Levels of total phosphorus, phytate-phosphorus, and phytase activity in three varieties of Western Australian wheats in response to growing region, growing season, and storage

Abstract

Two experiments were conducted to examine varietal, environmental, and storage influences on total phosphorus (P), phytate-P content, and phytase activity in a cohort of wheats grown in Western Australia. In Expt 1, a 3 × 3 × 2 factorial experiment examined the influence of wheat variety (Arrino, Stiletto, Westonia), growing region (high, medium, low rainfall zone), and harvest year (1999, 2000). In Expt 2, the effect of storage for 6 months on the P composition of the wheats was examined. The total P and phytate-P concentrations ranged from 1.66 to 4.48 g/kg (DM) and from 1.05 to 3.32 g/kg (DM), with mean values of 2.64 (s.e. ±0.142) and 1.79 g/kg (s.e. ±0.127), respectively. Phytase activity ranged from 327 to 811 phytase activity units (FTU)/kg, with a mean value of 563 FTU/kg (s.e. ±29.6). Phytate-P content was significantly correlated with total P concentration (r = 0.97, P < 0.001). Harvest year tended to influence the total P and phytate-P content (P = 0.079 and P = 0.082, respectively) of the wheats, whereas wheat variety had a significant effect on the phytase activity (P < 0.05). Precipitation level (mm) was positively correlated to total P and phytate-P contents (P < 0.05). Storage for 6 months after harvest did not change the P content of wheat.