Allelism for cold sweetening in native potatoes from Argentina

SILVANA COLMAN; MARTÍN CARBONI; MARCELO MONTE; MASSA GABRIELA ALEJANDRA; FEINGOLD SERGIO ENRIQUE

Arrail D´Ajuda

Conferencia; 11th Solanacea Conference (SOL2014).; 2014

The accumulation of reducing sugars in cold stored potato (Solanum tuberosum L.) tubers, a phenomenon referred to as cold-induced sweetening, is a persistent, costly problem for the potato processing industry. During potato chip and French fry production, reducing sugars in the tubers react with free amino acids in the non-enzymatic Maillard reaction to produce brown- to black-pigmented products that affect the aspect, flavor and nutritional quality of the product and are not acceptable for consumers. Andean potatoes (Solanum tuberosum Andigena Group) have a wide genetic diversity useful for breeding programs. They constitute sources for resistance to various biotic and abiotic factors, such as diseases, salinity, drought and frost. Also, Andean potatoes showed low levels of reducing sugars at harvest and after storage at low temperatures. Additionally, they present special nutritional characteristics as high concentration of vitamins, proteins and antioxidant compounds. Association mapping has become the preferred method to identify loci that control the transmission of complex traits. The main advantages are: i) increased mapping resolution, allowing test samples from natural populations ii) reduce research time and iii) analyze greater allele number. The aim of this study was identify alleles of genes with a functional role in carbohydrate metabolism associated with a low reducing sugars content and good quality chips in cold stored tubers. We used 52 accessions of Andigena Group, which were planted in randomized block field trials in three different years in the Northwest of Argentina. To study the cold-induced sweetening response we evaluated the chips quality and quantified reducing sugars of freshly harvested tubers and cold (4ºC) stored tubers for 60 days. Native accessions showed high diversity responses, and genotypes that presented low reducing sugars levels and good chip quality -even after cold storage- were identified. We determined the allelic variability of invertases genes, invGE/GF, invCD and invVac through microsatellites (SSR) located on or nearby these genes. SSRs showed PICs of 0.94, 0.82 y 0.64, for invGE/GF, invCD and invVac SSRs, respectively. We analyzed the population structure using six highly polymorphic nuclear SSRs which allowed the identification of two subgroups. We found alleles associated with cold-induced sweetening traits by using Tassel software and considering the population structure. InvGFssr_5 allele was associated with low reducing sugar levels and good chip quality in cold stored tubers. Conversely, invGFssr_4 allele was associated with high reducing sugars levels and bad chip quality after storage. InvGFssr_7 and invVacssr_1 alleles were also associated with high reducing sugars levels after cold storage, but no chip association was found. Lastly, invGFssr_9 was associated with bad chip quality in both freshly harvested and cold stored tubers; while invCD_1 allele was associated only to bad chip quality after storage.   Finally, we sequenced the corresponding invGF gene allele from each invGF SSR band associated with cold-induced sweetening. Each SSR allele corresponded to a unique invGF allele at both nucleotide and peptide levels.