DO NOT COPY. Genotypic variability of stem biomass accumulation & its drought regulation in sorghum : Insights for modelling ideotypes BIOSORG

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1 Genotypic variability of stem biomass accumulation & its drought regulation in sorghum : Insights for modelling ideotypes Delphine Luquet, Florian Larue, Lisa Perrier, Anne Clément Vidal, Sylvie Jaffuel, Jean Luc Verdeil, David Pot, Armelle Soutiras, Sandrine Roques, Christelle Baptiste, Frédéric Gatineau, Grégory Beurier, Lauriane Rouan BIOSORG , French National Agency , Agropolis & Cariplo

2 Context BIOSORG Improving biomass sorghum for end-use diversification (Southern France, West-Africa) Breeding target: stem biomass yield and quality in drought prone environments Genetic diversity Stem morphology, fiber & soluble sugar content drought tolerance Biomass end-use diversification Understand, at internode (tissue) level, stem biomass accumulation (GxE) Traits for genetic studies, ideotypes Lignin (Hemi)cellulose Soluble sugar

3 ? Objective of this study BIOSORG 1- Traits underlying stem biomass yield & quality & their co-variation (genotype, water status) 3- Implication for modelling biomass sorghum ideotypes?

4 Cumulated water (mm) d dry-down days Experimental design 2 field trials in Mauguio, 214 & 215 (INRA Diaphen platform; May-Sept) 8 biomass genotypes ( fiber/sugar, height, flowering 9 < < 13 Cd) 2 water treatments, 3 blocks (5 rows X 8m; 2 plants/m²) FLO predawn leaf water potential (bars) 1 Mauguio, France Average water deficit - 8 genotypes Days after dry-down onset C S

5 Cumulated water (mm) days Experimental design 2 field trials in Mauguio, 214 & 215 (INRA Diaphen platform; May-Sept) 8 biomass genotypes ( fiber/sugar, height, flowering 9 < < 13 Cd) 2 water treatments, 3 blocks (5 rows X 8m; 2 plants/m²) Main stem biomass & NIRS (ADL~lignin & soluble sugar) 25d dry-down FLO Mauguio, France Weekly: main stem leaf n, height, tillering, phenology Harvest: stem volume & (structural) density (g per cm 3 ) C S

6 Cumulated water (mm) days Experimental design 2 field trials in Mauguio, 214 & 215 (INRA Diaphen platform; May-Sept) 8 biomass genotypes ( fiber/sugar, height, flowering 9 < < 13 Cd) 2 water treatments, 3 blocks (5 rows X 8m; 2 plants/m²) Internode Samples IN-2 Top expanded Main stem biomass & NIRS (ADL~lignin & soluble sugar) 25d dry-down FLO IN-2 Mauguio, France Weekly: main stem leaf n, height, tillering, phenology Harvest: stem volume & (structural) density (g per cm 3 ) Wet chemistry: Lignin, soluble sugar Image based histology (FASGA staining) Red = lignin and blue = cellulose %Z1, %Z2, %RedZ1, %RedZ2 C Z2 S Zone Z1 1

7 Genotypic variability at stem and internode levels G effect at P<.1 for all traits (well-watered, final harvest) Main stem DW (g) Structural stem density (g/cm 3 ) 35 Main stem height ADL (~lignin, % stem DW) % Red (lignin) %redz2 Internode average length (cm) Zone 2 Zone 1 %RedZ1

8 Genotypic variability at stem and internode levels Main stem DW (g) Structural stem density (g/cm 3 ) 35 Main stem height ADL (~lignin, % stem DW) Tallest genotypes with the highest lignin content Negative correlation lignin / sugar contents Stem structural density related to lignin content (in Zone 2) % Red (lignin) Internode average length (cm) Zone 2 Zone 1 Stem height (cm) % redz2 (lginified tissue) %RedZ2 vs. density R² =.43 ADL vs. Stem height R² =.7 ADL vs. Soluble Sugar R² = Stem ADL (~lignin in %DW) Lignin vs. density R² = Stem structural density (g per cm 3 ) Stem soluble sugar content (%DW) Internode lignin (mm per g)

9 Response rate to drought % Response to drought at stem level 1 Stem DW in g Response rate to drought % Relations between response to drought (%) Sugar % DW ADL %DW stem dry weight & lignin accumulations (%DW) but not proportionally Soluble sugar content proportionally to lignin content 12 R² = Stem sugar vs ADL (lignin) content Stem height vs ADL (lignin) content R² =

10 Internode Length Response rate (%) Response to drought explained at internode level Length reduction % Z2 Z1 DO Internode Response rate (%) Relation between responses to drought (%) 8 8 Lignin %RedZ1 Internode Lignin vs. sugar 6 6 %RedZ2 Soluble sugar R² = Internode Lignin vs. length -4-6 R² = Eg Length (not diameter) & lignin content, but not proportionally Lignin, in Z2 (6%) more than Z1 (3%) Sugar content proportionally to lignin NOT COPY

11 Implications for modelling biomass sorghum phenotypes Stem structural density (g/cm 3 ) is genotype dependent & related to lignin content (zone2) To be considered as a model genotypic parameter (proxy of fiber content) Better prediction of C cost for stem growth & its negative impact on sugar content? Water deficit decreased internode growth & lignin content but soluble sugar content Can soluble sugar be predicted as an emerging property of stem structural growth? Can we produce more digestible biomass under managed water deficit?

12 Modelling biomass sorghum with Ecomeristem Plant growth at organ level in crop stand Luquet et al., (26, 212, 215); Fumey et al. 216 (FSPMA) Genotypic parameters define: 1) Organ growth & sizing potential => plant C & water demand (eg. leaf & internode potential sizing & structural density) 2) C & water supply potential at crop level 3) Sensitivity to plant C & water status (Supply/Demand) C S/D (IC) regulates growth, tillering, senescence, C storage Water S/D regulates organ growth, transpiration, C assimilation Response rate Genotypic threshold parameters Plant Supply/demand (C or water)

13 Model calibration: eg. 1 genotype (215, 2 water situations) Genotypic parameters estimation (genetic algorithm): Organ appearance rate, sizing, density, C assimilation Response to water deficit (growth, C assimilation) Well-watered Water-deficit

14 Well-watered Water-deficit Model validation (214 data - 8 genotypes) GxE correctly predicted

15 Simulation experiment: can water deficit favor digestible biomass production? 1 genotype: Biomass14 (high yield, moderate growth sensitivity to drought 215 trial water treatments (WW, WD) vs. real irrigation (SW, moderate WD) Ψp wks 1wk DAS WW SW WD FLO Main stem internode DW (g) WW SW WD DAS 1% reduction in SW compared to WW Main stem sugar content (g) DAS No reduction in SW compared to WW

16 Conclusions Genotypic covariation of stem biomass production & composition (internode / tissue level) Covariation not observed for their sensitivity to water deficit: opportunities for breeding? Compensation between stem sugar & fiber (lignin) content (genotype & environment) Ecomeristem model captured these GxE: Managed water deficit should favor the production of digestible biomass while saving water Next: Further study the relation between internode growth & histochemical response to drought Phenotyping of larger panels & GWAS (cf. talk by Pot et al. & poster by Audebert et al.; Jaffuel et al.) Calibrate Ecomeristem for larger panels: model based ideotyping (cf. poster by Larue et al.)