Herpobasidium filicinum (Eocronartiaceae,Platygloeales) occurs on Dennstaedtia wilfordii (Dennstaedtiaceae) in Japan

A fungus parasitic on a fern, Dennstaedtia wilfordii (Dennstaedtiaceae), was found at the foothill of Mt. Fuji, Yamanashi Prefecture, Japan. Its hyphae spread within host mesophyll cells and through intercellular spaces, forming coiled haustoria in the epidermal and mesophyll cells. The hyphae emerged either through stomata or by disrupting epidermal cell junctions. The hyphae spreading over the abaxial leaf surface generated one-septate, thin-walled basidia. All the morphological features observed were characteristic of the genus Herpobasidium. The species identification of the fungus as H. filicinum by morphology was supported by molecular phylogenetic analyses of the D1/D2 region of the large subunit rRNA gene.     

Phylogenetic study of indigenous grapevine leaf rust fungi in North America and biological identity of an invasive grapevine leaf rust fungus in Brazil

Two American grapevine leaf rust (GLR) fungi, Phakopsora muscadiniae and P. uva, were found to be phylogenetically different from Asian-Australasian GLR fungi. In the phylogram based on rDNA region sequences, a clade of the American fungi was sister to an inclusive clade of three autoecious species on Meliosma and a heteroecious species host-alternating between Meliosma and Parthenocissus. An invasive Brazilian GLR fungus (as P. meliosmae-myrianthae) was included in the Asian-Australasian GLR fungi clade, or the clade of the Thai population of Phakopsora sp. It could be assumed that the Brazilian GLR fungus originated from an inadvertently introduced Thai population.     

寄主和分布区系不同的球孢白僵菌菌株近缘关系的研究

观察、测定了来源不同的球孢白僵菌 1 9个菌株的培养性状、产孢量、萌发中时、水分活性、紫外照射活率、水浴活率等指标 ,将培养性状编码后 ,由所得的 8个指标对供试菌株求相关系数矩阵 .分析表明 ,不同菌株近缘关系的远近主要由菌株原始分布区系距离远近所决定 ,受寄主不同的影响次之 .来源于相同 (或相近 )地区的菌株相关系数可达极显著水平 ,而从相同寄主角度分析 ,得到菌株间的相关系数有高有低 ,多表现为相关不显著     

Host specialization in habitat specialists and generalists

Generalists and specialists use different cues to find their habitat and essential resources. While generalists have the advantage of exploiting a wider range of resources, they are predicted to be less efficient in using one particular resource compared to specialists. The level of specialization of parasitoids can be either at the habitat or at the host level; strategies used by either type are expected to differ. We examined interactions between three aphid parasitoid species that are a habitat specialist Aphidius rhopalosiphi, a habitat generalist Aphidius ervi, and a host generalist Praon volucre on three cereal aphids, Sitobion avenae, Metopolophium dirhodum and Rhopalosiphum padi. We compared total parasitism rate across behavioral and physiological variation in a non-choice test. Next, we addressed total parasitism in two phases to examine: (1) the response of parasitoids to different hosts through the behavioral sequence from antennation through oviposition, and (2) the physiological suitability of different hosts for oviposition and larval development. Parasitization typically involved the following behavioral steps: (1) antennal contact, (2) abdominal bending, and (3) ovipositor insertion (acceptance). A. rhopalosiphi had the same number of antennal contacts with the three aphids but showed fewer instances of abdominal bending towards R. padi. Pre-contact host preference was found for A. ervi but it did not correspond to the level of acceptance. The number of antennal contacts by P. volucre corresponded to the parasitization level of the aphid species but more mummies were produced on M. dirhodum than on R. padi. These results suggest that parasitoid species that are habitat specialists react similarly to the different host species present in the same habitat, whereas generalist species exhibit clear preferences during host selection. Preferences were, however, not always related to host suitability.     

