QTL analysis of fruit quality in fresh market tomato: a few chromosome regions control the variation of sensory and instrumental traits

The organoleptic quality of tomato fruit involves a set of attributes (flavour, aroma, texture) that can be evaluated either by sensory analyses or by instrumental measures. In order to study the genetic control of this characteristic, a recombinant inbred line (RIL) population was developed from an intraspecific cross between a cherry tomato line with a good overall aroma intensity and an inbred line with medium flavour but bigger fruits. A total of 38 traits involved in organoleptic quality were evaluated. Physical traits included fruit weight, diameter, colour, firmness, and elasticity. Chemical traits were dry matter weight, titratable acidity, pH, and the contents of soluble solids, sugars, lycopene, carotene, and 12 aroma volatiles. A panel of trained assessors quantified sensory attributes: flavour (sweetness and sourness), aroma (overall aroma intensity, together with candy, lemon, citrus fruit, and pharmaceutical aromas) and texture (firmness, meltiness, mealiness, juiciness, and skin difficult to swallow). RILs showed a large range of variation. Molecular markers were used to map a total of 130 quantitative trait loci (QTL) for the 38 traits. They were mainly distributed in a few chromosome regions. Major QTLs (R(2) >30%) were detected for fruit weight, diameter, colour, firmness, meltiness, and for six aroma volatiles. The relationships between instrumental measures and sensory traits were analysed with regard to the QTL map. A special insight was provided about the few regions where QTLs are related to multiple traits. A few examples are shown to illustrate how the simultaneous analysis of QTL segregation for related traits may aid in understanding the genetic control of quality traits and pave the way towards QTL characterization.     

Genetic analysis of organoleptic quality in fresh market tomato. 1. Mapping QTLs for physical and chemical traits

Improving organoleptic quality is an important but complex goal for fresh market tomato breeders. A total of 26 traits involved in organoleptic quality variation were evaluated, in order to understand the genetic control of this characteristic. A recombinant inbred line (RIL) population was developed from an intraspecific cross between a cherry tomato line with a good overall aroma intensity and an inbred line with a common taste but with bigger fruits. Physical traits included fruit weight, diameter, color (L,a,b), firmness and elasticity. Chemical traits were dry matter weight, titratable acidity, pH, and the contents of soluble solids, sugars, lycopene, carotene and 12 aroma volatiles. RILs showed a large range of variation for most of the traits and many of them were transgressive. Some correlations between aroma volatiles were in accordance with the metabolic pathway they originated from. A total of 81 significant QTLs were detected for the 26 traits by simple and composite interval mapping. They were mainly distributed in a few regions on chromosomes 2, 3, 4, 8, 9, 11 and 12. Major QTLs (R²>30%) were detected for fruit weight, diameter, and color, and for six aroma volatiles. Co-localization of QTLs controlling correlated traits was mainly found on chromosome 2. QTLs for fruit weight and sugar content or dry matter weight were often co-localized. However, a QTL for soluble-solids content and dry matter weight have been detected on chromosome 9 in a region without fruit weight QTLs. QTLs for seven aroma volatiles, lycopene content and fruit color were also co-localized. The QTL localizations were compared with those detected in crosses between Lycopersicon esculentum and wild tomato species. Received: 19 January 2000 / Accepted: 26 May 2000     

COMPARISON OF ATTRIBUTE LIKING AND JAR SCALES TO EVALUATE THE ADEQUACY OF SENSORY ATTRIBUTES OF MILK DESSERTS

Just-about-right (JAR) scales and attribute liking questions are usually used to study consumer perception of the sensory characteristics of food products. The aim of the present work was to compare the performance of attribute liking and JAR scales to evaluate consumers' perceived adequacy of flavor and texture of milk puddings. Two groups of consumers were asked to evaluate eight milk desserts using (1) overall liking followed by attribute liking for texture and flavor and (2) overall liking followed by JAR scales for thickness, creaminess, sweetness and vanilla flavor. Overall liking scores were significantly different when JAR scales or attribute liking questions were considered. Texture, flavor and overall liking scores were highly correlated to each other, providing the same information. JAR scales correlated better with the intensity of sensory attributes evaluated by a trained sensory panel, being JAR percentages a reliable tool to study the adequacy of sensory attributes.

