Allozyme Genotypes Research Articles

Ngāokeoke Aotearoa: The Peripatoides Onychophora of New Zealand.

(1) Background: Originally described as a single taxon, Peripatoides novaezealandiae (Hutton, 1876) are distributed across both main islands of New Zealand; the existence of multiple distinct lineages of live-bearing Onychophora across this spatial range has gradually emerged. Morphological conservatism obscured the true endemic diversity, and the inclusion of molecular tools has been instrumental in revealing these cryptic taxa. (2) Methods: Here, we review the diversity of the ovoviviparous Onychophora of New Zealand through a re-analysis of allozyme genotype data, mitochondrial DNA cytochrome oxidase subunit I sequences, geographic information and morphology. (3) Results: New analysis of the multilocus biallelic nuclear data using methods that do not require a priori assumptions of population assignment support at least six lineages of ovoviviparous Peripatoides in northern New Zealand, and mtDNA sequence variation is consistent with these divisions. Expansion of mitochondrial DNA sequence data, including representation of all existing taxa and additional populations extends our knowledge of the scale of sympatry among taxa and shows that three other lineages from southern South Island can be added to the Peripatoides list, and names are proposed here. In total, 10 species of Peripatoides can be recognised with current data.

Footprints of natural selection at the mannose-6-phosphate isomerase locus in barnacles

The mannose-6-phosphate isomerase (Mpi) locus in Semibalanus balanoides has been studied as a candidate gene for balancing selection for more than two decades. Previous work has shown that Mpi allozyme genotypes (fast and slow) have different frequencies across Atlantic intertidal zones due to selection on postsettlement survival (i.e., allele zonation). We present the complete gene sequence of the Mpi locus and quantify nucleotide polymorphism in S. balanoides, as well as divergence to its sister taxon Semibalanus cariosus We show that the slow allozyme contains a derived charge-altering amino acid polymorphism, and both allozyme classes correspond to two haplogroups with multiple internal haplotypes. The locus shows several footprints of balancing selection around the fast/slow site: an enrichment of positive Tajima's D for nonsynonymous mutations, an excess of polymorphism, and a spike in the levels of silent polymorphism relative to silent divergence, as well as a site frequency spectrum enriched for midfrequency mutations. We observe other departures from neutrality across the locus in both coding and noncoding regions. These include a nonsynonymous trans-species polymorphism and a recent mutation under selection within the fast haplogroup. The latter suggests ongoing allelic replacement of functionally relevant amino acid variants. Moreover, predicted models of Mpi protein structure provide insight into the functional significance of the putatively selected amino acid polymorphisms. While footprints of selection are widespread across the range of S. balanoides, our data show that intertidal zonation patterns are variable across both spatial and temporal scales. These data provide further evidence for heterogeneous selection on Mpi.

Genotypic and phenotypic characterization of Phytophthora infestans populations from potato in Turkey

Late blight disease caused by Phytophthora infestans is an important yield reducing, prolific, and destructive pathogen of Solanaceae family members, mainly tomato and potato. P. infestans may cause entire crop loss unless controlled by chemical and cultural control measures. The Cukurova region of Turkey is one of the main potato-producing areas of Turkey and climatic conditions incite P. infestans to develop and cause severe yield losses in the region. A total of 186 isolates of P. infestans were obtained through survey studies conducted during the 2013–2014 potato-growing seasons in the Cukurova region comprised of Hatay, Adana and Mersin provinces in Turkey. All the isolates were analyzed for their metalaxyl resistance, mating type, mitochondrial DNA (mtDNA) haplotype and allozyme genotype diversity. P. infestans isolates were metalaxyl sensitive and both mating types were found in the potato-growing areas of the Cukurova region. The A1 mating type was more common (68.8%) than A2 (22.5%) and 8.6% of the P. infestans isolates were self-compatible. mtDNA haplotypes were diverse in the region and Ia was the most common type. Allozyme analyses revealed that the US-1 (Gpi 86/100) and US-6 (Gpi 100/100) patterns were prevalent in the potato-growing areas of the Cukurova region. This study contains the first data on molecular and biochemical characterization of potato late blight in Turkey.

First Report of Late Blight Caused by Phytophthora infestans Clonal Lineage US-23 on Potato in Idaho.

