The capsanthin-capsorubin synthase gene: a candidate gene for the y locus controlling the red fruit colour in pepper

The red colour of pepper fruits is determined by the y⁺ dominant allele and the yellow colour by the y recessive allele. The capsanthin-capsorubin synthase (CCS) gene is activated specifically during the final stages of pepper fruit ripening. RFLP and specific-PCR polymorphisms derived from the CCS gene were analysed in a F2 progeny of a red by yellow-fruited cross. They cosegregated completely with fruit colour. Our results support the hypothesis that the yellow phenotype might result from a deletion of the CCS gene. These specific markers were integrated into the genetic map and will be useful for marker assisted plant breeding.     

A candidate gene approach identified phytoene synthase as the locus for mature fruit color in red pepper (Capsicum spp.)

Abstrat  The color of mature pepper fruit is determined by the composition of carotenoids. The fruit color of red pepper is genetically determined by three loci, y, c1, and c2. We have been developing a genetic map of hot pepper using RFLP and AFLP markers in the F₂ population of an interspecific cross between Capsicum annuum cv TF68 and Capsicum chinense cv Habanero. The color of the ripe fruit of TF68 is red and Habanero is orange. The red color is dominant over orange in the F₁ and the locus controlling this character has been marked in our SNU Linkage Group 7. To identify the gene or markers tightly linked to the red/orange locus, several candidate genes involved in the carotenoid biosynthesis pathway, namely FPS, GGPS, PSY, PDS, LCY and CCS, were examined. One of the candidate genes, phytoene synthase, cosegregated completely with fruit color in the F₂ population. QTL analysis of the pigment content of F₂ individuals quantified by HPLC also indicated that phytoene synthase is the locus responsible for the development of fruit color. The color, pigment content and genetic behavior of Habanero also suggest that phytoene synthase may be responsible for the c2 gene discriminating between red and orange cultivars. Received: 15 March 2000 / Accepted: 16 August 2000     

Molecular identification of the yellow fruit color (c) locus in diploid strawberry: a candidate gene approach

A candidate gene approach was used to determine the likely molecular identity of the c locus (yellow fruit color) in Fragaria vesca, a diploid (2n=2x=14) strawberry. Using PCR with degenerate primer pairs, intron-containing segments of structural genes coding for chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS) and one Del-like regulatory gene in the anthocyanin biosynthetic pathway, were amplified, cloned and sequenced. Intron length polymorphisms for each of these genes were detected among three diploid varieties: F. vesca Alpine variety ’Yellow Wonder’ (YW) (Europe); DN1C, a F. vesca clone collected from Northern California; and Fragaria nubicola FRA520, a U.S.D.A. accession collected in Pakistan. Using F₂ generations of the crosses DN1C×YW and YW×FRA520 as mapping populations, the six candidate genes were mapped in relation to previously mapped randomly amplified polymorphic DNA (RAPD) markers and morphological markers. The F3H gene was linked without recombination to the c locus in linkage group I, while the other five candidate genes mapped to different linkage groups. These results suggest that the wild-type allele (C) of the c (yellow fruit color) locus encodes an F3H necessary for red fruit color in F. vesca. Received: 28 August 2000 / Accepted: 21 December 2000     

QTL mapping of fruit-related traits in pepper (Capsicum annuum)

QTL analysis of pepper fruit characters was performed in an F₃ population derived from a cross between two Capsicum annuum genotypes, the bell-type cultivar Maor and the Indian small-fruited line Perennial. RFLP, AFLP^®1, RAPD and morphological markers (a total of 177) were used to construct a comparative pepper-tomato genetic map for this cross, and 14 quantitatively inherited traits were evaluated in 180 F₃ families. A total of 55 QTL were identified by interval analysis using LOD 3.0 as the threshold for QTL detection. QTL for several traits including fruit diameter and weight, pericarp thickness and pedicel diameter were often located in similar chromosomal regions, thus reflecting high genetic correlations among these traits. A major QTL that accounts for more than 60% of the phenotypic variation for fruit shape (ratio of fruit length to fruit diameter) was detected in chromosome 3. This chromosome also contained QTL for most of the traits scored in the population. Markers in linkage groups 2, 3, 8 and 10 were associated with QTL for multiple traits, thereby suggesting their importance as loci that control developmental processes in pepper. Several QTL in pepper appeared to correspond to positions in tomato for loci controlling the same traits, suggesting the hypothesis that these QTL may be orthologous in the two species.     

