Potato (Solanum tuberosum L.) is one of the three most important food crops worldwide; however, it is strongly affected by drought stress. The precise molecular mechanisms of drought stress response in potato are not very well understood. The diploid potato genotype P3-198 has been verified to be highly resistant to drought stress. Here, a time-course experiment was performed to identify drought resistance response genes in P3-198 under polyethylene glycol (PEG)-induced stress using RNA-sequencing. A total of 1665 differentially expressed genes (DEGs) were specifically identified, and based on gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, the transcription factor activity, protein kinase activity, and the plant hormone signal transduction process were significantly enriched. Annotation revealed that these DEGs mainly encode transcription factors, protein kinases, and proteins related to redox regulation, carbohydrate metabolism, and osmotic adjustment. In particular, genes encoding abscisic acid (ABA)-dependent signaling molecules were significantly differentially expressed, which revealed the important roles of the ABA-dependent signaling pathway in the early response of P3-198 to drought stress. Quantitative real-time PCR experimental verification confirmed the differential expression of genes in the drought resistance signaling pathway. Our results provide valuable information for understanding potato drought-resistance mechanisms, and also enrich the gene resources available for drought-resistant potato breeding.

Since 1950, more than 620 potato cultivars have been released from Chinese breeding programs, some of which have similar genetic background and phenotype. In this study, 16 parental cultivars widely used in breeding were used to screen 138 simple sequence repeat (SSR) markers. Out of 138 SSR markers, 20 were polymorphic that were used to analyze the genetic diversity of 217 potato cultivars grown in China. In total, 249 alleles were detected with these 20 markers and 244 of them (97.99%) showed polymorphism. The number of alleles ranged from 7 to 22 with an average of 12.45 alleles per primer and polymorphic information content (PIC) ranged from 0.64–0.93 with an average of 0.83. Fragment sizes varied from 80 to 380 bp. Based on PIC values and the clarity of PCR amplification bands, 11 SSR markers were selected and able to differentiate all of the 217 cultivars. The estimated similarity using these polymorphic SSR markers between the cultivars ranged from 0.63 to 0.99, indicating a narrow genetic base. Fingerprinting and genetic diversity analysis in this study provides useful information for the protection of intellectual property, as well as the exploration and utilization of these potato cultivars. Desde 1950, se han liberado más de 620 variedades de papa de los programas chinos de mejoramiento, algunos de los cuales tienen antecedentes genéticos y fenotipo similares. En este estudio, se usaron 16 variedades parentales utilizadas ampliamente en mejoramiento, para hacer un estudio de 138 marcadores de repeticiones simples de secuencia (SSR). De los 138 marcadores SSR, 20 fueron polimórficos que fueron usados para analizar la diversidad genética de 217 variedades de papa cultivadas en China. En total, se detectaron 249 alelos con estos 20 marcadores y 244 de ellos (97.99%) mostraron polimorfismo. El número de alelos tuvo un rango de 7–22 con un promedio de 12.45 alelos por iniciador, y el contenido de la información polimórfica (PIC) varió de 0.64–0.93 con un promedio de 0.83. Los tamaños de los fragmentos variaron de 80–380 pb. Con base en los valores PIC y la claridad de las bandas de amplificación, se seleccionaron 11 marcadores SSR y fue posible diferenciar a la totalidad de las 217 variedades. La similitud estimada usando estos marcadores polimórficos SSR entre las variedades varió de 0.63 a 0.99, indicando una base genética angosta. Los análisis de huellas y diversidad genética en este estudio proporcionan información útil para la protección de propiedad intelectual, así como para la exploración y utilización de estas variedades de papa.

Tuber shape is one of the most important quality traits in potato appearance. Since poor or irregular shape results in higher costs for processing and influences the consumers’ willingness to purchase, breeding for shape uniformity and shallow eye depth is highly important. Previous studies showed that the major round tuber shape controlling locus, the Ro locus, is located on chromosome 10. However, fine mapping and cloning of tuber shape genes have not been reported. In this study, the analyses of tissue sectioning and transcriptome sequencing showed that the developmental differences between round and elongated tuber shapes begin as early as the hook stage of the stolon. To fine map tuber shape genes, a high-density genetic linkage map of the Ro region on chromosome 10 based on a diploid segregating population was constructed. The total length of the genetic linkage map was 25.8 cM and the average marker interval was 1.98 cM. Combined with phenotypic data collected from 2014 to 2017, one major quantitative trait locus (QTL) for tuber shape was identified, which explained 61.7–72.9% of the tuber shape variation. Through the results of genotyping and phenotypic investigation of recombinant individuals, Ro was fine mapped in a 193.43 kb interval, which contained 18 genes. Five candidate genes were preliminarily predicted based on tissue sections and transcriptome sequencing. This study provides an important basis for cloning Ro gene(s).

Early maturity is one of the most important agronomical traits in potato breeding. To identify the DNA segment that codes for early maturity, a tetraploid potato segregation population of “Zhongshu 19” × “Zhongshu 3” was genetically analyzed, using a combination of high throughput simplified genome sequencing (2b-RAD) and bulked segregant analysis (BSA). The DNA segment related to the early-maturity trait was identified at the 3.7~4.2 Mb locus on the short arm of chromosome 5. Eight molecular markers were developed, of which five were closely linked to the early-maturity trait loci. Additionally, 42 simple sequence repeats (SSR) markers were constructed based on the reference sequence of Solanum tuberosum group Phureja DM1-3 516 R44 (DM). Using the TetraploidMap software, the linkage map of chromosome 5 was constructed with 50 markers. The total map length was 172 centiMorgan (cM), with an average genetic distance of 3.44 cM. Correlating molecular and phenotypic data of the segregating population, the mapped Quantitative Trait Loci (QTL) on the short arm of chromosome 5 contributed to 33.55% of the early-maturity phenotype. The early-maturity QTL was located at 84 cM, flanked by the SSR5-85-1 and SCAR5-8 markers. The QTL was fine-mapped to 471 kb. Using DNA sequence annotation, 34 genes were identified in this region, 12 of them with unknown function. Among the other 22 annotated genes, E3 ubiquitin ligase gene PUB14 could be related to maturity and regulation of tuber formation. The constructed QTL map is a useful basic tool for the cloning of early-maturity related genes in tetraploid potatoes.

High temperatures delay tuberization and decrease potato (Solanum tuberosum L.) yields. However, the molecular mechanisms and regulatory networks underlying tuberization under high temperatures remain largely unknown. Here, we performed the mRNA and miRNA sequencing of leaves and stems to identify genes and regulatory networks involved in tuberization under high temperatures. A total of 2804 and 5001 differentially expressed genes (DEGs) under high-temperature stress were identified in leaves and stems, respectively. These genes were significantly enriched in gene ontology terms regarding meristem development, the sucrose biosynthetic process, and response to heat. Meanwhile, 101 and 75 differentially expressed miRNAs (DEmiRNAs) were identified in leaves and stems, respectively. We constructed an interaction network between DEmiRNAs and DEGs, identifying 118 and 150 DEmiRNA–DEG pairs in leaves and stems, respectively. We found three miRNA–mRNA candidate modules involved in tuberization under high temperatures, including stu-miR8030-5p/StCPY714, stu-miR7981f-p5/StAGL8a, and stu-miR10532A/StAGL8b. Our study constructed an interaction network between miRNAs and target genes and proposes candidate miRNA–gene modules that regulate tuber formation under high temperatures. Our study provides new insights for revealing the regulatory mechanism of the high-temperature inhibition of tuberization and also provides gene resources for improving the heat tolerance in potatoes.