Pourquoi sélectionner de nouvelles variétés de blé tendre adaptées à l’agriculture biologique ?

International audienceLongtemps marginale en France, l’agriculture biologique est un secteur émergent à fort potentiel : les objectifs fixés par la loi Grenelle I ambitionnaient de faire passer les surfaces cultivées en agriculture biologique de 2% de la SAU française à 6% en 2012 puis de franchir un nouveau palier avec une couverture de 20% de la SAU en 2020. Même si en réalité c’est seulement 3% de la SAU qui est actuellement cultivée en agriculture biologique, les recherches consacrées à ce domaine, dont le cahier des charges interdit le recours aux produits de la chimie de synthèse, permettent d’anticiper le probable fort renchérissement du coût de l’énergie fossile (pic pétrolier).Ce travail pionnier de réduction des engrais et des pesticides sera alors utile à l’ensemble de l’agriculture. Tous les systèmes de culture ont bénéficié des progrès de la sélection végétale excepté l’agriculture biologique, parent pauvre de l’amélioration génétique. En effet la sélection s’est faite depuis 50 ans pour des itinéraires techniques artificialisés pour lesquels la fertilisation azotée minérale est abondante et où les herbicides sont utilisés pour lutter contre les adventices des cultures. Elle a conduit à l’obtention de variétés à paille courte donc peu concurrentielles vis-à-vis des mauvaises herbes et qui peinent en conditions de disponibilités réduites en azote, conditions rencontrées en agriculture biologique. La sélection variétale sur des critères adaptés à ces milieux aux contraintes fortes se justifie. Nous présenterons pourquoi elle peut être porteuse d’enseignements et discuterons de sa possible évolution au regard des premiers résultats obtenus

From selection to cultivation with the support of all stakeholders: first registration in France of two bread wheat varieties after VCU in organic farming system

As bread wheat is the most important cash crops for French organic farmers, the question of the kind of varieties farmers should be using is therefore very important. Most of varieties available were bred for intensive “conventional” farming systems (with high inputs of mineral fertilizers and pesticides), also screening current varieties for organic conditions becomes a necessity to identifiy suitable varieties for organic farming conditions in a short term experiment. After 20 years of selection and screening combined in two different crop management systems, low inputs and organic, two lines, Hendrix and Skerzzo, have been registered in the official catalogue with the special mention « organic farming ». For the second year of seed production, 150 hectares were sown in autumn 2013 to be sell to organic farmers in 2014. This successful process was possible with the support of all the agricultural organic sector associated in the initiative

Agronomic characteristics, grain quality and flour rheology of 372 bread wheats in a worldwide core collection

A core collection of 372 accessions representative of worldwide hexaploid bread wheat diversity [Balfourier, F.. Roussel, V., Strelchenko, P., Exbrayat-Vinson, F., Sourdille. P., Boutet, G., Koenig, J., Ravel, C.. Mitrofanova, O., Beckert, M., Charmer, G., 2007. A worldwide bread wheat core collection arrayed in a 384-well plate. Theoretical and Applied Genetics 114, 1265-1275] was used to evaluate the available genetic diversity of agronomic and quality characteristics. The traits assessed during the vegetative period were date of ear-emergence, date of flowering, lodging, disease susceptibility and pre-harvest sprouting. Thousand kernel weight, test weight, grain hardness, grain protein content, pentosan viscosity and grain colour were also measured. The rheological properties of the derived white flours were estimated using mixograph and alveograph tests. For most of the traits, a wide phenotypic variation was observed across all the accessions. Several parameters (mixograph width parameters before and after peak time, alveograph dough tenacity and extensibility, near infrared measurements, like those for protein content, and absorbance measurements of palmitic acid and linoleic acid content) made it easier to discriminate between the cultivars. The largest ranges of variation were found in landraces and old cultivars rather than in more recent varieties. This is evidence that there is sufficient variability available for rare alleles, which have been eliminated in breeding modern varieties to be detected. Such a core collection will therefore be a useful resource for future genetic studies on wheat quality

