A new fertility restorer locus linked closely to the Rfo locus for cytoplasmic male sterility in radish.

In this study, we have investigated a new fertility restorer (Rf) locus for cytoplasmic male sterility (CMS) in radish. We have obtained a CMS-Rf system consisting of sterile line '9802A1', maintainer line '9802B1' and restorer line '9802H'. F(1) plants from cross between sterile line '9802A1' and restorer line '9802H' were all male fertile, self pollination of F(1) plants produced an F(2) segregating population consisting of 600 individuals. The segregating population was found to fit a segregation ratio 3:1 for male fertile and sterile types, indicating that male fertility is restored by a single dominant gene (termed Rfo2) in the CMS-Rf system. Based on the DNA sequence of Rfo/Rfk1 (AJ535623), just one full length gene in the sterile line '9802A1', in the restorer line '9802H' and in the male fertile line '2006H', was cloned, respectively. The three sequences correspond to the same gene with two alleles: Rfob in '9802H' and rfob in '9802A1' and '2006H'. These two alleles differ from Rfo/Rfk1 and rfk1 (AJ535624) alleles by two synonymous base substitutions, respectively. Based on the differences between the Rfob and rfob genes, one PCR-based marker was developed, and designated Marker 1, which is identical to the corresponding region of Rfob by sequence analysis. In the F(2) segregating population described above, the Marker 1 was present in 5 sterile plants and in 453 fertile plants, absent in 4 fertile plants and in 138 sterile plants, and was found to fit a segregation ratio 3:1 indicating that Rfob was single copy in '9802H'. Linkage analysis showed that the Rfo2 locus for our CMS-Rf system was distant from the Rfo locus by about 1.6 cM. The sterile line '9802A1' was pollinated by the male fertile line '2006H' and the resulting F(1) plants were all male fertile. These results indicated that the male fertility of radish CMS can be restored by a new Rf locus, which linked tightly to the Rfo locus.

Genetic differentiation of relictual populations of Alsophila spinulosa in southern China inferred from cpDNA trnL-F noncoding sequences.

The genetic differentiation and phylogeographical pattern of 11 relictual populations of Alsophila spinulosa distributed across Hainan, Guangdong, and Guangxi in southern China were inferred from sequence variations of trnL-F noncoding regions of chloroplast DNA (cpDNA). The length of trnL-F noncoding sequences varied from 863 to 940 bp. The A + T content was 62.23-63.36%. Sequences were neutral in terms of evolution (Tajima's criterion D=-0.62417, P>0.10 and Fu and Li's test D*=-1.45455, P>0.10; F*=-1.32798, P>0.10). Thirty-four haplotypes were identified based on nucleotide variation. Relatively high levels of haplotype diversity (h=0.929) and nucleotide diversity (Dij=0.022263) were detected in A. spinulosa, probably associated with its long evolutionary history which allowed the accumulation of genetic variation within lineages. Both the minimum spanning network and the strict consensus tree of the most parsimonious trees generated for haplotypes demonstrated that the investigated populations of A. spinulosa were subdivided into two geographical groups: Hainan and Guangdong-Guangxi. An analysis of molecular variance (AMOVA) indicated that most of the genetic variation (87.48%, P<0.001) was partitioned among regions. Spatial structure measurements revealed that population genetic structure was not related to geographical distance. This research suggests that blocked gene flow by Qiongzhou strait and an inbreeding system might result in the geographical subdivision between Hainan and Guangdong-Guangxi (F(ST)=0.92, Nm=0.09). Within each region, the "star like" pattern of phylogeography of haplotypes implied a population expansion process during evolutionary history. Gene genealogies together with coalescent theory were useful tools for uncovering the phylogeography of A. spinulosa.

Genetic structure and variation in the relict populations of Alsophila spinulosa from southern China based on RAPD markers and cpDNA atpB-rbcL sequence data.

RAPD markers and sequences of chloroplast DNA (cpDNA) atpB-rbcL intergenic spacers were used to characterize the pattern of genetic variation and the phylogenetic relationships of the relict populations of Alsophila spinulosa located in Jian Feng Ling (JFL) and Diao Luo Shan (DLS), Hainan, and Tang Lang Shan (TLS), Ding Hu Shan (DHS), and Da Xi Shan (DXS), Guangdong, of southern China. 28 random primers generated 118 bands, out of which 26 (22.03%) were polymorphic loci, distinguishing 17 different RAPD phenotypes. Percentage of polymorphic loci, Shannon phenotypic diversity and Nei's gene diversity comprehensively indicated that JFL possessed the highest diversity, TLS and DHS in intermediate and DLS or DXS the least; the corresponding values of the population appeared correlated with the population size. Differentiation was detected among populations of A. spinulosa (1-Hpop/Hsp=0.7453, GST=0.7763, and phist=0.8145). AMOVA showed that 47.44% of the variance was partitioned among regions (Hainan and Guangdong), 34.01% attributed among populations within regions, whereas only 18.55% occurring within populations. Low level of intra-specific diversity was maintained in A. spinulosa with Shannon diversity and gene diversity merely 0.0560 and 0.0590, repectively. Sequence length of atpB-rbcL intergenic spacer varied from 724 bp to 730 bp. Base composition was with A+T content between 63.17% and 63.70%. 13 haplotypes of atpB-rbcL noncoding spacers were identified. UPGMA dendrogram of RAPD phenotypes, principal components analysis based on RAPD patterns, minimum spanning network and neighbour-joining (NJ) tree established on atpB-rbcL haplotypes consistently suggested the geographical subdivision of populations of A. spinulosa between Hainan and Guangdong. Breeding system and conservation strategy of A. spinulosa was discussed based on the information of population genetic structure and variation.