Tuesday, November 6, 2007 - 1:30 PM
166-7
Development and Evaluation of Low Phytate Crops.
The majority of phosphorus (P) in seeds is stored as phytic acid (myo-inositol-1,2,3,4,5,6 -hexakisphosphate). Phytic acid forms salts with nutritionally important cations such as Ca2+, Mg2+, Fe2+, and Zn2+. The P and minerals in these salts are not efficiently utilized by monogastric animals such as poultry, swine, fish and humans. Excretion of phytate salts can contribute to P management issues in livestock production and to mineral deficiencies in human population that rely on grains and legumes for staple foods. Low phytic acid (lpa) mutations have been isolated in several crop species, including maize, barley, wheat, rice, and soybean. Mutations have been identified at various points in phytate synthesis pathways and in a transport function important to the pathway. Reductions in seed phytic acid from 40% to 90% have been achieved, as compared to wild type plants. Reduction in grain phytate is usually matched by an increase in seed inorganic P, so that seed total P usually remains unchanged. Additional phenotypes associated with lpa alleles include changes in plant and seed dry weight accumulation and increased susceptibility to stress, both of which can contribute to reductions in yield. The reduction in dietary phytate achieved via the consumption of low-phytate grains can have a profoundly positive effect on animal and human nutrition. Many studies conducted to date have documented enhanced P utilization and reduced waste P in poultry, swine and fish that consume feeds prepared with low-phytate types. Of more immediate relevance to human nutrition, a number of studies with animal and human subjects have documented substantial enhancements in Ca, Mg, Fe and Zn absorption and utilization, when low-phytate foods are compared with "normal phytate" foods. Current and future directions in genetics, bioengineering, plant breeding and nutritional studies having to do with seed phytic acid will be summarized.
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