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Drought and unpredictable rainfall decrease sorghum (Sorghum bicolor, L. Moench) productivity in semiarid regions of West Africa. Understanding the genetic architecture of drought tolerance of sorghum germplasm from breeding programs could contribute to efficient molecular breeding in West Africa. This study aimed to dissect the genetic architecture of drought adaptation to develop high-throughput and breeder-friendly markers for rapid introgression of favorable trait-associated alleles into farmers' preferred varieties. First, we used genotyping-by sequencing to characterize 159,101 SNPs across 756 accessions of the West African sorghum association panel assembled from breeding programs of Senegal, Niger, Mali, and Togo. The genetic diversity structured by botanical types and subpopulations within botanical types across countries. Large-effect quantitative trait loci (QTL) for photoperiodic flowering indicate an oligogenic architecture of flowering time in West African sorghum. Secondly, we applied genome-wide association studies using pre- and post-flowering drought response variables from ten managed water stress environments to identify genomic regions associated with drought responses. Significantly positive pleiotropic associations contributed to high phenotypic variance and colocalized with known staygreen (Stg) loci. Results suggest the existence of Stg alleles in West African sorghum. Three marker loci associated with large-effect alleles were converted into breeder-friendly markers and used in marker-assisted selection for drought tolerance. These resources combined with discoveries from the global scientific community are used to accelerate the development of locally-adapted varieties through efficient genomics-assisted breeding to meet global food demand in semiarid regions of West Africa.

Tremendous progress has been made in terms of crop breeding in West-Africa. However, National breeding programs in West-Africa still have limited resources and are generally too isolated to access significant fundings allowing to develop more innovative breeding approaches. A regional network that brings together breeding programs on several crops including sorghum was initiated in 2018. It gathers 5 different countries in West-Africa (Burkina Faso, Mali, Niger, Senegal, and Togo) and creates the conditions of germplasm exchange as well as data and information sharing. The network is supported by a charter that establishes the rules and responsibilities of its members, covers intellectual property issues related to the exchange and use of germplasm and data, while ensuring a network as functional as possible, and confidence and trust among partners. Measurement variables and methods as well as experimental protocols have been collectively harmonized around common ontologies. Experimental data are stored and analyzed in a shared instance of the Breeding Management System (BMS) and accessible to the members of the network. Globally, since 2018, 61 sorghum varieties have been evaluated through experimental trials conducted in 21 different environments in West-Africa. Between 28 and 45 varieties were evaluated each year in 9 to 13 locations. The data produced so far provides a valuable database on the adaptation of a large set of sorghum varieties and breeding lines representative of the elite material that currently forms the core of national breeding programs in West-Africa. Germplasm exchange allowed breeders to test varieties from other countries and revealed them some interesting material for registration or as trait donors. The multi environment trials also provided valuable data to progress on characterization of photoperiod sensitivity and modeling of target environments. Perspectives to link and extend this network to on-farm testing networks and farmers' germp

Identifying the environmental and genetic drivers that occur in phenotype's expression can help to dissect complex traits. This study aims to identify the critical sorghum growth period sensitive to environmental stimuli and to assess genetic loci's effects along the environmental gradient. We evaluated a mapping population of 253 recombinant inbred lines (RIL) in five natural environments focusing on two photoperiod sensitivity traits: flag leaf ligulation and plant height as proxies for assessing grain mold resistance. Grain mold severity scores have been rated and yield components (panicle and grain weight per plant) have been measured. From initial results, variance component analysis attributed 21.50% of the flag leaf ligulation to the environment, and 41.22% of the variation to the genotype. For the plant height, environmental effects accounted for 51.16 % of the phenotypic variance, followed by the genotype effect (24.96%). Using environmental means, we applied the joint regression analysis to unravel the pattern underneath the trait variation. Further, we will implement the CERIS (Critical Environmental Regressor through Informed Search) framework to replace environmental means with an environmental index biologically informing. The combination of environmental parameters: photoperiod (daylength), growing degree day (GDD, °C), diurnal temperature range (DTR, °C), photothermal time (PTT, °C), precipitation (PR, mm); and growth windows with the strongest correlation will be chosen as the environmental index. By regressing again the phenotypes of each RIL on the environment index, two reaction-norm parameters (intercept and slope) will be obtained. The genetic map will then be built using reaction-norm values (as phenotypes) with 952 SNP markers from 3495 SNPs generated by DArTag technology, to identify the genetic loci underlying phenotypic plasticity along environment gradient.

Appartient à l’ensemble documentaire : GTextes1, Ouvrages illustrés, Catalogues

Appartient à l’ensemble documentaire : GTextes1, Ouvrages illustrés, Catalogues

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Appartient à l’ensemble documentaire : PrnS001

Appartient à l’ensemble documentaire : PrnS001

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Thèse de médecine de Paris n° 139

Thèse de médecine de Paris n° 139

Thèse de médecine de Paris n° 139

Thèse de médecine de Paris n° 139

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8 pages

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