Identification and characterization of a novel locus controlling early fruit development in tomato

Cultivated tomatoes (Lycopersicon esculen- tum) encompass a wide range of fruit size and shape variants. This variation provides the basis for dissecting the genetic and molecular pathways of ovary and fruit development. One fruit shape variant is displayed by the cultivar Sun 1642 (TA491). TA491 has an elongated fruit phenotype, while the wild relative L. pimpinellifolium LA1589 produces fruit that are nearly perfect spheres, a shape typical of wild tomatoes. Developmental studies indicated that the differences in fruit shape between TA491 and LA1589 are determined by events occurring immediately after pollination and extending to 14 days post-pollination. Quantitative trait mapping revealed a single major locus on chromosome 7 (named sun) to be responsible for the differential development of TA491 and LA1589 fruit. Other fruit shape loci characterized in tomato (e.g. fs8.1 and ovate) exert their effects before anthesis and early in ovary development. sun is the first major locus identified in tomato controlling fruit shape through post-pollination events. Received: 17 November 2000 / Accepted: 24 November 2000     

Nitrogen and energy requirements of the short-tailed fruit bat (Carollia perspicillata): fruit bats are not nitrogen constrained

 Nitrogen (N) and energy (E) requirements were measured in adult Carollia perspicillata which were fed on four experimental diets. Bats ate 1.3–1.8 times their body mass ⋅ day^-1 and ingested 1339.5–1941.4 kJ ⋅ kg^-0.75 ⋅ day^-1. Despite a rapid transit time, dry matter digestibility and metabolizable E coefficient were high (83.3% and 82.4%, respectively), but true N digestibility was low (67.0%). Mass change was not correlated with E intake, indicating that bats adjusted their metabolic rate to maintain constant mass. Bats were able to maintain constant mass with digestible E intake as low as 1168.7 kJ ⋅ kg^-0.75 ⋅ day^-1 or 58.6 kJ ⋅ . Metabolic fecal N and endogenous urinary N losses were 0.87 mg N ⋅ g^-1 dry matter intake and 172.5 mg N ⋅ kg^-0.75 ⋅ day^-1, respectively, and bats required 442 mg N ⋅ kg^-0.75 ⋅ day^-1 (total nitrogen) or 292.8 mg N ⋅ kg^-0.75 ⋅ day^-1 (truly digestible nitrogen) for N balance. Based on E and N requirements and digestibilities, it was calculated that non-reproductive fruit bats were able to meet their N requirements without resorting to folivory and without over-ingesting energy. It was demonstrated that low metabolic fecal requirements allowed bats to survive on low-N diets. Accepted: 23 June 1996     

Self-incompatibility in passion fruit: evidence of two locus genetic control

 The self-incompatibility in yellow passion fruit was previously described as homomorphic sporophytic with monofactorial inheritance. Five progenies were obtained by bud-selfing. The plants of these progenies were selfed, reciprocally crossed within each progeny and crossed with known incompatible phenotypes to identify their phenotypic group. Fruit set was evaluated at the 7th day after pollination. Two progenies consisted of two self-incompatible groups, the other three formed three suck groups. The groups were identified as S₁, S₂, S₃, S₄, S₅ and S₆. The results provide evidence that the self-incompatibility of passion fruit is controlled by two loci, the S-gene and another, whose expression needs to be investigated. Received: 20 June 1998 / Accepted: 13 July 1998     

Hyperhydricity in pepper plants regenerated in vitro: involvement of BiP (Binding Protein) and ultrastructural aspects

 Hyperhydricity in regenerated pepper plants was monitored by the induction of the ER-luminal resident protein, as observed by immunoblotting. Immunoblotting of total protein using an anti-soybean BiP serum indicated that the induction and accumulation of an 80-kDa protein was related to BiP (Binding protein), a 78-kDa ER-resident molecular chaperone. The anti-BiP serum cross-reacted with an 80-kDa protein which was significantly induced by hyperhydricity. Based on similar molecular weight and immunological reactivity we concluded that the 80-kDa protein induced in hyperhydric plants is a BiP homologue. The ultrastructural organisation of leaves in non-hyperhydric and hyperhydric pepper (Capsicum annuum L.) plants was investigated with the aim of identifying the subcellular changes associated with this phenomenon. In non-hyperhydric leaves the chloroplasts of the palisade cells had normally developed thylakoids and grana and a low accumulation or absence of starch grains and plastoglobules. In the hyperhydric plants, however, the chloroplasts exhibited thylakoid disorganisation, low grana number, an accumulation of large starch grains and a low accumulation or absence of plastoglobules. Although the structure of mitochondria and peroxisomes did not change in hyperhydric plants, the number of peroxisomes did increase. Received: 23 July 1998 / Revision received: 26 February 1999 / Accepted: 17 March 1999     

Graft-induced genetic changes and the inheritance of several characteristics in pepper (Capsicum annuum L.)

