Search Results
Abstract
Evaluation of progeny populations from crosses between tomato accessions (Lycopersicon spp.) with high and low alkaloid levels indicated that variation in α-tomatine content is controlled by the segregation of 2 co-dominant alleles at a single locus.
Abstract
When larvae of Heliothis zea (Boddie) were caged on fruits of varying developmental ages from 3 accessions of Lycopersicon, the length of the larval stage and mortality were positively correlated with fruit α-tomatine content. Larval growth rates and adult weights of H. zea were found to be inversely correlated with fruit alkaloid content. Growth and survival of caged Spodoptera exigua (Hubner) were not related to the levels of tomatine in the fruit. However, a highly significant correlation exists between fruit cuticular toughness and S. exigua mortality. Compared to the processing tomato line VF145B-7879, lower H. zea and S. exigua survival rates were observed when the larvae were reared on the tougher, higher-alkaloid fruits of L. esculentum var. cerasiforme and L. pimpinellifolium accessions. These results indicate a possibility of enhancing cultivar resistance to these insect pests through the development of tough-fruited, high-α-tomatine genotypes.
Abstract
Measurement of respiration rate and ethylene production at the climacteric of fruits of 4 tomato (Lycopersicon esculentum Mill.) cultivars and breeding lines—LA 1563 (1563), ‘VF145B-7879’ (‘7879’), ‘UC 134’ (‘134’), and R982 (982)—showed that fruits of ‘7879’ have lower rates of respiration and ethylene evolution than those of the other 3 genotypes. Analysis of progeny from a cross between 1563 and ‘7879’ suggested that a small number of genes with mostly additive effects control the difference in respiration rate between these 2 lines. A joint scaling test indicated that an additive-dominance model was adequate for analysis of the genetic variation. The number of effective factors was estimated to be 1.28 and the calculated narrow sense heritability was 0.49.
Abstract
Phosphorus concentration is an important factor in quality of tomato fruits because of its effect on the relationship between pH and titratable acidity. There was no significant change in P concentration of fruits from 4 to 10 weeks (cannery ripe) after anthesis in cultivar VF 145-7879. The P concentration was relatively high at 2 weeks and decreased during senescence. The inheritance of P concentration was studied with ‘Best of All’, ‘STEP 375’ and their F1, B1, B2, and F2 progeny. The data indicate a significant genotype-environment interaction. Partition of the genetic variance revealed that additive and dominant effects and additive × additive interaction are important in determining P concentration. There is evidence that 2 major genes are involved.
Abstract
Two tomato (Lycopersicon esculentum Mill.) genotypes, LA 1563, a high solids breeding line and ‘VF145B-7879’, an intermediate solids cultivar, were studied in an attempt to determine which morphological characteristics contribute to high solids content in the fruits, and to evaluate 1563 as genetic material for higher solids in processing tomato fruits. A genotypic difference in fruit solids was apparent from as early as 10 days after anthesis, and continued through fruit development. Between 10 and 50 days after anthesis, 1563 and ‘7879’ fruits increased in mean dry weight from 0.057 g to 5.16 g and from 0.101 g to 4.28 g, respectively. A growth analysis showed that lower harvest index, lower fruit yield and larger leaf area were associated with the higher solids of 1563, compared to 7879.
Abstract
High-temperature responses of heat-tolerant tomato (Lycopersicon esculentum Mill. cvs. Saladette, PI 262934, BL6807, S6916, CIAS161, and VF36) were studied at 38/27°C day/night temperature. Flower production was reduced in all cultivars except BL6807 which partitioned a greater proportion of total assimilates to the flowers. Only ‘Saladette’ and VF36 showed a total lack of stigma exsertion, which in effect is functional male sterility. Pollen production was reduced in all cultivars, and there was a lack of pollen dehiscence. Several techniques were used to evaluate gamete viability. There was poor agreement among the 3 methods used to assess pollen viability. ‘Saladette’ suffered the least reduction for in vitro germination but had the greatest loss in seed set when high-temperature pollen was used. Seed set is probably the most reliable method to measure gamete viability. CIAS 161 and S6916 had the least reduction in pollen viability according to seed set criteria. Ovule viability is much more difficult to adequately evaluate. According to seed set criteria PI 262934 ovules suffered the least damage due to high temperatures. Whether the male or female gamete was affected more severely depended on genotype. Pollen viability was greatly reduced in PI 262934 but ovule viability was less severely affected. In BL6807 ovule viability was more severely reduced than pollen viability.
