Search Results
Abstract
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.
In arid and semiarid areas, wine grapes are frequently managed using regulated deficit irrigation (RDI) to control vegetative growth. To understand the distribution of soil moisture using RDI in a drip-irrigated vineyard, we collected soil samples after several irrigation events around six drip emitters in two ‘Cabernet Sauvignon’ and two ‘Merlot’ vineyards from late July through Mar. 2002 and 2005. The March sampling depicts soil moisture status before budbreak after winter precipitation. Soil samples were collected in four depth increments at 16 locations in a half-circle radius from immediately below the emitter to a depth of 60 cm. Both gravimetric and volumetric soil moisture content were determined. Soil moisture varied by depth, distance from the emitter, and sampling time. During late-season irrigation events, 50% to 75% of the sampled area contained plant-available water, which was less than expected. When calculated as plant-available soil moisture, regardless of time of sampling, soil sampled across a 0- to 45-cm depth provided the most representative indication of soil moisture status. Additionally, sampling directly under the emitter or directly under the drip line could result in skewed measurements compared with the sampled area. The data suggest that collecting soil samples within a 20- to 40-cm radius, either diagonal or perpendicular to the drip line emitter position, will best reflect the amount of plant-available soil water. Additionally, monitoring should be conducted on both sides of the row around each emitter selected and then averaged to avoid any patterns from hilling or disruption in water flow patterns.
Abstract
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.
Abstract
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.
Abstract
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.
Abstract
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.
Abstract
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.
Abstract
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.
Abstract
Accessions of several wild tomato species [Lycopersicon hirsutum H. and B. (LA 1363 and LA 1777), L. chilense Dun. (LA 1969 and LA 1971), and Solanum lycopersicoides Dun. (LA 1964)] were examined for cold tolerance and compared to the fast germination of L. esculentum Mill. PI 341988 and to the normal germination of ‘UC82B’. The wild accessions were collected above 3000 m and presumed to be cold-tolerant because of natural habitat. A number of characteristics, including germination, emergence, chlorophyll fluorescence, electrolyte leakage, and plastochron index were used to evaluate chilling resistance. PI 341988 germinated faster than the other genotypes at temperatures above 10°C, but germination of this accession virtually ceased below 10°. The high-altitude accessions continued to germinate, albeit at a reduced rate, below 10°. Growth rates at 12°/6° (day/night) were compared to growth at 24°/18° and were found to be greater in the high-altitude accessions than ‘UC82B’ The reduction in chlorophyll fluorescence when leaf disks were exposed to 1° was less in the high-altitude accessions than in ‘UC82B’, indicating less effect of this temperature on photosynthesis in the wild species. Electrolyte leakage was greater in ‘UC82B’ and LA1777 (L. hirsutum) than high-altitude accessions of L. chilense and S. lycopersicoides, but evidence is presented that this method is not reliable in screening for cold tolerance. Crosses were made between ‘UC82B’ and the wild species, and segregating populations were screened using the methods mentioned above. In each population, there were plants that showed cold resistance similar to the wild parent, suggesting the possibility of developing cold-tolerant cultivars.
Abstract
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.