Multi-enzyme Phenotypes Research Articles

Diversity of Meloidogyne exigua (Tylenchida: Meloidogynidae) populations from coffee and rubber tree

AbstractIsozymes (esterase and malate dehydrogenase), SCAR and RAPD-PCR were studied in 15 populations of three races of Meloidogyne exigua collected in coffee-producing areas in Brazil, Bolivia and Costa Rica and one population from rubber tree plantations in Brazil. This study revealed four esterase phenotypes (E1, E2, E2a, E3) and three malate dehydrogenase phenotypes (N1, N1a, N2) for M. exigua populations. The most common multi-enzyme phenotype was E2N1. The enzymatic phenotypes do not separate M. exigua races. Sixteen populations of M. exigua were tested in Multiplex PCR using SCAR primers ex-D15F/R that allowed the identification of all M. exigua populations. Phylogenetic analyses showed high intraspecific polymorphism (25.9-59.6%) for all M. exigua studied. However, all populations clustered together with 100% bootstrap support, thereby demonstrating the consistency of species identification. In general, no correlation was found between enzymatic profile, race and genetic polymorphism of the studied populations.

Delimitation of taxa of Sphagnum subsecundum s.l. (Musci, Sphagnaceae) based on multienzyme phenotype and cytological characters

Delimitation of taxa of Sphagnum subsecundum s.l. (Musci, Sphagnaceae) based on multienzyme phenotype and cytological characters

Genetic structure and morphological variation of British populations of the hybrid Potamogeton x salicifolius

Potamogeton x salicifolius Wolfg. is one of the three most frequently recorded Potamogeton hybrids in the British Isles and Europe. It is thought to be the hybrid between P. lucens and P. perfoliatus. Its scattered distribution suggests that it has arisen several times in Britain. Most British populations of P. x salicifolius can be identified by their morphological characteristics, which are intermediate between those of the putative parents P. lucens and P. perfoliatus. However, the population at the Ouse Washes, Cambridgeshire, differs from other populations in its greater similarity to P. lucens. A genetic study of eight British populations, using six isozyme systems, revealed that most populations consist of a single multi-enzyme phenotype. This suggests that they were the result of a single hybridization event and are therefore maintained through vegetative reproduction. By contrast, the Ouse Washes population consists of three multi-enzyme phenotypes. This variation is likely to have resulted from multiple hybridization events, although we cannot exclude the possibility that the plants are partially fertile. The isozyme systems studied were unable to identify P. lucens and P. perfoliatus unambiguously, and consequently did not provide evidence for their putative parentage of P. x salicifolius. However, at a local level the banding patterns of the hybrids were generally consistent with the local multi-enzyme phenotypes of these putative parents. © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society, 2004, 144, 99–111.

Delimitation of some European species of Calypogeia Raddi (Jungermanniales, Hepaticae) based on cytological characters and multienzyme phenotype

Delimitation of some European species of Calypogeia Raddi (Jungermanniales, Hepaticae) based on cytological characters and multienzyme phenotype

Genetic variation within and between populations of Potamogeton pusillus agg.

Patterns of isozyme variation were examined in 17 populations of P. pusillus and P. berchtoldii, together with one population of P. trichoides taken for comparison. Both P. pusillus and P. berchtoldii displayed low levels of variation within populations associated with high levels of interpopulation differentiation. This pattern of partitioning of genetic variation within and between populations is attributed to the founder effect, frequent vegetative propagation by turions, dominant self-fertilization and limited seedling recruitment. The mechanism of pollen transfer was investigated in cultivation. Effective pollination takes place in air above the water surface (autogamy, geitonogamy, anemogamy), on the water surface (epihydrogamy) or below water surface (hydroautogamy). The species are self-compatible. The low level of infra-population variation together with rare occurrence of heterozygotes suggest that selfing is the most frequent mode of pollination, although the protogynous flowers may occasionally permit some cross-pollination. Unique enzyme markers were found for P. pusillus and P. berchtoldii, and also for the single population of P. trichoides. All multienzyme phenotypes were species-specific. Isozyme data support the separate position of P. pusillus and P. berchtoldii. UPGMA dendogram based on enzyme data of 133 plant samples revealed three distinct main enzymatic entities perfectly corresponding to the three morphologically defined species.

Chloroplast evidence for the multiple origins of the hybrid Potamogeton × sudermanicus Hagstr.

A previous study of the sole British population of Potamogeton× sudermanicus Hagstr. supported the putative origin of this taxon as a result of hybridization between Potamogeton acutifolius Link and Potamogeton berchtoldii Fieber. In this study, the TrnL (UAA) chloroplast region was used to identify the maternal parent of this hybrid. It was found that the two multi-enzyme phenotypes identified in previous studies had different chloroplast sequences. These sequences were shown to correspond to those of the two parental species. This is further evidence that this population is the result of at least two hybridization events and that the plants attributed to this hybrid are not an aneuploid of either of the parental species.

