in seeds is required to maximize nutritional and health benefits while reducing P waste to environment
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