PRACTICAL APPLICATIONS

Results from the present work showed that consumers might not be able to independently evaluate their liking of different sensory attributes of a product. For this reason, the use of attribute liking questions for studying the adequacy of sensory attributes in complex products would not be recommended. JAR scales were better indicators of the adequacy of sensory attributes. Consumers were able to independently evaluate texture and flavor attributes using JAR scales. However, the influence of JAR scales on overall liking scores should be taken into account when including these scales on consumer studies.     

IMPORTANCE OF SENSORY FACTORS IN PROCESSED SEAFOOD: METHODS AND RESULTS1

This paper considers “importance” of sensory attributes from the consumer point of view, with emphasis on processed seafood. There are three key measures of importance. Attitudinal importance measures what consumers think to be important and refers to general opinions about the category. Sensory system importance measures how strongly different sensory inputs (e.g., appearance, aroma, taste, texture) “drive” overall liking, and show the key sensory inputs to which consumers attend. Attribute level importance measures the relation between sensory intensity and overall liking for each attribute. It shows which specific attributes drive liking, how liking varies with the specific sensory attribute, and whether (and at what sensory level) there exists an optimal level.     

Sensory evaluation of fruit quality and nutritional composition of 20 breadfruit (Artocarpus, Moraceae) cultivars

Twenty breadfruit cultivars growing in afield genebank at Kahanu Garden, National Tropical Botanical Garden, Hana, Maui, Hawaii, were evaluated for sensory attributes and nutrient composition. A taste panel scored eight flavor/aroma attributes, five textural attributes, and color. There were significant differences (P ≤ 0.01) in aroma, visual texture, flavor intensity, sweetness, starchiness, moistness, stringiness, firmness, and color. The greatest differences were in color and texture. Nutrient analyses showed significant differences (P ≤ 0.05) for energy, carbohydrates, ash, crude protein, potassium, magnesium, sodium, iron, copper, and zinc. Considering the versatility of breadfruit as a food, its ease of production, and its nutritional value, the numerous good quality flavorful cultivars available should be more widely grown for sustainable agriculture and food security.     

Dissection of genetic and environmental factors involved in tomato organoleptic quality

Background  

One of the main tomato breeding objectives is to improve fruit organoleptic quality. However, this task is made somewhat challenging by the complex nature of sensory traits and the lack of efficient selection criteria. Sensory quality depends on numerous factors, including fruit colour, texture, aroma, and composition in primary and secondary metabolites. It is also influenced by genotypic differences, the nutritional regime of plants, stage of ripening at harvest and environmental conditions. In this study, agronomic, biochemical and sensory characterization was performed on six Italian heirlooms grown in different environmental conditions.     

Multiple evidence for the role of an Ovate-like gene in determining fruit shape in pepper

Background  

Grafting is a widely used technique contributing to sustainable and ecological production of many vegetables, but important fruit quality characters such as taste, aroma, texture and shape are known for years to be affected by grafting in important vegetables species including pepper. From all the characters affected, fruit shape is the most easily observed and measured. From research in tomato, fruit shape is known to be controlled by many QTLs but only few of them have larger effect on fruit shape variance. In this study we used pepper cultivars with different fruit shape to study the role of a pepper Ovate-like gene, CaOvate, which encodes a negative regulator protein that brings significant changes in tomato fruit shape.     

TEXTURE-FLAVOR INTERACTIONS IN LOW FAT STIRRED YOGURT: HOW MECHANICAL TREATMENT, THICKENER CONCENTRATION AND AROMA CONCENTRATION AFFECT PERCEIVED TEXTURE AND FLAVOR

The influence of thickening agent (0 and 7g/L), mechanical treatment (low and high) and flavoring agent concentration (2.2 to 63.2 μL/kg) on texture, taste and aroma of low fat stirred yogurts was investigated through sensory profiling by a panel of ten subjects trained on 13 attributes. Two assessment conditions were used: either in the presence or in the absence of olfactory perception (nostrils closed with nose clips). Sensory differences were greater for texture than for the other perception modalities. Olfactory perception enhanced yogurt astringency. If both thickener addition and mechanical treatment influenced texture attributes and rheology, the second factor had the strongest effect. Texture attributes were highly correlated with rheological parameters. Increasing flavoring agent concentration tended to decrease thickness and the addition of thickening agent depressed green apple notes and sweet taste, suggesting texture/flavor interactions.     