Late blight, caused by Phytophthora infestans (Mont.) de Bary, is a destructive disease of potato (Solanum tuberosum) and tomato (S. lycopersicum) in the United States. Prior to 2007, the US-8 clonal lineage was the predominant genotype in the United States (4). Since 2007, a significant genetic change in the population of P. infestans occurred in the eastern United States with the appearance of new isolates with unique genotypes and epidemiological characteristics (3). These new genotypes US-22, US-23, and US-24 are sensitive to metalaxyl and represent mating types A2, A1, and A1, respectively (1,2). Prior to 2012, only US-8 had been documented in Idaho (5). In 2013, late blight was discovered in late August on potato crops (cv. Russet Norkotah) in Bingham and Madison counties, ID. Infected foliage (four samples from Bingham County and five from Madison) was sent to Michigan State University and the University of Wisconsin for confirmation of P. infestans and characterization of the isolates. Five sections from the leading edge of lesions were excised with a sterilized scalpel and placed on potato tuber slices ('Dark Red Norkotah'). Pathogen sporulation on the excised lesions was enhanced by incubation in plastic boxes lined with moistened paper towels for 5 days at 18°C in the dark. The sporulating lesions were transferred onto pea agar medium (160 g peas, 5 g sucrose, 15 g agar, 700 ml distilled water) amended with 50 mg/ml vancomycin. Ten pure cultures were obtained for each of 4 isolates per county by hyphal tipping. Cellulose acetate electrophoresis was conducted to determine Gpi allozyme genotype of the 4 isolates (4). The allozyme banding patterns were 100/100 at the Gpi locus, consistent with previously reported analyses of the US-23 genotype (1,2). Genomic DNA was extracted from 10 pure cultures using the DNeasy Plant Mini Kit (Qiagen, Germantown, MD), and SSR analyses were performed. Microsatellite markers Pi02, Pi4B, Pi63, PiG11, and D13 were used in SSR analyses. Pi02, Pi4B, and Pi63 had alleles of 162/164, 213/217, and 270/279 bp in size, respectively which is consistent with the reference US-23 genotype (1). However, heterozygosity was detected at locus D13 in the Idaho genotype with allele size of 134/210 bp and an additional allele of 140/155/176 bp at locus PiG11. This is different from the standard US-23 genotype (homozygous alleles 134/134 at locus D13 and two alleles 140/155 at locus PiG11). These allele changes indicate the isolates may be variants of US-23 isolates as all other phenotypic characteristics were similar to those of reference US-23 isolates. The Idaho genotypes were sensitive to metalaxyl both in vitro on rye A agar medium amended with metalaxyl at <0.1 ppm, and in vivo on Ridomil treated foliage tests at <0.1 ppm (1,2). Mating type assays confirmed the pathogen to be the A1 mating type. In the 2009 and 2010 late blight epidemics in the eastern United States, US-23 was the predominant genotype, but to our knowledge this genotype has never been reported previously in Idaho. Thus, this is the first known report of P. infestans genotype US-23 causing late blight on potato in Idaho, indicating a change in the population of P. infestans. In Idaho, the source of this genotype remains unknown, although infected tomatoes have been implicated in the widespread dissemination of this genotype of P. infestans in the eastern United States.

Are Different Allozyme Genotypes of the ButterflyPolyommatus coridonAdapted to Resist Cold and Heat Shocks?

Polymorphisms are widely known in allozymes and are often assumed neutral in the context of phylogenetic and population genetic analyses. However, several studies revealed that, in some loci and species, selection is strongly acting on allozymes and that temperature seems to be an important selective agent. Therefore, we individually determined the recovery time from chill-coma and heat knock-down time of 542 individuals of P. coridon sampled at four sites. Afterwards, we analyzed patterns of allozyme variations in these butterflies by allozyme electrophoresis of eleven loci to test the enzymes' performance under thermal stress conditions and to investigate the possibility of adaptive genotypic variation in relation to temperature stress resistance traits. We obtained significant differences of reactions to cold and heat shocks between the sexes and between reared and wild-captured individuals, but no significant differences among genotypes were found for most of the investigated allozyme loci. However, the Aat1 locus showed significant differences between different genotypes in chill-coma recovery times (p < 0.001), and marginal differences in heat knock-down times (p = 0.073). Thus, Aat1 might be a target for thermal selection. Consequently, our results revealed no clear influence of temperature on most allozyme loci and the otherwise observed differentiation in P. coridon might be explained by stochasticity, and thus geographic structuring should reflect biogeographic processes.

