Fusarium root rot of coneflower seedlings and integrated control using <Emphasis Type="Italic">Trichoderma</Emphasis> and fungicides

Fusarium root rot (Fusarium spp.) is one of the most important seedling diseases of coneflower (Echinacea spp.) in Alberta greenhouses. Effects of microbial antagonists (Trichoderma spp.) and fungicides, including difenoconazole, fludioxonil, and a mixture of fludioxonil, metalaxyl and difenoconazole, on the management of this disease, were investigated in Alberta. Twenty Trichoderma isolates demonstrated antagonistic activity to Fusarium in agar plate bioassays, with inhibition rates ranging from 44 to 65%. Some Trichoderma isolates significantly ( p < 0.05) reduced disease incidence and severity on seedlings in greenhouse experiments. An in vitro bioassay indicated that difenoconazole and the mixture equally inhibited the growth of both Fusarium and Trichoderma, but, while fludioxonil strongly inhibited the growth of Fusarium, it had little effect on Trichoderma, according to the dose--response models developed ( p < 0.01, R²= 0.902-0.998). Two Trichoderma isolates, T1 and T13 were applied singly or in combination with a low rate of fludioxonil in greenhouse evaluations. The results suggested that fludioxonil and Trichoderma could be integrated into a disease management program for fusarium root rot in coneflower.     

A review of chromosome cytology in Hyacinthaceae subfamily Ornithogaloideae (Albuca, Dipcadi, Ornithogalum and Pseudogaltonia) in sub-Saharan Africa

The chromosome cytology of Hyacinthaceae subfamily Ornithogaloideae is reviewed within the framework of a recent molecular-based classification, with particular emphasis on its center of diversity in sub-Saharan Africa. We also provide new chromosome counts for sections that are unknown or poorly known cytologically. Albuca subgen. Namibiogalum (9 spp.) probably has an ancestral base number of x = 10 but subgen. Albuca (± 70 spp), subgen. Monarchos (9 spp.) and subgen. Osmyne (36 spp.) have x = 9. The pattern in subgen. Urophyllon (3 spp.) is remarkable: although x = 6 is likely, the species in the section exhibit a range of 2n = 12, 10, 8, 6 and 4 (exclusive of polyploidy). All karyotypes have three large chromosome pairs and a variable number of small chromosomes. Pseudogaltonia (2 spp.) has x = 9 and Dipcadi (26 spp.) possibly x = 9 in series Uropetalum and x = 6 in series Dipcadi, which exhibits a pattern of descending dysploidy leading to n = 3 in D. marlothii. In Ornithogalum (± 130 spp.) chromosome numbers are known for only 24 of the ± 84 sub-Saharan species, mostly from subgen. Aspasia and subgen. Ornithogalum sect. Linaspasia, both of which have x = 6, and from subgen. Galtonia, which has x = 8. In contrast, x = 7 is basic for the Eurasian sects. Honorius and Melophis, and x = 18 seems likely for sect. Cathissa. Sect. Ornithogalum, the cytology of which we does not examine in detail, may have x = 9. Polyploidy is apparently rare in the sub-Saharan African ornithogaloids, in marked contrast to the high frequency of polyploidy among Eurasian species. In Albuca just 3 or possibly 4 sub-Saharan species (9% or 13% of those counted) are exclusively polyploid and 5 more have diploid and polyploid races; and in sub-Saharan Ornithogalum, only the tropical O. gracillimum is exclusively polyploid, and the western southern African O. hispidum has diploid and polyploid races.     

Open field host selection and behavior by tamarisk beetles (Diorhabda spp.) (Coleoptera: Chrysomelidae) in biological control of exotic saltcedars (Tamarix spp.) and risks to non-target athel (T. aphylla) and native Frankenia spp.

Biological control of invasive saltcedars (Tamarix spp.) in the western U.S. by exotic tamarisk leaf beetles, Diorhabda spp., first released in 2001 after 15 years of development, has been successful. In Texas, beetles from Crete, Greece were first released in 2004 and are providing control. However, adults alight, feed and oviposit on athel (Tamarix aphylla), an evergreen tree used for shade and as a windbreak in the southwestern U.S. and México, and occasionally feed on native Frankenia spp. plants. The ability of tamarisk beetles to establish on these potential field hosts was investigated in the field. In no-choice tests in bagged branches, beetle species from Crete and Sfax, Tunisia produced 30–45% as many egg masses and 40–60% as many larvae on athel as on saltcedar. In uncaged choice tests in south Texas, adult, egg mass and larval densities were 10-fold higher on saltcedar than on adjacent athel trees after 2 weeks, and damage by the beetles was 2- to 10-fold greater on saltcedar. At a site near Big Spring, in west-central Texas, adults, egg masses and 1st and 2nd instar larvae were 2- to 8-fold more abundant on saltcedar than on athel planted within a mature saltcedar stand being defoliated by Crete beetles, and beetles were 200-fold or less abundant or not found at all on Frankenia. At a site near Lovelock, Nevada, damage by beetles of a species collected from Fukang, China was 12–78% higher on saltcedar than on athel planted among mature saltcedar trees undergoing defoliation. The results demonstrate that 50–90% reduced oviposition on athel and beetle dispersal patterns within resident saltcedar limit the ability of Diorhabda spp. to establish populations and have impact on athel in the field.     

