Table_1_Water Deficit-Responsive QTLs for Cell Wall Degradability and Composition in Maize at Silage Stage.XLSX

The use of lignocellulosic biomass for animal feed or biorefinery requires the optimization of its degradability. Moreover, biomass crops need to be better adapted to the changing climate and in particular to periods of drought. Although the negative impact of water deficit on biomass yield has often been mentioned, its impact on biomass quality has only been recently reported in a few species. In the present study, we combined the mapping power of a maize recombinant inbred line population with robust near infrared spectroscopy predictive equations to track the response to water deficit of traits associated with biomass quality. The population was cultivated under two contrasted water regimes over 3 consecutive years in the south of France and harvested at silage stage. We showed that cell wall degradability and β-O-4-linked H lignin subunits were increased in response to water deficit, while lignin and p-coumaric acid contents were reduced. A mixed linear model was fitted to map quantitative trait loci (QTLs) for agronomical and cell wall-related traits. These QTLs were categorized as “constitutive” (QTL with an effect whatever the irrigation condition) or “responsive” (QTL involved in the response to water deficit) QTLs. Fifteen clusters of QTLs encompassed more than two third of the 213 constitutive QTLs and 13 clusters encompassed more than 60% of the 149 responsive QTLs. Interestingly, we showed that only half of the responsive QTLs co-localized with constitutive and yield QTLs, suggesting that specific genetic factors support biomass quality response to water deficit. Overall, our results demonstrate that water deficit favors cell wall degradability and that breeding of varieties that reconcile improved drought-tolerance and biomass degradability is possible.

木质纤维素生物质（lignocellulosic biomass）用于动物饲料或生物炼制（biorefinery）时，需对其降解性进行优化。此外，生物质作物需更好地适应气候变化，尤其是干旱时期。尽管水分亏缺（water deficit）对生物质产量的负面影响常被提及，但其对生物质品质的影响直至近年才在少数物种中被报道。本研究结合玉米重组自交系群体（maize recombinant inbred line population）的定位效能与稳健的近红外光谱（near infrared spectroscopy）预测方程，以追踪与生物质品质相关的性状对水分亏缺的响应。该群体于法国南部连续三年在两种差异显著的水分管理模式下种植，并于青贮期（silage stage）收获。本研究发现，水分亏缺可提升细胞壁降解性与β-O-4连接的H型木质素亚基含量，同时降低木质素与对香豆酸（p-coumaric acid）的含量。本研究采用混合线性模型（mixed linear model）对农艺性状及细胞壁相关性状的数量性状位点（quantitative trait loci，QTLs）进行定位，并将这些QTLs划分为“组成型”（无论灌溉条件如何均发挥效应的QTL）与“响应型”（参与水分亏缺响应的QTL）两类。15个QTL簇涵盖了213个组成型QTL中的三分之二以上，13个簇覆盖了149个响应型QTL中的60%以上。值得注意的是，仅半数响应型QTL与组成型及产量QTL存在共定位现象，这表明支撑生物质品质对水分亏缺响应的是特异性遗传因子。总体而言，本研究结果证实水分亏缺可提升细胞壁降解性，且培育兼具耐旱性与良好生物质降解性的品种具备可行性。