Location: Plant Genetic Resources Research2012 Annual Report
1a. Objectives (from AD-416):
We will screen 139 tomato genotypes from the core collection of tomato for flavor, sugars, acids and volatiles. Fruits will be brought to the laboratory for physicochemical, sensory, and consumer preference measurements. Flavor is one of the most highly demanded consumer traits of tomato at present, and the lack of flavor is one of the most commonly heard complaints associated with modern varieties of tomato.
1b. Approach (from AD-416):
A list of 139 unique tomato germplasm accessions from the core collection has been identified (in consultation with the USDA tomato germplasm curator) to be characterized in this study. This list consists of heirloom, large fruited round, cherry, grape and plum tomato. Since flavor is the major concern of fresh market tomato, germplasm used is primarily from fresh market tomatoes. Accessions will be grown with two replicates at Mountain Horticultural Crops Research and Extension Center (MHCREC), Mills River in North Carolina. Six plants of each genotype will be grown with a plant to plant and row to row spacing of 45 cm and 150 cm, respectively. Fruits from the middle four plants will be harvested and used for physicochemical, sensory and consumers’ preference rating by untrained panelists. For each genotype, batches of 12 fruits will be sampled and measured for fruit weight, fruit firmness (measured by a Penetrometer), and fruit color L* (lightness), a* (green to red), and b* (blue to yellow) measured with Tomato Analyzer. Total soluble solids (TSS) content and total acidity will be determined using the tomato juice. The sensory analysis will be performed on tomato samples from both replicates. Samples will be assigned to the panelists at random. Definition of terms to be used for sensory analysis have the intensity of the descriptive terms will be rated at 0 to 5 scale, where 0= Extreme low, and 5= Extreme high. Panelists will rinse their mouth with tasteless carbonated mineral water to neutralize their palate between samples.
3. Progress Report:
There were highly significant differences (p<0.01) among tomato genotypes for overall flavor and flavor-contributing components except for herbaceous odor, herbaceous flavor and salty taste. Fruit firmness is claimed to be associated with fruit flavor. For that reason, firmness was measured in this core collection and average firmness was found to be 10.9 N ranging from 5.8 to 35.8 N, which was a wide range. Extremely soft (low firmness) genotypes were PI 128129, Tomate, M7281 and Tomate del Lugar whereas those with a high level of firmness were 888, Castle Rock and Sun1643. Average TTA was 0.3% ranging from 0.15 to 0.64%. However, average TSS was 4.9 ranging from 3.4 to 9%, which is a very good level of variation. Genotypes with high levels of TSS were LA2102, Sponzillo, AVRDC#6, LYC3249 and Red Pear. Average ratio of TSS to TTA was 16.4 ranging from 8.6 to 33.1 - the wider the ratio, the sweeter the tomato. Fruity odor of tomato ranged from 0.9 to 4.0 when measured on a scale from 0 to 5, 5 being an excellent fruity odor. With a similar ranking, sweet flavor ranged from 0.8 to 4.2 whereas acidic flavor ranged from 0.7 to 4.2. Fruity flavor ranged from 0.6 to 4.0 whereas melon flavor was virtually absent in this collection of tomato genotypes. Juicy texture ranged from 1.1 to 4.5 whereas mealy texture ranged from 0.9 to 3.8. Overall flavor rating, which is due to the interactions of individual components, ranged from 0.8 to 4.1 with an average of 2.6. The best genotypes for overall flavor were Jubilee, Polish Oxheart, Sponzillo, Zhongza No. 4, Hong Kong, and Rinon PI 118783. All these traits varied broadly, revealing the potential to utilize the available germplasm for fruit quality improvement.