Scientific advances in the analysis of direct risks of weed biological control agents to nontarget plants

Research on host specificity testing protocols over the last 10 years has been considerable. Traditional experimental designs have been refined and interpretation of the results is benefiting from an improved understanding of agent behavior. The strengths, weaknesses, and best practice for the different test types are now quite clearly understood. Understanding the concept of fundamental host range (the genetically determined limits to preference and performance) and using this to maximize reliability in predicting field host specificity following release (behavioral expression of the fundamental host range under particular conditions) are still inconsistently understood or adopted despite having been identified as the critical steps in analyzing the threats posed by biological control agents to the agriculture and biodiversity of novel environments. This needs to be consistently understood and applied so the process of testing can follow a recognized process of risk analysis from hazard identification (identifying life stages of the agent that pose a threat and defining their fundamental host range) to uncertainty analysis based on the magnitude (predicted field host specificity following release) and likelihood of threats (predicted actual damage and impact) to nontargets. Modern molecular techniques are answering questions associated with subspecific variation in biological control agents with respect to host use and the chance of host shifts of agents following release. Guidelines for assessment of nontarget impacts need to recognize and adopt such recent developments and emphasize a general increased understanding of the evolution of host choice and the phylogenetic constraints to shifts in host use. This review covers all these recent advances for the first time in one document, highlighting how inconsistent interpretation by biological control practitioners can be avoided.     

Inheritance of phenotypic traits in the progeny of a Ceratocystis interspecific cross

Ceratocystis fimbriata is a fungal plant pathogen that causes black rot on Ipomoea batatas. Based on inoculation studies on numerous tree species, the pathogen is known to be host specific. The closely related species, Ceratocystis manginecans, causes severe wilt on a broad range of tree hosts, including Mangifera indica, Acacia mangium and other leguminous tree species. The genetic factors underlying the pathogenicity and host specificity of Ceratocystis species have rarely been investigated. In this study, an F₁ population of 70 recombinant progeny from a cross between C. fimbriata and C. manginecans was generated and the inheritance of various phenotypic traits was investigated. Results showed that colony colour, growth rate, asexual spore production and aggressiveness to I. batatas and A. mangium are all quantitative traits with high levels of heritability. However, conidia production and aggressiveness appeared to be regulated by a small number of genes. No correlation could be found between aggressiveness and other phenotypic traits, suggesting that these are inherited independently. This is the first study to consider genetic inheritance of pathogenicity and host specificity in Ceratocystis species and the results will contribute, in future, to the identification of quantitative trait loci and candidate genes associated with the traits investigated.     

Wisconsin desmids. II. Aufwuchs and plankton communities of selected soft water lakes,hard water lakes and calcareous spring ponds

This report summarizes the results of summer studies of five soft water lakes, five hard water lakes and six calcareous spring ponds in Wisconsin with respect to the composition of the plankton and aufwuchs communities and the relative role of desmids in those communities. The results are compared with similar data obtained from selected acid bog lakes, alkaline bog lakes and closed bogs. Soft water lakes harbored a greater aufwuchs and plankton desmid diversity than hard water lakes or spring ponds; however, diversity in acid bog lakes was substantially greater than in any other lake type. Utricularia contained the greatest desmid diversity and population density in every lake where it occurred. Staurastrum was the most prevalent genus in the plankton and it was the only one recorded from hard water lakes and calcareous spring ponds. Desmid aufwuchs population densities were roughly comparable in hard water lakes, soft water lakes and acid bogs and the contribution of desmids to the total aufwuchs population was similar for the latter two lake types. However, the plankton of acid bog lakes generally harbored substantially greater desmid populations and these populations contributed much more to the total population than in any other lake type. Aufwuchs data are presented for several hosts and comparisons of population densities are given among hosts within a given lake and between the same host in different lakes of a given type. Data for other algal groups are also included.     

