Enzyme polymorphism inCitrullus lanatus andC. colocynthis in Israel and Sinai

Electrophoretic and morphological variation was studied in 13 cultivars ofC. lanatus and 31 accessions ofC. colocynthis from Israel. Twelve enzyme systems were assayed, representing 19 loci. We found 12 commercially grown cultivars to be monomorphic at all loci. OneC. lanatus accession collected from Israel is highly polymorphic and carries alleles ofC. colocynthis; this accession is probably a representative of a locally cultivated land race grown by Bedouins for animal feed. Over a range of 500 km two forms ofC. colocynthis were identified: one which grows along the coastal plains of the Mediterranean and the other in the arid Negev and Sinal deserts. A high level of electrophoretic and morphological divergence was found between plants of the two regions, whereas within the ecotypes little variation was observed.     

Somatic hybrid plants between Lycopersicon esculentum and Solanum lycopersicoides

Summary Leaf mesophyll protoplasts of Lycopersicon esculentum (2n=2x=24) were fused with suspension culture-derived protoplasts of Solanum lycopersicoides (2n=2x=24) and intergeneric somatic hybrid plants were regenerated following selective conditions. A two phase selection system was based on the inability of S. lycopersicoides protoplasts to divide in culture in modified medium 8E and the partial inhibition of L. esculentum protoplasts by the PEG/DMSO fusion solution. At the p-calli stage, putative hybrids were visually selected based on their hybrid vigor and lime-green coloration in contrast to slower growing parental calli characterized by a watery, whitish-brown coloration. Early identification of the eight hybrid plants studied was facilitated by isozyme analysis of leaf tissue samples taken from plants in vitro at the rooting stage. Regenerated plants growing in planting medium were further verified for hybridity by 5 isozymes marking 7 loci on 5 chromosomes in tomato. These included Skdh-1 mapped to chromosome 1 of tomato, Pgm-2 on chromosome 4, Got-2 and Got-3 on chromosome 7, Got-4 on chromosome 8, and Pgi-1 and Pgdh-2 both on chromosome 12. Fraction I protein small subunits further confirmed the hybrid nature of the plants with bands of both parents expressed in all hybrids. The parental chloroplasts could not be differentiated by the isoelectric points of the large subunit. Seven of the eight somatic hybrids had a chromosome number ranging from the expected 2n=4x=48 to 2n=68. Mixoploid root-tip cells containing 48, 53, 54 or 55 chromosomes for two of the hybrids were also observed.Michigan Agricultural Experiment Station Journal Article No. 11736. Supported by Grant No. I-751-84R from BARD — The United States — Israel Binational Agricultural Research and Development Fund     

ALLOZYME VARIATION IN SEVERAL CLOSELY RELATED DIPLOID SPECIES OF CHENOPODIUM OF THE WESTERN UNITED STATES

Twelve allozyme loci were examined in a complex of closely related diploid (2n = 18) members of the genus Chenopodium occurring in the western United States. These plants are generally treated taxonomically as belonging to C. atrovirens, C. desiccatum, C. hians, C. leptophyllum, and C. pratericola. Also included were populations referable to C. incognitum. The enzymes examined and the allelic designations are given as follows: leucine aminopeptidase, Lap; phosphoglucoisomerase, Pgi-1, Pgi-2; glutamate-oxaloacetate transaminase, Got-1, Got-2, Got-3; glutamate dehydrogenase, Gdh; phosphoglucomutase, Pgm-1, Pgm-2; malate dehydrogenase, Mdh-1, Mdh-2; and malic enzyme, Me. All populations were fixed for the same allele at Gdh, Pgi-2, and Mdh-1. Chenopodium hians was fixed for a unique allele at Got-3 and contained two alleles at the Lap locus and two at Pgi-1 which were not detected elsewhere. Chenopodium leptophyllum likewise has unique alleles at Lap and Pgi-1. The other three taxa, C. atrovirens, C. desiccatum and C. pratericola, have alleles at Lap and Pgi-1 which were not found in C. hians or C. leptophyllum. The former three species have the same alleles in highest frequency at all polymorphic loci except Me, where C. desiccatum is consistently separable from C. atrovirens and C. pratericola. Allozyme data are concordant with information from morphology, flavonoid chemistry and seed protein profiles in suggesting that: (1) Chenopodium hians and C. leptophyllum are best regarded as distinct species; (2) C. atrovirens and C. pratericola are very similar and perhaps should not be recognized at the specific level; (3) C. desiccatum appears most closely allied to C. pratericola; (4) plants referable to C. incognitum represent two biological entities, one the same as C. atrovirens, and the other conspecific with C. hians; (5) little genetic variation is detectable in any taxon of these weedy annuals; (6) interspecific hybridization is not a cause of taxonomic difficulties in these plants.     