Integration of biological control agents with other weed management technologies: Successes from the leafy spurge (Euphorbia esula) IPM program

An invasive weed can occupy a variety of environments and ecological niches and generally no single control method can be used across all areas the weed is found. Biological control agents integrated with other methods can increase and/or improve site-specific weed control, but such combinatorial approaches have not been widely utilized. The successful leafy spurge (Euphorbia esula L.) control program provides examples for future integrated weed programs that utilize biological control agents with traditional methods. Weed control methods can be used separately, such as when the leafy spurge gall midge (Spurgia esulae Gagné) reduced seed production in wooded areas while herbicides prevented further spread outside the tree line. Traditional methods also can be used directly with biological control agents. Incorporation of Aphthona spp. with herbicides has resulted in more rapid and complete leafy spurge control than either method used alone. Also, the insect population often increased rapidly following herbicide treatment, especially in areas where Aphthona spp. were established for several years but had been ineffective. Incorporation of Aphthona spp. with sheep or goat grazing has resulted in a larger decline in leafy spurge production than insects alone and in weed density than grazing alone. Controlled burns can aid establishment of biological control agents in marginally suitable environments, but timing of the fire must be coordinated to the insect’s life-cycle to ensure survival. Integration of biological control agents with revegetation programs required the agent to be the last method introduced because the cultivation and herbicide treatments necessary to establish desirable grasses and forbs were destructive to the insect. In a practical application, herbicides were combined with Aphthona spp. to help the insect establish and control leafy spurge in the habitat of the western prairie fringed orchid (Platanthera praeclara Sheviak and Bowles), an endangered species. Several experimental designs can be used to evaluate biological control agents with cultural, mechanical, and chemical control methods or with additional biological agents.     

Selection and identification of autochthonous potential probiotic bacteria from turbot larvae (Scophthalmus maximus) rearing units

The purpose of this study was to select, identify and characterise bacteria as a disease control measure in the rearing of marine fish larvae (turbot, Scophthalmus maximus). Thirty-four out of 400 marine bacterial strains exhibited in vitro anti-bacterial activity against three fish larval pathogens. Two strains originated from culture collections and thirty two strains were isolated directly from turbot larvae rearing units using a pre-selection procedure to facilitate detection of antagonists. Approximately 8,500 colonies from colony-count plates were replica-plated on agar seeded with Vibrio anguillarum, and 196 of them caused zones of clearing in the V. anguillarum agar layer. Of these, 32 strains exhibited reproducible antibacterial properties in vitro when tested against the fish pathogens V. anguillarum 90-11-287, V. splendidus DMC-1 and a Pseudoalteromonas HQ. Seventeen antagonists were identified as Vibrio spp. and four of twelve tested were lethal to yolk-sac larvae. The 15 remaining strains were identified as Roseobacter spp. based on phenotypic criteria and 16S rDNA gene sequence analysis of two strains representing the two major RAPD groups. Most of the remaining 164 strains selected in the initial replica plating were identified as Vibrionaceae or Pseudoalteromonas. Roseobacter spp. were not lethal to egg yolk sac turbot larvae and in two of three trials, the mortality of larvae decreased (p > 0.001) in treatments where 10(7) cfu/ml Roseobacter sp. strain 27-4 was added, indicating a probiotic potential.     

The potential of Ulocladium botrytis for biological control of Orobanche spp.

A strain of Ulocladium botrytis isolated from diseased Orobanche crenata shoots caused disease on the parasitic weed in pathogenicity tests. The potential of the fungus to be developed as a mycoherbicide for Orobanche spp. was further investigated. Although the fungus significantly decreased O. crenata germination in vitro by 80%, it did not generally lead to a decreased number of O. crenata shoots or tubercles in inoculated root chambers or pots. However, the number of diseased or dead tubercles and underground shoots was significantly increased compared to the noninoculated treatments. Postemergence inoculation of O. crenata shoots with a conidial suspension resulted in the death of almost all inoculated plants 14 days after application under greenhouse conditions. In preliminary host-range studies, the pathogen caused disease on Orobanche cumana on sunflower whereas on Orobanche aegyptiaca shoots parasitizing tomato only minimal disease symptoms could be detected after postemergence inoculation. Based on the results of our investigations, we conclude that Ulocladium botrytis has only a limited potential to be used as a biocontrol agent against Orobanche spp.     

