Cd-tolerant germplasm screen and QTL identification of single-segment substitution lines of Oryza glumaepatula at the germination period

Objective  To evaluate effects of Cd stress on seed germination and growth of seminal root and shoot in chromosome single-segment substitution lines (SSSLs) of Oryza glumaepatula after seed germination, screen for Cd-tolerant SSSLs, and identify QTLs related to Cd-tolerant characters in bud.

Method  The seed germination test was carried out using six varieties at CdCl₂ concentrations of 0, 30, 50, 100, 500 μmol·L⁻¹, and the proper treatment of CdCl₂ concentration and the related character indexes to evaluate CdCl₂ tolerance of SSSLs were determined. The lengths of seminal roots and shoots of experimental SSSLs were analyzed to screen for SSSLs with strong tolerance to CdCl₂ at P=0.01 level and identify QTLs related to Cd-tolerant characters.

Result  At the concentrations of 0, 30, 50, and 100 μmol·L⁻¹ CdCl₂, the seed germination rates of six varieties were distributed between 91%～95%, which were insignificant among different CdCl₂ concentrations. However, the growth of seminal roots and shoots were significantly inhibited by CdCl₂, and the significant differences were observed for the tolerance to CdCl₂ among different varieties. Using relative root length and relative shoot length on the 7th day after germination as tolerance indexes, at the concentrations of 50 and 100 μmol·L⁻¹, five relative root length QTLs including qRRL1-1, qRRL2-1, qRRL3-1, qRRL3-2 and qRRL6-1 were identified in eight SSSLs at P=0.01 level, the phenotypic contribution rates of additive effects ranged from 31.18% to 100.59%. Three relative shoot length QTLs including qRSL1-1, qRSL1-2, and qRSL2-1 were identified in five SSSLs, the phenotypic contribution rates of additive effects were 7.43%～18.95%.

Conclusion  SSSLs of O. glumaepatula carry Cd-tolerant QTLs at the germination period, which will be useful for exploring beneficial Cd-tolerant genes in rice.