Isozyme evidence for the origin of Potamogeton × sudermanicus as a hybrid between P. acutifolius and P. berchtoldii

Potamogeton × sudermanicus Hagstr. has been interpreted morphologically as a hybrid between P. acutifolius Link and P. berchtoldii Fieber. Both parents belong to section Graminifolii where hybrids appear to be less frequent than in other sections. This reputed hybrid has been recorded at only a few sites in Europe and at a single locality in Britain. Using seven different isozyme systems it was shown that all the bands present within the British population of the hybrid were found in P. acutifolius or P. berchtoldii, supporting the putative origin of this taxon. In addition, the identification of two multi-enzyme phenotypes implies that this hybrid has arisen at least twice at this site.

Population genetic structure of Potamogeton anguillanus in Lake Shinji, Japan

Enzyme electrophoresis was performed to investigate the genetic variation of Potamogeton anguillanus Koidz. in Lake Shinji, Shimane Prefecture, Japan. The collection was made in six local populations along the coast of the lake, and a total of 78 shoot samples were obtained. No variation among samples occurred in the six enzymes analyzed, and the whole population in Lake Shinji was proved to consist of only a single multienzyme phenotype. Clonal growth without sexual reproduction may have resulted in the genetic uniformity. The implication of the lack of genetic variation is briefly discussed from the viewpoint of conservation of the species in Lake Shinji.

Genetic diversity of the submerged macrophyte Hydrilla verticillata (L. f.) Royle in a river system in Japan

The genetic diversity of Hydrilla verticillata was studied in the Kako River system, Hyogo Prefecture, southwestern Japan, including some of its tributaries. Sex expression (monoecy or dioecy), ploidy level (diploid or triploid), and isoenzyme phenotypes were investigated for plant samples collected from 51 sites along the water course. Monoecious plants occurred at 10 sites and dioecious plants at 47 sites. Among dioecious plants, diploid and triploid plants occurred at 1 and 46 sites, respectively. Seven multienzyme phenotypes (MEPs) were recognized by electrophoretic analysis among dioecious triploid plants. The distribution pattern of nine biotypes based on sex expression, ploidy level, and MEPs suggested the possibility of ecological differentiation among different biotypes. The implications of genetic diversity demonstrated in this study were discussed in relation to the conservation strategy of biodiversity in a river system.

Genetic diversity of Potamogeton anguillanus in Lake Biwa, Japan

The genetic structure of Potamogeton anguillanus in Lake Biwa, Japan was surveyed by enzyme electrophoresis. Polymorphic banding patterns were observed in four of eight enzymes investigated. Based on the combination of the single enzyme phenotypes, 27 multi-enzyme phenotypes (MEPs) were determined in the whole lake based on 258 shoot samples collected from 14 local populations. Most of the local populations were polymorphic and involved one to eight unique MEPs. A mapping survey of MEPs in selected quadrats showed establishment of ramets with different genotypes and the clonal spread of the species. The origin of genetic diversity in the species may partly be due to recurrent hybridization. Sexual reproduction may also be involved.

Molecular markers indicate two cryptic, genetically divergent populations of Russian thistle (Salsola tragus) in California

Genetic variability among accessions of Russian thistle (Salsola tragus L.) from California was investigated using allozymes and DNA-based molecular markers. Aspartate aminotransferase and 6-phosphogluconate dehydrogenase displayed two multienzyme phenotypes that were widespread in plants throughout the state. Random amplified polymorphic DNA analysis was conducted on samples of the two isoenzymic phenotypes collected throughout California, as well as additional accessions from France and Turkey and Salsola paulsenii Litv. Six primers produced 23 polymorphic bands. Analysis of the patterns of bands by calculation of simple matching coefficients and cluster analysis confirmed the genetic distinctness of the two isoenzymic phenotypes of S. tragus; S. paulsenii was markedly different from both types. Mean fruit weights from plants grown under similar conditions were different between the two types as well. These results and preliminary cytological analysis together suggest that the two types are actually two different species of Salsola, only one of which has been previously recognized. Analysis of the DNA-based markers suggests that one of the genetic entities may be closely related to Salsola found in Europe, while the area of origin of the second entity is currently obscure.Key words: allozyme, genetic diversity, RAPD assay, Salsola tragus, Salsola paulsenii.

Intraspecific molecular variation inHieracium sect.Alpina (Asteraceae), an apomictic group

Intraspecific variation of four agamospecies of Hieracium sect. Alpina was studied using RAPD and isozyme techniques. No variation in either multiprimer RAPD or multi-enzyme phenotypes was observed within H. holosericeum, suggesting that this widespread species consists of only a single genotype. A low level of within-population isozyme variation was seen in H. tenuifrons and H. calenduliflorum, the origin of which appears to be consistent with somatic mutation. Most isozyme and all RAPD variation in these two species was partitioned between populations. A strong correlation with geography suggests that its cause may be due to polytopic (=polyphyletic?) origin or perhaps to mutation and dispersal. The most variable species was H. alpinum, in which isozyme variation occurred mostly within populations rather than between them, suggesting occasional sexual events or that the parents of H. alpinum were heterozygous. RAPD variation in this species, in contrast, was partitioned between Scottish and Swiss populations, suggesting the existence of geographical races.

