Sucrose Accumulation In Fruit Research Articles

Cloning and Expression Analysis of Tomato <i>SlSPS1</i> Gene

Sucrose is the main product of plant photosynthesis and participates in many physiological and biochemical reactions of plants. Sucrose phosphate synthase is one of the key rate-limiting enzymes necessary for sucrose to enter various metabolic pathways, and its activity directly reflects the ability of sucrose synthesis in plants. In order to study the mechanism of sucrose synthesis in tomato, this study cloned a sucrose phosphate synthase gene from tomato pulp and named it  SlSPS1 . Through bioinformatics analysis, it was found that its cDNA is 3488bp in length, encoding 1054 amino acids, and there are 3 functional domain. There are 4  SPS  genes in tomato, and their homology is relatively high. In Salicaceae crops, SlSPS1 protein is closely related to potatoes, peppers and eggplants. The results of tissue-specific analysis found that  SlSPS1  was expressed in all tomato tissues, among which the expression was relatively high in the seedling stage and different development stages of the fruit. In order to further study the mechanism of SlSPS1 in tomato growth and sucrose accumulation, an overexpression and knockout vector of  SlSPS1  was constructed and transformed into Micro-Tom to obtain transgenic positive lines. Analysis of the expression level of  SlSPS1  on the obtained transgenic lines showed that the expression levels of the overexpression lines at the seedling stage, fruit green ripe stage and ripening stage were significantly up-regulated compared with the wild type, and the enzyme activity and sucrose content increased. Compared with the wild type, the expression of  SlSPS1  at the seedling stage, green ripe stage and ripening stage of the knockout line was significantly down-regulated, and the enzyme activity and sucrose content were reduced. As for the mechanism of  SlSPS1  in tomato growth and fruit sucrose accumulation, functional verification is needed in the future.

Transcription Factor CitERF16 Is Involved in Citrus Fruit Sucrose Accumulation by Activating CitSWEET11d.

Sugars are the primary products of photosynthesis and play an important role in plant growth and development. They contribute to sweetness and flavor of fleshy fruits and are pivotal to fruit quality, and their translocation and allocation are mainly dependent on sugar transporters. Genome-wide characterization of Satsuma mandarin identified eighteen SWEET family members that encode transporters which facilitate diffusion of sugar across cell membranes. Analysis of the expression profiles in tissues of mandarin fruit at different developmental stages showed that CitSWEET11d transcripts were significantly correlated with sucrose accumulation. Further studies indicated that overexpression of CitSWEET11d in citrus callus and tomato fruit showed a higher sucrose level compared to wild-type, suggesting that CitSWEET11d could enhance sucrose accumulation. In addition, we identified an ERF transcription factor CitERF16 by yeast one-hybrid screening assay which could directly bind to the DRE cis-element on the promoter of CitSWEET11d. Overexpression of CitERF16 in citrus callus significantly induced CitSWEET11d expression and elevated sucrose content, suggesting that CitERF16 acts as a positive regulator to promote sucrose accumulation via trans-activation of CitSWEET11d expression.

The protein kinase FaSnRK1α regulates sucrose accumulation in strawberry fruits

In strawberry, sucrose is the major form of carbohydrate translocated from the leaves to the fruits and plays an important role in fruit ripening. As a conserved energy sensor, sucrose nonfermenting-1 (SNF1)-related kinase 1 (SnRK1) plays an important role in plant carbon metabolism. However, evidence that SnRK1 regulates sucrose accumulation in fruits is lacking. In this study, we transiently expressed FaSnRK1α in strawberry fruits and found that overexpression (OE) of the FaSnRK1α gene significantly increased the sucrose content, whereas repression of FaSnRK1α by RNA interference (RNAi) decreased the sucrose content. Further analysis revealed that FaSnRK1α increased the expression of FaSUS1 and FaSUS3 as well as the activity of sucrose synthase (SUS; EC 2.4.1.13) and that FaSPS1 expression and sucrose phosphate synthase (SPS; EC 2.4.1.14) activity were strongly downregulated, which decreased the accumulation of sucrose. However, the expression of FaSPS3, which is reported to contribute to sucrose accumulation, was induced by FaSnRK1α, and FaNI expression and invertase (INV; EC 3.2.1.26) activity were upregulated by FaSnRK1α. In addition, FaSnRK1α positively upregulated the expression of the sucrose transporter (SUT) genes FaSUT1 and FaSUT5 and interacted with FaSUS1, FaSPS1 and FaSPS3 proteins but not with FaSUS3, FaNI, FaSUT1 or FaSUT5 proteins. Overall, FaSnRK1α systematically regulates the expression of the genes and activities of key enzymes involved in the sucrose metabolic pathway and promotes the long-distance transport of sucrose, thereby increasing sucrose accumulation and ultimately promoting fruit ripening. However, the mechanisms by which sucrose transport and degradation are regulated by SnRK1 warrant additional research.

