Protein content and dry weight of seeds from various pea genotypes

Pea seed protein content (SPC) and seed dry weight (SDW) are both influenced by genetic and environmental factors. To assess the variations of these within-plant traits between seeds, six genotypes were field tested. The sequential seed development at nodes along the main stem was determined. Nitrogen fixation was measured by the acetylene reduction assay (ARA). At maturity, protein content and dry weight were measured according to seed position on the plant. Individual protein content was determined by near-infrared transmission spectroscopy. The results show a significant difference in protein content between nodes of the genotypes Solara, L765 and L833. Protein content tended to decrease from the bottom to the top of the plant for these genotypes. The difference in protein content between the lowest and the uppermost node was about 26 g kg(-1) for Solara, 40 g kg(-1) for L765 and 49 g kg(-1) for L833. There were also significant differences in dry weight between plant nodes for all genotypes, except Finale. In addition, the range of difference in dry weight between plant nodes was higher than that for protein content. Further, to determine the influence of morphological position on individual protein content and dry weight, multiple linear regression was established on node position, pod position on the node, and seed position within pods. The results showed that protein content and dry weight were not influenced either by within-pod seed position or pod position on the raceme. Moreover, protein content and dry weight were mainly influenced by node position on the main stem. However, for protein content, the effect of node position varied with genotype, indicating a genetic variability for this character. This genetic variability could be attributed to the difference between genotypes in the ability to maintain nitrogen fixation during the onset of seed filling. For dry weight, the decrease in seed weight for upper nodes of the plant also varied with genotype in relation to the duration of seed filling and the seed growth rate.