Esterase and Malate Dehydrogenase Phenotypes in Portuguese Populations of Meloidogyne Species

Nonspecific esterases and malate dehydrogenases of 1-5 females from 40 root-knot nematode populations from Portugal were analyzed by electrophoresis in 0.4-mm-thick polyacrylamide gels. Fourteen major bands of esterase activity were detected, corresponding to 10 distinct phenotypes, Meloidogyne javanica and M. hapla had distinct species-specific phenotypes. Two phenotypes occurred in M. arenaria. The most variability was found among M. incognita populations. Of the remaining two phenotypes, one was associated with M. hispanica and the other belonged to a new species. Three malate dehydrogenase phenotypes were discerned on the basis of particular combinations of the eight main bands of activity found. As previously found, esterases were more useful than malate dehydrogenases in identification of the major Meloidogyne species. The host plant had no effect on the nematode esterase or malate dehydrogenase phenotypes.     

Inseparability of X-Heterochromatic Functions Responsible for X:Y Pairing, Meiotic Drive, and Male Fertility in Drosophila melanogaster

Deficiencies encompassing part or all of the X heterochromatin of Drosophila melanogaster have been linked to three abnormalities in male meiosis and spermatogenesis: X-Y nondisjunction, skewed sperm recovery ratios favoring sperm with reduced chromatin content, and sterility in males carrying either a Y-autosome translocation or mal ⁺Y. In this study, 18 X heterochromatic deficiencies of varying sizes were tested in XY males for their spermatogenic phenotypes. All 18 proved to be either mutant for all three phenotypes or wild type for all three. Although variable among mutant deficiencies, expression levels of all three phenotypes were strongly correlated. Deficiencies that cause high levels of nondisjunction also cause severe recovery ratio distortion and are completely sterile in conjunction with mal⁺ Y. Low nondisjunction deficiencies cause comparable mild effects for the other phenotypes. The same deficiencies were also tested in males carrying a large heterochromatic free X duplication Dp(1; f)3. For all deficiencies which induce nondisjunction in XY males, the Y and free duplication pair regularly and the X fails to pair in XYDp males. Drive levels are constant across deficiencies in these males. Thus elimination of variability in the pairing phenotype also eliminates variability in sperm recovery ratios.     

Notes on the geographic distribution of howling monkeys in the marajó archipelago,pará, Brazil

I review the distribution of genus Alouattain the Marajó Archipelago based on geographic variation of pelage color patterns. Specific differences exist among the labeled specimens at Museu Paraense Emílio Goeldi, which are confirmed via new field information from wild populations. The animals from Marajó, Caviana, and Mexiana Islands possess color patterns of Alouatta belzebul,while Alouatta seniculusis confirmed as the species that inhabits Gurupá Island. The high variability of pelage coloration of the animals from Marajó, Caviana, and Mexiana Islands includes all phenotypes formerly designated as different subspecies. The howler populations from these three islands belong to the same subspecies as those populations that inhabit the region of Tucurui dam reservoir (area 4). Finally, it seems that, as also suggested by chromosome studies, A. belzebulprobably comprises different epiphenotypes without taxonomic validity.     

Variabilité biochimique et génétique de Sphaeroma ghigii,S. hookeri et S. serratum. Variations intraspécifiques

Electrophoresis on polyacrylamide gel of enzymes (esterases, phosphatases) and total proteins of Sphaeroma ghigii, S. hookeri and S. serratum shows the existence of important intraspecific variability. Esterases, alkaline phosphatases and major low ionic strength extractable proteins also demonstrate quantitative and qualitative differences between individuals; these differences are the expression of protein and enzyme polymorphism. Some of these variations represent sexual differences which are an expression of a biochemical sexual dimorphism that appears particularly in esterases and phosphatases. Among males, this variability leads to the delineation of several biochemical phenotypes and gives an insight into the genetic variability of populations based on the protein composition of organisms. Taking into consideration the ecological characteristics of the various species of genus Sphaeroma, this polymorphism provides a source of information on ecophysiological relations at the level of proteins and enzymes, that may lead to a better understanding of intraspecific variability.     