Genetic variability and stability of poultry feeding related characters in wheat, in relation to environmental variation

Thirty-four varieties of wheat were studied in a multisite experiment, under various environmental conditions. For all the characters affecting poultry feeding, except phosphorus, genotypic effects were highly significant. However, only potential applied viscosity appeared as a stable character essentially dependent on the genotype. Protein content, water-insoluble cell wall content and two characters corresponding to enzymatic activities (real applied viscosity and phytase activity) were influenced by environmental effects and genotype x environment interactions rather strongly. Nevertheless, for these four characters, some varieties were stably favourable, or stably unfavourable. Except a weak negative relation between protein content and yield, no antagonism between productivity and poultry feeding related characters appeared. (© Inra/Elsevier, Paris.)Étude de caractères importants pour l'alimentation des oiseaux d'élevage chez le blé tendre : variabilité génétique et stabilité de ces caractères par rapport aux variations du milieu. Une expérimentation multilocale a permis d'étudier 34 variétés de blé tendre d'hiver représentant une large gamme de variabilité génétique, dans des conditions environnementales contrastées. À l'exception de la quantité de phosphore total, les caractères importants pour l'alimentation des oiseaux d'élevage présentent tous un effet «génotype» hautement significatif. Cependant, seule la viscosité utile potentielle apparaît comme un caractère très stable et essentiellement sous la dépendance du génotype. La teneur en parois, la teneur en protéines et les deux variables qui traduisent des activités enzymatiques (viscosité utile réelle et activité phytasique) sont, elles, assez fortement soumises aux effets « milieu » et aux interactions « génotype x milieu ». Pour ces quatre caractères, on arrive néanmoins à identifier des variétés assez régulièrement favorables, ou assez régulièrement défavorables. Par ailleurs, exceptée une liaison faiblement négative entre le rendement et la teneur en protéines, il n'apparaît pas d'antagonisme entre la productivité et les caractéristiques importantes en alimentation des oiseaux d'élevage. (© Inra/Elsevier, Paris.

Genetic variability and stability of grain magnesium, zinc and iron concentrations in bread wheat

Four trials were conducted to study the grain magnesium (Mg), zinc (Zn) and iron (Fe) concentrations in bread wheat (Triticum aestivum L.). These trials used different sources of genotypes, including old French landraces, a worldwide germplasm collection and elite breeding lines or modem cultivars, grown in different environments. Mg concentration ranged from 600 to 1400 ppm in modem material, and reached 1890 ppm in some exotic genotypes. There was a negative correlation between grain yield and Mg concentration, but despite this dilution effect enough variability remains useful for selection purposes. Analysis of variance showed high genotype effects and Spearman rank correlations indicated moderate genotype by environment (G x E) interactions, so breeding for high Mg concentration can reasonably be envisaged. Zn concentration generally ranged from 15 to 35 ppm, but increased to 43 ppm in some genetic resources. Variation in Zn was also partly explained by a dilution effect. There was a significant effect of genotype, but also high G x E interactions, which would make direct selection more difficult than for Mg. However, as Zn and Mg concentrations appeared to be positively correlated, Zn concentration should respond favorably to selection for high Mg concentration. Fe concentration ranged from 20 to 60 ppm, and reached 88 ppm in non-adapted material. There were no significant genotype effects, very high G x E interactions, and the trait was poorly correlated to other mineral concentrations. Breeding for high Fe concentration will thus probably prove illusory

Economical optimization of a breeding scheme by selective phenotyping of the calibration set in a multi-trait context: application to bread making quality

