Genetic Analysis And Molecular Mapping Of Photoperiod (Thermo)-sensitive Genic Male Sterile And Heading-time Gene In Rice MS8S

The fertility of MS8S,a photoperiod(thermo)-sensitive genic male sterile(P(T)GMS) rice line,is regulated by environmental day-length(temperature) changes.Genetic analysis indicated that the sterility of MS8S was controlled by a single recessive gene.In this study, An F₂ population derived from the cross between MS8S and YC169 was used to indentified P(T)GMS gene.342 markers,interspersed on the 12 chromosomes and the average interval was less than 5.0cM,were selected to screen the marker of the gene.As a result,one SSR marker(RM324) on chromosome 2 were found to be loose linked to the target gene(here we temporarily named GMS).During the primary mapping process,an BC₂F₂ population consisting of more than 2000 individuals was developed and used for further mapping of the GMS gene.60 additional markers were selected for genetic mapping.Finally,the GMS was mapped between RM6378 and RM12847 at a distance of 8.5cM from RM6378 and 8.2cM from RM12847.The comparison of chromosomal locations suggested that GMS may be tightly linked or allelic to the tms5 gene in an indica rice variety,Annong S-1,previously reported by Wang et al.Alternatively,the photoperiod-sensitivity probable made a special contribution to safe and stable fertility transition in MS8S..To elucidate the genetic basis for its heading time,genetic analysis was carried out by crossing it with different varieties selected.One hundred and seventy one BC₁F₁ plants derived from a cross between MS8S andâ…¡-32B were developed and then used as a segregating population for QTL mapping.Ninty one markers showed polymorphism between this two parents were employed to identify QTLs.Scan-analysis revealed the existence of one QTL with large effects,temporarily designated as Hd-t, located on chromosome 10.The major QTL Hd-t explained 43.4%of the total phenotypic variation in the BC₁F₁ population.Further genetic mapping using SSR conbined with bulked extremes and recessive class also indicated the existence of Hd-t.Then the Hd-t was mapped to a vicinity region of RM258 at a distance of 8.9cM from RM184 and 4.9cM from RM258.The relationship between the other QTLs and known genes for heading date are discussed,showed that Hd-t maybe a new heading-time locus controlling photoperiod-sensitivity in rice.