Pea (Pisum sativum L.) is the third most important grain legume worldwide, and the increasing demand for protein-rich raw material has led to a great interest in this crop as a protein source. Seed yield and protein content in crops are strongly determined by nitrogen (N) nutrition, which in legumes relies on two complementary pathways: absorption by roots of soil mineral nitrogen, and fixation in nodules of atmospheric dinitrogen through the plant-Rhizobium symbiosis. This study assessed the potential of naturally occurring genetic variability of nodulated root structure and functioning traits to improve N nutrition in pea. Glasshouse and field experiments were performed on seven pea genotypes and on the 'Cameor' x 'Ballet' population of recombinant inbred lines selected on the basis of parental contrast for root and nodule traits. Significant variation was observed for most traits, which were obtained from non-destructive kinetic measurements of nodulated root and shoot in pouches, root and shoot image analysis, (15)N quantification, or seed yield and protein content determination. A significant positive relationship was found between nodule establishment and root system growth, both among the seven genotypes and the RIL population. Moreover, several quantitative trait loci for root or nodule traits and seed N accumulation were mapped in similar locations, highlighting the possibility of breeding new pea cultivars with increased root system size, sustained nodule number, and improved N nutrition. The impact on both root or nodule traits and N nutrition of the genomic regions of the major developmental genes Le and Af was also underlined.

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Marker-assisted breeding could significantly increase progress in improving crop drought tolerance, if QTL with significant effects on crop yield in stress environments can be identified. The objective of this research was to obtain a first assessment of a putative drought tolerance QTL on linkage group 2 (LG 2) of pearl millet. This was done by comparing hybrids made with topcross pollinators (TCP) based on progenies selected from the original mapping population for presence of the tolerant allele at the target QTL versus field performance in the phenotyping environments. A set of 36 topcross hybrids was evaluated in 21 field environments, which included both non-stressed and drought-stressed treatments during the flowering and grain filling stages. The QTL-based hybrids were significantly, but modestly, higher yielding in a series of both absolute and partial terminal stress environments. However, this gain under stress was achieved at the cost of a lower yield in the non-stressed evaluation environments. This particular pattern of adaptation in the QTL-based hybrids was consistent with their general phenotypeearly flowering, limited effective basal tillering, low biomass and a high harvest index (HI)-which resembled that of the drought tolerant parent of the original mapping population. The results thus confirmed the effectiveness of the putative drought tolerance QTL on LG 2, but suggested that it may enhance drought tolerance by favoring a particultar phenotype with adaptation to terminal stress. #

Long-chain acyl-CoA synthetase (LACS, EC 6.2.1.3) catalyzes the ATP-dependent activation of free fatty acid to form acyl-CoA, which, in turn, serves as the major acyl donor for various lipid metabolic pathways. Increasing the size of acyl-CoA pool by enhancing LACS activity appears to be a useful approach to improve the production and modify the composition of fatty acid-derived compounds, such as triacylglycerol. In the present study, we aimed to improve the enzyme activity of Arabidopsis thaliana LACS9 (AtLACS9) by introducing random mutations into its cDNA using error-prone PCR. Two AtLACS9 variants containing multiple amino acid residue substitutions were identified with enhanced enzyme activity. To explore the effect of each amino acid residue substitution, single-site mutants were generated and the amino acid substitutions C207F and D238E were found to be primarily responsible for the increased activity of the two variants. Furthermore, evolutionary analysis revealed that the beneficial amino acid site C207 is conserved among LACS9 from plant eudicots, whereas the other beneficial amino acid site D238 might be under positive selection. Together, our results provide valuable information for the production of LACS variants for applications in the metabolic engineering of lipid biosynthesis in oleaginous organisms.