Identification of growth processes involved in QTLs for tomato fruit size and composition

Many quantitative trait loci (QTLs) for quality traits havebeen located on the tomato genetic map, but introgression offavourable wild alleles into large fruited species is hamperedby co-localizations of QTLs with antagonist effects. The aimof this study was to assess the growth processes controlledby the main QTLs for fruit size and composition. Four nearlyisogenic lines (NILs) derived from an intraspecific cross betweena tasty cherry tomato (Cervil) and a normal-tasting large fruittomato (Levovil) were studied. The lines carried one (L2, L4,and L9) or five (Lx) introgressions from Cervil on chromosomes1, 2, 4, and 9. QTLs for fruit size could be mainly associatedwith cell division processes in L2 and L9, whereas cell expansionwas rather homogeneous among the genotypes, except Cervil forwhich the low expansion rate was attributed to low cell plasticity.The link between endoreduplication and fruit size remained unclear,as cell or fruit sizes were positively correlated with the cellDNA content, but not with the endoreduplication factor. QTLsfor fruit composition reflected differences in water accumulationrather than in sugar accumulation, except in L9 for which theup-regulation of sucrose unloading and hexose transport and/orstarch synthesis was suggested. This may explain the increasedamount of carbon allocated to cell structures in L9, which couldbe related to a QTL for fruit texture. In Lx, these effectswere attenuated, except on fruit size and cell division. Finally,the region on top of chromosome 9 may control size and compositionattributes in tomato, by a combination of QTL effects on celldivision, cell wall synthesis, and carbon import and metabolism. Key words: Cell division and expansion, endoreduplication, fruit quality, near isogenic line, osmotic regulation, quantitative trait locus, Solanum lycopersicum, starch, sugar and acid contents Received 22 July 2008; Revised 17 October 2008 Accepted 20 October 2008     

SENSORY PROPERTIES AFFECTING ACCEPTABILITY OF "BRESAOLA" FROM PODOLIAN YOUNG BULLS

Three muscles ( Semimembranosus, Quadriceps femoris, Adductor ) from Podolian young bulls (aged 18 months) were processed into bresaolas, which were compared with commercial products, in terms of sensory profile and preference expressed by consumers. Slope analysis was conducted to study the preference drivers. The preference of homogeneous groups of consumers and the relationships with sensory properties of bresaola were investigated using partial least squares (PLS) regression analysis. The products differed for several sensory properties, such as sweetness, flavor intensity ( P <  0.001), saltiness ( P <  0.01), peppered, seasoned and tenderness ( P <  0.05). The slope analysis showed that taste/flavor ( k =  0.86) and appearance ( k =  0.76) play an important role in orienting consumer preference, while texture ( k =  0.54) is less important. No general trend was found for product liking. Conversely, PLS regression clustered the consumers in homogeneous groups: one preferred the commercial products characterized by sensory properties such as peppered, saltiness, seasoned and marbling, another one was more oriented toward properties such as sweetness, odor and chewiness, which characterized Podolian bresaolas.

PRACTICAL APPLICATION

Partial least squares regression analysis clustered the consumers in homogeneous groups according to their liking: those preferring peppered, salty, seasoned and marbling bresaolas versus those oriented toward sweet and odorous products. In addition, the relationship between overall liking and attribute liking (appearance, taste/flavor and texture) was analyzed by linear regression analysis. This may be helpful in order to establish meaningful criteria for grading bresaolas and identify the particular attributes that move its acceptance (i.e., taste/flavor and appearance rather than texture).     

Marker-assisted introgression of five QTLs controlling fruit quality traits into three tomato lines revealed interactions between QTLs and genetic backgrounds

The evaluation of organoleptic quality of tomato fruit requires physical, chemical and sensory analyses, which are expensive and difficult to assess. Therefore, their practical use in phenotypic selection is difficult. In a previous study, the genetic control of several traits related to organoleptic quality of fresh-market tomato fruit was investigated. Five chromosome regions strongly involved in organoleptic quality attributes were then chosen to be introgressed into three different recipient lines through marker-assisted selection. A marker-assisted backcross (MABC) strategy was performed, as all the favorable alleles for quality traits were provided by the same parental tomato line, whose fruit weight (FW) and firmness were much lower than those of the lines commonly used to develop fresh market varieties. Three improved lines were obtained after three backcrossing and two selfing generations. The implementation of the MABC scheme is described. The three improved lines were crossed together and with the recipient lines in a half-diallel mating scheme, and the simultaneous effect of the five quantitative trait locus (QTL) regions was compared in different genetic backgrounds. Significant effects of the introgressed regions and of the genetic backgrounds were shown. Additive effects were detected for soluble solid and reducing sugar content in two genetic backgrounds. A partially dominant effect on titratable acidity was detected in only one genetic background. In contrast, additive to dominant unfavorable effects of the donor alleles were detected for FW and locule number in the three genetic backgrounds. Recessive QTL effects on firmness were only detected in the two firmest genetic backgrounds. Comparison of the hybrids in the half-diallel gave complementary information on the effects of: (1) the alleles at the selected regions, (2) the genetic backgrounds and (3) their interaction. Breeding efficiency strongly varied according to the recipient parent, and significant interactions between QTLs and genetic backgrounds were shown for all of the traits studied.     

