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CROP BREEDING & GENETICS

Quantitative Determination of Phytate and Inorganic Phosphorus for Maize Breeding

^a Dep. of Agronomy, Univ. of Wisconsin–Madison, Madison, WI 53706
^b USDA-ARS, Dep. of Agronomy, Iowa State Univ., Ames, IA 50011
^c Dep. of Agronomy, Iowa State Univ., Ames, IA 50011. This journal paper of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project No. 3755, was supported by the Hatch Act and State of Iowa funds. Part of a dissertation submitted by A.J. Lorenz in partial fulfillment of the requirements for the M.S. degree

^* Corresponding author (alorenz{at}wisc.edu).

Phytate is the dominant storage form of phosphorus (P) in mature cereal and oil grains. Phosphorus bound in phytate is nutritionally unavailable to monogastric animals and thus contributes to water pollution because it is excreted in the waste. Also, phytate can chelate certain minerals and exacerbate human mineral deficiencies. Our primary objective was to develop a rapid and inexpensive method of measuring phytate and inorganic P (P_i) concentrations in maize (Zea mays L.). The procedure reported herein was derived from previously published assays and used to screen 50 inbred lines to determine its potential in a selection program. Grain yield, protein, oil, methionine, lysine, tryptophan, and kernel weight were also measured. Field repeatability values for phytate and P_i (0.78 and 0.91, respectively) suggest that our protocol can be used to make heritable measurements on both traits. Phytate measurements taken with the procedure reported herein matched closely those obtained through ion exchange. The combination of adequate precision and simplicity make this method ideal for breeders interested in improving P_i and phytate levels simultaneously. The positive phytate:protein correlation reported commonly was also detected in this study. A relationship between phytate and kernel weight indicates that selection for low phytate may result in larger kernels.

Abbreviations: CV, coefficient of variation • CV_G, genetic coefficient of variation • lpa, low phytic acid • NSS, non–stiff stalk • OD, optical density • P_i, inorganic phosphorus • r_F, field repeatability • r_L, lab repeatability • RCBD, randomized complete block design • SS, stiff stalk.