 The general characteristics of several graft-induced changes in pepper were investigated in a cross experiment. F₁, F₂, and BC₁ progenies derived from crosses of the original stock and scion cultivars ‘Spanish Paprika’ and ‘Yatsubusa’, respectively, as well as their graft-induced variant strain G₅S₂₅ were analyzed for inheritance of the most conspicuous graft-induced variant traits. As part of a research program with the aim of revealing the mechanism of graft induction, the present study was carried out to examine the stability of the phenotypic changes and the characteristics of the graft-induced variants. For the fruit apex, a two-gene system was suggested, with other factors having a modifying influence. One of the two apex genes acted for pointed fruits and the other for inverted-blunt fruits. The inverted-blunt gene, the apex gene of the stock, was unambiguously present in the graft-induced variants, while the pointed gene that acted in the dominant mode in the original scion was inactive and expressed only under certain conditions in a mosaic state. The stable inverted-blunt cultivar used for the stock maintained certain factor(s) for pointed fruit, but the presence of that factor(s) could not be detected in graft-induced variants. The results of pungency analysis suggested a gene for non-pungency that appeared to be introduced in the graft-induced variants. The fruiting habit and fruiting direction that appeared in a mosaic state in graft-induced variants were found to combine factors of the stock with the appropriate characteristics of the scion asymmetrically. The bushy plant type appeared in a transgressive state in the variants, showing a definitely higher number of branches on the main stem and more frequent ramifications on the complete plant than on either the stock and scion cultivars or the progency derived from sexual crosses. A change in mature fruit color from red to yellow occurred in an early generation of graft-induced variants. Our results demonstrate that some of the characteristics of the stock were introduced into the progeny obtained from selfed seeds of the scion and that novel characteristics appeared as a result of graft induction. Received: 30 December 1997 / Accepted: 3 March 1998     

Fruit tree genetics at a turning point: the almond example

 The large size and the long generation time of fruit trees generally reduce the possibilities of obtaining genetic information on the transmission and heritability of useful agronomic traits in these species. However, from breeding work carried out with fruit trees, an important amount of data is now available, although large differences are apparent among the different species. There is not much information known about almond compared to what is available on other Prunus fruit species, but more data have been accumulated on it than on most of the other nut trees, thus making almond special among all the temperate fruit and nut species. Only five qualitative traits have been described in almond, with an additional two also possibly qualitative. Heritabilities have been estimated for an important number of quantitative traits, mainly phenological times and fruit characters. Important information is available on molecular markers, including enzymes, RFLPs, RAPDs and other recently developed markers. Linkages, however, have only been established among molecular markers, allowing accurate genetic maps to be built but not yet enabling agronomical characters to be located in these maps, probably because the latter have not been sufficiently studied. The effectiveness of the application of genetic maps in plant breeding will depend on the accuracy of the study of different agronomic traits and their expression, implying more field work and recognition of this work. Ultimately, any new fruit cultivar has to be grown in the field and has to allow the grower to make a profit. Received: 1 June 1997 / Accepted: 1 September 1997     

QTLs for a component of partial resistance to cucumber mosaic virus in pepper: restriction of virus installation in host-cells

 Ninety four doubled-haploid (DH) lines obtained from the F₁ between Perennial, a cucumber mosaic virus (CMV)-partially resistant Capsicum annuum line, and Yolo Wonder, a CMV-susceptible C. annuum line, were analysed with 138 markers including mostly RFLPs and RAPDs. Clustering of RAPD markers was observed on five linkage groups of the intraspecific linkage map. These clusters could correspond to the centromeric regions of pepper chromosomes. The same progenies were evaluated for restriction of CMV installation in pepper cells in order to map quantitative trait loci (QTLs) controlling CMV resistance. This component of partial resistance to CMV was quantitatively assessed using a CMV strain that induced necrotic local lesions on the inoculated leaves. The number of local lesions gave an estimation of the density of the virus-infection sites. Genotypic variance among the DH lines was highly significant for the number of local lesions, and heritability was estimated to be 0.94. Using both analysis of variance and non-parametric tests, three genomic regions significantly affecting CMV resistance were detected on chromosomes Noir, Pourpre and linkage group 3, together explaining 57% of the phenotypic variation. A digenic epistasis between one locus that controlled significant trait variation and a second locus that by itself had no demonstrable effect on the trait was found to have an effect on CMV resistance. For each QTL, the allele from Perennial was associated with an increased resistance. Implications of QTL mapping in marker-based breeding for CMV resistance are discussed. Received: 16 September 1996     