A LINGUISTIC METHOD FOR SENSORY ASSESSMENT

A linguistic format for sensory assessment of foods as well as computational methods to analyze taste panel opinions have been developed within the framework of fuzzy set theory. The methodology is demonstrated via sensory analysis of roasted peanuts. Sensory analysis was represented as linguistic values and associated truth values for attributes such as roast flavor, bitterness and overall quality. This format allowed panelists to describe and discriminate different roast characteristics. Replicate analyses of the same sample were reasonably consistent. The linguistic information was simple yet rich in meaning and could be used to make inferences for quality and process control. Yager's ordered weighted median aggregation operator was used to estimate the expected linguistic values for aroma, flavor, bitterness, sweetness, color and overall quality.     

Relationships among taste qualities assessed with response-context effects

Psychophysical judgments often depend on stimulus context. For example, sugar solutions are judged sweeter when a tasteless fruity aroma has been added. Response context also matters; adding a fruity aroma to sugar increases the rated sweetness when only sweetness is considered but not when fruitiness is judged as well. The interaction between stimulus context and response context has been explored more extensively in taste-odor mixtures than in taste-taste mixtures. To address this issue, subjects in the current study rated the sourness of citric acid mixed with quinine (bitter), sodium chloride (salty), and cyclamate (sweet) (stimulus context). In one condition, subjects rated sourness alone. In another, subjects rated both sourness and the other salient quality (bitterness, saltiness, or sweetness) (response context). Sourness ratings were most sensitive to response context for sour-salty mixtures (i.e., ratings of sourness alone exceeded ratings of sourness made simultaneously with saltiness) and least sensitive to context for the sour-sweet mixtures (sourness ratings made under the 2 conditions were essentially identical). Response-context effects for the sour-bitter mixture were nominally intermediate. The magnitudes of these context effects were related to judgments of qualitative similarity between citric acid and the other stimuli, consistent with prior findings. These types of context effects are relevant to the study of taste-taste mixture interactions and should provide insight into the perceptual similarities among the taste qualities.     

Confusing tastes and smells: how odours can influence the perception of sweet and sour tastes

This study investigated the relationship between perception of an odour when smelled and the taste of a solution to which the odour is added as a flavorant. In Experiment 1 (E1) sweetness, sourness, liking and intensity ratings were obtained for 20 odours. Taste ratings were then obtained for sucrose solutions to which the odours had been added as flavorants. Certain odours were found to enhance tasted sweetness while others suppressed it. The degree to which an odour smelled sweet was the best predictor of the taste ratings. These findings were extended in Experiment 2 (E2), which included a second tastant, citric acid, and employed four odours from E1. The most sweet smelling odour, caramel, was found to suppress the sourness of citric acid and, as in E1, to enhance the sweetness of sucrose. Again, odours with low sweetness suppressed the sweetness of tasted sucrose. The study demonstrated that the effects of odours on taste perception are not limited to sweetness enhancement and apply to sour as well as sweet tastes. The overall pattern of results is consistent with an explanation of the taste properties of odours in terms of prior flavour-taste associations.     

Inheritance of taste components in tomato

Components of tomato taste can be modeled from a set of instrumentally measured parameters. The inheritance was studied of two texture parameters with an effect of mealiness and pleasantness of taste: BFp and EBp. A recombinant inbred line population (F6) of the cross tomato cv Moneymaker x L. pimpinellifolium was analyzed for these parameters, and a molecular linkage map was developed for this population. A single QTL region on chromosome 9 was found with an effect on both BFp and EBp. The QTL explained 18.2 and 18.8% of the population variances, and 19.5 and 39.0% of the parental differences respectively for BFp and EBp.