Genetic structure of the continuous and ephemeral populations of the land snail Brephulopsis Cylindrica (Gastropoda; Pulmonata; Enidae)

Background. One may hypothesize that the land snail B. cylindrica distributed in small, isolated, ephemeral populations tends to decrease genetic polymorphism level (e. g., observed heterozygosity for allozyme loci). Thus, the present study aims at estimating the levels of allozyme polymorphism in the land snail B. cylindrica from continuously distributed populations and ephemeral ones. Materials and methods. In the Nikolaev urbanised areas 9 samples were taken and studied electrophoretically for four polymorphic allozyme system. In the Dubki, Neftebasa and Park Pobedy populations (continuously distributed populations - group N 1) the two localities, situated about 50 m apart, were sampled. While only single locality were investigated from the Kosmos, Morechodnaya and Mira populations (ephemeral populations - group N 2). Statistical analysis of electrophoretic data was performed with the program GenAIEx version 6.0. Results. In general, significant differences with respect to the level of genetic polymorphism between the continuous and ephemeral populations of the land snail B. cylindrical have not discovered on the basis of allozymes loci. However, when analyzing the distribution of multilocus allozyme genotypes in the populations studied, we have received fundamentally different results. In general, ephemeral populations differed from the continuous ones with respect to the frequency of studied multilocus allozyme genotypes although one populations has been disrupted this rule (Dubki-2). Conclusion. Based on these results it is concluded that small, isolated (including, urban) populations tend to reduce the level of genetic diversity, due to the manifestation of genetic and stochastic processes (genetic drift or founder effect). In addition, an important consequence of the latter there is a relatively high rate of unpredictable change genotypic profiles of such settlements, which leads to a significant increase in the level of genetic differentiation between them.

Patterns of genetic variation in Pilosella echioides and its selected relatives: results of variation in ploidy level, facultative apomixis and past and present hybridization

We used allozymes to elucidate the genetic variation of Pilosella echioides and P. rothiana in the Pannonian Basin and its relationship with morphology and modes of reproduction. The former species consists of sexual diploid, apomictic tetraploid, and very rare sexual tetraploid populations; the latter is exclusively tetraploid and apomictic. As expected, we detected the highest intra-population variation in diploid populations of P. echioides. Nonetheless, 73 % of populations of tetraploid P. echioides and 64 % of P. rothiana consisted of 2–7 multilocus allozyme genotypes, the means being 5.75 in P. echioides and 2.64 in P. rothiana. Both the proportion of distinguishable genotypes (G/N) per population and genotype diversity (D) per population significantly differed between diploid P. echioides (means 0.415 and 0.828, respectively) on the one hand and tetraploid P. echioides (means 0.252 and 0.387, respectively) and P. rothiana (means 0.213 and 0.347, respectively) on the other. Rather surprisingly, we found an excess of homozygotes (positive F IS) in diploids, which indicates inbreeding. Tetraploids of P. echioides have most likely originated from only a few polyploidization events and have spread thanks to agamospermy—at least populations from the NW part of the area under study seem to be monophyletic. Genetic differences within the putatively hybridogeneous species P. rothiana are small. It seems plausible that it has a common origin and that it spreads independently of its parents (P. echioides and P. officinarum). A certain level of genetic diversity can be caused by residual sexuality or less likely by repeated polytopic hybridization between P. echioides and P. officinarum. Pilosella sterrochaetia is reported here from Hungary for the first time. It is an extremely rare primary diploid hybrid between diploid P. echioides and P. leucopsilon. Its intermediate nuclear genome size also confirms its hybrid origin.

The effect of bird and bee visitation on pollination and reproductive success in Phormium tenax

To study how pollinator composition and abundance influence reproduction of Phormium tenax, we compared pollen deposition by bees and birds to unvisited flowers, and plant reproductive success and outcrossing rates in populations on island and mainland sites that vary in bird abundance. Bees deposited pollen on stigmas if stigmas were close to the anthers but deposited little pollen on stigmas of emasculated flowers, suggesting that they are largely depositing self pollen. Birds deposit pollen on both intact and emasculated flowers with well-exserted stigmas, suggesting they are depositing more outcross pollen. High frequencies of bird claw marks on inflorescences were associated with high fruit set, but not seed set. Seed set and seed outcrossing rates were positively correlated with the number of unique maternal allozyme genotypes in a population and seedlings also showed higher outcrossing rates than seeds, suggesting that genetic diversity, selfing and inbreeding depression limit reproductive success. These results highlight the interplay of pollination and breeding systems in determining plant reproductive success.

