Fruit Bitterness Research Articles

Генетика признаков огурца (Cucumis sativus)

The analysis of literary sources for the presence of monogenic, oligo and polygenic traits of cucumber (Cucumis sativus) was carried out. Valuable crop diseases include high yield, genetic absence of fruit bitterness, evenness, as well as cases of biotic and abiotic diseases. Keywords: CUCUMBER, GENE, TRAIT GENETICS

Fine-mapping reveals that the bHLH gene Cla011508 regulates the bitterness of watermelon fruit

The bitterness of the fruit seriously affects the taste of watermelon. Therefore, genetic research on bitterness is of great significance to improve watermelon fruit quality. However, there is no research on fine mapping of watermelon fruit bitterness. In the present study, an F2 population was developed, and two inbred lines, ‘9904’ (bitter flesh) and ‘Handel’ (non-bitter flesh) as parental materials. Genetic analysis indicated that the bitterness of watermelon was a dominant trait. The initial mapping revealed a 6.16 Mb region on chromosome 1. SNP and CAPS markers were used to narrowed the candidate region to 116.7 kb with four candidate genes (Cla011507, Cla011508, Cla011509, and Cla011510). Notably, Cla011508, and Cla011510 have high homology with gene Csa5G156220 and Csa5G157230, which regulate the bitterness trait in cucumber, and the mutation base at the locus 3,168,882 on chromosome 1 of Cla011508 led to the premature termination of the translation process; at the same time, a non-synonymous mutation caused the amino acid sequence change of Cla011510. The results of qRT-PCR showed that Cla011508 was highly expressed in watermelon flesh of ‘9904’, while no such significant difference was found in Cla011510. Furthermore, the analysis of 16 watermelon accessions showed that 8 bitterness accessions with base C at the locus 3,168,882 had higher gene expression level of Cla011508, which was significantly different from that of the 8 non-bitter accessions with base T. In conclusion, the bitterness of watermelon fruit may be controlled by Cla011508, and the important mutation loucs in this gene provide molecular insights for marker-assisted breeding of target trait.

The GORKY glycoalkaloid transporter is indispensable for preventing tomato bitterness.

Fruit taste is determined by sugars, acids and in some species, bitter chemicals. Attraction of seed-dispersing organisms in nature and breeding for consumer preferences requires reduced fruit bitterness. A key metabolic shift during ripening prevents tomato fruit bitterness by eliminating α-tomatine, a renowned defence-associated Solanum alkaloid. Here, we combined fine mapping with information from 150 resequenced genomes and genotyping a 650-tomato core collection to identify nine bitter-tasting accessions including the 'high tomatine' Peruvian landraces reported in the literature. These 'bitter' accessions contain a deletion in GORKY, a nitrate/peptide family transporter mediating α-tomatine subcellular localization during fruit ripening. GORKY exports α-tomatine and its derivatives from the vacuole to the cytosol and this facilitates the conversion of the entire α-tomatine pool to non-bitter forms, rendering the fruit palatable. Hence, GORKY activity was a notable innovation in the process of tomato fruit domestication and breeding.

Evaluation of Loofah Lines for Resistance to Tomato Leaf Curl New Delhi Virus and Downy Mildew, as well as Key Horticultural Traits

Two loofah (Luffa) species, the ridge gourd (Luffa acutangula (L.) Roxb.) and the sponge gourd (L. cylindrica (L.) M. Roem.; syn. L. aegyptiaca), are cultivated widely in Asia by smallholder famers. Both species have significant economic and nutritional importance. However, Tomato leaf curl New Delhi virus (ToLCNDV) and downy mildew (DM) caused by Pseudoperonospora cubensis are important biotic constraints to loofah production throughout Asia. Loofah landrace-derived breeding lines, developed at the World Vegetable Center (WorldVeg), were evaluated at the WorldVeg East and Southeast Asia Research and Training Station, Kasetsart University, Kamphaeng Saen, Thailand—where natural epidemics of ToLCNDV and DM regularly occur. The lines were also evaluated for other commercially important horticultural traits such as days to 50% staminate and pistillate flowering, fruit color, fruit bitterness, and market segment classification. Thirteen and 59 lines of ridge gourd and sponge gourd, respectively, were determined to be resistant to both ToLCNDV and DM. These lines covered all market segments of loofah and exhibited variability for all of the evaluated horticultural traits. The results of these evaluations and their implications on loofah breeding are discussed.