Abstract
The genetics of high-temperature fruit set was studied with a complete diallel cross using 5 cultivars with excellent high temperature tolerance and a California cultivar lacking stigma exsertion. The cultivars differed genetically for number of flowers per cluster, percent fruit set, number of seeds per fruit and stigma exsertion. At normal and high temperatures recessive genes are associated with greater flower number and heritability for this character was high. Percent fruit set is under the control of a largely additive system with a moderate heritability at high temperature. Nonallelic gene interaction was involved in seed set and dominance components exceeded additive at both temperatures. Heritability for seed set was low at high temperature. Stigma exsertion at high temperature is controlled by partially dominant genes with a high diallel additive component and heritability. The results suggest that a scheme of selection for specific combining ability would be useful to combine the strengths of the high temperature tolerant lines with needed characters from a successful cultivar.
Abstract
Three tomato (Lycopersicon esculentum Mill.) lines with divergent viscosities and their F1, BCP1, BCP2, and F2 progeny were analyzed for serum viscosity, gross viscosity, and five alcohol insoluble solids (AIS) components. The components were water soluble polysaccharides and polygalacturonides, water-insoluble polysaccharides and polygalacturonides, and acid-hydrolyzed polysaccharides. Stepwise regression analysis of data from parents and progeny was used to establish the relationships between a change in composition and a change in viscosity. The polygalacturonides accounted for most of the variation in gross viscosity among the parental lines. The data indicate that water-insoluble, pectinol-solubilized polysaccharides have the potential for making a large contribution to viscosity at higher concn. The water-soluble polysaccharides and complex polysaccharides (solublized in H2SO4) contributed little to gross viscosity. The sugars identified in the AIS were arabinose, ribose, xylose, mannose, galactose, and glucose. Galacturonic acid was the only organic acid detected. Concentration of the compounds varied among the fractions and among the parental lines.
Nineteen interspecific hybrid breeding lines were tested for resistance to a TSWV isolate using enzyme-linked immunosorbent assay (ELISA) to check for presence of the virus after inoculation. These lines were all BC1F6 lines derived from L. esculentum crosses with seven L. chilense accessions. All of these lines had been selected for high tolerance/resistance to tomato mottle virus (ToMoV), a geminivirus [Scott et al., Bemisia 1995: Taxonomy, Biology, Damage Control and Management 30: 357–367 (1996)]. The initial TSWV screening indicated that eight of the 19 original lines had “possible” TSWV resistance. Seed from these selected eight lines were then planted and inoculated with TSWV ≈3 weeks after emergence. Three weeks later, ELISA results indicated that all plants from all lines were infected with TSWV. However, none of the plants from Y118 (derived from the LA 1938 cross) showed visual TSWV symptoms. The Y118-derived plants were allowed to grow for several months, and at no time developed significant visual symptoms of the virus. The consistent lack of TSWV symptoms prompted a second ELISA test on the Y118 plants, and the results indicated the plants were completely free of TSWV. Further tests were then initiated with F2 (L. esculentum × Y118) seed, and results indicate a single dominant gene is responsible for TSWV resistance. Data from this segregating population, including a molecular marker study which screened 800 randomly amplified polymorphic DNA (RAPD) primers, will be presented. Approximately two to five RAPD primers are possibly linked to TSWV resistance.
Abstract
Twenty-seven accessions from 6 species of the genus Lycopersicon and 1 accession of Solanum pennellii were surveyed for content of the glycoalkaloid, α-to-matine. Significant variation in alkaloid content was found to exist among the accessions. L. esculentum cultivars were found to contain much lower concentrations of α-tomatine than accessions of L. esculentum var. cerasiforme, L. pimpinellifolium, and the L. peruvianum accession, LA 462.