Isozyme variation among soil isolates ofHistoplasma capsulatum

Three hundred and sixty-nine cultures ofHistoplasma capsulatum were isolated by means of soil-inoculated mice from four disjunct sites, three consisting of blackbird roosts and one a gull nesting area. Repeatable isozyme patterns of eight enzyme systems were obtained by starch-gel electrophoresis. Isozyme polymorphism was observed among the isolates from each soil sample in at least one of the enzyme systems. High levels of isozyme variation were found within and between the sample sites. Isolates from the three blackbird sites were phenotypically more variable but showed an overall greater similarity to each other than to those from the gull site. Isolates from tissues of individual mice produced from two to ten different isozyme phenotypes, with an average of 40.5% of the isolates differing from the predominant phenotype.     

Phylogenetic relationships among isolates of Cryptosporidium: evidence for several new species

Isolates of Cryptosporidium were characterized using nucleotide sequence analysis of the 18S rRNA and dihydrofolate reductase genes and also random-amplified polymorphic DNA analysis. Phylogenetic analysis confirmed the validity of the species of Cryptosporidium examined in this study such as Cryptospordium muris and Cryptosporidium baileyi, and also reinforced evidence from numerous researchers worldwide suggesting that Cryptosporidium parvum is not a single uniform species. The data obtained provided strong support for the validity of Cryptosporidium felis. Evidence suggests that the newly identified marsupial and pig genotypes may also be distinct and valid species, but biological studies are required for confirmation.     

Isozyme differentiation among 17 geographical isolates of Hirsutella thompsonii

Electrophoretic analysis of mycelial preparations of 17 isolates of Hirsutella thompsonii demonstrated extensive variability in isozyme content. Many isolates possessed distinct electromorphs used to group or separate individual isolates. Coefficients of similarity based on isozyme patterns closely followed the morphological scheme used to separate H. thompsonii into three varieties. One exception, the nonsynnematous vinacious variety was very close to the nonsynnematous grayish-green variety biochemically. The electrophoretic data demonstrate that extensive differentiation among the H. thompsonii isolates is occurring at the subcellular level without attendant morphological changes.     

Genetic diversity and vegetative compatibility among Trichoderma harzianum isolates

Trichoderma harzianum is the collective name of a set of asexual fungal strains which exhibit heterogeneity in genome structure, DNA sequence and behavior. Contour-clamped homogeneous field (CHEF) electrophoresis of the chromosomes of ten isolates of T. harzianum revealed six clearly distinct electrophoretic karyotypes. Of the ten isolates analyzed, four (GH12, G109, Y and YF) could be classified in a single group with identical karyotypes, while the strains T35 and 315 formed a second group. The genome size characteristic of the different isolates fell into a broad range varying from 29.6 to 56.1?Mb. Gene assignments to the resolved chromosomes showed that all genes analyzed were localized on equivalent chromosomes in the isolates belonging to the same group. Analysis of randomly amplified polymorphic DNAs from the ten isolates confirmed the classification into groups and allowed us to distinguish between isolates T35 and 315, as well as between isolates GH12, G109, Y and YF. Direct confrontation assays using isolates of the same group showed compatible interactions, whereas the same experiment carried out with isolates of different groups showed an incompatible interaction characterized by an area of cell damage. Microscopic observation of the compatible interactions showed hyphal fusions between the isolates, similar to those described for vegetative compatible groups in other fungi. The molecular karyotypes correlated well with the compatibility of the isolates. In addition, we have evaluated both electrophoretic karyotype and randomly amplified polymorphic DNAs analysis as criteria for grouping isolates within the genus according to their capacity for biocontrol of plant pathogens.     

Temporal variation in trophic relationships among three congeneric penguin species breeding in sympatry

Penguins are a monophyletic group in which many species are found breeding sympatrically, raising questions regarding how these species coexist successfully. Here, the isotopic niche of three sympatric pygoscelid penguin species was investigated at Powell Island, South Orkney Islands, during two breeding seasons (austral summers 2013–2014 and 2015–2016). Measurements of carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotope ratios were obtained from blood (adults) or feather (chicks) samples collected from Adélie Pygoscelis adeliae, chinstrap P. antarctica, and gentoo P. papua penguins. Isotopic niche regions (a proxy for the realized trophic niches) were computed to provide estimates of the trophic niche width of the studied species during the breeding season. The isotopic niche regions of adults of all three species were similar, but gentoo chicks had noticeably wider isotopic niches than the chicks of the other two species. Moderate to strong overlap in isotopic niche among species was found during each breeding season and for both age groups, suggesting that the potential for competition for shared food sources was similar during the two study years, although the actual level of competition could not be determined owing to the lack of data on resource abundance. Clear interannual shifts in isotopic niche were seen in all three species, though of lower amplitude for adult chinstrap penguins. These shifts were due to variation in carbon, but not nitrogen, isotopic ratios, which could indicate either a change in isotopic signature of their prey or a switch to an alternative food web. The main conclusions of this study are that (1) there is a partial overlap in the isotopic niches of these three congeneric species and that (2) they responded similarly to changes that likely occurred at the base of their food chain between the 2 years of the study.     

