Genotype-Dependent Gene Expression in Strawberry (Fragaria x ananassa) Plants Under High Temperature Stress.

The differences in tolerance to high temperatures were investigated on the basis of gene expressions in two strawberry (Fragaria x ananassa Duch) cultivars which were previously determined as high temperature tolerant (Redlands Hope = R. Hope) and sensitive (Festival). Plants were exposed incrementally to 35, 40, 45, and finally 50 °C for 24 h. qRT-PCR analyses were carried out with 19 known sequences from the databases. Protein expression analyses were based on SDS-PAGE results, sequenced and then separated due to their isoelectric points. Expression levels were determined at 35, 40, and 45 °C. According to the results, tolerance of 'R. Hope' to high temperature stress can be explained with the coordination of Hsp70, Hsp90, and small heat shock proteins (sHsps) having a vital and supplementary role in stress response. Sensitive cultivar 'Festival' can respond to high temperatures only with the low molecular weight protein and transcripts that do not take a central role in high temperature stress response. Moreover, allergen gene expression triggered by high temperature were detected in both cultivars with different expression levels. The greater expression level in allergen genes observed in the sensitive cultivar 'Festival' under high temperature indicates that there is possibly a negative correlation between expression level in allergen genes and heat stress tolerance. Future studies addressing allergen gene expression under high temperature stress are required to confirm on these findings and to expand on the potential use as a molecular marker in breeding process for enhanced tolerance to high temperature.

SNP Discovery by GBS in Olive and the Construction of a High-Density Genetic Linkage Map.

Genetic linkage maps are valuable tools for genetic, genomic, and crop breeding studies. Several genetic linkage maps were constructed for the olive (Olea europaea L.) genome, mainly using amplified fragment length polymorphisms (AFLPs) and simple sequence repeat (SSR) markers. However, AFLPs and SSR markers were not enough to develop a high-density olive linkage map. Genotyping-by-sequencing (GBS), a recently developed single-nucleotide polymorphism (SNP) identification methodology based on next-generation sequencing (NGS) technologies, has been demonstrated to be useful for the identification of a high number of SNP markers and the construction of high-density genetic linkage maps. In the present study, we identified a total of 10,941 SNPs from a cross between the olive cultivars 'Gemlik' and 'Edincik Su' using GBS and de novo SNP discovery implemented in the computer program "Stacks." A high-density genetic linkage map for the olive genome was constructed using 121 cross-pollinated full-sib F1 progeny and 5643 markers (21 SSRs, 203 AFLPs, and 5736 SNPs). This linkage map was composed of 25 linkage groups, covering 3049 cM of the olive genome, and the mean distance between the flanking markers was 0.53 cM. To the best of our knowledge, this map is the most saturated genetic linkage map in olive to date. We demonstrated that GBS is a valuable tool for the identification of thousands of SNPs for the construction of a saturated genetic linkage map in olive. The high-density genetic map developed in this study is a useful tool for locating quantitative trait loci and other economically important traits in the olive genome.