Acetohydroxyacid synthase and its role in the biosynthetic pathway for branched-chain amino acids

Summary. The branched-chain amino acids are synthesized by plants, fungi and microorganisms, but not by animals. Therefore, the enzymes of this pathway are potential target sites for the development of antifungal agents, antimicrobials and herbicides. Most research has focused upon the first enzyme in this biosynthetic pathway, acetohydroxyacid synthase (AHAS) largely because it is the target site for many commercial herbicides. In this review we provide a brief overview of the important properties of each enzyme within the pathway and a detailed summary of the most recent AHAS research, against the perspective of work that has been carried out over the past 50 years.     

Evaluation of genetic distances between pepper inbred lines for cultivar protection purposes: comparison of AFLP, RAPD and phenotypic data

Summary  We evaluated concordance of AFLP and RAPD markers for estimating genetic distances of 47 pepper inbred lines belonging to five varietal types. It enabled us to see the efficiency of these markers for identification, estimation of distances between varieties and variety discrimination. Genetic distance and multidimensional scaling results showed a general agreement between AFLP and RAPD markers. Based on pattern scores, dendrograms were produced by the UPGMA method. Phenetic trees based on molecular data were consistent with the classification of variety group. The precision of the estimation of the genetic distance was given. The molecular genetic distances were correlated with distances based on a set of discriminating agronomic traits measured for identification and distinctiveness tests. The relationship between molecular and morphological distances appeared to be triangular. These results and their implications in the cultivar protection purposes of pepper hybrids are discussed. Received: 25 March 2000 / Accepted: 11 July 2000     

Cloning of the polyketide synthase gene atX from Aspergillus terreus and its identification as the 6-Methylsalicylic acid synthase gene by heterologous expression

The geneCAL1 (also known asCDC43) ofSaccharomyces cerevisiae encodes the subunit of geranylgeranyl transferase I (GGTase I), which modifies several small GTPases. Biochemical analyses of the mutant enzymes encoded bycall-1, andcdc43-2 tocdc43-7, expressed in bacteria, have shown that all of the mutant enzymes possess reduced activity, and that none shows temperature-sensitive enzymatic activities. Nonetheless, all of thecall/cdc43 mutants show temperature-sensitive growth phenotypes. Increase in soluble pools of the small GTPases was observed in the yeast mutant cells at the restrictive temperature in vivo, suggesting that the yeast prenylation pathway itself is temperature sensitive. Thecall-1 mutation, located most proximal to the C-terminus of the protein, differs from the othercdc43 mutations in several respects. An increase in soluble Rholp was observed in thecall-1 strain grown at the restrictive temperature. The temperature-sensitive phenotype ofcall-1 is most efficiently suppressed by overproduction of Rholp. Overproduction of the other essential target, Cdc42p, in contrast, is deleterious incall-1 cells, but not in othercdc43 mutants or the wild-type strains. Thecdc43-5 mutant cells accumulate Cdc42p in soluble pools andcdc43-5 is suppressed by overproduction of Cdc42p. Thus, several phenotypic differences are observed among thecall/cdc43 mutations, possibly due to alterations in substrate specificity caused by the mutations.     

Spectrum of resistance to root-knot nematodes and inheritance of heat-stable resistance in in pepper (Capsicum annuum L.)

Capsicum annuum L. has resistance to root-knot nematodes (RKN) (Meloidogyne spp.), severe polyphagous pests that occur world-wide. Several single dominant genes confer this resistance. Some are highly specific, whereas others are effective against a wide range of species. The spectrum of resistance to eight clonal RKN populations of the major Meloidogyne species, M. arenaria (2 populations), M. incognita (2 populations), M. javanica (1 population), and M. hapla (3 populations) was studied using eight lines of Capsicum annuum. Host susceptibility was determined by counting the egg masses (EM) on the roots. Plants were classified into resistant (R; EM ≤ 5) or susceptible (H; EM >5) classes. The french cultivar Doux Long des Landes was susceptible to all nematodes tested. The other seven pepper lines were highly resistant to M. arenaria, M. javanica and one population of M. hapla. Variability in resistance was observed for the other two populations of M. hapla. Only lines PM687, PM217, Criollo de Morelos 334 and Yolo NR were resistant to M. incognita. To investigate the genetic basis of resistance in the highly resistant line PM687, the resistance of two progenies was tested with the two populations of M. incognita: 118 doubled-haploid (DH) lines obtained by androgenesis from F₁ hybrids of the cross between PM687 and the susceptible cultivar Yolo Wonder, and 163 F₂ progenies. For both nematodes populations, the segregation patterns 69 R / 49 S for DH lines and 163 R / 45 S for F₂ progenies were obtained at 22°C and at high temperatures (32°C and 42°C). The presence of a single dominant gene that totally prevented multiplication of M. incognita was thus confirmed and its stability at high temperature was demonstrated. This study confirmed the value of C. annuum as a source of complete spectrum resistance to the major RKN. Received: 2 July 1998 / Accepted: 11 March 1999     