International audienceTrait-assisted genomic prediction approach is a way to improve genetic gain by cost unit, by reducing budget allocated to phenotyping or by increasing the program's size for the same budget. This study compares different strategies of genomic prediction to optimize resource allocation in breeding schemes by using information from cheaper correlated traits to predict a more expensive trait of interest. We used bread wheat baking score (BMS) calculated for French registration as a case study. To conduct this project, 398 lines from a public breeding program were genotyped and phenotyped for BMS and correlated traits in 11 locations in France between 2000 and 2016. Single-trait (ST), multi-trait (MT) and trait-assisted (TA) strategies were compared in terms of predictive ability and cost. In MT and TA strategies, information from dough strength (W), a cheaper trait correlated with BMS (r = 0.45), was evaluated in the training population or in both the training and the validation sets, respectively. TA models allowed to reduce the budget allocated to phenotyping by up to 65% while maintaining the predictive ability of BMS. TA models also improved the predictive ability of BMS compared to ST models for a fixed budget (maximum gain: + 0.14 in cross-validation and + 0.21 in forward prediction). We also demonstrated that the budget can be further reduced by approximately one fourth while maintaining the same predictive ability by reducing the number of phenotypic records to estimate BMS adjusted means. In addition, we showed that the choice of the lines to be phenotyped can be optimized to minimize cost or maximize predictive ability. To do so, we extended the mean of the generalized coefficient of determination (CD) criterion to the multi-trait context (CD)

Phenomic selection in wheat breeding: identification and optimisation of factors influencing prediction accuracy and comparison to genomic selection

International audiencePhenomic selection is a promising alternative or complement to genomic selection in wheat breeding. Models combining spectra from different environments maximise the predictive ability of grain yield and heading date of wheat breeding lines. Phenomic selection (PS) is a recent breeding approach similar to genomic selection (GS) except that genotyping is replaced by near-infrared (NIR) spectroscopy. PS can potentially account for non-additive effects and has the major advantage of being low cost and high throughput. Factors influencing GS predictive abilities have been intensively studied, but little is known about PS. We tested and compared the abilities of PS and GS to predict grain yield and heading date from several datasets of bread wheat lines corresponding to the first or second years of trial evaluation from two breeding companies and one research institute in France. We evaluated several factors affecting PS predictive abilities including the possibility of combining spectra collected in different environments. A simple H-BLUP model predicted both traits with prediction ability from 0.26 to 0.62 and with an efficient computation time. Our results showed that the environments in which lines are grown had a crucial impact on predictive ability based on the spectra acquired and was specific to the trait considered. Models combining NIR spectra from different environments were the best PS models and were at least as accurate as GS in most of the datasets. Furthermore, a GH-BLUP model combining genotyping and NIR spectra was the best model of all (prediction ability from 0.31 to 0.73). We demonstrated also that as for GS, the size and the composition of the training set have a crucial impact on predictive ability. PS could therefore replace or complement GS for efficient wheat breeding programs

Genetic regions determine tolerance to nitrogen deficiency in European elite bread wheats grown under contrasting nitrogen stress scenarios

Increasing the nitrogen use efciency of wheat varieties is an important goal for breeding. However, most genetic studies of wheat grown at diferent nitrogen levels in the feld report signifcant interactions with the genotype. The chromo somal regions possibly involved in these interactions are largely unknown. The objective of this study was to quantify the response of elite bread wheat cultivars to diferent nitrogen feld stress scenarios and identify genomic regions involved in this response. For this purpose, 212 elite bread wheat varieties were grown in a multi-environment trial at diferent nitrogen levels. Genomic regions associated with grain yield, protein concentration and grain protein deviation responses to nitrogen defciency were identifed. Environments were clustered according to adjusted means for grain yield, yield components and grain protein concentration. Four nitrogen availability scenarios were identifed: optimal condition, moderate early defciency, severe late defciency, and severe continuous defciency. A large range of tolerance to nitrogen defciency was observed among varieties, which were ranked diferently in diferent nitrogen defciency scenarios. The well-known nega tive correlation between grain yield and grain protein concentration also existed between their respective tolerance indices. Interestingly, the tolerance indices for grain yield and grain protein deviation were either null or weakly positive meaning that breeding for the two traits should be less difcult than expected. Twenty-two QTL regions were identifed for the tolerance indices. By selecting associated markers, these regions may be selected separately or combined to improve the tolerance to N defciency within a breeding programme