Tung tree (Vernicia fordii) provides the sole source of tung oil widely used in industry. Lack of fatty acid composition and molecular markers hinders biochemical, genetic and breeding research. The objectives of this study were to determine fatty acid profiles and develop unigene-derived simple sequence repeat (SSR) markers in tung tree. Fatty acid profiles of 41 accessions showed that the ratio of α-eleostearic acid was increasing continuously with a parallel trend to the amount of tung oil accumulation while the ratios of other fatty acids were decreasing in different stages of the seeds and that α-eleostearic acid (18∶3) consisted of 77% of the total fatty acids in tung oil. Transcriptome sequencing identified 81,805 unigenes from tung cDNA library constructed using seed mRNA and discovered 6,366 SSRs in 5,404 unigenes. The di- and tri-nucleotide microsatellites accounted for 92% of the SSRs with AG/CT and AAG/CTT being the most abundant SSR motifs. Fifteen polymorphic genic-SSR markers were developed from 98 unigene loci tested in 41 cultivated tung accessions by agarose gel and capillary electrophoresis. Genbank database search identified 10 of them putatively coding for functional proteins. Quantitative PCR demonstrated that all 15 polymorphic SSR-associated unigenes were expressed in tung seeds and some of them were highly correlated with oil composition in the seeds. Dendrogram revealed that most of the 41 accessions were clustered according to the geographic region. These new polymorphic genic-SSR markers will facilitate future studies on genetic diversity, molecular fingerprinting, comparative genomics and genetic mapping in tung tree. The lipid profiles in the seeds of 41 tung accessions will be valuable for biochemical and breeding studies.

ABSTRACT. Camellia oleifera is an important edible oil woody plant in China. Lack of useful molecular markers hinders current genetic research on this tree species. Transcriptome sequencing of developing C. oleifera seeds generated 69,798 unigenes. A total of 6949 putative microsatellites were discovered among 6042 SSRcontaining unigenes. Then, 150 simple sequence repeats (SSRs) were evaluated in 20 varieties of C. oleifera. Of these, 52 SSRs revealed (2015) polymorphism, with the number of alleles per locus ranging from 2 to 15 and expected heterozygosity values from 0.269 to 0.888. The polymorphic information content varied from 0.32 to 0.897. Crossspecies transferability rates in Camellia chekangoleosa and Camellia japonica were 90.4 and 78.8%, respectively. The 52 polymorphic unigene-derived SSR markers serve to enrich existing microsatellite marker resources for C. oleifera and offer potential for applications in genetic diversity evaluation, molecular fingerprinting, and genetic mapping in C. oleifera, C. chekangoleosa, and C. japonica.

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Oil-tea tree is one of the most important woody edible oil plants; however, lack of useful molecular markers hinders current genetic research. We performed transcriptome sequencing of developing seeds and characterized microsatellites from transcriptome sequences to identify valuable markers for C. oleifera molecular genetics research. A total of 69,798 unigenes were identified, in which 6,949 putative SSR motifs from 6,042 SSR-containing unique putative transcripts were discovered. Twenty-nine primer pairs corresponding to 29 unigene loci were designed, of which 15 polymorphic genic-SSR markers were developed in 18 varieties and characterized by capillary electrophoresis. The number of alleles per locus (Na) ranged from 2 to 14, the expected heterozygosity (He) ranged from 0.374 to 0.876, and the polymorphism information content (PIC) values ranged from 0.498 to 0.887, respectively. Cross-species amplification was also conducted in 15 varieties of C. japonica. All 15 markers successfully amplified PCR products with expected size in C. japonica and exhibited polymorphisms. The 15 polymorphic genic- SSR markers will have potential for applications in genetic diversity evaluation, molecular fingerprinting identification, comparative genome analysis, and genetic mapping in the C. oleifera and C. japonica.

Many flowering plants exhibit an important intraspecific reproductive barrier phenomenon, that is, self-incompatibility (SI), in which S-RNase genes play a significant role. To clarify the specific function of S-RNase genes in Chinese pears, the full length cDNA of PbS 26 -RNase was isolated by rapid amplification of cDNA ends (RACE) technology from Chinese white pear (Pyrus bretschneideri) cultivar “Hongpisu.” The cDNA sequence for PbS 26 -RNase was deposited in GenBank under accession number EU081888. At the amino acid level, the PbS 26 -RNase displayed the highest similarity (96.9%) with PcSa-RNase of P. communis, and only seven amino acid differences were present in the two S-RNases. Phylogenetic analysis of rosaceous S-RNases indicated that the PbS 26 -RNase clustered with maloideous S-RNases, forming a subfamily-specific not a species-specific group. The PbS 26 -RNase gene was specifically expressed in the style but not other tissues/organs. The expression level of the PbS 26 -RNase gene rapidly increased at bell balloon stage (BBS), and then it dropped after pollination. However, the abundance of the PbS 26 -RNase gene transcript in the style was greater after cross-pollination than after self-pollination. In addition, a method for rapidly detecting the PbS 26 -RNase gene was developed via allele-specific primers design. The present study could provide a scientific basis for fully clarifying the mechanism of pear SI at the molecular level.