Isozymic gene linkage map of the tomato: Applications in genetics and breeding

Summary New linkage data are presented for the situation of five previously unlocated isozymic loci of the tomato and closely related species with homosequential chromosomes.Prx-1 lies on chromosome 1, where it is also linked withSkdh-1; Aps-2 is linked withGot-4 on chromosome 8;Tpi-2 has been allocated to chromosome 4; and a linkage has been detected betweenPgi-1 andEst-4, whose respective chromosome has not yet been determined. These and previously published data have been summarized in the form of an isozyme linkage map. Twenty-two loci have thus been mapped on nine of the twelve tomato chromosomes. We discuss some new applications of mapped isozymic genes. In certain types of segregations, isozymic genes are far more efficient than morphological markers in providing linkage information. They greatly expedite the cytogenetic investigation of species hybrids and can be utilized to facilitate backcross transfers of genes from wild to cultivated taxa.     

Genetics of mitochondrial glutamate-oxaloacetate transaminase (GOT-2) in Tigriopus californicus

Glutamate-oxaloacetate transaminase (GOT; EC 2.6.1.1) occurs as two electrophoretically distinguishable isozymes in the copepod Tigriopus californicus. The slower-migrating form, referred to as GOT2, is shown to be associated with the mitochondrial cell fraction. GOT2 phenotypes are inherited in typical Mendelian fashion, indicating that they are encoded by a nuclear gene. Allelic frequencies for electrophoretic variants of the two Got loci in 12 California populations of T. californicus show a sharp differentiation of local populations. Linkage studies demonstrated that Got-2 is linked to Got-1; a map of four loci in linkage group I is presented.This work was supported by NSF grant DEB-8207000 to R.S.B. and an NIH traineeship in Genetics to M.M.D.     

Georeferenced phylogenetic analysis of a global collection of wild and cultivated Citrullus species

The geographical origin of watermelon (Citrullus lanatus) remains debated. While a first hypothesis suggests the center of origin to be West Africa, where the endemic sister species C. mucosospermus thrives, a second hypothesis suggests northeastern Africa where the white‐fleshed Sudanese Kordophan melon is cultivated. In this study, we infer biogeographical and haplotype genealogy for C. lanatus, C. mucosospermus, C. amarus, and C. colocynthis using noncoding cpDNA sequences (trnT‐trnL and ndhF‐rpl32 regions) from a global collection of 135 accessions. In total, we identified 38 haplotypes in C. lanatus, C. mucosospermus, C. amarus, and C. colocynthis; of these, 21 were found in Africa and 17 appear endemic to the continent. The least diverse species was C. mucosospermus (5 haplotypes) and the most diverse was C. colocynthis (16 haplotypes). Some haplotypes of C. mucosospermus were nearly exclusive to West Africa, and C. lanatus and C. mucosospermus shared haplotypes that were distinct from those of both C. amarus and C. colocynthis. The results support previous findings that revealed C. mucosospermus to be the closest relative to C. lanatus (including subsp. cordophanus). West Africa, as a center of endemism of C. mucosospermus, is an area of interest in the search of the origin of C. lanatus. This calls for further historical and phylogeographical investigations and wider collection of samples in West and northeastern Africa.     

