Changes in acid content in fruits of tomato (Lycopersicon esculentum Mill.) left on the vine compared with those of fruits removed from the vine at one stage each of development and ripening. Developing fruits detached 28 days after anthesis had an increase in total acidity attributable to increased malic and citric acid concentrations. Detached developing fruits accumulated organic acids more rapidly than attached fruits. Mature fruits detached at the breaker stage decreased more in total acidity than attached fruits which was reflected in a decrease in malic and citric acids, with a greater decrease in malic acid. The data indicate that organic acid accumulation in detached fruits is determined by metabolism at the time of detachment.
Yield and quality are the primary goals of most plant breeding programs. Both of these general characteristics are multifaceted and extremely complicated. This complexity and a frequent negative relationship between them makes it difficult to deal successfully with them simultaneously in a breeding program.
The inheritance of malate in tomatoes was investigated by gas-liquid chromatography with trimethylsilyl derivatives. Studies of progeny from the crosses ‘Campbell 146’ x ‘Campbell 1327’ and ‘Delsher’ x PI 255842-SI indicated that concentration of malate is determined by a single factor with dominance for low concentration.
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.
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.
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.
The relative growth rates for tomato (Lycopersicon esculentum Mill.) genotypes differing in carboxylation efficiency (CE) were similar. Manapal (dg), which had a high CE, had a more rapid vegetative phase growth rate and LA 1098 (low CE) was slower growing. Specific leaf dry weight was greater in high CE genotypes indicating that it may be a useful selection criterion. Leaf thickness was greater in the high CE genotypes (Manapal (dg) and 067) than in the intermediate CE cultivars. Manapal (dg) and 067 (high CE) has much greater percent air space in the palisade tissue and much longer palisade cells than 7879 and VF 36 (intermediate CE). Conversely the number of palisade cells cm−2 was much less in the high CE genotypes. These results indicate that differences in gaseous diffusion potential may in part account for genotypic differences in CE. Differences in CE at 21 and 2% O2 indicated that genotypic differences for photorespiration rate was not an important contributor to the variation in CE.
Fruits of tomato (Lycopersicon esculentum Mill.) ripened on the plant had higher total solids, soluble solids, and reducing sugars than those which were analyzed at the “breaker” stage (incipient red color). Fruits detached as “breaker” and ripened off the plant lost solids and sugars during ripening. The total solids and reducing sugars concentration in fruits ripened on the plant were about 9% and 18% (‘Ace 55’) or 15% and 23% (‘Rick High Sugar’) higher, respectively, than in fruits ripened off the plant.
Fruits analyzed at the “breaker” stage contained only 69.2% (‘Ace 55’) or 43.6% (‘Rick High Sugar’) of their potential reduced ascorbic acid concentration if ripened on the vine to table-ripe. Fruits accumulated ascorbic acid during ripening on or off the plant, but the increase was 16% to 27% greater for those fruits left on the plant.
The mode of inheritance of carboxylation efficiency (CE) of tomato (Lycopersicon esculentum Mill.) was studied using parents, F1, BCP1, BCP2, and F2 progeny from the crosses Ottawa 67 (067) × VF 145-7879 (7879) and 067 × LA959. The inheritance of chlorophyll content was studied with the cross 067 × LA959. The difference in CE between 067 and 7879 is controlled by a single gene with high CE apparently conditioned by the high pigment (hp) gene from 067. The differences in CE and chlorophyll content between 067 and LA959 are under digenic control. The differences appear to be controlled by hp from 067 and lurida (lur) from LA959. A causal relationship between chlorophyll content and CE may not exist, but the evidence presented indicates the two characteristics are closely related.
Several characteristics of the cultivated tomato (Lycopersicon esculentum Mill.) and several wild relatives were explored as factors in resistance to the pink form of the potato aphid. Foliage volatiles of resistant and susceptible plants were found to be qualitatively similar but quantitatively different. Olfactometric tests revealed that the aphids did not react in any detectable way to the aroma variation conditioned by these quantitative differences. Epidermal hairs (non-glandular) of the normal genotypes were not a factor influencing degree of attack by the aphids. In the field the aphids avoided both an excessively hairy compound mutant stock Ln-Wom and the wild tomato relative L. hirsutum. However, under infestation in the laboratory the insects managed to feed on these plants. Pubescence in the normal genotype is not a factor affecting resistance. However, increase of hair density and length tends to restrict aphid feeding activity under field conditions. The presence of anthocyanin in the foliage did not inhibit aphids from feeding. No anatomical obstacles to reaching the feeding site, the internal phloem, were found in resistant accessions of the green-fruited species L. hirsutum, however, thick cortex in the stems might prevent aphids from reaching vascular tissue. Comparative analysis of foliage of susceptible and resistant plants revealed higher sucrose, lower quinic acid, and higher alanine and tyrosine contents and a trend toward higher total free amino-acid concentration in the former. Furthermore, susceptible plants were unique as a source of o-phosphoethanol amine.