Can Soil Seed Banks Serve as Genetic Memory? A Study of Three Species with Contrasting Life History Strategies

We attempted to confirm that seed banks can be viewed as an important genetic reservoir by testing the hypothesis that standing (aboveground) plants represent a nonrandom sample of the seed bank. We sampled multilocus allozyme genotypes from three species with different life history strategies: Amaranthus retroflexus, Carduus acanthoides, Pastinaca sativa. In four populations of each species we analysed the extent to which allele and genotype frequencies vary in consecutive life history stages including the summer seed bank, which has been overlooked up to now. We compared the winter seed bank (i.e., seeds collected before the spring germination peak), seedlings, rosettes, the summer seed bank (i.e., seeds collected after the spring germination peak) and fruiting plants. We found that: (1) All three species partitioned most of their genetic diversity within life history stages and less among stages within populations and among populations. (2) All genetic diversity parameters, except for allele frequencies, were similar among all life history stages across all populations in different species. (3) There were differences in allele frequencies among life history stages at all localities in Amaranthus retroflexus and at three localities in both Carduus acanthoides and Pastinaca sativa. (4) Allele frequencies did not differ between the winter and summer seed bank in most Carduus acanthoides and Pastinaca sativa populations, but there was a marked difference in Amaranthus retroflexus. In conclusion, we have shown that the summer seed bank is not genetically depleted by spring germination and that a majority of genetic diversity remains in the soil through summer. We suggest that seed banks in the species investigated play an important role by maintaining genetic diversity sufficient for recovery rather than by accumulating new genetic diversity at each locality.

Re-emergence of the Ib mitochondrial haplotype within the British and Irish Phytophthora infestans populations

Since its arrival in the British Isles in 1845 Phytophthora infestans has remained the most destructive pathogen of potato. In the ensuing period, the British and Irish P. infestans populations have undergone major displacements following the immigration of novel strains. Here we report the re-emergence of the Ib mitochondrial DNA haplotype in the British and Irish P. infestans populations associated with the 6_A1 genotype. Historically associated with the previously panglobally distributed clonal lineage US-1, the Ib haplotype has not been detected (with the exception of a single isolate in the mid 1990s) in the British or Irish P. infestans populations since the early 1980s. The 6_A1 isolates analysed possessed mtDNA Ib, but were otherwise quite unlike US-1, having the Pep allozyme genotype 96/96 and novel RG57 and SSR fingerprints. These genetic characteristics strongly suggest that the appearance of the 6_A1 genotype in these populations has resulted from migration (possibly after a recombination event elsewhere). This study highlights the advantages of utilising a range of different markers in pathogen monitoring.

Phosphoglucose isomerase genotype effects on life history depend on latitude and food stress

Summary1.Phosphoglucose isomerase (Pgi) genotypes differ in life‐history traits and shifts in their frequencies are thought to contribute to latitudinal gradients in life history. Yet, it is unstudied whether the life‐history effects of Pgi are invariant across latitudes. Further, while genetic variation at the Pgi locus is thought to be maintained by genotype‐by‐environment interactions and by life‐history trade‐offs involving resource allocation, the effects of food stress on Pgi genotype effects are largely unstudied.2.We compared Pgi allozyme genotype effects on life history between northern and southern populations of the damselfly Ischnura elegans in a common garden experiment where we manipulated food stress.3.Pgi genotypes differed in larval development time and body mass, but neither in larval growth rates nor in adult life span.4.The effect of the Pgi genotype on larval development time differed between latitudes, suggesting interactions with the latitude‐specific genetic background and/or maternal effects. Pgi genotype effects on both development time and body mass were dependent on food stress and indicated a trade‐off between both fitness‐related traits associated with the Pgi gene.5.The newly identified interaction between the Pgi genotype and latitude, the poorly studied Pgi genotype‐by‐food stress interactions and the observed life‐history trade‐offs associated with the Pgi genotypes can all potentially contribute to maintaining genetic variation at the Pgi locus and to latitudinal patterns in life history. Both types of interactions may also explain the poorly understood differences in the Pgi genotype effects on life history among studies of the same species.