AFLP analysis of relationships among cassava and other Manihot species

 Despite the worldwide importance of cultivated cassava (M. esculenta Crantz) its origin and taxonomic relationships with other species in the genus have not been clearly established. We evaluated a representative sample of the crop’s diversity and six wild taxa with AFLPs to estimate genetic relationships within the genus. Groupings of accessions of each species by data analysis corresponded largely with their previous taxonomic classifications. A mixed group, consisting of Manihot esculenta subsp. flabellifolia and M. esculenta subsp. peruviana, was most similar to cassava, while M. aesculifolia, M. brachyloba, and M. carthaginensis were more distant. Species-specific markers, which may be useful in germ-plasm classification or introgression studies, were suggested by the unique presence of AFLP products in samples of each of the three wild species. Heterogeneity of similarities among individuals of certain species suggested the existence of intraspecific gene pools, a hypothesis that was supported by morphological or ecogeographic evidence with varying degrees of success. Quantitative assessment of genetic diversity revealed greater homogeneity among cassava accessions than among itsclosest wild relatives. The demonstration of unique genetic diversity in the two M. esculenta subspecies and their genetic similarity to the crop supports the hypothesis that these materials may be the ancestors of cassava. Received: 4 November 1996 / Accepted: 20 December 1996     

Isozyme analysis of Taenia solium isolates from Mexico and Colombia

Mexican and Colombian Taenia solium cysticerci and some species of Taenia adults were assayed using cellulose acetate electrophoresis to distinguish between isolates. Isozyme patterns for ARK, GOT, G3PD, GPI, and MPI were identical in all cysticerci suggesting homozygotic profiles. G6PD and MDH showed different patterns between Mexican and Colombian cysticerci, suggesting regional differences. ME activity was mainly detected in the adult stage suggesting that this enzyme is active in anaerobic environment, while MDH, detected in cysticerci, could be related to an environment that contains oxygen. Finally, the species of taeniid adults analyzed showed different patterns among them.     

Genetic relationships among Aster species by multivariate analysis and AFLP markers

Fourteen species of Aster were characterized for morphological traits of commercial interest, chromosome number and genetic diversity by AFLP markers to exploit this material not only for breeding purposes but also as source of pharmaceuticals. The variation observed among the Aster species for five morphological traits was summarized by means of discriminant analysis. Three significant canonical variables, accounting for about 96% of total variance, were mainly correlated with capitulum diameter, number of ligulae and leaf length. The morphological variation appeared related to ploidy level of the species. A diploid chromosome number ranging from 10 to 18 was evident in seven species whereas the other species are polyploids with variable chromosome numbers up to 52. The pollen production and stainability were quite variable among Aster species. Furthermore, seven species produced big pollen grains besides normally-sized ones, at a frequency ranging from 1 to 12%, possibly due to 2n pollen production. The possibility that evolution of Aster genus could be driven by 2n gametes and sexual polyploidization is discussed. Implications of 2n gametes for Aster breeding are also mentioned. AFLP analysis of the fourteen Aster species based on six primer combinations revealed a total number of 421 polymorphic amplified DNA fragments. The genetic similarities estimated between the Aster species, based on both shared and unique amplification products ranged from 0.335 to 0.604 across all species and revealed a geographically based clustering within the genus. The highest similarity was detected between A. alpinus and A. amellus with Eurasian origin.     

Detection of relationships among microsporidan isolates by electrophoretic analysis: hydrophilic extracts

Hydrophilic spore proteins were extracted from Nosema sp. and Nosema trichoplusiae. These proteins were subjected to electrophoretic analysis. The resulting electrophoretic spectra were found to be unstable when (1) two genera of hosts were used for spore propagation, (2) hosts were reared at a variety of temperatures, (3) protein was extracted from spores stored for different periods of time, or (4) spore incubation period was varied. Comparison of the major bands obtained from spore protein of the isolates indicated no overlap in relative migration values. Although variation in spectra was observed, the use of major band patterns indicate electrophoretic analysis of hydrophilic spore protein can provide characters useful in the separation and identification of microsporidan isolates. Nosema sp. and Nosema trichoplusiae are not considered to be closely related phylogenetically.     

