Guillermo Raúl Pratta

Protein profiling in F1 and F2 generations of two tomato genotypes differing in ripening time

Pericarp polypeptide profiles were analyzed at three ripening stages in the F1 hybrid and the F2 population from the cross between the accessions: LA1385 (Lycopersicon esculentum var. cerasiforme) and 804627 (L. esculentum, a homozygous genotype for the nor mutant). Six polymorphic polypeptides were observed in LA1385, while no polymorphic polypeptides among ripening stages was observed in 804627. On the other hand, some polypeptides in the F1 hybrid were not observed in the parents whereas others were present in both parental genotypes and were unnoticeable in the hybrid genotype. From a cluster analysis on the protein profiles of the F2 population, the differential expression of proteins allowed to distinguish mature green (MG) stage from the others two stages, while for breaker stage (BR) and red ripe stage, the genetic background was more important in forming groups. The differential expression of proteins could be associated with fruit morphology traits such as a 72 kDa polypeptide present in MG stage with fruit diameter, height and mass and a 47 kDa polypeptide found in BR with fruit shelf life.

Phenotypic and molecular characterization of selected tomato recombinant inbred lines derived from the cross Solanum lycopersicum × S. pimpinellifolium

An important trait defining fresh tomato marketability is fruit shelf life. Exotic germplasm of Solanum pimpinellifolium is able to prolong shelf life. Sixteen recombinant inbred lines with differing values of shelf life and fruit weight were derived by antagonistic-divergent selection from an interspecific cross involving Solanum pimpinellifolium. The objective of this study was to evaluate these recombinant inbred lines for many fruit quality traits such as diameter, height, size, acidity, colour, firmness, shelf life and weight, and to characterize them by amplified fragment length polymorphism markers. For most traits, a wide range of genetic variability was found and a wide range of molecular variation was also detected. Both sets of data allowed the identification of recombinant inbred lines by means of cluster analysis and principal component analysis. Genetic association among some amplified fragment length polymorphism markers and fruit quality traits, suggested by the principal component analysis, could be identified by single point analysis. Potential molecular markers underlying agronomical traits were detected in these recombinant inbred lines.

Characterization of the segregating generation of a tomato hybrid carrying nor and exotic genes

The objective of this work was to study recombination of the productive and fruit quality traits in the segregating generation of the hybrid between a cultivated variety of Lycopersicon esculentum homozygous for nor and the accession LA1385 of L. esculentum var. cerasiforme using multivariate statistical analysis. F 1 and F2 generations and the parents were evaluated for vegetative and productive traits (internode length, stem perimeter at the basal, middle and apical parts, number of flowers per cluster, number of clusters per plant and days to harvest) and quality fruit traits (weight, shape, soluble solids content, acidity, firmness, color and shelf life). A canonical correlation between vegetative and productive traits and those of fruit quality and clustering for fruit traits performed with the F 1 and F2 and the parents were used. The productive and fruit quality traits showed recombination in the segregating generation. Shelf life was the most outstanding fruit trait to discriminate groups in the F2. For three cluster levels each group of F 2 individuals behaved each one of the parents and the F 1.

Transgressive segregation for fruit quality traits in a cross between exotic and mutant genotypes of Lycopersicon

Abstract A cross between a Lycopersicon esculentum accession carrying the mutant nor and an accession of L. esculentum var. cerasiforme was made to analyse the joint genetic effect upon the phenotypic segregation of some fruit quality traits in the F2 generation. Fruit from the F1, F2, and the parents (as testers) were evaluated for shelf life and another quality traits. Because of the presence of individuals falling beyond their parental phenotypes in the F2, a transgressive inheritance was estimated by a chi‐square test. Transgressive inheritance was present for relevant traits such as shape, colour, firmness, and shelf life. The broad sense heritability values were highly significant for all traits and the shelf life was not associated with any other fruit quality trait. The use of this wild accession as a parent in tomato breeding programmes becomes an alternative for increasing fruit quality and especially prolonging the fruit shelf life.