High concentrations of CPPU promotes cucurbitacin B accumulation in melon (Cucumis melo var. makuwa Makino) fruit by inducing transcription factor CmBt

N-(2-Chloro-4-pyridyl)-N′-phenylurea (CPPU) is a cytokinin-like plant growth regulator, which application in melon fruit set often produced bitter fruit caused by cucurbitacin B (Cu B) accumulation. However, more evidence is required to uncover the role of CPPU in regulating Cu B synthesis. In this study, two oriental melon cultivars ‘YMR’ (easy to present bitter fruit in maturation) and ‘HDB’ (hardly produce bitter fruit at maturity) were used. Four concentrations of CPPU (2.5, 5, 10 and 20 mg L−1) were set and hand pollination was used as control. Cu B accumulated in roots and fruit of 7 days after flower (7 DAF), which in ‘YMR’ was higher than those in ‘HDB’, and consistent with Cu B biosynthetic genes expression patterns. Furthermore, Cu B content in fruit significantly increased with CPPU concentrations and reached the highest level at 7 DAF, then decreased after 14 DAF, and which treated by 20 mg L−1 CPPU was always higher than that of controls and other low CPPU concentrations. Meanwhile, fruit bitterness evaluation suggested 20 mg L−1 CPPU increased the occurrence of bitterness during melon maturation. Transcription analysis suggested that the expression of Cu B biosynthetic genes (CmBi, Cm710, CmACT) and CmBt, the fruit-specific transcription factor, were significantly induced by 20 mg L−1 CPPU. Transient over-expression of CmBt in young fruit of ‘YMR’ increased Cu B biosynthetic genes (CmBi, CmACT, Cm710 and Cm890) expression and promoted Cu B accumulation. Taken together, this study demonstrates that 20 mg L−1 CPPU promotes Cu B accumulation in melon fruit by inducing CmBt and its biosynthetic genes.

Molecular Genetic Mapping of Two Complementary Genes Underpinning Fruit Bitterness in the Bottle Gourd (Lagenaria siceraria [Mol.] Standl.).

Fruit bitterness is a serious problem threatening the bottle gourd (Lagenaria siceraria [Mol.] Standl.) industry worldwide. Previous genetic studies indicated that fruit bitterness in the bottle gourd was controlled by a pair of complementary genes. In this study, based on two non-bitter landraces “Hangzhou Gourd” and “Puxian Gourd,” each of which carries a single bitterness gene, and their derived segregation populations, we mapped the complementary genes causing fruit bitterness. Quantitative trait locus (QTL) scanning based on an F2 population detected two QTLs, which was QBt.1 locating in a 17.62-cM interval on linkage group (LG)2 corresponding to a 1.6-Mb region on chromosome 6, and QBt.2 mapped to a 8.44-cM interval on LG9 corresponding to a 1.9-Mb region on chromosome 7. An advanced bulked segregant analysis (A-BSA) well validated the QTL mapping results. Sequence-based comparative analysis showed no syntenic relationship between QBt.1/QBt.2 and the known bitterness genes in cucumber, melon, and watermelon, suggesting that causal genes underlying QBt.1 and QBt.2 were not direct orthologs of the reported cucurbit bitterness genes. Our results shed light on the molecular genetic mechanisms underlying fruit bitterness in the bottle gourd and is useful to guide breeders to properly select parental lines to avoid the occurrence of bitter fruits in breeding programs.