Use of Enzyme Phenotypes for Identification of Meloidogyne Species

Enzyme phenotypes were obtained for 291 populations from 16 species of Meloidogyne originating from 65 countries. Soluble proteins from macerates of individual egg-laying females were separated by electrophoresis in 0.7-mm-thick polyacrylamide gels. Enzymes investigated were nonspecific esterases, malate dehydrogenase, superoxide dismutase, and glutamate-oxaloacetate transaminase. Esterases were polymorphic and most useful in identification of major species. About 94% of the populations of M. hapla, 98% of M. incognita, and 100% of M. javanica could be identified to species on the basis of esterase phenotypes alone. About 84% of the populations of M. arenaria exhibited three distinct phenotypes. Two of them were highly species specific (accuracy of identification 98-100%). The third, and least prevalent, phenotype occurred also in two other species. Another 12 less common Meloidogyne species, of which only one or a few populations of each were studied, exhibited a variety of esterase phenotypes, some of which may prove to be species specific. Superoxide dismutase phenotypes similarly were helpful in the characterization of certain species; however, the same phenotype was often observed in more than one species. The remaining two enzymes, with few exceptions, proved to be less useful for identification of Meloidogyne species. Multienzyme phenotypes represented by two or more enzymes often offered biochemical profiles more valuable for definitive characterization of Meloidogyne species than single enzymes.     

Morphometric divergence in populations of Anastrepha obliqua (Diptera,Tephritidae) from Colombia and some Neotropical locations

The West Indian fruit fly, Anastrepha obliqua, is one of seven species of quarantine importance of its genus and is one of the most economically important fruit fly pests in Colombia. The taxonomic status of this species is a key issue for further implementation of any pest management program. Several molecular studies have shown enough variability within Anastrepha obliqua to suggest its taxonomic status could be revised; however, there are no morphological studies supporting this hypothesis. The aim of this work was to describe the morphological variability of Colombian populations of Anastrepha obliqua, comparing this variability with that of other samples from the Neotropics. Measurements were performed on individuals from 11 populations collected from different geographic Colombian localities and were compared with populations from Mexico (2), Dominica Island (1), Peru (1) and Brazil (2). Linear morphometric analyses were performed using 23 female morphological traits, including seven variables of the aculeus, three of the thorax, and six of the wing; seven ratios among them were also considered. Discriminant function analyses showed significant morphological differentiation among the Colombian populations, separating them into two groups. Furthermore, in the comparisons between Colombian samples with those from other countries, three clusters were observed. The possibility of finding more than one species within the nominal Anastrepha obliqua population is discussed.     

A codominant molecular marker in linkage disequilibrium with a restorer-of-fertility gene (Ms) and its application in reevaluation of inheritance of fertility restoration in onions

To reveal the linkage relationship between the Ms locus, a restorer-of-fertility gene for cytoplasmic male-sterility (CMS) caused by CMS-S cytoplasm in onion (Allium cepa L.) and previously reported molecular markers linked to the Ms locus, 11 recombinants selected from 4,273 segregating plants originating from the cross between male-sterile maternal and male-fertile paternal lines were analyzed. Results showed that genotypes of a codominant marker, jnurf12, were perfectly matched with the male-fertility phenotypes in all recombinants, but that this marker was not applicable in diverse breeding lines due to multiple band patterns. For the development of more reliable markers, a 12-bp indel was identified from the sequences which were obtained by genome walking, and was used to develop a simple PCR marker which was designated jnurf13. When 104 diverse breeding lines containing CMS-S cytoplasm were analyzed with the jnurf13 marker, male-fertility phenotypes of all breeding lines were perfectly matched with marker genotypes. To our surprise, phenotypes of 153 breeding lines containing CMS-T-like cytoplasm were also matched with genotypes of the jnurf13 marker which was linked to the Ms locus for the CMS-S system. Furthermore, phenotypes of four F₂ populations containing CMS-T-like cytoplasm co-segregated perfectly with jnurf13 genotypes. Allelic segregation distortion was detected in two F₂ populations using the jnurf13 maker. The results of this study were in conflict with a previous model for inheritance of fertility restoration in the CMS-T system. Therefore, we proposed a new model based on the data analyzed with the jnurf13 marker, which was in linkage disequilibrium with restorer-of-fertility genes for both CMS systems.     

Diversity and Distribution of Escherichia coli Genotypes and Antibiotic Resistance Phenotypes in Feces of Humans, Cattle, and Horses

Escherichia coli is the most completely characterized prokaryotic model organism and one of the dominant indicator organisms for food and water quality testing, yet comparatively little is known about the structure of E. coli populations in their various hosts. The diversities of E. coli populations isolated from the feces of three host species (human, cow, and horse) were compared by two subtyping methods: ribotyping (using HindIII) and antibiotic resistance analysis (ARA). The sampling effort required to obtain a representative sample differed by host species, as E. coli diversity was consistently greatest in horses, followed by cattle, and was lowest in humans. The diversity of antibiotic resistance patterns isolated from individuals was consistently greater than the diversity of ribotypes. E. coli populations in individuals sampled monthly, over a 7- to 8-month period, were highly variable in terms of both ribotypes and ARA phenotypes. In contrast, E. coli populations in cattle and humans were stable over an 8-h period. Following the cessation of antibiotic therapy, the E. coli population in the feces of one human experienced a rapid and substantial shift, from a multiply antibiotic-resistant phenotype associated with a particular ribotype to a relatively antibiotic-susceptible phenotype associated with a different ribotype. The high genetic diversity of E. coli populations, differences in diversity among hosts, and temporal variability all indicate complex population dynamics that influence the usefulness of E. coli as a water quality indicator and its use in microbial source tracking studies.     

