In order to contribute to the inventory of genomic areas involved in maize cell wall lignification and degradability, QTL analyses were investigated in a RIL progeny between an old Minnesota13 dent line (WM13) and a modern Iodent line (RIo). Significant variation for agronomic- and cell wall-related traits was observed for the RIL per se (plants without ears) and topcross (whole plants) experiments after crossing with both old (Ia153) and modern tester (RFl) lines. Three QTLs for stover (plant without ear) yield were observed in per se experiments, with alleles increasing yield originating from RIo in two genomic locations with the highest effects. However, no QTL for whole plant yield was detected in topcross experiments, despite the fact that two QTLs for starch content were shown with increasing alleles originating from the modern RIo line. Fifteen lignin QTLs were shown, including a QTL for Klason lignins in per se experiments, located in bin 2.04, which explained 43 % of the observed genetic variation. Thirteen QTLs for p-hydroxycinnamic acid contents and nine QTLs related to the monomeric composition of lignin were shown in per se experiments, with syringaldehyde and diferulate QTLs explaining nearly 25 % of trait variations. Nine and seven QTLs for cell wall digestibility were mapped in per se and topcross experiments, respectively. Five of the per se QTLs explained more than 15 % of the variation, up to nearly 25 %. QTL positions in bins 2.06, 5.04, 5.08 and 8.02 for ADL/NDF, IVNDFD, lignin structure and/or p-hydroxycinnamic acid contents have not been previously shown and were thus first identified in the RIo × WM13 progeny. Based on QTL colocalizations, differences in cell wall degradability between RIo and WM13 were less often related to acid detergent lignin (ADL) content than in previous RIL investigations. QTL colocalizations then highlighted the probable importance of ferulate cross linkages in variation for cell wall digestibility. No colocalizations of QTL for cell wall phenolic-related traits were shown with genes involved in monolignol biosynthesis or polymerization. In contrast, colocalizations were most often shown with MYB and NAC transcription factors, including orthologs of master genes involved in Arabidopsis secondary wall assembly. QTL colocalizations also strengthened the probable involvement of members of the CoA-dependent acyltransferase PF02458 family in the feruloylation of arabinoxylan chains.

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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.

The objectives of this study were to determine the effect of low mineral supply on plant growth and the uptake and redistribution of mineral N by different plant organs according to the period of uptake. A glasshouse study was conducted on two pea genotypes, L833 and cv. Frisson, fed without or with 4 mM NO 3. Plants fed with 4 mM N were labelled for 5 days with 15 N at three stages: 7 leaf stage, beginning of flowering, and beginning of seed filling. Plants were harvested at day 6 and at later stages. The results indicated for the two genotypes that supplying 4 mM N to the plants significantly increased their total dry weight up to the beginning of seed filling, whereas nodule dry weight was reduced. Genotype differences in N uptake and redistribution among plant organs were minor. When plants were labelled with 15 N at early stages of growth, about 60% of total plant 15 N was located in leaves. At maturity the proportion of 15 N recovered in seeds was about 60% for both genotypes. When plants were labelled at the beginning of seed filling, 15 N was mainly located in young organs such as upper leaves, pods and seeds. During seed fill the remobilisation of 15 N to seeds occurred from all organs of the plant. At physiological maturity about 70% of 15 N was located in seeds.

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