Inheritance and linkage relationships of ten isozyme genes in hazelnut

Summary The inheritance of 6-phosphogluconate dehydrogenase (6PGD), malate dehydrogenase (MHD), aconitase (ACO), phosphoglucomutase (PGM), phosphoglucoisomerase (PGI), and glutamate-oxalacetate transaminase (GOT) polymorphic isozymes was studied in leaf extracts of nine hazelnut progenies using horizontal starch gel electrophoresis. Evidence of Mendelian inheritance was obtained for ten loci: 6-Pgd-2, Mdh-1, Aco-1, Aco-2, Pgm-1, Pgm-2, Pgm-3, Pgi-2, Pgi-3, and Got-2, which permitted the analysis of 28 alleles (2.8 per locus). The presence of null alleles was detected in Pgm-1 and Pgm-3. Joint segregation analysis of pairs of isozymes revealed four linkages: Mdh-1-Pgi-2, Aco-2-Pgm-2, Pgm-1-Pgm-3, and 6Pdg-2-Pgm-2.     

A genetic linkage map for watermelon derived from a testcross population: ( Citrullus lanatus var. citroides x C. lanatus var. lanatus) x Citrullus colocynthis

A genetic linkage map was constructed for watermelon using a testcross population [Plant Accession Griffin 14113 (Citrullus lanatus var. citroides) 2 New Hampshire Midget (NHM; C. lanatus var. lanatus)] 2 U.S. Plant Introduction (PI) 386015 (Citrullus colocynthis). The map contains 141 randomly amplified polymorphic DNA (RAPD) markers produced by 78 primers, 27 inter-simple sequence repeat (ISSR) markers produced by 17 primers, and a sequence-characterized amplified region (SCAR) marker that was previously reported as linked (1.6 cM) to race-1 Fusarium wilt [incited by Fusarium oxysporum Schlechtend.:Fr. f. sp. niveum (E.F.Sm.) W.C. Synder &; H.N. Hans] resistance in watermelon. The map consists of 25 linkage groups. Among them are a large linkage group that contains 22 markers covering a mapping distance of 225.6 cM and six large groups each with 10-20 markers covering a mapping distance of 68.8 to 110.8 cM. There are five additional linkage groups consisting of 3-7 markers per group, each covering a mapping distance of 36.5 to 57.2 cM. The 13 remaining linkage groups are small, each consisting of 2-11 markers covering a mapping distance of 3.5-29.9 cM. The entire map covers a total distance of 1,166.2 cM with an average distance of 8.1 cM between two markers. This map is useful for the further development of markers linked to disease resistance and watermelon fruit qualities.     

Isozyme and seed protein phylogeny of the genusCitrullus (Cucurbitaceae)

Electrophoretic analysis of 26 enzyme coding genes was conducted on accessions of threeCitrullus species and the relatedPraecitrullus fistulosus andAcanthosicyos naudinianus. The isozyme phylogeny of the genusCitrullus and the related species was constructed based on pairwise measurements of the respective genetic distances between the species and races.P. fistulosus andA. naudinianus form two distinct outgroups toCitrullus which is characterized by two main clusters: The first includes twoC. colocynthis races and the second,C. lanatus andC. lanatus var.citroides, which are more closely related to each other than they are toC. ecirrhosus. The isozyme phylogeny is consistent with the variability in six seed protein bands and with the crossability relations among the examined species.     

Linkage relationships and chromosomal locations of enzyme-coding genes in pepper,Capsicum annuum

The linkage relationships and chromosomal locations of 14 enzyme-coding genes were investigated in Capsicum annuum L. (garden pepper) by monitoring segregations in backcross and F₂ progeny of an interspecific cross between C. annuum cv. NM6-4 and C. chinense CA4 and by studying allele dosage effects in five hybrid primary trisomics. These conclusions can be reached: 6Pgdh-i is on the metacentric chromosome corresponding to the noir trisomie; Idh-1 and Est-3 are on chromosome 12; an aerocentric chromosome which corresponds to the pourple trisomie; Idh-1 is near the centromere and Est-3 is distal on the long arm of that chromosome. The other loci can be arranged in the following linkage groups and are apparently not located on the trisome corresponding to any of the trisomics tested: Est-4-18cM-(Pgi-1-3cM-Pgm-1); Prx-7-2cM-Tk-1; Pgm-2-2cM-Skdh-1; Est-1-OcM-Est-7. Linkage and dosage data combined with karyotype and meiotic analyses of the two species and F₁ hybrids suggest that Idh-1 and Skdh-1/Pgm-2 are near the breakpoints on the two chromosomes involved in a reciprocal translocation for which the two species differ. One locus, Pgm-3, was detected only in C. annuum cultivars and is apparently the result of a duplication of Pgm-2 which codes for cytosolic phosphoglucomutase activity. Pgm-2 and Pgm-3 are not tightly linked (approximately 20% recombination) which supports the proposal that Pgm-3 originated from a mechanism other than unequal crossing over. A comparison of the linkage relationships of enzyme-coding genes in pepper with those of putative orthologous loci in tomato reveals that two linkage blocks, Est-1-Est-7 and Pgi-1-Est-4, may have remained intact since the divergence of Capsicum and Lycopersicon.     