Exogenous Application of Sucrose Promotes Postharvest Ripening of Kiwifruit

Sucrose is an important component of fruit flavor, but whether sucrose signaling affects the postharvest ripening process of kiwifruit is unclear. The aim of this article was to study the effect of sucrose application on postharvest kiwifruit ripening to clarify the effect of sucrose in this process. Our present study found that exogenous sucrose can promote ethylene synthesis, which increases the ethylene content during fruit ripening, thereby accelerating the ripening and softening of kiwifruit after harvest. A significantly higher expression of AcACS1 and AcACO2 was found in sucrose-treated fruits compared to that in mannitol-treated fruits. Blocking the ethylene signal significantly inhibited the sucrose-modulated expression of most selected ripening-related genes. Sucrose transport is essential for sucrose accumulation in fruits; therefore, we isolated the gene family related to sucrose transport in kiwifruit and analyzed the gene expression of its members. The results show that AcSUT1 and AcTST1 expression increased with fruit ripening and AcSUT4 expression decreased with ripening, indicating that they may have different roles in the regulation of fruit ripening. Additionally, many cis-elements associated with phytohormones and sugar responses were found in the promoter of the three genes, which suggests that they were transcriptionally regulated by sugar signal and phytohormones. This study demonstrates the effect of sucrose on postharvest ripening of kiwifruit, providing a good foundation for further research.

Potassium enhances the sugar assimilation in leaves and fruit by regulating the expression of key genes involved in sugar metabolism of Asian pears

Potassium (K) plays an important role in fruit quality, and is well known as the most important quality element. A field experiment was conducted with four K levels of 0 (control), 150 (K150), 300 (K300), 450 (K450) kg K2O ha−1 in 2014–2015. The aim was to elucidate the roles of K in fruit growth, and the mechanism of K in regulating sugar metabolism between the leaves and fruit of Asian pear (Pyrus L.). The results showed that the K concentration and accumulation in leaves and fruit with the net photosynthetic rate and SPAD value of leaves were found to increase with the increase of K application rates. Increasing K application rates also led to promote the effectiveness of accumulation of glucose, fructose, sorbitol, and sucrose in fruit. During the early fruit development stage, the increase of all soluble sugars in leaves was correlated with the up-regulation expression of gene AIV and S6PDH. Furthermore, with fruit development, the expression of AIV1, SPS1 and SUS, S6PDH and SDH3 involved in sugar metabolism in leaves were up-regulated by increasing the K application rates, resulting in higher accumulation of soluble sugars in leaves. Interestingly, at the fruit maturity stage the expression of SUT in leaves, and SPS1, SUS and SUT in fruit was significantly up-regulated, leading to higher sucrose accumulation in fruit. Thus, K-promoted sugar accumulation of the leaves and fruit might result from up-regulated expression levels of key genes involved in sugar metabolism by K in leaves and fruit.

Isolation, phylogenetic relationship and expression profiling of sugar transporter genes in sweet orange (Citrus sinensis)

