Small Number Of Genotypes Research Articles

Effects of thiophanate-methyl and azoxystrobin on the composition of Cercospora kikuchii populations with thiophanate-methyl-resistant strains

Azoxystrobin was recently registered in Japan for the control of purple seed stain of soybean caused by Cercospora kikuchii, because the pathogen has developed resistance to thiophanate-methyl. To investigate the effects of these fungicides on the frequency of C. kikuchii strains resistant to thiophanate-methyl and on the genotype structure of the population, we sowed purple-stained seeds, approximately 40% of which were infected with resistant strains, as inocula with asymptomatic seeds and applied thiophanate-methyl and azoxystrobin during the reproductive growth of soybeans. The isolation frequency of resistant strains increased more than 99% by thiophanate-methyl but was not significantly increased by azoxystrobin. In amplified fragment length polymorphism (AFLP) DNA fingerprinting, genotypic diversity was significantly decreased by thiophanate-methyl but was not affected by azoxystrobin. In addition, the similarity of the AFLP genotype structure was increased by thiophanate-methyl but not by azoxystrobin. These results suggest that thiophanate-methyl selectively inhibited the proliferation of sensitive strains, which resulted in a small number of genotypes, most of which were resistant strains. Azoxystrobin was found to nonselectively inhibit proliferation of the pathogen, which retained a large number of genotypes including thiophanate-methyl-sensitive or thiophanate-methyl-resistant strains or both.

Epidemiology and natural history of Gaucher's disease

Gaucher's disease was first described by Philippe Gaucher in 1882, who recognized that this was a systemic disease. The biochemical defect, genetic basis and molecular epidemiology have subsequently been characterized. Gaucher's disease arises as a result of a deficiency of glucocerebrosidase and is the commonest of the lysosomal storage disorders. The overall incidence is approximately 1:40,000 individuals, but it is much commoner amongst individuals of Ashkenazi Jewish origin. A small number of genotypes are characteristically encountered amongst this population and the commonest of these (N370S) encodes an enzyme that has sufficient residual enzyme activity to ensure that significant neurologic disease does not occur. The main clinical features of adult Gaucher's disease are organ enlargement (liver and spleen), bone marrow infiltration leading to anaemia, thrombocytopenia and leucopenia, and skeletal involvement leading to bone pain and pathological fracture. There is also an association with Parkinson's disease, cancer and lymphoproliferative disease, illustrating that Gaucher's disease is a multi-system disorder with manifestations in most organ systems. The underlying pathophysiology is imperfectly understood, but it is increasingly clear that inflammation mediated by cytokines is responsible for a significant part of the pathology.

Pigments in the Fruit of Red-Fleshed Kiwifruit (Actinidia chinensis and Actinidia deliciosa)

Kiwifruit cultivars (Actinidia chinensis and A. deliciosa) generally have fruit with yellow or green flesh when ripe. A small number of genotypes also have red pigments, usually restricted to the inner pericarp but varying in intensity and in distribution within the fruit. Carotenoids, chorophylls, and anthocyanins were extracted from the fruit pericarp of such red-fleshed kiwifruit selections. Pigments were analyzed by HPLC and identified by comparison with authentic standards and by liquid chromatography-mass spectroscopy to obtain a tentative identification of the major anthocyanins in red-fleshed kiwifruit. The yellow and green colors of the outer fruit pericarp are due to different concentrations and proportions of carotenoids and chlorophylls. The red color found mainly in the inner pericarp is due to anthocyanins. In the A. chinensis genotypes tested the major anthocyanin was cyanidin 3-O-xylo(1-2)-galactoside, with smaller amounts of cyanidin 3-O-galactoside. In the A. deliciosa genotypes analyzed, cyanidin 3-O-xylo(1-2)-galactoside was not detected; instead, the major anthocyanins identified were cyanidin 3-O-galactoside and cyanidin 3-O-glucoside. However, the two species did not differ consistently in anthocyanin composition.

Assessing the genetic structure of three Japanese flounder ( Paralichthys olivaceus) stocks by microsatellite markers

Ten highly variable microsatellite loci were used to investigate one common population and two selected hatchery populations of Japanese flounder Paralichthys olivaceus. All of the 10 microsatellite loci screened in this study showed marked polymorphism. A total of 76 different alleles were observed over all loci. The number of alleles per locus ranged from 3.67 to 8.67. The average of observed (Ho) and expected heterozygosity (He) ranged from 0.610 to 1.000, and from 0.536 to 0.821, respectively. A total of 14 unique alleles were found in common population, and 3 unique alleles each were found in susceptible and resistant populations. The effective number of alleles varied from 2.14 for Po35 to 5.60 for Po91. The number of genotypes ranged from 5.33 for Po56 to 12.33 for Po1. Compared with the common population, the two selected hatchery populations, susceptible and resistant, showed significant genetic changes such as fewer alleles per locus, a smaller number of low-frequency alleles, and a small number of unique alleles and a small number of genotypes, all indicative of a reduction in genetic diversity. Intentional or accidental release of selected Japanese flounders into natural sea areas might result in disturbance of local gene pools and loss of genetic variability. So, it is needed to monitor genetic variability of selected hatchery populations for the conservation of natural Japanese flounder resources.