Genetic variability in two hydrophilous species ofPotamogeton, P. pectinatus andP. filiformis (Potamogetonaceae)

Genetic variability inPotamogeton pectinatus andP. filiformis was studied by means of isozymes. The overall levels of variability were similar to some other well studied hydrophilous species, and were shown to be distributed more between than within populations. This partitioning of variability was attributed to three main factors. (1) Clonal growth (as measured by the frequency of multi-enzyme phenotypes) was shown to be a major factor in both species, although more important inP. pectinatus. (2) Low levels of sexual reproduction were shown to be a likely contributor to the partitioning of variability inP. pectinatus; such reproduction is probably limited by seedling recruitment rather than by infrequent flowering. (3) Geographical isolation was indicated as a factor regulating gene flow at distances of more than about 1000 km in both species, with the data suggesting that dispersal between populations is mainly by seed rather than by vegetative means.

Isozyme evidence for hybridization between Potamogeton natansand P. nodosus(Potamogetonaceae) in Britain

A population of pondweeds from the River Stour in Dorset intermediate in morphology between Potamogeton natansL. and P. nodosusPoir. is shown by means of isozyme evidence to be the hybrid P.× schreberiG. Fisch. It is represented by a single multi-enzyme phenotype which, together with its sterility, suggests it reproduces vegetatively and may well constitute a single clone. It is genetically distinct from the morphologically similar hybrid between P. lucensL. and P. natans( P.× fluitansRoth).

Isozyme evidence for hybridization between Potamogeton natans and P. nodosus (Potamogetonaceae) in Britain

A population of pondweeds from the River Stour in Dorset intermediate in morphology between Potamogeton natans L. and P. nodosus Poir. is shown by means of isozyme evidence to be the hybrid P. × schreberi G. Fisch. It is represented by a single multi-enzyme phenotype which, together with its sterility, suggests it reproduces vegetatively and may well constitute a single clone. It is genetically distinct from the morphologically similar hybrid between P. lucens L. and P. natans (P. x fluitans Roth).

Genetic variation within and between populations of Myriophyllum alterniflorum DC

The degree of genetic variation within and between populations of the freshwater angiosperm Myriophyllum alterniflorum DC. was determined using gel electrophoresis on plants grown under standard conditions. Two hundred and seventy-three individuals were examined from 13 populations, of which ten were from a limited area in the northwest of Scotland, and one each from central Scotland, the south of England and Norway. Of the 12 enzymes studied, eight were polymorphic across the 13 populations: acid phosphatase, aspartate aminotransferase, α-esterase, fluorescent esterase, malic enzyme, peroxidase, phosphoglucose isomerase and tetrazolium oxidase (equivalent to superoxide dismutase). The plants studied showed a high degree of variation. Fifty-eight multi-enzyme phenotypes, based on five enzymes, were distinguished, distributed across the 13 populations and the 263 individuals which could be analysed. Twenty (35%) of these phenotypes were represented by one individual and 36 (62%) phenotypes were restricted to one site. The two most frequent phenotypes were found in five sites and one of these was found in 21 individuals (8% of the plants studied). No population was encountered with a single multi-enzyme phenotype. Simpson's index of diversity ( D) varied between 0.536 at the least variable site and 0.978 at the most variable site, with a mean of 0.792. Even for sites within one watershed, the variation was great; thus, for tetrazolium oxidase, plants at the head, middle and foot of the watershed comprised 96% Phenotype A, 100% Phenotype C and 100% Phenotype A, respectively. A cluster analysis of the populations based on the presence or absence of single- and multi-enzyme phenotypes revealed four clusters of varying composition separated at the 53% and 17% level, respectively, but these were not correlated with presence in a watershed, geographic distance or site alkalinity. The majority of the populations appeared to be in Hardy-Weinberg equilibrium for two loci (α-esterase-2 and tetrazolium oxidase-2), where analysis was possible, which suggests that sexual reproduction is common in these populations and that it occurs via random mating. Calculations for these loci using Wright's F statistics revealed that complete panmixia was not occurring ( F IT = 0.498), largely because of genetic subdivisions between populations ( F ST = 0.469) rather than inbreeding within populations ( F IS = 0.054). The possible reason for the high genetic variation uncovered here is discussed in terms of the stability of populations, frequency of the species in nearby sites, flowering frequency, pollination mechanism and the distribution of the species in different types of water body. The mitotic chromosome number was 2 n = 14 for all the material studied.