Contribution of Different Organs to Grain Filling in Durum Wheat under Mediterranean Conditions I. Contribution of Post-Anthesis Photosynthesis and Remobilization

Under Mediterranean conditions, drought affects cereals production principally through a limitation of grain filling. In this study, the respective role of post‐anthesis photosynthesis and carbon remobilization and the contribution of flag leaf, stem, chaff and awns to grain filling were evaluated under Mediterranean conditions in durum wheat (Triticum turgidum var. durum) cultivars. For the purpose, we examined the effects of shading and excision of different parts of the plant and compared carbon isotope discrimination (Δ) in dry matter of flag leaf, stem, chaff, awns and grain at maturity and in sap of stem, flag leaf, chaff and awns, this last measurement providing information on photosynthesis during a short period preceding sampling. Source–sink manipulations and isotopic imprints of different organs on final isotope composition of the grain confirmed the high contribution of both carbons assimilated by ears and remobilized from stems to grain filling, and the relatively low contribution of leaves to grain filling. Grain Δ was highly and significantly associated with grain yield across treatments, suggesting the utilization of this trait as an indicator of source–sink manipulations effects on grain yield. Chaff and awns Δ were better correlated with grain Δ than stem and leaf Δ, indicating that chaff were more involved in grain filling than other organs. Moreover, in chaff, sap Δ was highly significantly correlated with dry matter Δ. These results suggest the use of Δ for a rapid and non‐destructive estimation of the variation in the contribution of different organs to grain filling

Participation of green organs to grain filling in triticum turgidum var durum grown under mediterranean conditions

In wheat, flag leaf, stem, chaff and awns contribute to grain filling through photosynthesis and/or re-mobilization. Environmental and genetic effects on the relative contribution of each organ were examined by analyzing the consequences of sink-source manipulations (shading and excision) and by comparing carbon isotope discrimination (D) values in dry matter (at maturity) and sap (two weeks after anthesis) in six durum wheat genotypes grown in two contrasting seasons. The contribution of flag leaf, stem, chaff and awns to grain filling, estimated by sink-source manipulations, highly varied with the season. The contribution of ear photosynthesis and re-mobilization from the stem increased with post-anthesis water stress. They showed a large genetic variation that was, however, not clearly associated to morphological characteristics of ear and stem. Isotopic imprints of chaff on grain D were identified as a possible surrogate of the destructive and cumbersome sink-source manipulations to evaluate the contribution of carbon assimilated in ears or re-mobilized from stem. This might facilitate screening of genetic resources and allow the combining of favourable drought tolerance mechanisms in wheat

Multitraits evaluation of Pakistani ecotypes of berseem clover (<i>Trifolium alexandrinum</i> L.) under full-irrigation and water restriction conditions

Summary Berseem clover (Trifolium alexandrinum L.) is an important forage crop in Pakistan and many ecotypes are grown across the country. Its yield is however frequently affected by insufficient irrigation due to unavailability of water. In the present study, twenty Pakistani ecotypes of berseem clover have been evaluated in lysimeters under full irrigation and water restriction conditions. In the full irrigation treatment soil humidity was maintained at field capacity, while in the water restriction treatment water was only supplied after severe wilting and to maintain humidity in the deep profile of the soil. Assessed traits included forage yield, calculated as the sum of the biomass harvested at 70 and 110 DA days after emergence, and morpho-physiological traits. Significant effects of water restriction were noted on yield, leaf gas exchange parameters, canopy temperature and osmotic adjustment. Most morpho-physiological traits had higher broad sense heritability than forage yield, both under full irrigation and water restriction conditions. Water restriction increased genetic and phenotypic variability and heritability of most traits under study. Under these conditions forage yield was positively associated to leaf temperature and recovery rate index and, under full irrigation, to net photosynthetic rate, canopy depression temperature and leaf area. The possible use of these traits as indirect selection criteria in berseem clover breeding programs is discussed. Some ecotypes with favorable traits such as high forage yield potential, good adaptation to water restriction and aptitude to multiple harvesting have also been identified.

