Inheritance of the Low-Phytate Trait in Pea

Field pea (Pisum sativum L.) is the most widely grown pulse crop in Canada and has total seed P concentration greater than 3 mg g(-1). However, about 60 to 80% of the total P is stored as phytate, an organic molecule that binds with some mineral cations and is excreted due to the lack of phytase enzymes in humans and non-ruminant animals. This causes nutrient deficiency as well as environmental pollution. The objective of this research was to determine the genetic control of the low-phytate trait in two recently developed pea lines: 1-150-81 and 1-2347-144. Both lines and two normal-phytate cultivars were used in crosses to develop five populations, including one reciprocal. The F-1 seeds from the five crosses all had normal phytate concentration, indicating recessive inheritance. The F-2 segregation ratios for the five crosses fit a phenotypic ratio of 3 normal:1 low phytate. The F-2 individuals from 12 backcross populations fit a ratio of 3:1 with the exception of one population (1-150-81/CDC Meadow//CDC Meadow). The segregation of 1057 F-2:4 lines from the six single cross-derived populations were tested and five of six populations fit a ratio of 1:2:1 homogeneous normal phytate:segregating:homogeneous low phytate. Taken together, these data support a single gene model with the low-phytate phenotype being recessive. The two low-phytate lines were intercrossed and the F-2 seeds all displayed the low-phytate phenotype indicating that the mutated genes were allelic.