Allozyme variation in a dimeric esterase of the oriental fruit fly,Dacus dorsalis (insecta: tephritidae), from peninsular malaysia

• 1.1. Seven natural populations of Dacus dorsalis were analyzed for a dimeric esterase by means of horizontal starch-gel electrophoresis.
• 2.2. The electrophoretic phenotypes were governed by nine codominant Est-D alleles.
• 3.3. The commonest allele in all seven population samples was Est-D¹⁰⁰ which encoded an electrophoretic band with intermediate mobility.
• 4.4. The distribution of EST-D phenotypes were in accordance with Hardy-Weinberg expectations.
• 5.5. There was no geographic variation in the distribution of Est-D alleles.

     

Genetic Variability of Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) Populations from Latin America Is Associated with Variations in Susceptibility to Bacillus thuringiensis Cry Toxins

Bacillus thuringiensis strains isolated from Latin American soil samples that showed toxicity against three Spodoptera frugiperda populations from different geographical areas (Mexico, Colombia, and Brazil) were characterized on the basis of their insecticidal activity, crystal morphology, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of parasporal crystals, plasmid profiles, and cry gene content. We found that the different S. frugiperda populations display different susceptibilities to the selected B. thuringiensis strains and also to pure preparations of Cry1B, Cry1C, and Cry1D toxins. Binding assays performed with pure toxin demonstrated that the differences in the toxin binding capacities of these insect populations correlated with the observed differences in susceptibility to the three Cry toxins analyzed. Finally, the genetic variability of the three insect populations was analyzed by random amplification of polymorphic DNA-PCR, which showed significant genetic diversity among the three S. frugiperda populations analyzed. The data presented here show that the genetic variability of S. frugiperda populations should be carefully considered in the development of insect pest control strategies, including the deployment of genetically modified maize in different geographical regions.     

Variability of Orobanche ramosa populations in France as revealed by cross infestations and molecular markers

The dramatic spread of root holoparasite Orobanche ramosa L. (branched broomrape) has been observed in the last few years in France in fields of Brassica napus L., Nicotiana tabacum L., and Cannabis sativa L. In the face of this occurrence and considering its tremendous capacity to adapt to its host, the question about variability of O. ramosa populations arises. The virulence of broomrape populations was investigated by cross infestations performed under greenhouse conditions using the three host species mentioned above and broomrape seeds collected from Orobanche plants parasitizing them. After 45 days of co-culture, the intensity and kinetics of infestation were determined. In all cases, parasites developed but differences were observed among associations between the host species and the broomrape population. Differences in virulence of O. ramosa populations and greater affinity between a host species and “its own” broomrape population were demonstrated by statistical analyses (F-test, CFAs). These results led to the concept of host specificity and suggestions about the existence of three different pathovars in O. ramosa. Analysis of genetic variability of the three O. ramosa populations by PCR of RAPD markers confirmed that they may be considered as three distinct pathovars.     

The molecular basis of mutations at the Waxy locus from Amaranthus caudatus L.: evolution of the waxy phenotype in three species of grain amaranth

Polymorphisms at the Waxy locus of Amaranthus caudatus L. collected from a wide range of regions were used to investigate genetic diversity and mutation sites. A comparison of the Waxy locus revealed a very high level of sequence conservation. This result clearly showed low environmental and evolutionary variability in the Waxy gene. We also performed screening to confirm the mutation sites in the coding sequences of all accessions. The results indicate that one insertion in the coding region of Waxy genes was responsible for the change in perisperm starch leading to the waxy phenotype in all accessions of this species, and thus that a single mutation event altered the regulation of the Waxy gene during the domestication of this crop. In addition, phylogenetic analysis showed that waxy phenotypes within each of three species, A. caudatus, A. cruentus and A. hypochondriacus, originated separately or differentiated from nonwaxy phenotypes of each species through a single mutational event (i.e., a frame shift or base substitution). We also compared obvious structural features of the coding sequence of waxy and nonwaxy phenotypes with those of low-amylose phenotypes in A. caudatus. The Waxy coding sequences of low-amylose phenotypes do not show polymorphisms and are identical with those of waxy phenotypes. This could mean that there is another gene that encodes a key enzyme responsible for amylose synthesis as the elementary quantity in tissues other than perisperm in A. caudatus.     

