Genotypic covariations of traits underlying sorghum stem biomass production and quality and their regulations by water availability: Insight from studies at organ and tissue levels

Abstract

Sweet and biomass sorghum are expected to contribute increasingly to bioenergy production. Better understanding the impacts of the genotypic and environmental variabilities on biomass component traits and their properties is essential to optimize energy yields. This study aimed to evaluate whether traits contributing to stem biomass growth and biochemical composition at different biological scales (co)vary with the genotype and the water status in sorghum. Height genotypes were studied over two years in field conditions in southern France under two water treatments (well watered vs. 25 days’ dry down during stem elongation). Main stem internode number, size, (non)structural carbohydrate, and lignin contents were measured at the end of the stress period and/or at final harvest, together with biochemical and histological analyses of the youngest expanded internode. The tallest genotypes showed the highest stem dry weights and lignin contents. Stem (structural) biomass density was positively correlated with lignin content, particularly in internode parenchyma. Stem soluble sugar and lignin contents were inversely proportional across genotypes and water conditions. Genotypes contrasted for drought sensitivity and recovery capacity of stem growth and biochemical composition. The length and cell wall deposition of internodes expanding under water deficit were reduced and did not recover, these responses being weakly correlated. Genotypic variability was pointed out in the growth recovery of internodes expanding under re‐watered conditions. According to the observed genotypic variability and the absence of antagonistic correlations between the responses of the different traits to water availability, it is suggested that biomass sorghum varieties optimizing their responses to water availability in terms of growth and cell wall deposition can be developed for different bioenergy targets.

Responses of Maize Internode to Water Deficit Are Different at the Biochemical and Histological Levels

“…We showed that most of the biochemical traits were impacted by the NI scenario in both years. These findings have already been reported in maize (El Hage et al, 2018;Virlouvet et al, 2019), sorghum (Luquet et al, 2019), and miscanthus (Van Der Weijde et al, 2017). Nevertheless, what is striking in the present analysis is that even if rainwater was supplied in large quantities from the onset of the stress period and of the development of the internode below the ear in 2015, biochemistry traits (such as PCAest and lignin contents) and in vitro digestibilities of the internodes were impacted similarly in 2014 and 2015, while the histological traits were not.…”

Mobilizing sorghum genetic diversity: Biochemical and histological‐assisted design of a stem ideotype for biomethane production

“…Moderate to high broad sense heritability associated with genetic coefficients of variation over 10% was observed for all the histological traits These results confirm the detection of significant genotype effects in previous studies performed by Perrier et al, (2017) and Luquet et al, (2019) on narrower panels of genotypes (2 and 8, respectively). Although histological analyses were only performed on one site over 3 years, questioning the existence of genotype by site interactions, the medium to high inter‐year correlations observed combined with the weak effects of genotype by year and genotype by water availability treatments reported by Luquet et al, (2019, see their Table 5) suggest a relatively stable ranking of the genotypes across environmental conditions. Broad sense heritability observed for the outer Z1 region area roughly corresponds with the repeatability reported by Gomez et al, (2018) on sorghum for their “rind area” trait (0.72).…”

Transcriptional Regulation of Sorghum Stem Composition: Key Players Identified Through Co-expression Gene Network and Comparative Genomics Analyses

“…Although functional validation is the gold standard toward the validation of gene function, complementary approaches are also relevant to improve the identification of the most relevant genes to use in future breeding schemes. Assessment of the expression differences of genotypes harboring different patterns of accumulation Luquet et al, 2019) and in different environmental conditions (Perrier et al, 2017;Luquet et al, 2019;Virlouvet et al, 2019) would probably allow to refine our choices to maximize their transposition to breeding programs in the future. In addition, it would be interesting to increase the resolution of the transcriptomic analyses through the analysis of expression of specific groups of cells (e.g., parenchyma vs. vascular bundles.…”