Detection of relationships among microsporidan isolates by electrophoretic analysis: hydrophobic extracts

Hydrophobic spore proteins were extracted from 11 microsporidan isolates obtained from 9 species of insects for which these microorganisms are pathogenic. Hydrophobic protein spectra were found to be stable when (1) two different genera of hosts were used for spore propagation, (2) hosts were reared at a variety of temperatures, or (3) protein was extracted from spores harvested at different stages of sporogenesis. Five consistent and distinct electrophoretic spectra were observed. Spectrum I was represented by 6 isolates including Nosema necatrix, Thelohania diazoma, Nosema plodiae, and Nosema sphingidis; spectrum II by Pleistophora sp; Spectrum III by Nosema whitei; spectrum IV by Thelohania legeri; and spectrum V by Nosema trichoplusia. The highly reproducible nature of these analyses indicated polyacrylamide gel disc electrophoresis of hydrophobic extracts can be used for the identification of Microsporida. Moreover, these analyses do not support the present classification, based mainly on the number of spores in a pansporoblast, inasfar as (1) some species of Nosema have the same pattern (I) as a species of Thelohania and (2) two species of Nosema have different patterns (III and V) in contrast to the Nosema species showing pattern I.     

Genetic relationships among Orobanche species as revealed by RAPD analysis

RAPD markers were used to study variation among 20 taxa in the genus OROBANCHE: O. alba, O. amethystea, O. arenaria, O. ballotae, O. cernua, O. clausonis, O. cumana, O. crenata, O. densiflora, O. foetida, O. foetida var. broteri, O. gracilis, O. haenseleri, O. hederae, O. latisquama, O. mutelii, O. nana, O. ramosa, O. rapum-genistae and O. santolinae. A total of 202 amplification products generated with five arbitrary RAPD primers was obtained and species-specific markers were identified. The estimated Jaccard's differences between the species varied between 0 and 0.864. The pattern of interspecific variation obtained is in general agreement with previous taxonomic studies based on morphology, and the partition into two different sections (Trionychon and Orobanche) is generally clear. However, the position in the dendrogram of O. clausonis did not fit this classification since it clustered with members of section TRIONYCHON: Within this section, O. arenaria was relatively isolated from the other members of the section: O. mutelii, O. nana and O. ramosa. Within section Orobanche, all O. ramosa populations showed a similar amplification pattern, whereas differences among O. crenata populations growing on different hosts were found. Orobanche foetida and O. densiflora clustered together, supporting the morphological and cytological similarities and the host preferences of these species.     

七种风铃草属植物亲缘关系的ISSR分析

为了解四川风铃草属植物的资源丰富度和遗传进化情况,该研究利用ISSR分子标记,探究了四川7种风铃草属植物的亲缘关系,为风铃草属植物的分子标记辅助鉴定、资源保护、花卉品种的开发与育种提供理论基础。结果表明:40条ISSR引物中有28条引物能够扩增出清晰的条带,扩增总条带数为164,其中有98.8%的扩增条带具有多态性,供试的7种风铃草属植物遗传相似性系数在0.421～0.945之间,其中钻裂风铃草与藏滇风铃草的遗传相似度最高为0.945,说明它们之间的亲缘关系很近。此外,ISSR分子标记聚类结果表明,7种风铃草属植物可以明显聚为4大类:西南风铃草、灰毛风铃草、灰岩风铃草为一类;紫斑风铃草与流石风铃草各成一类,这两种在形态上与其它各种风铃草差异较大;最后是钻裂风铃草与藏滇风铃草为一类。     

Taxonomy and phylogenetic relationships of two species of Hypocrea with Trichoderma anamorphs

Hypocrea patella is reevaluated. Its Trichoderma anamorph is described and the phylogenetic position of the species is determined through sequences of the ITS regions of rDNA. It is sister to a clade that includes Trichoderma longibrachiatum/H. schweinitzii. Hypocrea patella f. tropica is accepted for a Costa Rican collection. Hypocrea neorufa and its Trichoderma anamorph are described. Its phylogenetic position is determined by sequences of the ITS region of rDNA and the protein-coding translation-elongation factor (EF-1α). It is derived from within a clade that includes T. viride/H. rufa, T. atroviride/H. atroviridis, T. koningii/H. koningii and T. asperellum. Deceased August 2002.     

Serological relationships among rice yellow mottle virus isolates

Serological studies on five isolates of RYMV collected from the Ivory Coast (IC), Sierra-Leone (SL), Niger (Nr), Kenya (K) and Nigeria (N) indicated that these isolates are serologically related. Gel double diffusion and direct ELISA tests showed that the five isolates could be arranged into three serological groups here designated RYMV-N, SL-IC and K-NR. However, the ISEM studies did not reveal any clear grouping of the heterologous isolates tested.