Soluble sugars, including sucrose, glucose and fructose, are crucial components that determine the nutritional and commercial quality of sweet oranges (Citrus sinensis). Sugar transporters have been well demonstrated to mediate the long distance transportation and the subcelluar distribution of sugars in plants. Here, a genome-wide characterization of the sweet orange sugar transporter gene family was reported. We identified a set of putative orange sugar transporter genes containing 3 sucrose transporters (SUTs), 58 monosaccharide transporters (MSTs) that could be classified into 7 distinct subfamilies, and 16 SWEET transporters. Phylogenetic analysis among Arabidopsis thaliana, orange and Vitis vinifera allowed us to identify orthologous groups among these species. Three SUTs, CsSUT1, CsSUT2 and CsSUT4, were expressed in fruits, and exhibited increased transcripts levels as fruit sucrose accumulated, which suggested they participated in fruit sucrose accumulation. A large number of MSTs, CsSTPs, CsPMTs, CsVGTs, CspGlcTs, CsTMTs, CsERD6Ls and CsSWEETs showed fruit-expressed and up-regulated profiles, while glucose and fructose did not obviously accumulate as the fruit ripened. We then discussed the possibilities that fruit glucose and fructose had no evident accumulation, which was in contrast to sucrose. Additionally, many cis-elements such as ACGTATERD1, ARR1AT, MYCCONSENSUSAT, WRKY71OS, IBOXCORE, WBOXNTERF3, SUCROSE BOX 3 and WBOXHVISO1 were found in the promoter regions of orange sugar transporter genes, which suggested that they were transcriptionally regulated by sugars, phytohormones and stresses. This study might provide insights into the genomic organizations, evolutionary characteristics and expression profiling of the orange sugar transporter gene family.

Impact of secondary-lateral branch removal during watermelon production

The cultural practice of removal of the secondary-lateral branch of watermelon during the production in greenhouse requires intensive input of human labor. Secondary-lateral branch removal practices were examined in horizontally trained two watermelon cultivars (Citrullus lanatus), ‘Sambock-gul’ and ‘Speed-honey’ to determine the comparative differences in labor input as well as to understand their impact on plant and fruit growth and fruit sugar accumulation. Two experiments were conducted. Experiment 1 consisted of two treatments for plants trained with one main stem and two lateral branches: removal of the entire secondary-lateral branch or removal of the secondary-lateral branch below the fruit set node (partial removal). Experiment 2 consisted of three treatments for plants trained with either two or three lateral branches after topping the main stem: removal of the entire secondary-lateral branch, removal of the secondary-lateral branch below fruit set node, or removal of the secondary-lateral branch below the 5th node above fruit set node. Results showed that removal of the secondary-lateral branch below the fruit set node lowered human labor input by 50% compared with removal of the entire secondary-lateral branch. Additionally, some physiological benefits were also found for the plant treated by partial removal of the secondary-lateral branch. While fruit growth rate and fruit sucrose accumulation were much slower than those under other treatments until 3 weeks after pollination, 4 weeks after pollination sucrose accumulation started to increase steeply, and reached the highest concentration observed, 18.2 mg·mL−1. A greater increase in the length of fine roots, 0.2 mm in diameter, was observed under the partial removal treatment than for the entire removal treatment. During the fruit ripening period, the younger and developing leaves on secondary-lateral branches had a higher growth rate and higher photosynthetic activity than those of leaves on lateral branches. The integrated data indicate that active leaves on the secondary-lateral branch are likely to compete with the fruit as a sink during the fruit growing period, leading to slow fruit growth. However, during fruit ripening, the leaves on the secondary-lateral branch are likely to become a supportive source of carbon, leading to enhancement of sucrose accumulation in fruit.

Effects of Maleic Hydrazide Treatment on the Size and Number of Cells and Sugar Accumulation in the Fruit of Melons (Cucumis melo L.)

The relationships between the size and the number of cells and sugar accumulation in melon fruit have been examined. Maleic hydrazide (MH) was used to investigate the relationships. Although cell size was markedly larger in MH-treated fruit than in untreated fruit in the early stages of fruit development, the number of cells in MH-treated fruit was less than in untreated fruit in latter fruit development. Sucrose, glucose, and fructose content were higher in MH-treated fruit than in untreated fruit. It is therefore suggested that sucrose accumulation in fruit subjected to MH treatment is accelerated as a result of early cell enlargement and that sucrose content increases further as a result of the decrease in the number of cells in the fruit during late development.

