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Chromosome segment substitution line (CSSL) in rice is important for functional analysis and design breeding of target genes. Here, a novel rice CSSL-Z431 was identified from indica restorer line Xihui18 as recipient and Huhan3 as donor. Z431 contained six segments from Huhan3, with an average substitution length of 2.12 Mb. Compared with Xihui18, Z431 increased panicles per plant (PN) and displayed short-wide grains. The short-wide grain of Z431 were caused by reducing of cell length and increasing of cell width in the glume. Then, thirteen QTLs were identified in a secondary F2 population derived from Xihui18/Z431. Among them, six QTLs (qPN3, qGL3, qGW5, qRLW2, qRLW3, qGWT-5-2) were validated by four single-segment substitution lines (SSSLs, S1-S4) developed in F3. In addition, thirteen QTLs (qPN1, qPN2, qPL1, qPL2, qGPP1, qGPP2, qGL2, qGW1, qGW2, qGW3, qRLW5-2, qRLW1, qGWT2) were detected by these SSSLs, while not be identified in the F2 population from Xihui18/Z431. Increase of panicles per plant in Z431 was controlled by qPN3, qPN1 and qPN2. OsIAGLU should be the candidate gene for qPN3 by DNA sequencing. The short-wide grain of Z431 was controlled by qGL3, qGL2, qGW5, qGW2 and qGW3. By sequencing between Xihui18 and according SSSL, three candidate genes for qGL3 and two candidate genes for qGW5 were identified, respectively. In addition, pyramid of different QTLs (qPN1and qPN3; qPN2 and qPN3 etc.) yielded different epistatic effects. These results lay good foundation in molecular mechanism analysis of unreported genes and rice molecular design breeding. |
