Abstract
AbstractSorghum currently contributes to the species portfolio that is supporting bioenergy production including anaerobic digestion. Although agro‐morphological ideotypes maximizing biogas production have been recently proposed, there is a crucial need to refine our understanding of the impacts of the stem composition and structure on this processing trait in order to ensure genetic gains in the mid to long terms. This study aims to assess the potential of Sorghum bicolor ssp bicolor stem genetic diversity to maximize genetic gains for biogas production and define a biogas stem ideotype. In this context, a panel of 57 genotypes, encompassing most of the stem composition variability available in cultivated sorghum, was characterized over five sites. Simultaneous histological and biochemical characterizations were performed. A high broad sense heritability associated with a moderate genetic variability was detected for stem biogas potential ensuring significant genetic gains in the future. In addition, the development of a stem histological phenotyping pipeline made it possible to describe the genetic diversity available for the internode anatomy and the repartition of key cell wall components. Consistently with previous studies, moderate to high heritability was observed for stem biochemical components. Genetic correlation, hierarchical clustering, and multiple stepwise regression analyses identified soluble sugar content as the first main driver of biogas potential genetic variability. Nevertheless, breeding programs should anticipate that biogas yield improvement will also rely on the monitoring of the cell wall components and their distribution in the stem jointly with the soluble sugar content. According to the assets of sorghum in terms of adaptation to environmental stresses and the present results regarding the identification of stem ideotypes suitable for different value chains, this species will surely play a key role to optimize the economic and environmental sustainability of the agrosystems that are currently facing the effects of climate change.
Highlights
With the aim to determine a sorghum stem ideotype maximizing methane production potential, the variability of this trait was explored over a panel of 57 genotypes including landraces, breeding material, and commercial hybrids
This analysis was focused on methane production potential per stem dry matter unit in order to allow an in-depth analysis of this yield component independently of the total dry matter production
The explorations initiated by Mahmood and Honermeier (2012) (5 cultivars), Mahmood et al, (2013) (14 cultivars), Windpassinger et al, (2015) (13 cultivars), and Pasteris et al, (2021) (6 cultivars) on whole plant samples were extended to a larger set of sorghum genotypes and targeted toward the stem compartment which represents 70–40% of the dry biomass yield for this category of sorghum cultivars
Summary
The relevance of sorghum as a feedstock to support bioenergy production has been underlined at the economic and environmental levels in the United States (Cai et al, 2013; Fertitta-Roberts et al, 2017; Fulton-Smith and Cotrufo, 2019; Gautam et al, 2020; Moore et al, 2021; Oikawa et al, 2015), China (Liu et al, 2015), Latin America (Almeida et al, 2019; Rezende & Richardson, 2017), Africa (Vries et al, 2012), and Europe (Jankowski et al, 2020; Shu et al, 2020; Szambelan et al, 2018; Vlachos et al, 2015). Up to now, studies dealing with sorghum biomethane production mainly analyzed the impacts of whole aboveground biomass yield, organ proportions (Windpassinger et al, 2015), and whole plant biomass quality on methane yield (Pasteris et al, 2021) whereas they did not directly address the contributions of the stem biochemical and histological properties to the methane yield As these two types of traits can have complementary impacts on the degradability of the biomass, there is an obvious interest to clarify their specific effects on methane production potential and determine, if these effects are significant, a stem sorghum ideotype to maximize methane production potential. Vandenbrink et al, (2010) used a panel of 381 field-grown sorghum varieties to study whole plant enzymatic hydrolysis yield and El Hage et al, (2018) used 11 maize inbred lines to study cell wall digestibility variability This last study incorporated the use of internode histological traits to improve the description of the stem biomass properties. The relationships between biomethane potential, in vitro dry matter digestibility, and higher heating value (a proxy for combustion) and their specific determinants were analyzed to define whether different ideotypes should be developed for these targets
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