La poésie haïtienne des origines à nos jours

L’article présente une rétrospective de la poésie haïtienne, depuis ses origines (areytos précolombiens et poésie populaire créole) jusqu’à nos jours. Après un bref rappel de l’histoire du pays qui a fortement marqué littérature et poésie, les principaux mouvements qui se sont succédé jusqu’à la fin du XXe siècle sont décrits, des « pionniers » ou « pseudo-classiques » jusqu’au surpluréalisme ». Compte tenu de l’impact considérable de l’exil (lié à la situation politique, économique et sociale) sur les arts haïtiens et la poésie en particulier, une place à part a été réservée, dans la poésie de la fin du XXe et du début du XXIe siècle, à la poésie de la diaspora, ainsi qu’à celle des poètes « errants », des poètes retournés après l’exil au pays natal, et des poètes « de l’intérieur ». Les principaux auteurs sont présentés, leurs principales œuvres publiées sont indiquées et commentées, éventuellement accompagnées de brefs extraits.The article presents a retrospective of Haitian poetry, from its origins (pre-Columbian areytos and popular creole poetry) to the present day. After a brief reminder of the history of the country, which has strongly marked literature and poetry, the main successive movements until the end of the XXth century are described, from the "pioneers" or "pseudo-classics" to the “surplurealism”. Considering the significant impact of exile (linked to the political, economic and social situation) on Haitian arts and poetry in particular, a special place was reserved in the poetry of the late XXth and early XXI^st^ century, to the poetry of the diaspora, as well as that of "wandering" poets, poets who returned after the exile to their native country, and poets "from the inside". The main authors are presented and their main published works indicated and commented, sometimes accompanied by brief extracts

Un siècle de poésie brésilienne

L’article présente une rétrospective de la poésie brésilienne depuis un siècle. Les principales caractéristiques des mouvements poétiques qui se sont succédé jusqu’à 1964 (modernisme, postmodernisme, génération 45, et mouvements d’avant-garde et de poésie populaire de l’après-guerre) sont décrites et mises en relation avec le contexte sociopolitique, et les principaux auteurs sont présentés. Le développement progressif de la création poétique hors des grandes villes du Sud, et en particulier dans le Nordeste, est souligné. Les différentes formes d’expression poétique lors de la dictature militaire (1964-1985) (poema/processo, poésie marginale, mouvement catequese poética, poètes indépendants) sont évoquées. Sont ensuite décrits les formes et styles très divers sous lesquels s’exprime la poésie au lendemain de la dictature, l’accent étant mis sur la poésie écrite par les femmes et les minorités discriminées ou exploitées (Noirs, homosexuels, habitants des favelas). Sont enfin évoqués le repente et la littérature de cordel, formes poétiques populaires toujours bien vivantes aujourd’hui, ainsi que la poésie en langues indigènes qui commence peu à peu à se développer et à se faire mieux connaître. En conclusion sont analysées les caractéristiques majeures de la poésie brésilienne contemporaine. L’essai est complété par un choix de textes de douze poètes brésiliens contemporains, traduits en français.The article presents a retrospective of the Brazilian poetry along the last century. The main characteristics of the poetic movements that followed each other until 1964 (modernism, postmodernism, generation 45, and the avant-garde and popular poetry movements of the post-war period) are described and connected with the socio-politic context, and the main authors are presented. The progressive development of the poetic creation out of the big cities of the South, in particular in the Nordeste, is highlighted. The various forms of poetic expression during the military dictatorship (1964-1985) (the poema/processo movement, the marginal poetry, the catequese poética movement, and some “independent” poets) are then evoked. The various forms and styles in which poetry is expressed in the aftermath of the dictatorship are described, with emphasis on the poetry written by women and discriminated or exploited minorities (Black people, homosexuals, inhabitants of the favelas). Lastly, the repente and the cordel literature, popular poetic forms still very much alive today, are mentioned, as well as the poetry in indigenous languages, which is gradually beginning to develop and become better known. In conclusion, we analyse the major characteristics of the Brazilian contemporary poetry. The essay is completed by a selection of texts of twelve contemporary Brazilian poets, translated into French