Effects of the Lycopersicon chmielewskii sucrose accumulator gene (sucr) on fruit yield and quality parameters following introgression into tomato

A gene controlling fruit sucrose accumulation, sucr, was introgressed from the wild tomato species Lycopersicon chmielewskii into the genetic background of a hexose-accumulating cultivated tomato, L. esculentum. During introgression, the size of the L. chmielewskii chromosomal segment containing sucr was reduced by selection for recombination between RFLP markers for the sucr gene and flanking loci. The effects of sucr on soluble solids content, fruit size, yield and other fruit parameters were studied in the genetic background of the processing tomato cultivar 'Huntl00'. In a segregating BC5F2 generation, the smallest introgression containing sucr-associated markers was necessary and sufficient to confer high-level sucrose accumulation, the effects of which were completely recessive. Fruit of sucr/sucr genotypes were smaller than those of +/sucr or +/+ genotypes at all stages of development. The timing of sugar accumulation and total sugar concentration were unaffected by sugar composition. No differences in total fruit biomass (fresh weight of red and green fruit) at harvest were observed between the genotypes, and sucrose accumulators produced greater numbers of fruit than hexose accumulators in one family. However, the proportion of ripe fruit at harvest, and hence yield of ripe fruit, as well as average ripe fruit weight and seed set were reduced in sucr/sucr genotypes. Sucrose accumulation was also associated with increased soluble solids content, consistency, serum viscosity, predicted paste yield and acidity, and decreased color rating. In the first backcross to L. chmielewskii, hexose accumulators (+/sucr) had larger fruit than sucrose accumulators (sucr/sucr), while no difference in soluble solids was detected.

Differences in sucrose metabolism relative to accumulation of bird‐deterrent sucrose levels in fruits of wild and domestic Vaccinium species

We examined variability in sucrose levels and metabolism in ripe fruits of wild and domestic Vaccinium species and in developing fruits of cultivated blueberry (V. ashei and V. corymbosum). The objective was to determine if sufficient variability for fruit sucrose accumulation was present in existing populations to warrant attempts to breed for high‐sucrose fruit, which potentially would be less subject to bird predation. Threefold differences in fruit sucrose concentration were found among Vaccinium species, ranging from 19 to 24 mg (g fresh weight)−1 in V. stamineum and V. arboreum to approximately 7 mg (g fresh weight)−1 in cultivated blueberry (V. ashei and V. corymbosum) and V. darrowi. Hexose levels were similar among species, ranging from 90 to 110 mg (g fresh weight)–1, and glucose and fructose were present in equal amounts. Soluble acid invertase (EC 3.2.1.26) activity was negatively correlated with fruit sucrose concentration. There was no apparent correlation between fruit sugar concentration and either sucrose synthase (EC 2.4.1.13) or sucrose phosphate synthase (EC 2.4.1.14) activities, both of which were low for all species studied. Developmental increases in fruit sugar levels of cultivated blueberry followed a pattern similar to that observed in fruit fresh weight accumulation. Hexose concentrations ranged from 6 to 30 mg (g fresh weight)−1 during the first 60 days after anthesis. Between 60 days and fruit ripening (80 days), hexose levels rose from 30 to 80 mg (g fresh weight)−1. Sucrose was not detected in fruits until ripening, when low levels were found. Insoluble acid invertase activity was relatively high early in fruit development, decreasing as soluble acid invertase activity increased. Between 60 days and fruit ripening, soluble acid invertase activity increased from 3 to 55 μmol (g fresh weight)–1 h–1. Both sucrose synthase and sucrose phosphate synthase activities were low throughout development. The extent of sucrose accumulation in fruits and the degree of variability for this trait among Vaccinium species support the feasibility of developing high sucrose fruits, which would be a potentially valuable addition to current strategies of minimizing crop losses to birds.

746 PB 102 DIFFERENCES IN SUCROSE METABOLISM RELATIVE TO ACCUMULATION OF BIRD-DETERRENT SUCROSE LEVELS IN FRUIT OF VACCINIUM SPECIES

Variability in sucrose levels and metabolism in ripe fruit of several Vaccinium species were examined. The objective was to determine if sufficient variability for fruit sucrose accumulation was present in existing populations to warrant attempts to breed for high-sucrose fruit, which potentially would be less subject to bird predation. Three-fold differences in fruit sucrose concentration were found among species, ranging from 19 to 24 mg·(g fw)-1 in V. stamineum and V. arboreum to about 7 mg·(g fw)-1 in cultivated blueberry (V. ashei and V. corymbosum) and V. darrowi. Soluble acid invertase activity was negatively correlated with fruit sucrose concentration. There was no apparent correlation between fruit sugar concentration and either sucrose phosphate synthase or sucrose synthase activities, both of which were low for all species studied. The degree of variability in fruit sucrose accumulation among Vaccinium species supports the feasibility of developing high sucrose fruit, which would be a potentially valuable addition to current strategies of minimizing crop losses to birds.

