Genetic Analysis Of Fertility Stability And Restoring Of Rice Cytoplasmic Male Sterile Lines L-orf290 And L-orfH79

To investigate the relationship between 2 sterile genes（orfH79 and orf290）of Hong-Lian cytoplasmic male sterility（HL-CMS）and 2 restorer genes（Rf5 and Rf6）,the candidates of isonuclear alloplasmic sterile lines,L-orfH79 and L-orf290,and isonuclear isocytoplasmic near-isogenic restorer lines,L-Rf5 and L-Rf6 were previously constructed by method of orfH79-and orf290-molecular markers aided selections in our laboratory.In this study,the genetic studies on those materials were carried out and the following results were obtained:1.When L-orfH79 containing only sterile gene orfH79 but not sterile gene orf290 was crossed with L-Rf5 and L-Rf6,the expression of orfH79 in F₁ plants was significantly down-regulated.When L-orfH79 was crossed with W34A27,the isonuclear isocytoplasmic near-isogenic fertile lines without Rf5 and Rf6,F₁ plants of L-orfH79/W34A27 was fertile.It is suggested that W34A27 might contain a novel restorer gene,which could be used for the specific restoring of the new CMS line L-orfH79.2.The Low-fertility L-orf290 candidate materials,Z597-290 and Z604-290,were obtained by successive backcrossing Z597 and Z604 with YTB（BC₇F₁）.There were only orf290 and partial sequence of sterile gene WA352 detected in the Z597-290 and Z604-290lines by molecular marker identifications of orf290,orfH79,Rf5,Rf6 as well as WA352.When YTB was crossed with Z597-290（BC₅F₁）,the fertility of F₁ plants of reciprocal cross YTB/Z597-290 was significantly higher than that of Z597-290（BC₅F₁）/YTB.These conformed that the sterility of L-orf290 lines,Z597-290 and Z604-290,was controlled by cytoplasmic genes.3.Molecular identification and genetic analysis of gene-edited L-Rf6 showed that there were the homozygous plants without base editing and the heterozygous plants inserted with base A in L-Rf6 of T₁ generation,of which the ratio of heterozygotes and homozygotes was about 2:1.The positive T₀ plant with hygromycin resistance of gene-edited L-Rf5 line was characteristc of sterility,which could not restored by L-Rf5,but no base edited sites were found in the target Rf5 gene region of the positive T₀ plant with hygromycin resistance of gene-edited L-Rf5 plants.