Tomato plants (Lycopersicon esculentum Mill.) were grown under 4 irrigation treatments. In the first three an attempt was made to maintain soil water at a different level for each treatment. The fourth treatment was an approximation of the varied moisture levels that would be encountered with furrow irrigation. Leaf water potential (ΨL) was affected more during a day by atmospheric factors than by soil water availability. Hourly changes in ΨL and air water potential (Ψ air) were highly correlated (range .94*** and .99***). ΨL decreased as the plant aged, apparently due to decreasing soil water availability, decreasing root activity, and increasing resistance to water flow in stems and leaves. The stress factor, (which is an integration of the area below −6 bars; a critical level for tomatoes) was determined from the second degree polynomial regression of time versus ΨL and is proposed as a useful integration of ΨL. By using stepwise regression it was found that plant water status as evaluated by tensiometer reading, stress factor, the ratio of soil water/soil water at field capacity, and daily pan evaporation had the greatest effect on yield and total soluble solids content of tomato fruit.
High sugar and acid F1 hybrids of tomatoes (Lycopersicon esculentum Mill.) were rated higher in sweetness, sourness, and overall flavor intensity than the standard cultivar ‘Cal Ace’. Titratable acidity and soluble solids content were responsible for most of the differences in overall flavor intensity among these hybrids, their parents, and ‘Cal Ace’. The results support the idea that improved tomato flavor can be achieved via increased sugar and acid content.
Sugars, acids and their interactions were important to sourness, sweetness, and overall flavor intensity in tomato (Lycopersicon esculentum Mill.). Fructose and citric acid were more important to sweetness and sourness than glucose and malic acid, respectively. The pH was a better objective measure of sourness than titratable acidity. An interaction between glucose and citric acid on sweetness was observed. Quantitative differences in 11 volatile compounds were found among the cultivars. Several of these volatiles were significantly related to variation in the flavor characteristics studied. Three compounds (peaks (20–21), 51, and 75) appeared to be more important to the “tomato-like” character.
Locular content ranged between 14.4 and 35.0% among 7 cultivars of tomato (Lycopersicon esculentum Mill.): ‘Calmart’, ‘Cal Ace’, ‘Ace 55’, ‘Early Pak 7’, ‘Earliana’, ‘Rick High Sugar’, and ‘Cherry’. There was a strong negative correlation between fruit weight and percent locular tissue. Based on means of all cultivars, the pericarp portion contained about 20% more reducing sugars and 36% more glucose than the locular portion. No significant differences in soluble solids content or fructose concentration were noted. The locular portion had 48 and 57% higher titratable acidity and citric acid, respectively, than the pericarp, but no differences in malic acid concentration or pH were observed. Cultivars with large locular portion and with high concentration of acids and sugars are those which have previously been found to be of good flavor quality.
Four amino acids (glutamic, γ-aminobutyric, glutamine, and aspartic) make up about 80% of the total free amino acids in fruits of tomato (Lycopersicon esculentum Mill., cv. Cal Ace). Fruits harvested at the table-ripe stage contained more alanine and less glutamic acid than those picked green or at the breaker (incipient red color) stage and ripened at 20°C to table-ripe. The higher glutamic acid concentrations in fruit picked at the breaker or earlier stages were paralled to higher scores for “off-flavor,” as described by a taste panel, relative to fruits picked table-ripe. However, when monopotassium glutamate (60, 120, or 180 mg/l00g) was added to diced table-ripe fruits, the panelists were not able to detect flavor differences due to increased glutamic acid concn. Differences in amino acid composition associated with fruit ripeness when picked do not appear to be directly related to flavor differences.
Composition and sensory characteristics were investigated to determine the effect of ripeness at picking on fresh market flavor of ‘Cal Ace’ (1974, 1975, 1976) and ‘Cherry’, ‘Calmart’, and ‘Early Pak 7’ (1976) tomato (Lycopersicon esculentum Mill.). Tomatoes picked at earlier stages of ripeness and ripened at 20°C were evaluated by panelists as being less sweet, more sour, less “tomato-like” and having more “off-flavor” than those picked at the table-ripe stage. Objective tests showed these fruits had less sugars and reduced ascorbic acid, and varied significantly in volatile composition. The magnitude of these differences varied greatly among the cultivars. In ‘Cal Ace’ the “off-flavor” characteristic was largely correlated with a volatile compound (peak 43) but in other cultivars seven other volatile compounds also appeared to play a role.
Sensory evaluations and chemical analyses were used to investigate the effects of various postharvest handling procedures on composition and flavor quality of ‘Cal Ace’ tomatoes (Lycopersicon esculentum Mill.) harvested at the mature-green and light-pink stages. Ethylene treatment to speed ripening of green tomatoes at 20°C resulted in a higher reduced ascorbic acid content at the table-ripe stage and did not influence flavor when compared with fruits ripened without added ethylene. Using a low-O2 atmosphere to retard ripening had less of an effect on flavor than stage of ripeness at harvest. No differences were found between fruits where ripening was delayed by using 4% O2-atmosphere at 20° or by using low temperature (12.5°). Exposing fruits to 5° for 7 days before ripening at 20° affected flavor; i.e., chilled fruits were more acid. Above the chilling range (0-12.5°); duration of holding after harvest was more important than storage temperature. Lower holding periods resulted in loss of characteristic “tomato-like” flavor and development of “off-flavors.” Mature-green fruits, ripened at 20° under restricted air flow, had increased “off-flavors” when compared to those ripened under accelerated air exchange. Light-pink fruits subjected to impact bruising before ripening had more “off-flavor” and less “tomatolike” flavor than those without physical damage. Quantitative differences in a few volatile components were found with certain treatments, but no qualitative differences were detected and there was no significant difference in total volatile content among any of the treatments tested.
For many horticultural crops, selection is based on quality as well as yield. To investigate the distribution of trait variation and identify those attributes appropriate for developing selection indices, we collected and organized information related to fruit size, shape, color, soluble solids, acid, and yield traits for 143 processing tomato (Solanum lycopersicum L.) lines from North America. Evaluation of the germplasm panel was conducted in a multiyear, multilocation trial. Data were stored in a flat-file format and in a trait ontology database, providing a public archive. We estimated variance components and proportion of variance resulting from genetics for each trait. Genetic variance was low to moderate (range, 0.03–0.51) for most traits, indicating high environmental influence on trait expression and/or complex genetic architecture. Phenotypic values for each line were estimated across environments as best linear unbiased predictors (BLUPs). Principal components (PC) analysis using the trait BLUPs provided a means to assess which traits explained variation in the germplasm. The first two PCs explained 28.0% and 16.2% of the variance and were heavily weighted by measures of fruit shape and size. The third PC explained 12.9% of the phenotypic variance and was determined by fruit color and yield components. Trait BLUPs and the first three PCs were also used to explore the relationship between phenotypes and the origin of the accessions. We were able to differentiate germplasm for fruit size, fruit shape, yield, soluble solids, and color based on origin, indicating regional breeding programs provide a source of trait variation. These analyses suggest that multitrait selection indices could be established that encompass quality traits in addition to yield. However, such indices will need to balance trait correlations and be consistent with market valuation.