The influence of genotype and environment on the nutritional composition of field peas grown in Canada

Abstract

Six field pea (Pisum sativum) varieties from five different growing locations in Saskatchewan in the 2006 and 2007 growing years were analyzed to determine the effect of genotype, environment and year on the total dietary fibre, insoluble dietary fibre, soluble dietary fibre, total phenolic content, simple phenolic content and antioxidant activities. Samples were analyzed for dietary fibre using the enzymatic-gravimetric method of fibre analysis in accordance to the AACC method 32-05. Growing location had a very significant effect (p<0.0001) on the IDF, SDF and TDF content. Genotype had a strong effect (p<0.0001) on both IDF and TDF while having no significant effect (p=0.4556) on SDF content. Crop year also displayed a significant effect on SDF and TDF (p<0.0001) while having a smaller effect on IDF content (p=0.0139). Green varieties yielded significantly higher IDF (p=0.0041) and TDF (p=0.0028) than yellow varieties. Significant genotype x location (0.0155) and location x year (p=0.0002) interaction terms were also observed for TDF. The total phenolic contents were assessed using the Folin-Ciocalteu method of total phenolic content (TPC) analysis, while the contents of 10 individual simple phenolic acids were assessed using reversed-phase UPLC. A significant genotype, environment, and genotype by environment (G x E) interaction effect on the TPC was observed. The seed coat colour and growing season did not show a significant effect on the TPC. The UPLC analysis showed that ferulic acid comprised the majority of the phenolic content of the field pea samples. There was also a genotype, seed coat colour, location, growing season and G x E effect on the total simple phenolic acid content. As well, a modified microplate method for antioxidant activity using the free radical DPPH was assessed against the conventional cuvette method based system. Both methods showed that genotype (p<0.05) and location (p<0.05) had a significant effect on antioxidant activity. A larger, significant effect was seen in the genotype by environment (G x E) interaction (p<0.0001) in the 2007 and 2008 growing years. Growing year did not have a significant on antioxidant activity. Although there was some variation in the resulting AOA values between the two methods, these differences were found not to be statistically significant by means of a folded F-Test (p < 0.05), and the AOA between the two methods was highly correlated (R² = 0.8866). This indicates that a microplate may be used in place of cuvettes to determine AOA using the DPPH free radical to increase testing speed while reducing the amount of sample and reagent used in testing. The research performed on the influence of genotype and environment could potentially allow plant breeders, food scientists and nutraceutical manufacturers to manipulate field pea genotypes and growing conditions to attain an ideal nutritional profile for use in functional foods and nutraceuticals.