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.

Maturity is one of the important traits of potato. In order to get the genetic segment of potato early maturity trait, a tetraploid potato maturity segregation population of Zhongshu 19 × Zhongshu 3 was used for genetic analysis through the combination of high throughput simplified genome sequencing (2b-RAD) and bulked segregation analysis (BSA). A genetic segment related to the early maturity trait at the 3.7~4.2 Mb locus on the short arm of chromosome 5 was obtained and eight markers were developed based on this segment, while five of them were closely linked to the early maturity trait loci. Moreover, 42 SSR markers were developed based on the reference sequence of DM. Finally, a genetic map of chromosome 5 contained 50 markers was constructed using the Tetraploidmap software. The total map length was 172 cM with an average genetic distance of 3.44 cM. Combining with phenotypic data of the segregation population, we mapped the early maturity trait QTL with the contribution of 33.55% on the short arm of chromosome 5, located at 84cM between the flanking markers SSR5-85-1 and SCAR5-8 with the physical interval of 471kb. Gene annotation showed that there exist 34 genes in this region, 12 of them are unknown function. Among the other 22 annotated genes, E3 ubiquitin ligase gene PUB14 may be related to maturity and regulate tuber formation. Our fine mapping of the early maturity QTL made a solid foundation for cloning of the early maturity controlled gene or genes. Key message: Early maturity site was mapped using a tetraploid potato segregation population derived from cv. Zhongshu 19 and Zhongshu 3. One major QTL with 33.55% contribution to early maturity was fine mapped in physical interval of 471kb on chromosome 5.

Senescence impacts plant growth and yields in tetraploid potatoes (Solanum tuberosum L.). Because of their homogenous tetraploid features, it is a major challenge to understand the genetic basis and molecular mechanisms of senescence. Here, we identified a novel central senescence regulator (Nicotinate-nucleotide pyrophosphorylase QPT/StNADC) through map-based cloning. Overexpression of StNADC^Z3 accelerated senescence in the late-senescence variety, with NAD content declining by around 40%. CRISPR/Cas9-induced StNADC mutant cr2–11 exhibited extremely early senescence, and the NAD content was reduced by 87% along with reduced chlorophyll content and photosynthesis. Moreover, the downstream products of the NAD synthesis pathway, such as NaMN, NAD, or niacin, can refresh the cr2–11 mutant to grow normally. Further, the transcriptomics and metabolomics data unveiled that the disrupting of StNADC impairs NAD metabolism, accelerating plant senescence through multiple biological levels. Our results show that StNADC is indispensable for NAD synthesis, and targeting the StNADC-mediated NAD synthesis pathway could be a useful strategy to regulate senescence in potato breeding preprograms.