Variability of digestibility criteria in maize elite hybrids submitted for registration in the French official catalogue

Since 1995, a methodological study has been conducted to determine the feasibility and accuracy of various in vitro digestibility criteria used to estimate genotypic variation in silage maize elite hybrids in the framework of French registration official trials. The study dealt with eighteen early hybrids, amongst which seven official control hybrids and eleven new hybrids submitted for French registration in 1995. Experiments were conducted at seven locations in 1995 and ten locations in 1996. The biochemical components and in vitro digestibility of whole-plant and cell-walls were predicted by near infra-red reflectance spectroscopy. Genotypic variation was significant for all criteria studied. In vitro whole-plant and cell-wall digestibility assessments and the predicted net energy value (UFL) were all notably accurate, discriminant and relevant, with some differences according to the method of assessment. Ranges observed between hybrids tested within the official French registration network were similar to those obtained with control genotypes known for their low or high digestibility values, from previous experiments. Data suggested that, in addition to the usual agronomic characteristics, digestibility or net energy value criteria should also be considered in the silage maize registration process. (© Inra/Elsevier, Paris.)Variabilité pour les critères de digestibilité au sein d'hybrides de maïs proposés à l'inscription au catalogue français. Depuis 1995, une étude méthodologique a été entreprise dans le but d'étudier la faisabilité et la précision de différents critères liés à la digestibilité in vitro pour estimer la variabilité génotypique au sein d'hybrides élites de maïs ensilage testés dans le cadre des essais officiels pour l'inscription au catalogue français. Cette étude porte sur 18 hybrides précoces incluant sept témoins d'inscription et onze nouveaux hybrides proposés à l'inscription en France en 1995, expérimentés dans sept lieux en 1995 et dix lieux en 1996. Par spectroscopie de réflectance dans le proche infrarouge, les composants biochimiques et les digestibilité in vitro de plantes entières et de parois ont été prédits. Tous les critères étudiés étaient variables génotypiquement. Les estimations de digestibilités de plantes entières et de parois, ainsi que la prédiction de la valeur énergétique nette (UFL), étaient précises, discriminantes et pertinentes, avec quelques différences selon les méthodes utilisées. Les écarts de digestibilité et de valeur énergétique nette observés entre ces hybrides élites testés dans le réseau officiel d'inscription sont équivalents à ceux obtenus pour des génotypes témoins déjà connus pour leur faible ou forte digestibilité. L'intérêt d'introduire un critère de digestibilité ou de valeur énergétique nette, en plus des critères agronomiques habituels, pour l'inscription des variétés de maïs ensilage en France a clairement été montrée. (© Inra/Elsevier, Paris.

Variability of digestibility criteria in maize elite hybrids submitted for registration in the French official catalogue