Genetic Relationships among Populations of Florida Bass

AbstractFlorida bass Micropterus floridanus are endemic to peninsular Florida and co‐occur with largemouth bass M. salmoides in a natural intergrade zone in the northern portions of the state. In this study, we resolved the genetic population structure among populations of largemouth bass, Florida bass, and their interspecific hybrids from 48 lakes and streams across Florida, and we updated and refined the southernmost boundary of introgression. Nuclear (allozyme and microsatellite) and mitochondrial (restriction fragment length polymorphism) markers produced somewhat different results. Microsatellite genotypes alone and the combination of all nuclear genotypes resolved genetic structure among four regional groups within Florida: (1) northwest, (2) north‐central, (3) central‐west, and (4) south, central‐east, and northeast. Allozyme genotypes alone did not resolve well‐defined groups. The distribution of mitochondrial haplotypes suggested that populations from the St. Johns River drainage should be considered their own distinct group (rather than be included in the south—central‐east—northeast Florida group). Although mitochondrial markers failed to detect introgression throughout much of the intergrade zone, nuclear markers revealed an expected decline in introgression from west to east as well as from north to south. Largemouth bass alleles, however, were detected at low frequencies in 12 populations below the southern boundary of the accepted intergrade zone, some of which are the result of stocking. There was no evidence of nonrandom mating or selection against hybrids in the distribution of nuclear genotypes; however, the rarity of largemouth bass mitochondrial haplotypes suggests either assortative mating or reduced fitness in the progeny of female largemouth bass × male Florida bass crosses.

Genetic Structure of Phytophthora infestans Populations in China Indicates Multiple Migration Events

One hundred isolates of Phytophthora infestans collected from 10 provinces in China between 1998 and 2004 were analyzed for mating type, metalaxyl resistance, mitochondrial DNA (mtDNA) haplotype, allozyme genotype, and restriction fragment length polymorphism (RFLP) with the RG-57 probe. In addition, herbarium samples collected in China, Russia, Australia, and other Asian countries were also typed for mtDNA haplotype. The Ia haplotype was found during the first outbreaks of the disease in China (1938 and 1940), Japan (1901, 1930, and 1931), India (1913), Peninsular Malaysia (1950), Nepal (1954), The Philippines (1910), Australia (1917), Russia (1917), and Latvia (1935). In contrast, the Ib haplotype was found after 1950 in China on both potato and tomato (1952, 1954, 1956, and 1982) and in India (1968 and 1974). Another migration of a genotype found in Siberia called SIB-1 (Glucose-6-phosphate isomerase [Gpi] 100/100, Peptidase [Pep] 100/100, IIa mtDNA haplotype) was identified using RFLP fingerprints among 72% of the isolates and was widely distributed in the north and south of China and has also been reported in Japan. A new genotype named CN-11 (Gpi 100/111, Pep 100/100, IIb mtDNA haplotype), found only in the south of China, and two additional genotypes (Gpi 100/100, Pep 100/100, Ia mtDNA haplotype) named CN-9 and CN-10 were identified. There were more diverse genotypes among isolates from Yunnan province than elsewhere. The SIB-1 (IIa) genotype is identical to those from Siberia, suggesting later migration of this genotype from either Russia or Japan into China. The widespread predominance of SIB-1 suggests that this genotype has enhanced fitness compared with other genotypes found. Movement of the pathogen into China via infected seed from several sources most likely accounts for the distribution of pathogen genotypes observed. MtDNA haplotype evidence and RFLP data suggest multiple migrations of the pathogen into China after the initial introduction of the Ia haplotype in the 1930s.

Nucleotide Polymorphism at a Gene (Pgi) under Balancing Selection in a Butterfly Metapopulation

The Glanville fritillary butterfly (Melitaea cinxia, Nymphalidae) has a large, well-studied metapopulation in the Aland Islands in Finland. Previous studies have found that the common allozyme genotypes at the phosphoglucose isomerase (PGI) locus are associated with individual variation in performance and fitness, with phenotypic data suggesting ongoing balancing selection via heterozygote advantage. Here, we analyze nucleotide polymorphism in the coding region of the Pgi gene. Pgi is exceptionally polymorphic, in contrast to three other metabolic genes (Mdh, Idh, and Gapdh) with low levels of polymorphism. Most of the variation is due to two common haplotype clades, which are highly divergent and exhibit extensive linkage disequilibrium. These two clades correspond to the two most common allozyme alleles previously studied. Molecular tests of selection and coalescence simulations indicate that patterns of nucleotide polymorphism depart from neutrality and are consistent with long-term balancing selection. The split between the two main haplotype clades is estimated to predate the last common ancestor of a clade of five extant Melitaea species. Comparative structural analysis of Pgi polymorphism in M. cinxia and the unrelated Colias eurytheme butterfly suggests a similar but not identical target of balancing selection. Our results indicate convergent evolution between these two species at both the phenotypic and molecular levels.

