Domestication And Inheritance Of Tuber Flesh Steroidal Glycoalkaloids In Diploid Potato

Potato?Solanum tuberosum L.?is the third most important staple food crop worldwide after wheat and rice in terms of human consumption.China is the world's largest potato producing and consuming country.The potato industry is related to China's food security,precision poverty alleviation and the stable economic and social development of the major producing areas.Steroidal glycoalkaloids?SGAs?are toxic specialized metabolites commonly found in Solanaceae and Liliaceae plants.A critical domestication trait for potato is the decrease of SGAs in tuber flesh.Recently,the pathway of SGA biosynthesis has been well studied.However,there were few studies on domestication and metabolic regulation genes related to the SGA in tuber flesh.Here,the domestication and inheritance of SGAs content in tuber flesh were analyzed and explored using the natural population of diploid potatoes and the F₂ segregating population derived from a cross between Solanum tuberosum and the wild potato species S.chacoense.A domesticated gene ERF9?Ethylene Response Factor?,a member of the ERF claster genes on chromosome 1,and two QTL genetic loci q STR2 and q STR8 were found to responsible for SGAs content in tuber flesh.These findings lay the foundation for exploiting the molecular mechanisms of domestication and inheritance of SGAs content in tuber flesh and provide a theoretical basis for the application of wild resources to modern potato breeding as well as the development of new varienties.The main contents are as follows:1)Quantitative analysis of the SGAs content of potato peels and flesh in 317 potato natural resources showed that the peels of landraces and wild species and the flesh of most wild contained very high levels of SGAs.The content in landrace tuber flesh is low below 100 mg/kg FW.The SGAs in tuber flesh showed obvious domestication characteristics.2)Analysis of the SGAs content in RH tissues showed that the order of the SGAs level was pistils,young stamens,old leaves,tuber peels,stolons,roots,stems and tuber flesh.It was noted that the tissues aboveground mainly contented ?-solanine,while the tissues belowground contented ?-solanine and ?-chaconine,with the ratio of ?-solanine and ?-chaconine ranging from 0.9 to 2.1.3)By analysis the GWAS and variation selectivity of the landraces and candolleanums,the signals of domestication overlapped with GWAS signal of SGAs content in tuber flesh,and located in the ERF gene cluster region on chromosome 1.The expression patterns of 10 genes in the ERF gene cluster were analyzed,and one of the ERFs,named ERF9,identified to be a candidate domesticated gene as a negative regulator of flesh SGAs.The haplotype analysis showed that ERF9 had strong domestication selectivity characteristics.4)With hairy root transformation system,we carried out overexpression and CRISPR/Cas9 knockout experiments and domesticated that ERF9 was negatively responsible for SGAs content in tuber flesh.5)We used a diploid F₂ segregating population to map the quantitative trait loci?QTLs?associated with the regulation of SGAs content in tuber flesh by QTL-seq.In a three-year study,we identified two QTLs on chromosomes 2 and 8,q STR2?ch02: 27.0–32.3 Mb?and q STR8?ch08: 3.5–6.3 Mb?,affecting SGAs content in tuber flesh.By transcriptome analysis,an MYC transcription factor in the q STR8 genome region may play a role in the regulation of the biosynthesis of tuber flesh SGAs.