Transgenic Pinus radiata from Agrobacterium tumefaciens-mediated transformation of cotyledons.

A method for Agrobacterium tumefaciens-mediated transformation of Pinus radiata cotyledon explants was developed using commercially available open-pollinated seed. Pinus radiata is the most widely planted commercial conifer species in the Southern Hemisphere. Reports on transformation of this species have relied on particle bombardment of embryogenic callus derived from immature embryos. The main drawback to the method is the small number of genotypes that are amenable to transformation and regeneration. Since more than 80% of genotypes of radiata pine can be regenerated using cotyledons from mature seed, cotyledon explants were cocultivated with A. tumefaciens strain AGL1 containing a plasmid coding for the neomycin phosphotransferase II (nptII) gene and the beta-glucuronidase (GUS) gene (uidA). Transformed shoots were selected using either geneticin or kanamycin. Critical factors for successful transformation were survival of the cotyledons after cocultivation and selection parameters. Of the 105 putative transformants that were recovered from selection media, 70% were positive for integration of the nptII gene when analysed by PCR. GUS histochemical assay for uidA expression was unreliable because of reaction inhibition by unidentified compounds in the pine needles. Further, only 4 of the 26 independent transformants characterised by PCR and Southern analysis contained an intact copy of both genes. The remaining 22 transformants appeared to have a truncated or rearranged copy of the T-DNA. It is possible that the truncation/rearrangements are due to the Cauliflower mosaic virus (CaMV) 35S promoter. Analysis of the T-DNA junction sites and sequencing of the introduced DNA will help elucidate the nature of T-DNA insertion so that genetic modification of radiata pine can be targeted effectively.

Scale-free networks in evolution

In this paper we address the emergence of scale-free behavior in a simple evolutionary model. We model a growing population that starts from a small number of genotypes and then starts to grow due to an unlimited amount of available resources. These genotypes are subjected to the action of natural selection and mutation and increase in number according to their Malthusian rates. We show that the distribution of links for the genotypes is well described by a scale-free distribution. This is an evidence that combinatorial optimization processes can yield scale-free patterns.

Response of quaking aspen genotypes to enriched CO2: foliar chemistry and tussock moth performance

Abstract Genetic variation in the phytochemical responses of plants to CO2 enrichment is likely to alter trophic dynamics, and to shift intraspecific selection pressures on plant populations. We evaluated the independent and interactive effects of atmospheric CO2 and quaking aspen (Populus tremuloides Michx.) genotype on chemical composition of foliage and performance of the whitemarked tussock moth (Orgyia leucostigma J. E. Sm.). This research was conducted at the Aspen FACE (Free Air CO2 Enrichment) site in northern Wisconsin, U.S.A. Leaf samples were collected periodically from each of three genetically variable aspen genotypes growing under ambient and elevated CO2, and analysed for levels of primary and secondary metabolites. Tussock moth larvae were reared in situ on experimental trees, and development times and pupal masses were recorded. Foliar chemical composition varied among aspen genotypes and in response to CO2 enrichment. However, chemical responses of trees to elevated CO2 were generally consistent across genotypes. Larval development times varied among host genotypes and increased slightly for insects on high‐CO2 plants. Enriched CO2 tended to reduce insect pupal masses, particularly for females on one of the three aspen genotypes. CO2 × genotype interactions observed for plant chemistry and insect performance in this study with a small number of genotypes are probably too few, and too weak, to shift selection pressures in aspen populations. These results differ, however, from earlier work in which more substantial CO2 × genotype interactions were observed for plant chemistry.

Glycoalkaloid content in tubers of hybrid and backcross populations from aSolanum tuberosumx s. chacoense cross

The glycoalkaloid contents of foliage were measured in populations derived from a cross ofSolanum chacoense Bitter (PI 472810) with a composite sample of genotypes from a randomly matedSolanum tuberosum L. population. The mean total glycoalkaloid contents of the parent PI 472810 andtuberosum populations, and the F2 and F4 populations were 856, 121, 286, and 279 mg/100g fresh weight, respectively. The total glycoalkaloid content of the first backcross population, F2 xtuberosum, was 290 mg/100 g, close to the content of the F2. In a second backcross totuberosum, the mean total content was 148 mg/100 g, close to the content of the parenttuberosum population. Only the glycoalkaloids α-solanine and α-chaconine were found in PI 472810, whereas in the parenttuberosum, hybrid, and backcross populations, the glycoalkaloids α & β-solamarine also were found in a small number of genotypes. The ratios of chaconine to solanine contents were significantly (P≤.05) different in the parent PI 472810 andtuberosum populations, 2.55 and 2.12, respectively. The ratios in the F2 and F4 populations were similar to that of PI 472810, whereas the ratios in the backcross populations were closer to that of thetuberosum parent. The levels of foliage glycoalkaloids in the hybrid and backcross populations paralleled the levels of potato leafhopper,Empoasca fabae Harris, resistance measured in a previous study.