Pathways to defense metabolites and evading fruit bitterness in genus Solanum evolved through 2-oxoglutarate-dependent dioxygenases

The genus Solanum comprises three food crops (potato, tomato, and eggplant), which are consumed on daily basis worldwide and also producers of notorious anti-nutritional steroidal glycoalkaloids (SGAs). Hydroxylated SGAs (i.e. leptinines) serve as precursors for leptines that act as defenses against Colorado Potato Beetle (Leptinotarsa decemlineata Say), an important pest of potato worldwide. However, SGA hydroxylating enzymes remain unknown. Here, we discover that 2-OXOGLUTARATE-DEPENDENT-DIOXYGENASE (2-ODD) enzymes catalyze SGA-hydroxylation across various Solanum species. In contrast to cultivated potato, Solanum chacoense, a widespread wild potato species, has evolved a 2-ODD enzyme leading to the formation of leptinines. Furthermore, we find a related 2-ODD in tomato that catalyzes the hydroxylation of the bitter α-tomatine to hydroxytomatine, the first committed step in the chemical shift towards downstream ripening-associated non-bitter SGAs (e.g. esculeoside A). This 2-ODD enzyme prevents bitterness in ripe tomato fruit consumed today which otherwise would remain unpleasant in taste and more toxic.

Construction of A High-Density Genetic Map and Mapping of Fruit Traits in Watermelon (Citrullus Lanatus L.) Based on Whole-Genome Resequencing.

Watermelon (Citrullus lanatus L.) is an important horticultural crop that is grown worldwide and has a high economic value. To dissect the loci associated with important horticultural traits and to analyze the genetic and genomic information of this species, a high-density genetic map was constructed based on whole-genome resequencing (WGR), a powerful high-resolution method for single-nucleotide polymorphism (SNP) marker development, genetic map construction, and gene mapping. Resequencing of both parental lines and 126 recombinant inbred lines (RIL) resulted in the detection of 178,762 single-nucleotide polymorphism (SNP) markers in the parental lines at a sequencing depth greater than four-fold. Additionally, 2132 recombination bin markers comprising 103,029 SNP markers were mapped onto 11 linkage groups (LGs). Substantially more SNP markers were mapped to the genetic map compared with other recent studies. The total length of the linkage map was 1508.94 cM, with an average distance of 0.74 cM between adjacent bin markers. Based on this genetic map, one locus for fruit bitterness, one locus for rind color, and one locus for seed coat color with high LOD scores (58.361, 18.353, 26.852) were identified on chromosome 1, chromosome 8, and chromosome 3, respectively. These prominent loci were identified in a region of 6.16 Mb, 2.07 Mb, and 0.37 Mb, respectively. On the basis of current research, the high-density map and mapping results will provide a valuable tool for identifying candidate genes, map-based gene cloning, comparative mapping, and marker-assisted selection (MAS) in watermelon breeding.

Flavan-3-ols and procyanidins in grape seeds: biodiversity and relationships among wild and cultivated vines

Flavan-3-ol monomers and polymers composition of seeds from wild (17) and autochthonous (8) Vitis vinifera grapes growing in northern Tunisia were evaluated. Wild grape seeds were spherical with a small beak and relatively a high seed/berry ratio (~ 18.1%w/w). Local cultivars developed pyriform-shaped seeds with a well-developed beak representing on average 2.2% of total weight of the berry. Flavanol concentrations ranged between 40.9 and 67.5 mg/g FW in seeds from wild accessions and between 48.9 and 96.7 mg/g FW in seeds from cultivated grapes. Differences between accessions were highly significant (p (−)-epicatechin (Ec) > (−)-epicatechin-3-O-gallate (EcG). The Cat/Ec ratio was approximately 1.7 for wild grapes while it was about 2.5 for cultivated grapes. Procyanidins in wild seeds differed from cultivated ones by a lower mDP and higher proportions of galloylated derivatives, likely to affect fruit bitterness and astringency. (−)-epicatechin was the main extension subunit in grape seed procyanidins, reaching on average 52% in wild and 58% in cultivated seeds. Hierarchical cluster analysis based on seeds morphometry and procyanidin profile indicated close proximity between some wild and cultivated grapes suggesting that some cultivars derived from ancestral events of local domestication or cross hybridization with native wild plants.

