Abstract
BackgroundIn cereal crops, stem lodging can be classified into two types: stem-breaking type and stem-bending type. To improve stem-lodging resistance, the strong culm traits of superior lodging-resistant varieties must be characterized. The identification of quantitative trait loci (QTLs) and the corresponding genes associated with the parameters for bending moment at breaking (M) and flexural rigidity (FR) is expected to enable the efficient development of lodging-resistant varieties. A set of Chromosome Segment Substitution Lines (CSSLs) derived from the cross between Takanari and Koshihikari were used in this study to identify QTLs associated with lodging resistance.ResultsThe indica variety Takanari possesses large M due to its large section modulus (SM) despite its small bending stress (BS), whereas Takanari also has large FR due to its large secondary moment of inertia (SMI) and Young’s modulus (YM). The QTLs for BS were assigned to chromosomes 3, 5, 6, 8, 9, 10, 11, and 12. Koshihikari alleles increased BS in these QTLs. The YM was increased by substitution of the Koshihikari chromosomal segments on chromosomes 2, 10, and 11. Other QTLs mapped to chromosomes 7 and 12, such that the Koshihikari alleles contributed to the decrease of YM. QTLs for cellulose density were assigned to chromosomes 1, 3, and 5, which were replaced by substitutions of Koshihikari segments. The QTLs for hemicellulose, cellulose, and holocellulose densities identified on chromosome 5 overlapped with those for BS, indicating the positive effect of the Koshihikari segment on increasing BS.ConclusionsThese results suggested that the QTLs for the densities of cell wall materials in japonica varieties contributed to increased BS and might be utilized for improving lodging resistance in indica varieties of rice.
Highlights
IntroductionStem lodging can be classified into two types: stem-breaking type and stem-bending type
In cereal crops, stem lodging can be classified into two types: stem-breaking type and stem-bending type
In 2016, at the long arm region on chromosome 5, a reciprocal effect of T-Chromosome Segment Substitution Lines (CSSLs) and KCSSLs was observed for both bending stress (BS) and cellulose densities (Figs. 5a, b and 6a, b). This showed that the Quantitative trait loci (QTL) for BS and cellulose density were detected in the same region (Fig. 7) for each CSSLs background. These results suggested that the QTLs for cellulose density on chromosome 5 contributed to the increase BS in the Takanari genetic background
Summary
Stem lodging can be classified into two types: stem-breaking type and stem-bending type. The improvement of lodging resistance in rice by alterations to the semi-dwarf gene (sd1) alone has reached a limitation This plateau reflects the fact that decreases in total biomass production potentially disrupt the balance between the source and sink capacities, as in Mulsanti et al Rice (2018) 11:25 the case of dwarf rice plants with diminished grain yields. Mutation of sd, which encodes a gibberellin (GA) biosynthetic factor, reduces culm strength by decreasing culm diameter and thickness (Okuno et al 2014) Because of these pleiotropies, using semi-dwarf genes to increase lodging resistance is difficult. Other studies show that lignin contributes to culm strength (Li et al 2003; Jones et al 2001)
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