Association of four isozyme loci with a reciprocal translocation between 1R/4R chromosomes in cultivated rye (Secale cereale L.)

Summary The progeny of four crosses between a structural heterozygote for a reciprocal translocation and a homozygote for the standard chromosome arrangement were analyzed in rye (Secale cereale L. cv Ailés) for the electrophoretic patterns of eight different leaf and endosperm isozymes and also for the meiotic configuration at metaphase I. The Pgi-1, 6-Pgd-2 and Mdh-1 loci are linked to each other and also to the reciprocal translocation. These loci have been located on chromosome 1R. The Mdh-1 locus is located in the interstitial segment of chromosome 1R, between the centromere and the breakpoint. The Pgm-1 locus has been located on chromosome arm 4RS and is linked to Pgi-1, 6-Pgd-2, Mdh-1 and the reciprocal translocation. The estimated distance between the Pgm-1 locus and the centromere is 14.98 ± 2.27 cM. Therefore, the reciprocal translocation involves the 1R and 4R chromosomes. Other linked loci detected have been Mdh-2b and Est-2 (7.40 ± 2.90 cM) and Got-3 and Est-2 (5.62 ± 3.07 cM). These three last loci are located on chromosome 3R and their order most probably is Mdh-2b — Est-2 — Got-3.     

Molecular phylogeny ofForsythia (Oleaceae) based on chloroplast DNA variation

Phylogenetic relationships of ten wild species and several cultivars ofForsythia were reconstructed based on the chloroplast (cp) DNA variation. A total of 216 cpDNA variants, 44 of which were potentially phylogenetically informative, was detected using 24 restriction endonucleases. Phylogenetic analysis usingFontanesia andAbeliophyllum as outgroups revealed four well defined species groups in the genus: 1)F. suspensa, 2)F. europaea — F. giraldiana, 3)F. ovata — F. japonica — F. viridissima, and 4)F. koreana — F. manshurica — F. saxatilis. The amount of support for each monophyletic group was evaluated by various methods including character number, decay analysis, parsimony bootstrapping, Neighbour-Joining (NJ) — bootstrapping, NJ-jackknifing, and the topology-dependent permutation tail probability (T-PTP) test. The data do not support the hybrid origin ofF. intermedia fromF. suspensa andF. viridissima. The disjunctly distributed European species,F. europaea, was identified as a sister species of the ChineseF. giraldiana and it was probably derived through recent long distance dispersal.     

Genetic analysis of ecological relevant morphological variability in Plantago lanceolata L.

Summary Morphological variability was analysed in an F₂-generation derived from crosses between two ecotypes of Plantago lanceolata L. Six allozyme loci, localised in five linkage groups, were used as markers. For two marker loci, Got-2 and Gpi-1, segregations did not fit monogenic ratios. In the linkage groups to which these two loci belonged, male sterility genes appeared to be present. In these crosses, male sterility (type 3, as described by Van Damme 1983) may be determined by two recessive loci located in the linkage groups of Got-2 and of Gpi-1. Many correlations of morphological and life history characters with allozyme markers were observed. The quantitative trait loci did not appear to be concentrated in major gene complexes. Often many loci were involved, sometimes with effects opposite to those expected from the population values. Main effects of the linkage groups appeared to be more important than interaction effects in determining variability. It also appeared that there is a positive correlation between the number of heterozygous allozyme loci and generative growth.Grassland Species Research Group Publication No. 115     

Inheritance of some marker genes in Setaria italica (L.) P. Beauv.

