SCAR marker for sex identification of Pistacia chinensis Bunge (Anacardiaceae)

Transcriptome Analysis and Identification of a Female-Specific SSR Marker in Pistacia chinensis Based on Illumina Paired-End RNA Sequencing

Pistacia chinensis Bunge (P. chinensis), a dioecious plant species, has been widely found in China. The female P. chinensis plants are more important than male plants in agricultural production, as their seeds can serve as an ideal feedstock for biodiesel. However, the sex of P. chinensis plants is hard to distinguish during the seedling stage due to the scarcity of available transcriptomic and genomic information. In this work, Illumina paired-end RNA sequencing assay was conducted to unravel the transcriptomic profiles of female and male P. chinensis flower buds. In total, 50,925,088 and 51,470,578 clean reads were obtained from the female and male cDNA libraries, respectively. After quality checks and de novo assembly, a total of 83,370 unigenes with a mean length of 1.3 kb were screened. Overall, 64,539 unigenes (77.48%) could be matched in at least one of the NR, NT, Swiss-Prot, COG, KEGG, and GO databases, 71 of which were putatively related to the floral development of P. chinensis. Additionally, 21,662 simple sequence repeat (SSR) motifs were identified in 17,028 unigenes of P. chinensis, and the mononucleotide motif was the most dominant type of repeats (52.59%) in P. chinensis, followed by dinucleotide (22.29%), trinucleotide (20.15%). The most abundant repeats were AG/CT (13.97%), followed by AAC/GTT (6.75%) and AT/TA (6.10%). Based on these SSR, 983 EST-SSR primers were designed, 151 of which were randomly chosen for validation. Of these validated EST-SSR markers, 25 SSR markers were found to be polymorphic between male and female plants. One SSR marker, namelyPCSSR55, displayed excellent specificity in female plants, which could clearly distinguish between male and female P. chinensis. Altogether, our findings not only reveal that the EST-SSR marker is extremely effective in distinguishing between male and female P. chinensis but also provide a solid framework for sex determination of plant seedlings.

Conserved DNA-derived polymorphism, new markers for genetic diversity analysis of Tunisian Pistacia vera L

Pistachio trees (Pistacia vera L.) have been cultivated in Tunisia for decades and the plantation was extended mostly in the center of the country contributing to the economic growth of marginalized areas. Herein we used conserved DNA derived polymorphism (CDDP) technique, which target specifically conserved sequences of plant functional genes, to assess the genetic diversity and construct genetic relationships among 65 Tunisian pistachio trees. A set of nine primers were used and 157 CDDP markers were revealed with an average of 17.44 showing a high degree of polymorphism (99.37%). The average of polymorphism information content of CDDP markers was of 0.86, which indicates the efficiency of CDDP primers in the estimation of genetic diversity between pistachios. UPGMA dendrogram and the principal component analysis showed four clusters of analyzed pistachios trees. Our results showed that the genetic structure depends on: (1) the gene exchanges between groups, (2) the geographical origin and (3) the sex of the tree. The same result was revealed by the Bayesian analysis implemented in STRUCTURE at K = 4, in which the pistachio genotypes of El Guettar, Kasserine and Sfax were assigned with more than 80% of probability. Our results prove polymorphism and efficiency of CDDP markers in the characterization and genetic diversity analysis of P. vera L. genotypes to define conservation strategy.

SCAR Marker for Gender Identification in Date Palm (Phoenix dactylifera L.) at the Seedling Stage

Date palm (Phoenix dactylifera L.) is cultivated in arid and semiarid regions worldwide. Given the dioecious nature of this plant, gender identification is very important at the seedling stage. Molecular markers are very effective tools that help in gender identification at this stage. A sequence characterized amplified region (SCAR) marker linked to sex-specific regions in the genome of date palm was developed. Of the 300 tested randomly amplified polymorphic DNA (RAPD) primers, only one primer (OPC-06) produced reproducible band (294 bp) in male plants. The PCR product of this primer was cloned and sequenced. The specific primers were synthesized for amplification of a 186 bp fragment in male date palm plants. These primers were validated in male and female date palm plants, wherein the designed SCAR marker was reported only in male plants and no amplification was observed in female plants. The developed SCAR marker was used with seedlings of date palm and proved very effective in identification of gender.