QTLs detection for fruit quality traits in a cross among an Argentinean tomato cultivar and a Solanum pimpinellifolium accession

PEREIRA DA COSTA, JAVIER H; ORLANDINI, AGOSTINA; VEGA, TATIANA ALEJANDRA; RODRÍGUEZ, GUSTAVO RUBÉN; PRATTA, GUILLERMO RAUL; ZORZOLI, ROXANA; PICARDI, LILIANA AMELIA

Málaga

Encuentro; XVIIth EUCARPIA Meeting - Section Vegetables Working Group of Tomato; 2011

Increasing tomato (Solanum lycopersicum) fruit quality should be a fundamental objective of breeding programs as consumers are very critic to tomatoes presently offered at the market. Poor quality is due either to genotypes under standard production or to the early ripening stage in which fruits are harvested with the aim of prolonging their commercial life. The Argentinean cultivar Caimanta produces large and flat in shape fruits having good taste and color but short fruit shelf life. Wild species are a reservoir of genes to improve organoleptic traits as well as prolonging fruit shelf life and can be efficiently incorporated to breeding programs by using molecular markers. Different types of DNA polymorphism analysis were applied to identify this new genetic variation. The objective was to detect QTLs (Quantitative Trait Loci) for tomato fruit quality traits by using Simple Sequence Repeats (SSR) and Sequence-Related Amplified Polymorphism (SRAP) in a Backcross I generation (BCI) of an interspecific cross among cultivar Caimanta (recurrent parent) and wild accession LA722 of S. pimpinellifolium (donor parent). Seventy four BC1 plants were evaluated for fruit height, diameter, shape index (height/diameter ratio), fruit shelf life, weight, soluble solids content, pH, titrable acidity, firmness, and color by the chroma index a/b and the reflectance percentage L. Parents and the F1 and BC1 generations were characterized by 30 SSR markers equally covering the 12 tomato chromosomes (Chr) and SRAP markers generated with 4 forward and reverse primer combinations. Single point analysis was applied to detect QTLs and estimate their phenotypic effects. All traits had normally distributed variation. Twenty three significant QTLs were detected with a p-value < 0.01, while they would reduce to six if p-value < 0.001. Five markers [SSR038 (Chr8), SSR70 (Chr9), SSR596 and SSR318 (Chr10), and SSRH301 (Chr12)] were simultaneously associated to two or more traits, and also some traits as diameter, weight, shape index and titrable acidity were explained by more than one SSR marker. QTLs for weight, height and diameter were found at Chrs 8, 9, 10, and 12, while QTLs for pH and titrable acidity were located at Chrs 2, 5, 9, and 12. A single QTL associated to firmness mapped to Chr 3 and two QTLs associated to shape index mapped to Chrs 8 and 10. For color, one QTL at Chr 7 was associated to L and other at Chr 9, to a/b. The percentage of phenotypic variance explained by each SSR ranged between 9 - 18 %. A single SRAP band (r9397) was associated to L (p < 0.01), its presence increased the trait value and it explained the 10% of the phenotypic variation. QTL alleles contributed by the wild parent increase phenotypic mean values for firmness, pH, and a/b whereas diminishing for weight, height, and L traits. Instead, the effects were variable for diameter, shape index and titrable acidity. SSR and SRAP marking the detected QTLs for fruit quality traits will be applied for assisting selection in a breeding programs tending to develop elite tomato genotypes adapted to Argentinean crop and consumer preferences.