Biochemical and folk assessment of variability of andean cultivated potatoes

Isozyme markers were used to survey the genetic variability of non-bitter potatoes in 10 subsistence fields of Andean farmers at 3600-3850 m above sea level. Sixty-seven percent of the varieties were tetraploids corresponding to the speciesSolanum tuberosum ssp.andigena, 14% were triploids, probably corresponding to the speciesS. x chaucha, and 13% were diploids corresponding to the speciesS. stenotomum, S. phureja, andS. goniocalyx. The isozyme information served to determine the consistency of the folk naming system. We found a high degree of correspondence between farmer identification and electrophoretic phenotypes. The consistency of the folk system in electrophoretic terms depended on the farmer who was interviewed. The most common incongruity consisted of calling different electrophoretic phenotypes by the same variety name, leading to a slight underestimation of genetic variability present in the fields. The amount of variability observed in the sample of the Andean potato population was superior to that present in North American and European varieties. This was measured in terms of number ofalleles, number of electrophoretic phenotypes and percent of heterozygosity. This finding supports the impression that a substantial amount of yet unexploited variability remains in Andean potato populations.     

Extrinsic and intrinsic influences on the phylogeography of the Austrocochlea constricta species group

Although extrinsic factors, such as oceanic currents and isolation induced by sea level maxima during Plio-Pleistocene glacial cycles, are often suggested as principal determinants of marine phylogeography, they are not always complete explanations. The counterexamples to predominant phylogeographic patterns in southeastern Australia suggest for example, that intrinsic factors such a habitat preference or reproductive mode can have significant influence.We collected DNA sequences from mitochondrial cytochrome c oxidase I (COI) and two nuclear gene introns from the Austrocochlea constricta species group to determine whether its porcata and constricta phenotypes are genetically distinguishable, to examine the phylogeographic effects of the Bassian Isthmus landbridge formed between Tasmania and Victoria during glacial maxima, and to investigate the importance of intrinsic factors in structuring its genetic variability.No fixed genetic differences between the porcata and constricta phenotypes were identified in any gene so the number of species comprised by the group cannot yet be determined. The two major clades recovered in COI analyses were respectively found principally east or west of the Bassian Isthmus. A. constricta is the first lecithotrophic or estuarine invertebrate known to show this pattern. There were no fixed differences, for any of the three genes, between specimens from estuarine and marine populations within either the eastern or western COI clades. Other intrinsic factors such as breeding period (possibly) and larval type (probably) may play roles in modulating phylogeographic patterns.     

Variability of Meloidogyne exigua on Coffee in the Zona da Mata of Minas Gerais State,Brazil

Minas Gerais is the major coffee-producing state of Brazil, with 28% of its production coming from the region of Zona da Mata. Four major species of root-knot nematode attacking coffee (Meloidogyne incognita, M. paranaensis, M. coffeicola, and M. exigua) have been reported from Brazil. To determine the variability in Meloidogyne spp. occurring in that region, 57 populations from 20 localities were evaluated for morphological, enzymatic, and physiological characteristics. According to the perineal pattern, all the populations were identified as M. exigua; however populations from the municipality of São João do Manhuaçu exhibited patterns very similar to M. arenaria. The identity of all the populations was confirmed by the phenotypes of esterase, malate dehydrogenase, superoxide dismutase, and glutamate-oxaloacetate transaminase. Thirteen populations (22.8%) showed the typical one-band (E1) esterase phenotype, whereas the others (77.2%) had a novel two-band phenotype (E2). No intraspecies variability was found in any population. All populations were able to reproduce on tomato, pepper, beans, cacao, and soybean. Reproduction was greater on tomato and pepper than on coffee seedlings, the susceptible standard.     

Distribution of Pyrethroid Resistant Populations of Triatoma infestans in the Southern Cone of South America

BackgroundA number of studies published during the last 15 years showed the occurrence of insecticide resistance in Triatoma infestans populations. The different toxicological profiles and mechanisms of resistance to insecticides is due to a genetic base and environmental factors, being the insecticide selective pressure the best studied among the last factors. The studies on insecticide resistance on T. infestans did not consider the effect of environmental factors that may influence the distribution of resistance to pyrethroid insecticides. To fill this knowledge gap, the present study aims at studying the association between the spatial distribution of pyrethroid resistant populations of T. infestans and environmental variables.Conclusions/SignificanceThe occurrence of these two groups concentrated over a particular region that coincides with the area where populations of the intermediate cytogenetic group were found might reflect the spatial heterogeneity of the genetic variability of T. infestans, that seems to be the cause of the insecticide resistance in the area, even on sylvatic populations of T. infestans, never before exposed to pyrethroid insecticides, representing natural and wild toxicological phenotypes. The strong linear relationship found between LD₅₀ and RR₅₀ suggest RR₅₀ might not be the best indicator of insecticide resistance in triatomines.     