Since 1995, a methodological study has been conducted to determine the feasibility and accuracy of various in vitro digestibility criteria used to estimate genotypic variation in silage maize elite hybrids in the framework of French registration official trials. The study dealt with eighteen early hybrids, amongst which seven official control hybrids and eleven new hybrids submitted for French registration in 1995. Experiments were conducted at seven locations in 1995 and ten locations in 1996. The biochemical components and in vitro digestibility of whole-plant and cell-walls were predicted by near infra-red reflectance spectroscopy. Genotypic variation was significant for all criteria studied. In vitro whole-plant and cell-wall digestibility assessments and the predicted net energy value (UFL) were all notably accurate, discriminant and relevant, with some differences according to the method of assessment. Ranges observed between hybrids tested within the official French registration network were similar to those obtained with control genotypes known for their low or high digestibility values, from previous experiments. Data suggested that, in addition to the usual agronomic characteristics, digestibility or net energy value criteria should also be considered in the silage maize registration process. (© Inra/Elsevier, Paris.)Variabilité pour les critères de digestibilité au sein d'hybrides de maïs proposés à l'inscription au catalogue français. Depuis 1995, une étude méthodologique a été entreprise dans le but d'étudier la faisabilité et la précision de différents critères liés à la digestibilité in vitro pour estimer la variabilité génotypique au sein d'hybrides élites de maïs ensilage testés dans le cadre des essais officiels pour l'inscription au catalogue français. Cette étude porte sur 18 hybrides précoces incluant sept témoins d'inscription et onze nouveaux hybrides proposés à l'inscription en France en 1995, expérimentés dans sept lieux en 1995 et dix lieux en 1996. Par spectroscopie de réflectance dans le proche infrarouge, les composants biochimiques et les digestibilité in vitro de plantes entières et de parois ont été prédits. Tous les critères étudiés étaient variables génotypiquement. Les estimations de digestibilités de plantes entières et de parois, ainsi que la prédiction de la valeur énergétique nette (UFL), étaient précises, discriminantes et pertinentes, avec quelques différences selon les méthodes utilisées. Les écarts de digestibilité et de valeur énergétique nette observés entre ces hybrides élites testés dans le réseau officiel d'inscription sont équivalents à ceux obtenus pour des génotypes témoins déjà connus pour leur faible ou forte digestibilité. L'intérêt d'introduire un critère de digestibilité ou de valeur énergétique nette, en plus des critères agronomiques habituels, pour l'inscription des variétés de maïs ensilage en France a clairement été montrée. (© Inra/Elsevier, Paris.

Dissecting Bread Wheat Heterosis through the Integration of Agronomic and Physiological Traits

International audienceTo meet the challenge of feeding almost 10 billion people by 2050, wheat yield has to double by 2050. However, over the past 20 years, yield increase has slowed down and even stagnated in the main producing countries. Following the example of maize, hybrids have been suggested as a solution to overcome yield stagnation in wheat. However, wheat heterosis is still limited and poorly understood. Gaining a better understanding of hybrid vigor holds the key to breed for better varieties. To this aim, we have developed and phenotyped for physiological and agronomic traits an incomplete factorial design consisting of 91 hybrids and their nineteen female and sixteen male parents. Monitoring the plant development with normalized difference vegetation index revealed that 89% of the hybrids including the five higher yielding hybrids had a longer grain filling phase with a delayed senescence that results in larger grain size. This average increase of 7.7% in thousand kernel weight translated to a positive mid-parent heterosis for grain yield for 86% of hybrids. In addition, hybrids displayed a positive grain protein deviation leading to a +4.7% heterosis in protein yield. These results shed light on the physiological bases underlying yield heterosis in wheat, paving new ways to breed for better wheat hybrids

In search of a maize ideotype for cell wall enzymatic degradability using histological and biochemical lignin characterization.

International audienceGrass cell wall degradability is conventionally related to the lignin content and to the ferulic-mediated cross-linking of lignins to polysaccharides. To better understand the variations in degradability, 22 maize inbred lines were subjected to image analyses of Fasga- and Mäule-stained stem sections and to chemical analyses of lignins and p-hydroxycinnamic acids. For the first time, the nearness of biochemical and histological estimates of lignin levels was established. Combination of histological and biochemical traits could explain 89% of the variations for cell wall degradability and define a maize ideotype for cell wall degradability. In addition to a reduced lignin level, such an ideotype would contain lignins richer in syringyl than in guaiacyl units and preferentially localized in the cortical region rather than in the pith. Such enrichment in syringyl units would favor wall degradability in grasses, contrary to dicots, and could be related to the fact that grass syringyl units are noticeably p-coumaroylated. This might affect the interaction capabilities of lignins and polysaccharides

Genetic and molecular basis of grass cell-wall biosynthesis and degradability. II. Lessons from brown-midrib mutants

International audienceThe brown-midrib mutants of maize have a reddish-brown pigmentation of the leaf midrib and stalk pith, associated with lignified tissues. These mutants progressively became models for lignification genetics and biochemical studies in maize and grasses. Comparisons at silage maturity of bm1, bm2, bm3, bm4 plants highlighted their reduced lignin, but also illustrated the biochemical specificities of each mutant in p-coumarate, ferulate ester and etherified ferulate content, or syringyl/guaiacyl monomer ratio after thioacidolysis. Based on the current knowledge of the lignin pathway, and based on presently developed data and discussions, C3H and CCoAOMT activities are probably major hubs in controlling cell-wall lignification (and digestibility). It is also likely that ferulates arise via the CCoAOMT pathway