Variability for the in vitro culture response in tomato recombinant inbred lines

The aim of this work was to estimate genetic variability for in vitro culture response of recombinant inbred lines (RILs) of the genus Lycopersicon. The callus percentage (C), the regeneration percentage (R) and the productivity rate (PR) were evaluated 45 d after culture initiation in a set of 16 elite tomato RILs and their parents. The narrow sense heritability (h2) values were 0.38 ± 0.04 for C, 0.46 ± 0.04 for R, and 0.28 ± 0.03 for R, while the genetic correlation (rg) values were −0.96 ± 0.07 between C and R, 0.81 ± 0.14 between PR and R, and −0.79 ± 0.16 between PR and C. Three AFLP markers associated to the in vitro traits were identified.

Multivariate analysis as a tool for measuring the stability of morphometric traits in Lycopersicon plants from in vitro culture

Abstract The phenotypic stability of morphometric traits in Lycopersicon spp. (stem perimeter at the base, middle and top, and number of flowersper cluster) was measured by multivariate analysis through a progeny test in order to estimate the genetic stability of these t raits. Principalcomponents were calculated for two groups of Lycopersicon spp., non-regenerated plants and the progeny of regenerated plants.Analysis of variance was performed to support principal component analysis. Both groups presented similar eigenvalues and eigen vec-tors, while no significant differences were found between any of the traits studied. These results indicated that the phenotypi c structurewas the same among the progeny of regenerated and non-regenerated plants, so that no variation would occur in in vitro culture.Multivariate analysis proved to be an appropriate methodology for the measurement of the stability of morphometric traits after oneregeneration cycle. CONICET (Consejo Nacional de Investigaciones Cientificas y Tecnicas) - CIUNR (Consejo de Investigaciones de la Universidad Nacional de Rosario) -Catedra de Genetica, Facultad de Ciencias Agrarias, Universidad Nacional de Rosario, Caixa Postal 14, 2123 Zavalla, Argentina.Send correspondence to G.P. Fax: +54-341-497-0080/85. E-mail: gpratta@fcagr.unr.edu.ar

Molecular markers detect stable genomic regions underlying tomato fruit shelf life and weight

Received 30 September 2010Accepted 6 January 2011ABSTRACT - Incorporating wild germplasm such as S. pimpinellifolium is an alternative strategy to prolong tomato fruit shelf life(SL) without r educing fr uit quality . A set of r ecombinant inbr ed lines with discr epant values of SL and weight (FW) wer e derived byantagonistic-diver gent selection fr om an interspecific cr oss. The general objective of this r esear ch was to evaluate Genotype x Y ear(GY) and Marker x Y ear (MY) interaction in these new genetic materials for both traits. Genotype and year principal effects and GYinteraction were statistically significant for SL. Genotype and year principal effects were significant for FW but GY interaction wasnot. The marker principal effect was significant for SL and FW but both year principal effect and MY interaction were not significant.Though SL was highly influenced by year conditions, some genome regions appeared to maintain a stable effect across years ofevaluation. Fruit weight, instead, was more independent of year effect.Key words: amplified fragment length polymorphism; plant breeding; plant genetic resources; Solanum section Lycopersicon;quantitative genetics.

A 54-kDa polypeptide identified by 2D-PAGE and bulked segregant analysis underlies differences for pH values in tomato fruit

Fruit pH is an important quality attribute in tomato and it is defined during ripening. The aims of this work were to detect pericarp polypeptides associated with pH in an interspecific tomato BC1 generation by 1D-PAGE and to identify those differentially expressed polypeptides by comparing 2D-PAGE protein profiles from bulked segregant analysis (BSA). Polypeptide patterns were resolved by 1D-PAGE in a BC1 population obtained by crossing the cv. ‘Caimanta’ of Solanum lycopersicum (recurrent parental genotype) and the accession LA722 of S. pimpinellifolium (donor parental genotype). Putative QTL for fruit quality were detected by single point analysis. The presence of a 54-kDa band at the mature green stage (MG) carried by the wild genotype decreased the mean value of the pH trait. A BSA combined with 2D-PAGE was applied to the extreme phenotypes for pH in the BC1 segregating population. Four differentially expressed spots were detected when the polypeptide patterns of the bulks were compared. The spots had the expected molecular mass (around 54-kDa), and they were present in the lower-pH bulk and absent in the higher-pH one. The spots were identified by MS MALDI-TOF and two of them showed homology with the ATP synthase CF1 alpha subunit of S. lycopersicum. These results indicate that the association between the polypeptide marker and a fruit quantitative trait detected by 1D-PAGE not only would indicate genetic linkage but also could be directly related with the gene underlying the quantitative trait.