Inheritance and genetic mapping of fruit sucrose accumulation in Lycopersicon chmielewskii

Fruit of the domestic tomato (Lycopersicon esculentum Mill.) accumulate soluble sugars primarily in the form of the hexoses, glucose and fructose. In contrast, the predominant sugar in fruit of the wild tomato relative, L. chmielewskii, is sucrose. In the present study, the inheritance and linkage relations of sucrose accumulation were examined in interspecific L. esculentum x L. chmielewskii populations. In backcrosses to either the wild or domestic tomato, segregation for sucrose accumulation permitted qualitative analysis of the trait and indicated monogenic recessive control, although deviations from Mendelian inheritance were observed in some populations. This major gene, designated sucr, was mapped in F2, F3, and BC1F2 populations using a set of 95 informative RFLP and isozyme markers covering the tomato genome. A map location near the centromere of chromosome 3 was established, with tight linkage to the genomic clone TG102. Association of sucrose accumulation with yellow fruit, encoded by an allele of the r gene, permitted alignment with the classical map, thereby confirming the map location of sucr. A linkage map of the region surrounding sucr was obtained by monitoring recombination between flanking markers in the back‐crosses to tomato. A cDNA clone of tomato fruit acid invertase, TIV1, was mapped to TG102 and sucr, with no recombination between the two RFLP markers observed in over 1700 meiotic products. Despite the tight linkage, TG102 and TIV1 hybridize to distinct restriction fragments, hence do not represent the same gene. The genetic data strongly suggest that sucr is an allele of the invertase gene and thus support previous biochemical studies that demonstrated low invertase activity in sucrose‐accumulating fruit. L. hisutum, another low‐invertase, sucrose‐accumulating species, was hybridized with L. chmielewskii and the resulting F1 plants accumulated sucrose, indicating that genetic control of soluble sugar composition is conserved in these two species.

Levels and Role of Sucrose Synthase, Sucrose-phosphate Synthase, and Acid Invertase in Sucrose Accumulation in Fruit of Asian Pear

Soluble sugar content and activities of the sucrose-metabolizing enzymes sucrose synthase (SS) (EC 2.4.1.13), sucrose-phosphate synthase (SPS) (EC 2.4.1.14), and acid invertase (EC 2.4.1.26) were analyzed in the pericarp of fruit from pear cultivars that differed in their potential to accumulate sucrose to identify key enzymes involved in sucrose accumulation in Asian pears. The Japanese pear `Chojuro' [Pyrus pyrifolia (Burro. f.) Nakai] was characterized as a high-sucrose-accumulating type based on the analysis of mature fruit, while the Chinese pear `Yali' (P. bretschneideri Rehd.) was a low-sucrose-accumulating type throughout all developmental stages. The activity of SS and SPS in `Chojuro' increased during maturation concomitant with sucrose accumulation, whereas the activity of these enzymes in `Yali' did not increase during maturation. The activity of SS and SPS in the former were seven and four times, respectively, higher than those in the latter at the mature stage. Further, among 23 pear cultivars, SS activity was closely correlated with sucrose content, while SPS activity was weakly correlated. Soluble acid invertase activity in `Chojuro' and `Yali' decreased with fruit maturation, but the relationships between soluble invertase activity and sucrose content were not significant. The results indicate that SS and SPS are important determinants of sucrose accumulation in Asian pear fruit and that a decrease of soluble acid invertase activity is not absolutely required for sucrose accumulation.

Sucrose phosphate synthase and other sucrose metabolizing enzymes in fruits of various species