Genetic control and prospects of predictive breeding for European winter wheat's Zeleny sedimentation values and Hagberg-Perten falling number

Sedimentation values and falling number in the last decades have helped maintain high baking quality despite rigorous selection for grain yield in wheat. Allelic combinations of major loci sustained the bread-making quality while improving grain yield. Glu-D1, Pinb-D1, and non-gluten proteins are associated with sedimentation values and falling number in European wheat. Zeleny sedimentation values (ZSV) and Hagberg-Perten falling number (HFN) are among the most important parameters that help determine the baking quality classes of wheat and, thus, influence the monetary benefits for growers. We used a published data set of 372 European wheat varieties evaluated in replicated field trials in multiple environments. ZSV and HFN traits hold a wide and significant genotypic variation and high broad-sense heritability. The genetic correlations revealed positive and significant associations of ZSV and HFN with each other, grain protein content (GPC) and grain hardness; however, they were all significantly negatively correlated with grain yield. Besides, GPC appeared to be the major predictor for ZSV and HFN. Our genome-wide association analyses based on high-quality SSR, SNP, and candidate gene markers revealed a strong quantitative genetic nature of ZSV and HFN by explaining their total genotypic variance as 41.49% and 38.06%, respectively. The association of known Glutenin (Glu-1) and Puroindoline (Pin-1) with ZSV provided positive analytic proof of our studies. We report novel candidate loci associated with globulins and albumins-the non-gluten monomeric proteins in wheat. In addition, predictive breeding analyses for ZSV and HFN suggest using genomic selection in the early stages of breeding programs with an average prediction accuracy of 81 and 59%, respectively

Whole Genome Association Mapping of <em>Fusarium</em> Head Blight Resistance in European Winter Wheat (<em>Triticum aestivum</em> L.)

<div><p>A total of 358 recent European winter wheat varieties plus 14 spring wheat varieties were evaluated for resistance to <i>Fusarium</i> head blight (FHB) caused by <i>Fusarium graminearum</i> and <i>Fusarium culmorum</i> in four separate environments. The FHB scores based on FHB incidence (Type I resistance)×FHB severity (Type II resistance) indicated a wide phenotypic variation of the varieties with BLUE (best linear unbiased estimation) values ranging from 0.07 to 33.67. Genotyping with 732 microsatellite markers resulted in 782 loci of which 620 were placed on the ITMI map. The resulting average marker distance of 6.8 cM allowed genome wide association mapping employing a mixed model. Though no clear population structure was discovered, a kinship matrix was used for stratification. A total of 794 significant (−log₁₀(p)-value≥3.0) associations between SSR-loci and environment-specific FHB scores or BLUE values were detected, which included 323 SSR alleles. For FHB incidence and FHB severity a total of 861 and 877 individual marker-trait associations (MTA) were detected, respectively. Associations for both traits co-located with FHB score in most cases. Consistent associations detected in three or more environments were found on all chromosomes except chromosome 6B, and with the highest number of MTA on chromosome 5B. The dependence of the number of favourable and unfavourable alleles within a variety to the respective FHB scores indicated an additive effect of favourable and unfavourable alleles, i.e. genotypes with more favourable or less unfavourable alleles tended to show greater resistance to FHB. Assessment of a marker specific for the dwarfing gene <i>Rht-D1</i> resulted in strong effects. The results provide a prerequisite for designing genome wide breeding strategies for FHB resistance.</p> </div

Allelic effects of dwarfing gene <i>Rht-D1</i> in a population of 372 European wheat varieties.

<p>Varieties carrying the mutant allele <i>Rht-D1b</i> (dwarfing type) showed an increased FHB score resulting in decreased resistance in four different environments.</p