The tomato high-pigment (hp) locus maps to chromosome 2 and influences plastome copy number and fruit quality

 The tomato (Lycopersicon esculentum) high-pigment (hp) locus was originally described as having enhanced fruit-quality characteristics and has also been shown to regulate responses to light during growth and development. Specifically, the hp phenotype suggests that the normal HP gene-product serves as a negative regulator of light signal-transduction, as has been proposed for many of the previously described Arabidopsis thaliana photomorphogenic mutants. Consequently, hp represents a tool for both genetic dissection of light signal-transduction and manipulation of fruit quality in tomato. As a first step toward isolation of the HP gene, the hp locus was mapped to tomato chromosome 2, adjacent to the 45s rDNA locus, using DNA markers and an interspecific cross of L. esculentum×L. cheesmannii. We have simultaneously identified DNA markers which may be useful for gene isolation and marker-assisted selection. We have additionally extended characterization of the hp phenotype to demonstrate increased sucrose and flavonoid accumulation in ripe hp/hp fruit. Analysis of plastid DNA copy number relative to genomic DNA content indicates that the hp locus regulates plastome DNA concentration, and possibly plastid number, in response to light. Received: 26 June 1997 / Accepted: 22 July 1997     

Regulation and activation of phytoene synthase, a key enzyme in carotenoid biosynthesis, during photomorphogenesis

 During photomorphogenesis in higher plants, a coordinated increase occurs in the chlorophyll and carotenoid contents. The carotenoid level is under phytochrome control, as reflected by the light regulation of the mRNA level of phytoene synthase (PSY), the first enzyme in the carotenoid biosynthetic pathway. We investigated PSY protein levels, enzymatic activity and topological localization during photomorphogenesis. The results revealed that PSY protein levels and enzymatic activity increase during de-etiolation and that the enzyme is localized at thylakoid membranes in mature chloroplasts. However, under certain light conditions (e.g., far-red light) the increases in PSY mRNA and protein levels are not accompanied by an increase in enzymatic activity. Under those conditions, PSY is localized in the prolamellar body fraction in a mostly enzymatically inactive form. Subsequent illumination of dark-grown and/or in far-red light grown seedlings with white light causes the decay of these structures and a topological relocalization of PSY to developing thylakoids which results in its enzymatic activation. This light-dependent mechanism of enzymatic activation of PSY in carotenoid biosynthesis shares common features with the regulation of the NADPH:protochlorophyllide oxidoreductase, the first light-regulated enzyme in chlorophyll biosynthesis. The mechanism of regulation described here may contribute to ensuring a spatially and temporally coordinated increase in both carotenoid and chlorophyll contents. Received: 14 February 2000 / Accepted: 15 March 2000     

QTLs involved in the restriction of cucumber mosaic virus (CMV) long-distance movement in pepper

Partial restriction of cucumber mosaic virus (CMV) long-distance movement originating from the Capsicum annuum inbred line ’Vania’ was assessed in a doubled-haploid progeny using two screening methods: the first allowed one to assess the resistance of adult plants decapitated above the fourth leaf and inoculated on the third leaf using a common CMV strain, and the second allowed one to assess CMV resistance to long-distance movement on seedlings inoculated using an atypical CMV strain. For both resistance tests, the behavior of the F₁ hybrid between ’Vania’ and the susceptible line ’H3’ indicated that partial resistance is inherited as a dominant trait. Phenotypic data from the two screening methods were correlated but the one performed on seedlings was much more severe. A subset of 184 molecular markers well-distributed over the pepper genome was selected for QTL mapping using the composite interval mapping (CIM) method. A total of seven genomic regions, including one major effect and several minor effect QTLs, were shown to be associated with partial restriction of CMV long-distance movement. These results are compared with those already obtained in pepper and also in other solanaceous crops, potato and tomato. Received: 22 March 2001 / Accepted: 9 July 2001