Summary A study on a series of genetic markers was run on five hybrids of foxtail millet, Setaria italica, and on one interspecific hybrid S. viridisxS. italica (S. viridis is the wild relative of S. italica). Seven enzymatic systems were investigated using starch gel electrophoresis (esterase, alcohol dehydrogenase, glutamate oxaloacetate transaminase, acid phosphatase, malate dehydrogenase, 6-phosphogluconate dehydrogenase, cathodic peroxidase). This genetic analysis of the 6 F2 has allowed us to define 12 polymorphic loci: Est-1, -2 and -3, Adh-1, Got-1 and -2, Acph-1, Mdh-1 and -2, Pgd-1 and -2, and Pox-1. All of them behaved like dimers, except Est-1 and Est-2 which showed monomeric structures. Two other markers were examined: waxy endosperm, which appeared to be controlled by one locus, and anthocyanic pigmentation of the collar, for which at least two loci are responsible. Studies of linkage carried out on three F2 showed two linkage groups: Mdh-1, Pox-1, Wx, Est-3, and a locus for collar colour, and Est-2, and one or two other loci of colouring.     

Linkage group IV of fish of the genus Xiphophorus (Poeciliidae): Assignment of loci coding for pyruvate kinase-1, glucosephosphate isomerase-1, and isocitrate dehydrogenase-1

Electrophoretic variation ascribable to three enzyme loci, coding for a pyruvate kinase (PK1), a glucose phosphate isomerase (GPI1), and an isocitrate dehydrogenase (IDH1), was observed in three species of fish of the genus Xiphophorus. Electrophoretic patterns in F₁ hybrid heterozygotes confirmed the dimeric structures of GPI and IDH, and indicated a multimeric structure for pyruvate kinase. Variant alleles at the three loci exhibited normal Mendelian segregation in backcross hybrids. Linkage analyses indicate a gene order and estimated recombination of PK1—10%—GPI1—41%—IDH1. No significant interference or sex- or population-specific recombination difference was detected. This group (designated linkage group IV) was shown to assort independently from the nine loci comprising linkage groups I, II, and III and from 23 other informative markers, within the limits of the data. No conclusions with respect to homology of linkage relationships could be reached, due to the presence of presumably duplicated loci in these fish coding for isozymes whose homology with enzymes in other vertebrate species is as yet unestablished.This work was supported in part by Public Health Service Research Grant CA-28909.     

Segregation and linkage relationships of isoenzymes in shortleaf pine (Pinus echinata Mill.)

 Segregation and linkage relationships were analyzed between 28 isoenzyme loci in ten natural stands representing much of the natural range of Pinus echinata Mill. (shortleaf pine). A total of 203 possible two-locus combinations were tested. Three linkage groups were revealed in this study at a linkLOD of 4.0. The first linkage group (A) consisted of Pgi and Adh-1; Gdh, Idh, Skdh-2, G6pd-2 and Aco were mapped to the second linkage group (B); the third group (C) had 2 loci: Mdh-2 and Mdh-3. A moderate linkage between Mnr-2 and Dia-2 and weak linkages between Mnr-1 and Dia-1, and Got-2 and 6pgd-2 were also detected. The significance of these results in shortleaf pine is discussed and compared to linkage maps previously reported in other conifers, including pines. Received: 7 April 1997 / Accepted: 25 April 1997     

Tight linkage between a nuclear male-sterile locus and an enzyme marker in tomato

Summary The linkage relationship of a nuclear male sterile locus, ms-10, was tested with two enzyme marker loci known to be on the same chromosome (long arm of chromosome 2). The results indicate the gene order is Est-1 — 18 cM — Prx-2 — 1.5 cM — ms-10. The linkage intensity of ms-10 and Prx-2 (1.5 cM) suggests that Prx-2 might provide a selectable marker for male-sterility. In accordance with this idea, the ms-10 allele was placed in cis with a rare-allele of Prx-2 (Prx-2 ¹). Selection on the basis of the codominant Prx-2 ¹ allele should allow for more rapid and efficient transfer of the recessive male sterile allele into an array of genetic backgrounds, thus promoting its use in hybrid seed production.     