Characterization of Phytophthora infestans Isolates from Jersey, Channel Islands

Potato production on the island of Jersey, in the English Channel, is dominated by Jersey Royal, a selection of the early cultivar International Kidney. Jersey Royal is very susceptible to Phytophthora infestans, the cause of potato late blight, and Jersey’s climate is frequently conducive to infection. During 2004–2006, isolates of P. infestans were obtained from Jersey Royal plant samples from 41 different sites (24 crops, one infected tuber, 16 volunteers) and from five outdoor tomato crops and characterised by mating type, mtDNA haplotype, Gpi and Pep allozyme genotype, metalaxyl resistance and RG57 fingerprint. A subset of 17 isolates was additionally characterised by simple sequence repeat (SSR). All but one isolate from potato belonged to a single A1 multilocus genotype or a variant. The five isolates from tomato represented three distinct genotypes, none of which was found on potato and included one which was A2 mating type. The populations of P. infestans on potato and tomato in Jersey appear distinct, with that on potato being highly clonal.

Testing for local adaptation in Avena barbata: a classic example of ecotypic divergence

Forty years ago, Robert Allard and colleagues documented that the slender wild oat, Avena barbata, occurred in California as two multi-locus allozyme genotypes, associated with mesic and xeric habitats. This is arguably the first example of ecotypes identified by molecular techniques. Despite widespread citation, however, the inference of local adaptation of these ecotypes rested primarily on the allozyme pattern. This study tests for local adaptation of these ecotypes using reciprocal transplant and quantitative trait locus (QTL) mapping techniques. Both ecotypes and 188 recombinant inbred lines (RILs) derived from a cross between them were grown in common garden plots established at two sites representative of the environments in which the ecotypes were first described. Across four growing seasons at each site, three observations consistently emerged. First, despite significant genotype by environment interaction, the mesic ecotype consistently showed higher lifetime reproductive success across all years and sites. Second, the RILs showed no evidence of a trade-off in performance across sites or years, and fitness was positively correlated across environments. Third, at QTL affecting lifetime reproductive success, selection favoured the same allele in all environments. None of these observations are consistent with local adaptation but suggest that a single genotype is selectively favoured at both moist and dry sites. I propose an alternative hypothesis that A. barbata may be an example of contemporary evolution--whereby the favoured genotype is spreading and increasing in frequency--rather than local adaptation.

Different survival of chromium-exposed Oxya chinensis among allozyme genotypes

The goal of the present study was to compare the different survival of Oxya chinensis exposed to chromium(VI) among allozyme genotypes to gain a better understanding of the relationship between the genetic variations and environmental disturbance. This study analyzed the occurrence of genotypes in O. chinensis population exposed to Cr(VI). O. chinensis samples were collected at Yuanping, Shanxi Province, China and used in acute toxicity tests. Specimens were assigned to Cr(VI) exposure (LD50: 291.0 mg/kg) for 24 h. The genetic composition of both dead and survived specimens was analyzed with horizontal starch gel electrophoresis in four enzymes (GPI, PGM, LDH, and ME). The results indicated that under Cr(VI) exposure, specimens with different genotypes had various mortalities at the four loci in laboratory conditions, and there was a genetic basis for tolerance in O. chinensis during acute exposure to Cr(VI).

Mating behaviour as a fitness component involved in maintaining allozyme polymorphism in Drosophila melanogaster. III. The amount of variation among allozyme genotypes in the Est-6 and Lap-A allozyme systems.

The components of phenotypic variation for mating activity, fertility and egg-adult viability were estimated in the leucine aminopeptidase-A and esterase-6 allozyme systems in Drosophila melanogaster. It was shown that variation among separate genotypes of these enzyme systems contributed considerably to the total phenotypic variation. For mating activity and fertility, 24% and 12% respectively of the total phenotypic variation was attributed to differences among allozyme genotypes, whereas for viability this component only amounted to 4%.