Localization of a New Gene for Bitterness in Cucumber

Bitterness in cucumber fruit and foliage is due to the presence of cucurbitacins. Several genes have been described that control the trait, with bi (bi-1) making fruit and foliage bitter free and Bt (Bt-1) making the fruit highly bitter. Previous studies have reported the inheritance and molecular markers linked to bi-1 or Bt-1, but we were interested in studying the inheritance of fruit bitterness in the progeny of 2 nonbitter fruit inbred lines. The objective was to determine the inheritance of cucumber fruit and foliage bitterness and to locate them on a current linkage map using a recombinant inbred lines (RILs) population derived by crossing 9110Gt and 9930. It was concluded from the inheritance analysis that there were 2 loci controlling fruit bitterness in the population. One locus was in the same position as the location previously identified for bi-1, and another locus was for bi-3. Using a simple sequence repeat (SSR) linkage map, 2 loci for fruit bitterness in this RILs population were mapped. The locus of bi-1 was located at the region between SSR0004 and SSR02309 within the genetic distance of 5.2 cM on chromosome 6. The locus of bi-3 was placed in the region of SSR00116-SSR05321 within the genetic distance of 6.3 cM on chromosome 5. The physical distances for the regions of bi-1 and bi-3 were 11,430.94 Kb with 160 predicted genes and 1528.23 Kb with 198 predicted genes, respectively. Among 160 predicted genes for bi-1, there is a terpene synthase gene named Csa008595, which was speculated as the candidate gene of bi-1.

Identification of QTLs related to sugar and organic acid composition in melon using near-isogenic lines

The soluble sugar and organic acid composition of melon ( Cucumis melo L.) fruit flesh has become a major focus of plant breeding worldwide in an attempt to improve taste. Thus, sugar and organic acid profiles were characterized using near-isogenic lines (NILs) derived from the Spanish cultivar Piel de Sapo (PS) and the exotic Korean accession Shongwan Charmi (PI 161375). Fruits were cultivated in only one environment. These data were used to map 60 quantitative trait loci (QTLs): 18 for individual sugars, eight for sucrose equivalents, five for the glucose-to-fructose ratio, seven for the total sugar content and 21 for organic acids. Within the QTLs that were associated with the sugar profile, 27 defined the sugar content: eight for fructose, six for glucose, four for sucrose, and nine for sucrose equivalents. Although increased sweetness of selected NILs compared with the parental PS was achieved by an increased glucose or fructose content, only glucose heritability was above 0.5. A total of 21 QTLs (two with positive effects and nineteen with detrimental effects compared with the PS levels) controlled the organic acid profile: l-glutamic, ascorbic and succinic acids (the principal ones) and fumaric, citric, oxalacetic, and isocitric acids. The levels of sugars imparted by the PI 161375 introgression frequently decreased the score grades given to NILs by consumers. Within the 32 QTLs mapped for sensory traits, 27 were associated with lower scores in taste (nine QTLs), sweetness (eight QTLs) or global quality appreciation (nine QTLs); two with increased fruit sourness or sweetness and three with increased fruit bitterness. The QTLs defined herein may assist breeders to understand the overall organoleptic balance (sweetness, sourness, and umami taste) in melon fruit, particularly those located within linkage groups III, V, VI, and VIII to XI.