Glutamate oxalate transaminase (GOT) genetics in Mus musculus: Linkage,polymorphism, and phenotypes of the Got-2 and Got-1 loci

A comparison of electrophoretic patterns of F₁ and backcross progeny of two inbred strains of mice has revealed a new autosomal variant of the mitochondrial form of GOT. The loci controlling the production of the soluble and mitochondrial forms of GOT have been designated Got-1 and Got-2, respectively. The two alleles of the Got-2 locus have been designated Got-2 ^a and Got-2 ^b, which represent the slow- and fast-migrating electrophoretic forms. Twenty-seven inbred strains of mice have been classified for Got-2 ^a and Got-2 ^b. It has been demonstrated that the polymorphism of Got-2 is widely distributed in feral mice. Got-2 was shown to be linked to Es-1, and evidence is also presented for linkage between Got-2 and Es-2, Es-5, and oligosyndactyly (Os). The absence of linkage of Got-2 to seven other loci has also been demonstrated. GOT was expressed in vitro in cell lines derived from human and mouse tissues.     

Comparative analysis of chloroplast DNA variability in wild and cultivated<Emphasis Type="Italic"> Citrullus</Emphasis> species

PCR amplification and restriction site analysis of chloroplast (cp) DNA regions was used to detect inter- and intraspecific differences in the genus Citrullus. More than 55 C. lanatus and 15 C. colocynthis accessions collected from diverse geographical areas, C. ecirrhosus and C. rehmii were used. Most of the cpDNA variation within Citrullus was the result of large indels and transitions and transversions. Indels at the ndhA, trnS-trnfM and trnC-trnD regions and several substitutions at restriction enzyme sites can be used to separate C. colocynthis from the other Citrullus species. A nucleotide substitution at a restriction enzyme site at the 3 flanking region of ndhF provided a diagnostic haplotype for C. lanatus var. lanatus, the cultivated watermelon. Similarly, a nucleotide substitution at an intergenic spacer region of the trnC-trnD region resulted in a diagnostic haplotype for citron, C. lanatus var. citroides. Several C. lanatus var. citroides accessions showed the var. lanatus haplotype. C. rehmii showed almost the same haplotype as C. lanatus var. citroides with the exception of a unique insertion at a cpSSR site. Since C. ecirrhosus lacks the derived diagnostic nucleotide substitutions of C. lanatus, it is probably the progenitor of the cultivated watermelon. Intraspecific haplotypes detected within C. colocynthis were associated with geographic origin.Communicated by J. Dvorak     

Genetics of esterases in species of Lycopersicon

Summary Improvements in plant culture and electrophoretic technique permit detection and genetic analysis of seven esterase loci in Lycopersicon esculentum and related species with homosequential chromosomes. At all of these loci except one, each allele codes for a single anodal band, and the electrophoretic variants are inherited in monogenic fashion. For the exceptional Est-4, allozymes are 1–3 banded in various combinations at four positions, and rare recombinants in one cross appeared at a frequency of 0.0005, suggesting the existence of several very tightly linked genes. Est-2 segregated solely for intensity differences in dominant/recessive fashion; Est-3 and Est-4 behave as monomers; the remaining Est-l, 5, 6, and 7 — coding for contiguous bands in the region closest to the origin — are dimeric. The latter group are tightly linked inter se in the proximal portion of 2L (long arm of chromosome 2), the total map distance of the complex being approximately 1.5 cM; Est-2 is situated on 9L between ah and marm; Est-3 on 1L between inv and dgt; Est-4 has not yet been located. Even in the interspecific hybrids, map distances are similar to the standard values for L. esculentum. Tandem duplication is hypothesized for the origin of the Est-l, 5–7 complex, which adds another example to the growing list of linked mimic genes in the tomato genome. In respect to the position of their bands and tight inter se linkage, this series exactly parallels the EA, EB, EC esterase series in Hordeum vulgare — a fact which suggests great antiquity for this block of genes.