First Report of the A2 Mating Type of Phytophthora infestans on Tomato Crops in Taiwan, Republic of China

In a study of the Phytophthora infestans population in Taiwan, samples with symptoms typical of late blight were collected from field crops in an important potato- (Solanum tuberosum) and tomato-(Lycopersicon esculentum) production area in the central highlands region. Isolates were obtained by surface disinfecting leaf sections and plating them onto antibiotic-amended rye A agar (1). After subculturing, the pathogen was confirmed as P. infestans on the basis of morphological characters (2). Mating type was determined by co-inoculating unamended rye agar plates with mycelial plugs of the test isolate and a reference P. infestans isolate of either the A1 or A2 mating type (four plates per test isolate, two with different A1, and two with different A2 reference isolates). After incubation (15°C darkness, 7 to 14 days), plates were examined microscopically for the presence of oospores where the colonies interacted. In 2004, one isolate of 200 tested, and in 2006, one isolate of 102 tested, produced oospores only with A1 reference isolates and were concluded to be A2 mating type. In vitro testing showed the two A2 isolates were metalaxyl-resistant (ED50 values >100 mg of metalaxyl per liter on rye grain agar), which is typical of recent P. infestans isolates from potato and tomato in this area (2). Twenty-one single-sporangial isolates from each of the two A2 strains were tested for mating type against two different A1 isolates of P. infestans and confirmed as A2. These isolates were characterized using the techniques described by Deahl et al. (1) and had the allozyme genotype 100/100/111, 100/100 at the loci coding for glucose-6-phosphate isomerase and peptidase, respectively, and were mitochondrial haplotype IIb. This multi-locus genotype is characteristic of recent P. infestans isolates from tomato and potato in Taiwan, but all previous such isolates were A1 mating type and attributed to the US-11 clonal lineage (1). When evaluated on differential hosts, both A2 isolates were tomato race PH-1 and complex potato race R 0,1,2,3,4,7,9,11. RG57 fingerprinting showed that the A2 isolates had fingerprints identical to each other and to A1 P. infestans isolates of the US-11 clonal lineage from tomato in Taiwan (101 011 100 100 110 101 011 001 1). Koch's postulates were completed and the two A2 isolates were found to be highly aggressive on cultivars of potato and tomato. To our knowledge, this is the first report of A2 mating type strains of P. infestans in the field in Taiwan, but currently, their incidence is very low (<1%). One crop from which an A2 isolate was obtained also yielded an A1 isolate, while A1 isolates were obtained from crops in the vicinity of the other. The concurrent presence of the two mating types of P. infestans poses a risk of sexual reproduction and oospore formation in tomato or potato in Taiwan.

Population genetic structure and mating system in the hybrid zone between Pinus sibirica Du Tour and P. pumila (Pall.) Regel at the Eastern Baikal Lake shore

Genetic structure of sympatric Pinus sibirica Du Tour and P. pumila (Pall.) Regel populations and putative interspecific hybrids between them was analyzed in the Baikal Lake region (Barguzin Biosphere Natural Reserve, Davsha River basin) by means of 31 allozyme loci controlling 18 enzyme systems. Several alleles at loci Adh-1, Fest-2, Lap-3, Pgi-1, Sod-3 and Skdh-1 were diagnostic for P. sibirica, while alleles typical for P. pumila were detected at loci Gdh, Got-3, Lap-3, Mdh-2, Mdh-4, Pepca, Pgi-1, Pgd-2, Pgd-3, Pgm-1 and Pgm-2. All hybrids were heterozygous for the diagnostic Skdh-2 locus. Classification into hybrids and parental species using PCA analysis of multilocus allozyme genotypes had good correspondence with diagnoses made by morphological and anatomical analyses. Approximately 27% of embryos in P. pumila seeds had P. sibirica paternal contribution, and 8% of haplotypes in effective pollen pool combined alleles typical for P. pumila and P. sibirica, and therefore were classified as pollinated by the hybrids. About 83% of embryos in seeds from the hybrids most likely originated from fertilization by P. sibirica pollen, 14% from P. pumila and 3% from hybrid trees. This result favours the view that hybrids make both male and female contributions to the reproductive output of the population and confirm the presence of backcrosses and F2 hybrids.