Recent reports have suggested that sucrose phosphate synthase (EC 2.4.1.14), a key enzyme in sucrose biosynthesis in photosynthetic “source” tissues, may also be important in some sucrose accumulating “sink” tissues. These experiments were conducted to determine if sucrose phosphate synthase is involved in sucrose accumulation in fruits of several species. Peach (Prunus persica NCT 516) and strawberry (Fragaria x ananassa cv. Chandler) fruits were harvested directly from the plant at various stages of fruit development. Kiwi (Actinidia chinensis), papaya (Carica papaya), pineapple (Ananas comosus) and mango (Mangifera indica) were sampled in postharvest storage over a period of several days. Carbohydrate concentrations and activities of sucrose phosphate synthase, sucrose synthase (EC 2.4.1.13), and acid and neutral invertases (EC 3.2.1.26) were measured. All fruits contained significant activities of sucrose phosphate synthase. Moreover, in fruits from all species except pineapple and papaya, there was an increase in sucrose phosphate synthase activity associated with the accumulation of sucrose in situ. The increase in sucrose concentration in peaches was also associated with an increase in sucrose synthase activity and, in strawberries, with increased activity of both sucrose synthase and neutral invertase. The hexose pools in all fruits were comprised of equimolar concentrations of fructose and glucose, except in the mango. In mango, the fructose to glucose ratio increased from 2 to 41 during ripening as sucrose concentration more than doubled. The results of this study indicate that activities of the sucrose metabolizing enzymes, including sucrose phosphate synthase, within the fruit itself, are important in determining the soluble sugar content of fruits of many species. This appears to be true for fruits which sweeten from a starch reserve and in fruits from sorbitol translocating species, raffinose saccharide translocating species, and sucrose translocating species.

Sucrose Metabolism in Ripening Muskmelon Fruit as Affected by Leaf Area

Muskmelon (Cucumis melo L.) fruit lack a stored starch reserve and therefore depend on translocated photoassimilate from the leaf canopy for sugar accumulation during ripening. The influence of canopy photosynthesis on sucrose' accumulation within muskmelon fruit mesocarp was examined. Canopy photosynthetic activities were estimated in a sweet and a nonsweet genotype. Photosynthetic rate of the nonsweet genotype, on a per-plant basis, was only 56% of that of the sweet genotype. The effect of limiting leaf area of the sweet genotype on carbohydrate concentrations and sucrose metabolizing enzymes within the fruit was evaluated. A 50% reduction of leaf area 8 days before initiation of fruit sucrose accumulation resulted in canopy photosynthesis similar to that of the nonsweet genotype. Reduced photosynthetic activity resulted in slightly lower soluble-carbohydrate concentration in the fruit; however, fruit sucrose concentration was three times higher than that reported previously for the nonsweet genotype. The extent to which `fruit sucrose phosphate synthase (SPS) activity increased during maturation was diminished by leaf removal. Acid invertase activity declined in all fruit in a similar manner irrespective of defoliation. A reduction of leaf area of a sweet genotype reduced sucrose accumulation within the fruit. Lower fruit sucrose concentration was associated with lower concentration of raffinose saccharides and lower SPS activity within the fruit. Additionally, insufficient assimilate supply was judged not to be the factor responsible for low sucrose accumulation in a nonsweet genotype.

Sucrose Phosphate Synthase and Acid Invertase as Determinants of Sucrose Concentration in Developing Muskmelon (Cucumis melo L.) Fruits

Fruits of orange-fleshed and green-fleshed muskmelon (Cucumis melo L.) were harvested at different times throughout development to evaluate changes in metabolism which lead to sucrose accumulation, and to determine the basis of differences in fruit sucrose accumulation among genotypes. Concentrations of sucrose, raffinose saccharides, hexoses and starch, as well as activities of the sucrose metabolizing enzymes sucrose phosphate synthase (SPS) (EC 2.4.1.14), sucrose synthase (EC 2.4.1.13), and acid and neutral invertases (EC 3.2.1.26) were measured. Sucrose synthase and neutral invertase activities were relatively low (1.7 +/- 0.3 micromole per hour per gram fresh weight and 2.2 +/- 0.2, respectively) and changed little throughout fruit development. Acid invertase activity decreased during fruit development, (from as high as 40 micromoles per hour per gram fresh weight) in unripe fruit, to undetectable activity in mature, ripened fruits, while SPS activity in the fruit increased (from 7 micromoles per hour per gram fresh weight) to as high as 32 micromoles per hour per gram fresh weight. Genotypes which accumulated different amounts of sucrose had similar acid invertase activity but differed in SPS activity. Our results indicate that both acid invertase and SPS are determinants of sucrose accumulation in melon fruit. However, the decline in acid invertase appears to be a normal function of fruit maturation, and is not the primary factor which determines sucrose accumulation. Rather, the capacity for sucrose synthesis, reflected in the activity of SPS, appears to determine sucrose accumulation, which is an important component of fruit quality.