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T. Casey Garvey and John D. Hewitt

A study using Lycopersicon cheesmanii Riley LA 1449 (typicum), a low soluble solids content (SSC) accession, and L. cheesmanii f. minor LA 528 (minor), a high SSC accession, was undertaken to characterize the accumulation of starch, sugar, and total SSC. Fruit of each accession was sampled throughout development to identify differences in SSC, starch accumulation, and sugar distribution. Osmetric analysis indicated that the minor race had higher SSC content throughout the ontogeny of fruit development than the typicum. Typicum contained more starch than minor, and both accessions showed a rapid decline in percent starch as the fruit ripened. Sucrose remained low throughout all stages of fruit development for both accessions. Glucose increased in the minor and declined in the typicum. Fructose increased in both accessions. Total reducing sugar content at the full ripe stage was higher in minor than the typicum.

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T. Casey Garvey and John D. Hewitt

An interspecific hybrid was made between an accession of Lycopersicon cheesmanii f. minor Riley (LA 1508) from the Galapagos Islands, Ecuador, and L. pennellii (Corr.) D'Arcy (LA 716). LA 1508 was used because of its high soluble solids content (SSC). It was crossed with LA 716 to test for linkage between isozymes and morphological markers and loci conditioning high SSC. For both accessions, chromosome numbers are equal and there are large differences between SSC and no barriers to crossing. Modified BC1 populations derived from the hybridization were assayed for isozyme markers using starch gel electrophoresis. Associations between marker loci and quantitative-trait loci (QTL) conditioning high SSC were determined using analysis of variance. Six isozymes located on five chromosomes and one morphological marker had significant associations with SSC, indicating linkage to QTL. Digenic epistatic interactions between pairs of independent markers did not appear to play an important role in the interactions between QTL that condition SSC.

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Michael C. Shannon and Anne F. Wrona

A salt-tolerance selected F5 generation from a cross between the wild tomato species, Lycopersicon cheesmanii, ecotype LA 1401, and the cultivated species, L. esculentum Mill. (cv Heinz 1350) was compared to the wild parental line in a solution culture experiment to determine the effects of selection on salt tolerance, and ion discrimination and accumulation characteristics in the selected line. Seedlings were transplanted to nutrient solutions at the 3 to 4-leaf stage of growth and after a 1-week period of adjustment, were salinized at 25 mM NaCl day-1 (approximately -1 bar osmotic potential) to final salt concentrations of 0, 50, and 100 mM. Plasmalemma and tonoplast vesicles were isolated from fresh root samples, and ATPase and Na+/H+ antiport activity was determined using fluorescence assays. The selected line restricted Na uptake into the shoot and maintained higher shoot K+ than did the wild parent. Growth rate under salinity was greater in the selected line than in the wild species, but relative salt tolerance was higher in the wild parent. Interspecific hybridization appears to be a useful process for the transfer of salt tolerance characters from wild to cultivated tomato.

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Y. Saranga, D. Zamir, A. Marani, and J. Rudich

Abbreviations: acc., accessions; ECe, electrical conductivity of saturated soil extract; ECi, electrical conductivity of irrigation water; Lc, Lycopersicon cheesmanii ; Le, Lycopersicon esculentum ; Lpen, Lycopersicon pennellii ; Lper

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V. Fernández-Ruiz, M.C. Sánchez-Mata, M. Cámara, M.E. Torija, C. Chaya, L. Galiana-Balaguer, S. Roselló, and F. Nuez

The characterization of Lycopersicon germplasm for internal quality properties is essential to choose suitable donor parents for breeding programs. When donor parents belong to species of subgenus Eulycopersicon, which are phyletically closer to L. esculentum Mill., the recovery of agronomic traits is faster. When using these materials, a careful selection of donor parents which could improve several internal quality properties allows the acceleration of these breeding programs. In this work, we combine general determinations, such as soluble solid content, titratable acidity, pH, total sugars, pectic substances and total protein contents with precise high-performance liquid chromatography (HPLC), quantitations of individual compounds (vitamin C; citric, malic, fumaric and oxalic acids; glucose, fructose, and sucrose), in order to obtain a more complete characterization of flavor intensity and nutritional properties in Lycopersicon germplasm. The multidimensional analysis of all these variables allows classification of several accessions of L. esculentum Mill. and L. pimpinellifolium (Jusl.) Mill., according to their usefulness for internal quality breeding programs of fresh tomato. The classification obtained and the comparison of accessions quality characteristics with selected controls show that five of the L. pimpinellifolium (Jusl.) Mill. accessions tested can be of great usefulness for being used in breeding for internal quality characteristics. A flavor intensity ≈625% higher than commercial hybrids was obtained in the best accession tested. Some of these L. pimpinellifolium (Jusl.) Mill. accessions showed better flavor intensity properties than a high SSC L. cheesmanii Riley control, traditionally used in internal quality breeding. In addition, three of the L. esculentum Mill. accessions tested with medium-to-high flavor intensity value could be useful in advanced stages of breeding programs.

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John R. Stommel, Judith A. Abbott, and Robert A. Saftner

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John R. Stommel, Judith A. Abbott, T. Austin Campbell, and David Francis

Fruit firmness is a key quality component of tomatoes (Lycopersicon esculentum Mill.) for fresh-market and processed product applications. We characterized inheritance of firmness in processing tomato germplasm developed from interspecific L. esculentum Mill. × L. cheesmanii f. minor (Hook. f.) C.H. Mull. and intraspecific L. esculentum crosses. Although firmness is a key quality attribute of tomato, there is no standard method for measuring it. We measured the elastic portion of firmness by compression (compression Fmax) and puncture (puncture Fmax), and the viscoelastic portion by force-relaxation. The experimental design incorporated six genotypes in a complete 6 × 6 diallel. Compression Fmax and force measurements recorded at 0.5, 1.0, 5.0, and 10.0 seconds of relaxation were strongly related to each other, while relaxation parameters (A, B, C) describing relaxation curve shape were generally independent. Compression Fmax, relaxation curve parameter A, and puncture Fmax were significantly different among hybrids. Significant differences between Maryland and Ohio environments were evident for compression Fmax and relaxation curve parameter A. The patterns of firmness means differed among firmness measurement methods, namely for compression Fmax and puncture Fmax, indicating that they measure different aspects of tomato fruit firmness. Soft-fruited parents generally exerted a negative effect on compression Fmax, whereas firm-fruited parents most often exerted a positive effect on compression Fmax. The force required for fruit compression best approximated subjective assessment of fruit firmness. Force required for fruit puncture was subject to a significant environmental × hybrid influence in the genotypes evaluated. Shape of the force relaxation curve (i.e., parameter A) was not predictive of relative fruit firmness. General combining ability (GCA) and specific combining ability were both significant with GCA being the principal source of genetic variation. In agreement with combining ability estimates, narrow-sense heritability estimates for compression Fmax and puncture Fmax were relatively high.

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Y. Saranga, D. Zamir, A. Marani, and J. Rudich

Abbreviations: ECi, electrical conductivities; Lc, Lycopersicon cheesmanii; Le, Lypopersicon esculentum; Lpen, Lycopersicon pennellii; Lper, Lycopersicon peruvianum; TD, total dry matter. 1 Deceased May 1986. This research was conducted within