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. 2018 Feb 26;8(1):3636.
doi: 10.1038/s41598-018-21741-y.

Genetic Loci Simultaneously Controlling Lignin Monomers and Biomass Digestibility of Rice Straw

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Free PMC article

Genetic Loci Simultaneously Controlling Lignin Monomers and Biomass Digestibility of Rice Straw

Zhen Hu et al. Sci Rep. .
Free PMC article

Abstract

Lignin content and composition are crucial factors affecting biomass digestibility. Exploring the genetic loci simultaneously affecting lignin-relevant traits and biomass digestibility is a precondition for lignin genetic manipulation towards energy crop breeding. In this study, a high-throughput platform was employed to assay the lignin content, lignin composition and biomass enzymatic digestibility of a rice recombinant inbred line population. Correlation analysis indicated that the absolute content of lignin monomers rather than lignin content had negative effects on biomass saccharification, whereas the relative content of p-hydroxyphenyl unit and the molar ratio of p-hydroxyphenyl unit to guaiacyl unit exhibited positive roles. Eight QTL clusters were identified and four of them affecting both lignin composition and biomass digestibility. The additive effects of clustered QTL revealed consistent relationships between lignin-relevant traits and biomass digestibility. Pyramiding rice lines containing the above four positive alleles for increasing biomass digestibility were selected and showed comparable lignin content, decreased syringyl or guaiacyl unit and increased molar percentage of p-hydroxyphenyl unit, the molar ratio of p-hydroxyphenyl unit to guaiacyl unit and sugar releases. More importantly, the lodging resistance and eating/cooking quality of pyramiding lines were not sacrificed, indicating the QTL information could be applied to select desirable energy rice lines.

Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Frequency distributions of lignin-relevant traits and sugar releases in the RIL population. The values of two parents are indicated by “H” (Huahui-3) and “Z” (Zhongguoxiangdao) over the corresponding histogram. The short horizontal and vertical lines indicate the range and average value of two parents.
Figure 2
Figure 2
Correlations between lignin-relevant traits and sugar release. Red colors indicate positive correlations, while the green indicate negative correlations between traits. * and ** indicate that the correlations are significant at p < 0.05 and 0.01, respectively.
Figure 3
Figure 3
QTL identified and co-mapped for lignin monomers and sugar release. The positive and negative additive effects indicated that the positive alleles came from ZX and HH-3, respectively. The QTL clusters were framed with dotted lines.
Figure 4
Figure 4
Comparing lignin-relevant traits, sugar releases, plant height, breaking force and lodging resistance of pyramiding lines (n = 8) and other lines (n = 91 in AD,FH and n = 207 in E). (A) Lignin content; (B) absolute content of lignin monomers; (C) molar percent of lignin monomers; (D) molar ratios between lignin monomers; (E) sugar releases; (F) plant height; (G) breaking force; (H) lodging index.

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