Comparative study of phytic acid estimation by enzymatic and indirect assays in maize germplasm (Zea Mays.L)

Phytic acid is an abhorrent anti-nutritional factor ascertaining several micronutrient deficiencies to monogastric animals by their chelating ability. Hence, screening of germplasm accessions by a rapid assay is necessary to identify the potential donors for low phytic acid in maize. This compound involves in a complex pathway inhabiting the role of several genes, establishes the difficulties in the molecular screening and elaborates the importance of an initial rapid assay in facilitating the screening of germplasm resources. Although, several methods have been followed for phytic acid content estimation, the direct estimation of phytic acid by Megazyme kit is found to be more precise than any other methods adopted. This Megazyme kit utilizes the natural phytase enzyme to liberate the free phosphorous from the samples and measures the phytate phosphorous content. But, estimating by this kit increases the cost of estimation while going for screening of a large number of samples. Thus an alternate rapid method that estimates the phytic acid content with a similar efficiency to this Megazyme assay has to be followed to facilitate the screening in a larger population. Among all the known methods, the Indirect assay described by Davies and Reid (1979) is found to be rapid and easy to be carried out in the initial screening of germplasm resources. Hence, a comparative study of phytic acid content estimated by these two protocols in a set of fiftyeight lines were subjected to a chi-square and paired t test. The phytic acid estimated by direct assay ranged from 2.04 to 15.59 mg/g and by indirect assay the range was observed from 2.77 to 16.70 mg/g. Although there were minor variations, there was not much difference observed between the two protocols. The chi-square test revealed a perfect goodness of fit between the protocols (χ²Calculated<χ² Table). Simultaneously, the paired t test between the means of phytic acid estimated from two protocols also exhibited a null difference (t calculated < t table) among them.

Thus, we can conclude that the rapid indirect assay described by Davies and Reid (1979) could be effectively followed for initial screening of large number of germplasm accessions to identify the spontaneous donors of low phytic acid content in maize.