Tetraploid wheat (Triticum turgidum L. var. durum) cv. ‘Langdon’ (LDN) and its near‐isogenic recombinant substitution line no. 68 (RSL no. 68) carrying the high grain protein gene Gpc‐B1 from emmer wheat, were compared in three greenhouse experiments to establish in which way Gpc‐B1 increases grain protein concentration (GPC). At anthesis, RSL no. 68 had higher soluble protein and amino acids concentrations in the flag leaf than LDN. At maturity, both lines presented a similar above ground biomass and grain yield. However, RSL no. 68 showed a higher total N content in ears, grain and chaff than LDN; N harvest index (NHI) was also higher because of a lower straw N concentration and higher grain N concentration. When both lines were grown with a low N supply, and when N supply was interrupted before anthesis, similar trends were observed but the differences in GPC were smaller. It is concluded that RSL no. 68 accumulates a higher GPC than LDN mainly because of a more efficient N remobilization from the leaves to the ears during grain filling.

Wheat grain protein content (GPC) is important for human nutrition and has a strong influence on the quality of pasta and bread. The objective of this study was to analyse the introduction of the Gpc-B1 allele into two Argentinean bread wheat cultivars. Near-isogenic lines were developed in 'ProINTA Oasis' and 'ProINTA Granar' using marker-assisted selection. Gpc-B1 lines showed a significant (P = 0.01) increase in GPC and a significant (P = 0.001) decrease in grain weight in comparison with control lines without Gpc-B1. Differences in yield were not significant (P = 0.49) between lines. Gpc-B1 lines significantly reduced (P = 0.02) straw nitrogen concentration at maturity and significantly increased (P = 0.02) the nitrogen harvest index. When data were analysed by genotype and environment, differences in some analysed parameters were found, indicating that Gpc-B1 expression may be affected by different genetic backgrounds and environmental conditions. These results suggest that the introgression of the Gpc-B1 allele into Argentinean wheat germplasm could be a valuable resource for improving GPC with no detrimental effect on grain yield.

The induction of two subtilisin-like proteases (P1 and P2) associated with stress-induced senescence in young plants was investigated in adult wheat plants during the grain-filling period. Western blot analysis of flag leaf extracts showed that P1 was induced very late in the life cycle of the plants (9 days post-anthesis) and that 7 days later it reached a 2.5-fold increase with respect to the initial value at anthesis. On the other hand, the P2 signal was already detected previous to anthesis and increased soon after anthesis, reaching a fourfold increase by the end of the grain-filling period. The induction of P1 and P2 temporally correlates with the degradation of the Rubisco small and large subunits in the flag leaf, as well as with nitrogen (N) accumulation in the ears. At the same time, a decrease in the endogenous concentration of the cytokinins isopentenyladenine and isopentenyladenosine (iP ? iPA) in the leaves was observed. In detached leaves senescing in the dark, the levels of both proteases were affected by 6-benzylaminopurine application: the induction of P1 was completely prevented, whereas the induction of P2 was reduced. Our findings demonstrate that both P1 and P2 are expressed in leaves of adult plants and are induced during natural senescence. These results enable us to postulate their participation in N remobilization to developing grains during monocarpic senescence and their regulation by a cytokinin-mediated mechanism.

The pasture legume Lotus glaber Mill. has colonized the Flooding Pampa (Argentina) in spite of high environmental heterogeneity. Morphological characters of plants from different populations were compared to evaluate if plastic or genetic differentiation could have contributed to such a widespread geographic distribution. Plants were collected at random from six different sites and grown in a greenhouse for five months. Clonal replicates of those plants were cultivated in pots on a native and a common soil. Populations were replicated three times and each replicate (pot) had three plants from the same clone. The number of primary shoots, internode length, leaf length and width and shoot length were recorded and the significance of population mean differences determined. All characters, except for leaf width, differed between populations on each sampling in both sets of experiments. This variability is therefore best explained by genetic differentiation of the populations. morphological variation / environmental heterogeneity / naturalized species / Lotus glaber Mill. / genetic differentiation Résumé-Étude de la variabilité morphologique dans les populations de Lotus glaber Mill. (Fabaceae). La légumineuse fourragère Lotus glaber Mill a colonisé la Pampa inondée en Argentine malgré la très grande hétérogénéité des conditions environnementales. Dans cette étude nous comparons la morphologie de différentes populations afin de déterminer si une plasticité phénotypique ou une différenciation écotypique ont permis une aussi large dispersion géographique de l'espèce. Des plantes représentatives de 6 sites ont été transplantées et cultivées en serre durant 5 mois. Des boutures de ces différents plants ont également été cultivées dans des pots remplis avec le sol original des sites correspondants ainsi qu'avec un sol unique provenant d'un autre site. Le nombre de pousses primaires, la longueur des inter-noeuds, la longueur et la largeur des feuilles et la longueur des pousses ont été mesurées et la validité statistique des différences à la moyenne de la population a été déterminée. Toutes les caractéristiques morphologiques, sauf la largeur des feuilles ont montré des différences pour chaque échantillon et dans chaque série d'expériences. Ce type de variabilité pourrait être mieux expliqué par une différenciation d'écotypes que par une plasticité phénotypique. variabilité morphologique / hétérogénéité environnementale / adaptation des espèces / Lotus glaber Mill. / écotype

No abstract