Incorporation of genes from wild species has been a major contributor to tomato improvement in recent years. Solanum ochranthum, a woody non-tuber bearing species, is a potential source of resistance against tomato diseases and insect pests but is genetically isolated from tomato. Somatic hybridization methods were developed to facilitate the use of S. ochranthum for tomato germplasm improvement. Leaf mesophyll protoplasts of S. ochranthum and a Lycopersicon esculentum hybrid were chemically fused with polyethylene glycol. The protoplasts were initially cultured in Shepard's CL, a MS based medium, containing 1 mg·1-1 NAA, 0.5 mg·1-1 BAP and 0.5 mg·1-1 2,4-D. Hybrid regenerants and regenerants of the L. esculentum parent were recovered; S. ochranthum did not regenerate. Hybridity was established by morphological characters, peroxidase isozyme and RAPD markers. Use of these somatic hybrids for tomato improvement was evaluated.
Ruth S. Kobayashi, Stephen L. Sinden, and John R. Stommel
P. P. Barbano and L. D. Topoleski
Lycopersicon esculentum Mill. X Lycopersicon esculentum (E X E) and interspecific Lycopersicon esculentum × Lycopersicon peruvianum (L.) Mill. (E × P) ovules were studied to determine the sequence of events leading to embryo and endosperm deterioration in E × P ovules. At 7 days, the single-celled zygote and multicellular endosperm stage, the E × P ovule showed no signs of abnormality. Endosperm deterioration was the first indication of anatomical abnormality. The endosperm had disintegrated totally by 10 days after pollination. The ExP embryo did not follow normal stages of embryo development but divided randomly, and at 17 days filled the embryo sac with an undifferentiated mass of cells. Deterioration of both the E x P embryo and the cells of the proliferated endothelium was complete by 24 days. The embryo sac cavity size of 14-day E × P ovules and the weight of 13-day ExP ovules also indicated that endosperm and embryo breakdown began in this interspecific cross earlier than the 30- to 40-day age reported by other researchers.
John R. Stommel and Kathleen G. Haynes
Fruit of the cultivated tomato (Lycopersicon esculentum Mill.) store predominantly glucose and fructose whereas fruit of the wild species L. hirsutum Humb. & Bonpl. characteristically accumulate sucrose. Reducing sugar and sucrose concentrations were measured in mature fruit of parental, F1, F2, and backcross (BC1) populations derived from an initial cross of L. esculentum `Floradade' × L. hirsutum PI 390514. Generational means analysis demonstrated that additive effects were equal to dominance effects for percentage of reducing sugar. It was determined that a single major gene, dominant for a high percentage of reducing sugar, regulates the percentage of reducing sugar in tomatoes. We propose that this gene be designated sucr. Only additive effects were demonstrated to be important for glucose: fructose ratios. Using L. hirsutum as a donor parent for increasing total soluble solids concentration in the cultivated tomato is discussed.
Toshihiko Ikenaga, Seiji Kikuta, Miyuki Kistuki, Midori Yamada, and Kenichiro Nakashima
Solarium aculeatissimum Jacq. contains the steroid saponins aculeatiside A and aculeatiside B at high levels in the root, whereas they are lacking in all organs of tomatoes (Lycopersicon esculentum Mill). We examined the site of synthesis of these steroid saponins by using grafts between S. aculeatissimum and tomato plants. When S. aculeatissimum was grafted onto a stock of tomato (S.a./Tom.), a small amount of steroid saponin was found in the leaves and the stem of S. aculeatissimum but not in the roots of the tomato. However, when tomato was grafted onto stocks of S. aculeatissimum (Tom. /S.a.), steroid saponin occurred only in the roots of S. aculeatissimum. These results suggest that the steroid saponins are mainly synthesized in the roots of S. aculeatissimum. The lack of transport of steroid saponins from the roots of S. aculeatissirnum to the leaves and stem of the tomato remains unexplained.
Carol A. Lemke and Martha A. Mutschler
The absence or presence of type IV trichomes seemed to be simply inherited in crosses of the tomato, Lycopersicon esculentum Mill, and Lycopersicon pennellii Correll. F2 and BC1 data showed a good fit to a 15 : 1 and 3 : 1 ratio, respectively, suggesting that the presence of type IV trichomes is controlled by 2 unlinked genes. Broad sense heritability estimates of type IV trichome density were high. Generation means analysis of type IV trichome density indicated that genic interaction was important in the 3 crosses. All plants examined possessed type VI trichomes. Density of type VI trichomes seemed to be under large environmental influences. Broad sense heritability estimates for the density of type VI trichomes were low to moderate. Correlation coefficients comparing adaxial and abaxial trichome density measurements of both types of trichomes were significant for most of the populations studied. Correlation coefficients comparing type IV and type VI trichomes were not significant in most of the populations studied.
Marcelino Bazan Tene, Juan Manuel González Gonzalez, Francisco Radillo Juarez, and Pablo Enrique Ramírez Castillo
The tomato (Lycopersicon esculentum Mill.), is native to South America. It occupies the second place in worldwide vegetable consumption. Because of this, the evaluation of tomato varieties for the fresh consumption is important. The Mexican production is 1,908,607 tons of fresh product (SAGARPA, 2004). In the state of Colima, production has a mean efficiency of 18.13 t·ha-1 (INEGI, 2000). The following genotypes were evaluated `Peralta', `Montijo', Pavia', `Grande River', and `Yaqui' (control). A randomized experimental block was used, with five treatments and four repetitions. The obtained results indicate that `Yaqui' (control) had the better yield of fresh fruit, with 37.5 t·ha-1, followed by `Peralta' (27.2t·ha-1), and `Montijo' (12.6 t·ha-1), respectively. The height of plant in `Yaqui' was 68.8 cm and 60.26 cm in `Pavia'. In the days to flowering, after showing a homogenous behavior, pronouncing itself up to 27 days after the transplant; whereas the variety `Grande River' was pronounced up to 40 days. With respect to the number of total fruits by plant, a highly significant difference was observed. `Yaqui' produced 91 fruits, with `Pavia' and `Peralta' producing 50 and 37 fruits per plant, respectively. In conclusion, `Yaqui' was the genotype with greater yield and vigor.