Segregation and Linkage of Several Genes in Cucumber

Gene linkage was investigated in 11 families using 18 genes in cucumber (Cucumis sativus L.). The genes studied were B (black spine), B-3 (Black spine-3), B-4 (Black spine-4), bi (bitterfree cotyledons), Bt (bitter fruit), Bt-2 (bitter fruit-2), D (dull fruit skin), df (delayed flowering), de (determinate habit), F (female sex expression), gl (glabrous foliage), lh (long hypocotyl), ns (numerous spines), pm-h [powdery mildew (Sphaerotheca fuliginea Schlecht.:Fr.) resistance expressed on the hypocotyl], ss (small spines), Tu (tuberculate fruit), u (uniform immature fruit color), and w (white immature fruit color). A major objective of this study was to measure linkages of genes for fruit bitterness (Bt and Bt-2), and spine color (B-3 and B-4) relative to previously studied loci: B, bi, D, de, df, F, gl, lh, ns, pm-h, ss, Tu, u, and w. The F2 progeny of LJ 90430 × PI 173889 segregated 13 bitter fruit: 3 nonbitter fruit, indicating that different genes are controlling fruit bitterness in these lines. Bt-2 is proposed as the gene controlling bitterness of fruit in LJ 90430. It is a separate locus from Bt, that causes bitter fruit in PI 173889. Several new gene linkages were found: bi—Bt, (Bt-2)—de, D—(Bt-2), D—ns, gl—F, ss—(Bt-2), Tu—(Bt-2), and u—(Bt-2). The Bt gene appears to be linked to bi and may be located on linkage group I. Bt-2 appears to be linked with several genes that could connect linkage groups I and IV. Bt-2 was linked to u, Tu, D, and ss, that are all on linkage group IV. Bt-2 was also found to be linked loosely to de, that is on linkage group I. No linkages were found between B-3 and B-4 and the genes evaluated in this study. Weak linkages (>25 cM) between several gene combinations [(Bt-2)-de, de—ns, de—ss, de—Tu, de—u, ns—F, and ss—F] provided more evidence that linkage group I and IV may be linked. Due to the weak linkages, more information needs to be obtained using larger populations and more markers to confirm these findings.

Crop/Weed gene flow:Cucurbita argyrosperma Huber andC. fraterna L. H. Bailey (Cucurbitaceae)

A mixed population of Cucurbita at Vado El Mow in northern Tamaulipas, Mexico showed an anomalous pattern of fruit bitterness. Some domesticated plants (C. argyrosperma andC. moschata) expressed cucurbitacin bitterness whereas some sympatric free-living plants produced non-bitter fruits. This reversal of typical cucurbitacin expression suggested gene flow between crop and weed at the site. Isozyme analysis provided little insight as to taxa involved in gene exchange, although progeny from a single free-living plant carried IDH allozymes that are associated with Mexican landraces ofC. pepo. Synthetic hybridization revealed that fertile F, hybrids are produced from crosses involvingC. fraterna as the pistillate parent andC. argyrosperma as the staminate parent. Interspecific crop/weed hybrids can produce viable progeny upon self-pollination or backcrossingto either parent, andF2 families display normal allozyme segregation. Hybrid fertility, as indicated by pollen stainability, increases in progeny produced by backcrossingfrom theC. argyrosperma parent. Interspecific hybridfertility represents a potential for crop/weed gene flow that would be realized under natural conditions if pollen flow occurs betweenC. fraterna andC. argyrosperma in the fields of Tamaulipas. Oligolectic “squash bees” (Teponapis), efficientCucurbita pollen vectors, are present at the site. Thus, it is likely that natural interspecific crop/weed hybridization has occurred at Vado El Moro and this might at least partially explain the anomalous distribution of fruit bitterness among extant populations at the site.

Inheritance of Fruit Bitterness in a Cross of Cucurbita mixta × C. pepo

Abstract A cross of ‘Green Striped Cushaw’ pumpkin (Cucurbita mixta) × ‘Goldbar’ hybrid summer squash (C. pepo), neither of which have bitter fruit, produced an F1 having extremely bitter fruit. Inheritance data suggest that fruit bitterness in this cross is conditioned by three dominant, complementary genes with two contributed by ‘Goldbar’ and the third by ‘Green Striped Cushaw’.