Genetic diversity, population structure, and differentiation of Siberian larch, Gmelin larch, and Cajander larch on SSR-marker data

The genetic diversity of SSR markers was studied in six populations of Siberian larch, two popu-lations of Gmelin larch, and four populations of Cajander larch. Seven pairs of nuclear microsatellite loci were used for this analysis. 103 allelic variants were detected in 365 individuals of three species of larch. According to the AMOVA results, the variability proportion that characterizes the differences between three Larix species was twice as higher (15%) than the proportion that accounts for among-population differences within the species (6%). The differentiation of the populations of three species of larch based on SSR markers exceeded 12% (F _ST = 0.121). A significant correlation of the genetic distances with the geographic distances between populations was found (r = 0.835, P = 0.01).     

Multiple alleles and low variability of glycerol-3-phosphate dehydrogenase in Aedes albopictus (Diptera: Culicidae) from Peninsular Malaysia

1. A total of 8 samples from three natural populations and a laboratory strain of Aedes albopictus were analysed for glycerol-3-phosphate dehydrogenase phenotypes by means of horizontal starch-gel electrophoresis. 2. The electrophoretic phenotypes were governed by three codominant Gpd alleles. 3. There was low variability, with the heterozygosity in the variable samples ranging from 0.02 to 0.12. 4. The commonest allele in all the population samples was GpdB which encoded an electrophoretic band with intermediate mobility. 5. There was no temporal or spatial variation.     

Genetic variation in small,isolated fern populations

Abstract. Differences in genetic variability of several small, isolated populations of four fern species in a restricted area in the Swiss lowlands reflect differences in breeding system, population size, the degree of population fragmentation, and ecological requirements. The investigated populations of Asplenium septentrionale show only little genetic variability (isozyme variation) without gene flow among populations (based on the banding pattern of multi-locus phenotypes), and they persist for long periods despite the small population sizes. In Asplenium ruta-muraria, genetic variability is correlated with age. Young populations show no genetic variation, while old populations show some. All individuals of Polypodium vulgare investigated, either epiphytic or epilithic, share exactly the same enzyme phenotype. The results for these three species can be related to predominance of inbreeding, lack of inbreeding depression, polyploidy, long-distance dispersal, production of large amounts of diaspores, single-spore colonization, and perennial life cycles. Genetic variability in these three species does not seem to be absolutely necessary for the maintenance of their populations. Ecological and demographic factors are considered to be more important. An isolated, glacial relict population of diploid Asplenium viride shows high variability in two out of eight enzyme systems, which may be due to prevailing outbreeding. We discuss aspects of the importance of genetics and life history for conservation biology.     

Signatures of adaptation and genetic structure among the mainland populations of Pinus radiata (D. Don) inferred from SNP loci

Insights into the relative contributions of locus specific and genome-wide effects on population genetic diversity can be gained through separation of their resulting genetic signals. Here we explore patterns of adaptive and neutral genetic diversity in the disjunct natural populations of Pinus radiata (D. Don) from mainland California. A first-generation common garden of 447 individuals revealed significant differentiation of wood phenotypes among populations (P _ST), possibly reflecting local adaptation in response to environment. We subsequently screened all trees for genetic diversity at 149 candidate gene single nucleotide polymorphism (SNP) loci for signatures of adaptation. Ten loci were identified as being possible targets of diversifying selection following F _ST outlier tests. Multivariate canonical correlation performed on a data set of 444 individuals identified significant covariance between environment, adaptive phenotypes and outlier SNP diversity, lending support to the case for local adaptation suggested from F _ST and P _ST tests. Covariation among discrete sets of outlier SNPs and adaptive phenotypes (inferred from multivariate loadings) with environment are supported by existing studies of candidate gene function and genotype–phenotype association. Canonical analyses failed to detect significant correlations between environment and 139 non-outlier SNP loci, which were applied to estimate neutral patterns of genetic differentiation among populations (F _ST 4.3 %). Using this data set, significant hierarchical structure was detected, indicating three populations on the mainland. The hierarchical relationships based on neutral SNP markers (and SSR) were in contrast with those inferred from putatively adaptive loci, potentially highlighting the independent action of selection and demography in shaping genetic structure in this species.