Md. Shahidul Islam, S. Khan, and T. Matsui
Sucrose metabolism was followed in developing fruit of domesticated cherry tomato (Lycopersicon esculentum var. cerasiforme Alef.). The high amounts of reducing sugars were consistently linked to high soluble acid invertase (EC 22.214.171.124), whereas sucrose synthase (EC 126.96.36.199) followed the same pattern of sucrose levels and reached a peak of activity during early stage of maturation and then decreased to near nil. In comparison, sucrose phosphate synthase (EC 188.8.131.52) activity remain relatively constant throughout development. Thus, sucrose synthase and acid invertase, rather than sucrose phosphate synthase, are the critical enzymes regulating sucrose accumulation in tomatoes. Cultivated cherry tomato sucrose synthase (UDP-glucose: D-fructose 2-glucosyltransferase) was purified to homogeneity by ammonium sulfate precipitation, anion exchange chromatography on DEAE-Toyopreal 650, and gel filtration on Sephadex G-200. Further purification to homogeneity resulted from a single band from SDS-PAGE. The enzyme was identified as a homotetramer with a total molecular mass of 370 kDa and subunits of 92 kDa. The enzyme showed maximum activity for the cleavage and synthesis of sucrose was at pH 7.0 and 8.0, respectively, and the optimum temperature was 40°C in both directions for HEPES-KOH buffer. The enzymatic reaction followed typical Michaelis–Menten kinetics, with the following parameters: Km (fructose),7.4; Km (UDP-glucose), 0.2612; Km (sucrose), 33.24; Km (UDP), 0.0946. The enzyme was very sensitive to inhibition by heavy metals.
James Nienhuis, Julie Rodriguez, Wilber Phillips, Peter Hanson, and Liliway Engle
Worldwide, there are cuurently more than 60 germplasm banks that contain tomato (Lycopersicon esculentum) collections ranging is size from a few dozen to several thousands of accessions. In the utilization of these genetic resources sampling from only one germplasm bank may result in limiting available genetic diversity, whereas sampling from several germplasm banks may result in unnecessary redundancy. The current lack of knowledge regarding the relative magnitudes of genetic diversity contained within different collections makes it difficult to develop a core collection that maximizes genetic diversity. Two large tomato collections are housed at the Asian Vegetable Research and Development Center (AVRDC), Sanhua, Taiwan, R.O.C., and the Centro Agronomico Tropical de Investigacion y Enseoanza (CATIE), Turrialba, Costa Rica. Ninety-six accessions from CATIE and 102 accessions from AVRDC were randomly sampled from each base collection. The total of 198 accessions were charcterized for 103 polymorphic RAPD molecular marker bands. The results indicated that the two germplam banks sampled different genetic diversity. In addition, the magnitude of genetic diversity was greater in the AVRDC collection compared to CATIE.
John R. Stommel and Kathleen G. Haynes
Anthracnose, caused by Colletotrichum coccodes, is a serious ripe tomato fruit rot disease. Genetic resistance to anthracnose is not available in commercial tomato cultivars, but has been reported in small-fruited Plant Introductions (P.I.), and with lesser intensity in a number of breeding lines. Transfer of high levels of resistance from these breeding lines or P.I.s to elite materials has proven difficult. Inheritance of resistance has been described as complex with at least six loci influencing resistance reactions. Segregating populations originating from a cross between a susceptible tomato breeding line and a large-fruited breeding line (88B147) with resistance derived from Lycopersicon esculentum var. cerasiforme P.I. 272636, were evaluated for anthracnose resistance. Analysis of anthracnose resistance in puncture-inoculated fruit indicated small, but significant, additive genetic effects for resistance. Additional populations were developed from crosses of a susceptible inbred processing tomato cultivar with: 1) the resistant P.I. 272636, 2) an unadapted small-fruited resistant line developed from P.I. 272636, and 3) the large-fruited breeding line 88B147, also with resistance derived from P.I. 272636. Small additive effects identified in large-fruited material, in comparison to the resistant P.I., suggests that resistance loci have been lost during germplasm development. This is consistent with the relatively larger lesions observed in large-fruited lines derived from P.I. 272636. Positive correlations were noted between small fruit size and high levels of anthracnose resistance. Identification of molecular markers linked to resistance genes in the respective populations will be discussed.
Catherine D. Carter and John C. Snyder
A full-sib family of F2 individuals from a cross between mite-susceptible Lycopersicon esculentum Mill and mite-resistant Lycopersicon hirsutum Humb and Bonpl. was assayed for trichome characters and resistance to spider mites (Tetranychus urticae Koch). Mite responses primarily were associated with density of the Type IV trichome and, to a much less degree, with the leaflet surface bioassayed and phenol content of the Type VI trichome tip. Mite survival on F2 hybrids with at least 5.6 Type IV trichomes per mm2 was comparable to that on L. hirsutum.