Contribution à l'étude de la résistance à la sécheresse chez le blé tendre (Triticum aestivum L.) et chez le blé dur (Triticum durum Desf.) : étude de l'accumulation de la proline au cours du cycle de développement

International audienc

Spontaneous hybridization between bread wheat (Triticum aestivum L.) and its wild relatives in Europe

Correspondance: [email protected] audienceIn Europe, wild wheat relatives of the Triticum–Aegilops complex grow in sympatry with cultivated bread wheat (Triticum aestivum L.) and spontaneous hybridization is known to occur. With the development of transgenic wheat, an understanding of the likelihood and occurrence of hybridization and introgression between wheat and its relatives is needed for use in risk assessment. To assess the probability of wheat to wild relative gene introgression, the distribution and biology of wheat wild relatives and their genome affinity and crossability with bread wheat were reviewed. Twelve of the 22 known Aegilops species, as well as one wild Triticum species, T. monococcum L. subsp. aegilopoides (Link) Thell., are known to occur in Europe near or within wheat cultivation. Five tetraploid species, Ae. cylindrica Host., Ae. triuncialis L., Ae. geniculata Roth., Ae. neglecta Req. ex Berthol., and Ae. biuncialis Vis., have wide distribution in most European countries. Bread wheat, wild Aegilops species, and Triticum species are predominantly autogamous (except Ae. speltoides Tausch, typically allogamous), but outcrossing among species is possible depending on species sympatry, concurrent flowering, and sexual compatibility. Spontaneous hybridization with wheat was reported for most of the tetraploid Aegilops species. The probability of gene transfer and gene retention in hybrid progenies is, however, higher when a gene is located on a shared genome, particularly on the D genome shared with Ae. cylindrica and Ae. ventricosa Tausch. Case-by-case and region-by-region assessments are needed to evaluate the risk associated with production and competitiveness of hybrids and their progen

Low nitrogen tolerance in tropical quality protein maize (Zea mays L.): value of predictive traits

E-mail Addresses: [email protected] audienceIn the tropics, maize ( Zea mays L.) is often grown under low N conditions. Information on the respective role of N uptake and partitioning at anthesis in determining grain yield under low N is scarce. Senescence traits have been proposed as secondary traits to select for low N tolerance, but the stability of their association with yield under different environmental conditions has been rarely described. In the present study we analyzed the associations between grain yield, N uptake and partitioning at anthesis, dry matter matter partitioning, and senescence traits during two seaons in QPM (quality protein maize) hybrids. Association between grain yield and N uptake at anthesis, when found, was mainly explained by a close relationship between grain yield and above-ground biomass. No relationship was found between grain yield and N partitioning at anthesis. In both seasons grain yield was significantly positively associated with ear to above-ground biomass and ear to tassel weight ratios. The magnitude of the correlation between grain yield and senescence traits highly depended on climatic condition

Is crop breeding the first step to fill the yield gap? Understanding the impact and constraints of developing new improved varieties

International audienceOne of the main challenges of the present century is to face the increasing food demand by enhancing farmers’ yield, but with less area and less water. The present paper analyzes how crop improvement and agronomic management have contributed to this objective, until now either by improving crop yield potential or by filling the gaps between yield potential and farmers’ yield. It reviews critically whether better varieties can replace or reduce the need of good agronomic practices in the future. It finally attempts to describe the role to be played by crop management technologies over the next decades to allow the genetic potential of new varieties to be expressed.Un des principaux défis de notre siècle est de faire face à la demande alimentaire croissante, avec moins de surface cultivable et moins d’eau, en améliorant les rendements paysans. Le présent article analyse dans quelle mesure l’amélioration végétale et celle des techniques culturales ont contribué à cet objectif, jusqu’à présent en augmentant le rendement potentiel ou en comblant l’écart entre rendement potentiel et rendement paysan. Il examine de manière critique si de meilleures variétés peuvent, dans le futur, remplacer ou réduire le besoin de bonnes pratiques agronomiques. Il tente finalement de décrire le rôle que pourraient jouer les techniques culturales au cours des prochaines décades dans l’expression du potentiel génétique