The novel methods of development of the maintainer and cytoplasmic male sterile lines with different cytoplasms based on chromosome single-segment substitution lines in rice


Abstract: The present study was carried out with the objective of developing new parental lines of hybrid rice based on chromosome single-segment substitution lines (SSSLs), on which the restorer and maintainer genes Rf3 (rf3) and Rf4 (rf4) were harbored in rice. To develop the new 3-line hybrid, the SSSL W23-19-06-06-11 with the genotype Rf3Rf3/Rf4Rf4 [a strong restorer line for wild abortive (WA), dwarf-wild abortive (DA), and Yegong (Y) cytoplasmic male sterile (CMS) lines] was crossed 4 times as the male parent with 4 CMS lines: 2 typical WA-type CMS lines of Bobai A and Zhenshan 97A, 1 typical Y-type CMS line of Y-Huanong A, and 1 typical DA-type CMS line of Xieqingzao A. In the BC_3F_2 populations, the male sterile plants (MSPs) with WA-, Y-, and DA-type CMS sources and nuclear background of W23-19-06-06-11 and their maintainer plants (MPs) were developed by backcrossing and marker-assisted selection. All the MSPs showed 100% pollen and spikelet sterility and the panicle length ranged from 20 to 22.6 cm. The extent of incomplete panicle exertion in the entries ranged from -40.7 to -48.5. The pollen grain viability assay with I_2KI of the MSPs revealed 100% pollen sterility, consisting of both typical and spherical abortive pollen grains. The MPs showed normal pollen (spikelet) fertility. A genome-wide DNA marker survey revealed that the numbers of the substituted chromosome segments carried by the MSPs and MPs were 0.8 and 0.6, while the lengths of the substituted chromosome segments corresponding to the Rf3 (or Rf4) locus were, on average, 26.2 cM and 17.0 cM (or 15.3 cM and 15.1 cM).

Keywords: Three-line hybrid rice, chromosome single segment substitution line, development of restorer line, maintainer line, molecular marker-assisted selection

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