Pseudoracemes in papilionoid legumes: their nature, development, and variation

Pseudoracemes in papilionoid legumes: their nature, development, and variation. Cymelike partial inflorescences called fascicles have been reported in the inflorescences of several papilionoid tribes. The total inflorescence is termed a ‘pseudoraceme’ because of the multiple flowers in each bract axil. Pseudoraceme development has been studied in 22 taxa in five papilionoid tribes (Abreae, Desmodieae, Millcttieae, Phaseoleae and Psoraleeae). Two to twelve flowers occur per bract axil among various taxa, with three the most common number.Pongamia pinnata and Clitoris fairchildiana have only two flowers per axil; Vigna radiata, Phaseolus vulgaris, and Apios americana have four to five commonly, and Dioclea aff.ucayalina and Abrus precalorius have up to 12. The ‘fascicle’ usually consists of a triad of three flowers; each triad resembles a dichasial cyme in that the middle flower appears terminal. The middle flower however is subtended by a bract on the abaxial side, so that the middle flower is technically lateral. When the first-order axis elongates, each triad may either remain intact or be separated by axis intervalS. Many variations on the basic triad pattern occur in the species studied: 1.one or two flowers may develop while others that are initiated remain suppressed; 2. Additional flowers may be produced that replicate the first triad; 3. Additional flowers may form medianly only, on the abaxial side. The second-order inflorescence axis which has produced the three flowers persists to produce more flowers in replication of the triad pattern in several taxa (Apios americana, Vigna radiata, Phaseolus vulgaris, and Dioclea aff.ucayalina). In Butea monosperma the second-order inflorescence apex produces subsequent flowers (after the triad) in a helix. In Erylhrina perrieri, there is no indication of a persistent second-order inflorescence apex after the central flower; such a condition could be interpreted as a cyme, except for the abaxial subtending bract. The triad in Psoralea pinnata is a true cyme; the middle flower lacks a subtending bract other than that subtending the entire fascicle. Developmentally, the difference between a cyme and an early-determinate raceme (as in the triad type of pseudoraceme) is rather slight. Comparison of the types of inflorescences described here may indicate how the transition may have occurred between racemes and cymes in the evolution of legumes.     

单殖吸虫的生态学

单殖吸虫是一类宿主专一性较强的寄生虫,外环境和宿主特征对单殖吸虫有明显的影响。本文对目前单殖吸虫生态学方面的研究作了一个概述,主要论述了宿主、环境等对单殖吸虫的影响、单殖吸虫之间的关系以及单殖吸虫种群的空间分布。     

寄主植物的功能性状对桑寄生寄主专一性的影响初探

为探讨寄主多样性和寄主功能性状对桑寄生植物的寄主专一性的影响,调查了西双版纳热带植物园内桑寄生和寄主植物种类。结果表明,桑寄生植物共有2科5属6种1变种,感染隶属于58科190属286种寄主植物1 323株。桑寄生在不同生境的寄生强度具有极显著差异(P0.01),单一种植园的寄生强度最高,而在森林的分布最少。不同种类桑寄生的寄主范围存在较大差异,专一性程度(H′)为1.92～7.05,多度较高的植物更容易被感染。冗余分析表明,寄主植物的胸径、树皮含水量和树皮粗糙度对不同桑寄生的寄主利用差异有显著影响,而木质密度和树皮pH的影响不显著。因此,不同种类桑寄生在热带植物群落的寄主专一性程度有较大差异,对寄主植物特定功能性状的偏好能解释部分差异。     

Genotyping of Staphylococcus aureus isolated from humans, bovine subclinical mastitis and food samples in Argentina

The aim of the present study was to characterize genotypically 45 Staphylococcus aureus strains isolated from humans, bovine subclinical mastitis and food samples in Argentina by rep-PCR and PCR amplification of virulence genes. Resistances to various antibiotics could be observed for the human S. aureus, less pronounced for the bovine strains, but not for the eight S. aureus isolated from food samples. The strains could be classified genotypically by rep-PCR and by amplification of the genes encoding protein A, coagulase, clumping factor, the collagen adhesin domains A and B, capsular polysaccharide 5 and 8, the accessory gene regulator agr classes I to III, and the S. aureus gene regulator sae. rep-PCR analyses and the different gene patterns revealed that the strains could be divided into seven groups mostly matching with the origin of the isolates. The present study describes genotypic variations of S. aureus strains isolated from different origins in Argentina. The study provides a valuable insight into molecular specificities of this important pathogen.