Real-time PCR分析滴虫性阴道炎患者微生物组成的变化

目的探寻滴虫性阴道炎患者阴道微生物组成的特点,为临床诊治及减少疾病的复发提供参考依据。方法选取2016年5-6月复旦大学附属华东医院妇科门诊45岁以下确诊为滴虫性阴道炎的育龄期患者16例,以同期18例45岁以下育龄期健康女性为对照,采集患者和健康人上阴道壁1/3处的分泌物,进行常规临床分析和革兰染色,并以21种常见的阴道细菌的特异引物进行Real-time PCR检测,分析并比较这些细菌在滴虫性阴道炎患者和健康人阴道内的组成及变化。结果在18例健康人中,其中13例的阴道微生物组成以乳酸杆菌(Lactobacillus)为优势菌,3例的阴道微生物组成无明显优势菌群或者优势菌不为检测的21种常见阴道微生物,2例的阴道微生物组成以加德纳菌为优势菌;在16例滴虫性阴道炎患者中,只有2例患者的阴道微生物菌群以乳酸杆菌为优势菌,14例以厌氧菌如普雷沃属(Prevotella)、纤毛菌(Leptotrichia)和斯尼思菌(Sneathia)为优势菌。经Metastats进行组间差异分析,结果表明Lactobacillus crispatus、Leptotrichia amnionii、Eggerthella sp.和Peptostreptococcus sp.在两组之间差异有统计学意义(P≤0.05)。PCoA主成分析结果亦显示滴虫性阴道炎患者的阴道常见21种微生物组成与健康人有显著差别。结论滴虫性阴道炎患者阴道内微生物组成的多样性增加,普雷沃属、纤毛菌及斯尼思菌的明显增高可能滴虫性阴道炎的炎症发生有关,此结果对于临床治疗滴虫性阴道炎的及减少复发提供新的方向,具有一定的指导意义。     

Phylogeny of marine Gregarines (Apicomplexa)--Pterospora, Lithocystis and Lankesteria--and the origin(s) of coelomic parasitism

Gregarines constitute a large group of apicomplexans with diverse modes of nutrition and locomotion that are associated with different host compartments (e.g. intestinal lumena and coelomic cavities). A broad molecular phylogenetic framework for gregarines is needed to infer the early evolutionary history of apicomplexans as a whole and the evolutionary relationships between the diverse ultrastructural and behavioral characteristics found in intestinal and coelomic gregarines. To this end, we sequenced the SSU rRNA gene from (1) Lankesteria abbotti from the intestines of two Pacific appendicularians, (2) Pterospora schizosoma from the coelom of a Pacific maldanid polychaete, (3) Pterospora floridiensis from the coelom of a Gulf Atlantic maldanid polychaete and (4) Lithocystis sp. from the coelom of a Pacific heart urchin. Molecular phylogenetic analyses including the new sequences demonstrated that several environmental and misattributed sequences are derived from gregarines. The analyses also demonstrated a clade of environmental sequences that was affiliated with gregarines, but as yet none of the constituent organisms have been described at the ultrastructural level (apicomplexan clade I). Lankesteria spp. (intestinal parasites of appendicularians) grouped closely with other marine intestinal eugregarines, particularly Lecudina tuzetae, from polychaetes. The sequences from all three coelomic gregarines branched within a larger clade of intestinal eugregarines and were similarly highly divergent. A close relationship between Pterospora schizosoma (Pacific) and Pterospora floridiensis (Gulf Atlantic) was strongly supported by the data. Lithocystis sp. was more closely related to a clade of marine intestinal gregarines consisting of Lankesteria spp. and Lecudina spp. than it was to the Pterospora clade. These data suggested that coelomic parasitism evolved more than once from different marine intestinal eugregarines, although a larger taxon sample is needed to further explore this inference.     

Prevalence of tick-borne pathogens in ixodid ticks (Acari: Ixodidae) collected from European wild boar (<Emphasis Type="Italic">Sus scrofa</Emphasis>) and Iberian red deer (<Emphasis Type="Italic">Cervus elaphus hispanicus</Emphasis>) in central Spain

Emerging tick-borne diseases of humans and animals have occurred frequently during the past 30 years. These disease outbreaks appear to result from changes in the distribution of tick and vertebrate hosts, and the introduction of humans and domestic animals into tick–pathogen–wildlife cycles. Use of molecular technologies now available for identification of pathogens in ticks can provide valuable information that allows for risk analysis of emerging tick-borne diseases. In this study, the prevalence of selected pathogens in ticks collected in six locations in central Spain from the major wild ungulate species, European wild boar (Sus scrofa) and Iberian red deer (Cervus elaphus hispanicus), was determined by PCR. Tick species collected included Ixodes ricinus, Dermacentor marginatus, Rhipicephalus bursa and Hyalomma m. marginatum. Pathogens identified in ticks included piroplasmids, Anaplasma spp., Ehrlichia spp. and Rickettsia spp. Piroplasmids were identified in all tick species except I. ricinus. Ehrlichia spp. were detected in all tick species and collection locations, while Rickettsia spp., which proved to be R. slovaca and a recently identified Rickettsia sp. DnS28, were identified only in D. marginatus. A. marginale and A. phagocytophilum were detected in D. marginatus, R. bursa and Hy. m. marginatum. Concurrent infections of these pathogens were frequently observed in ticks. Notably, A. phagocytophilum, which is infective for a broad host range that includes humans and domestic and wild animals, was identified in ticks from all collection locations. The variety of ticks and tick-borne pathogens demonstrated in this study suggests a risk in central Spain for the emergence of tick-borne diseases in humans and domestic animals.     

Effects of different Beauveria bassiana isolates on field populations of Lygus lineolaris in pigweed (Amaranthus spp.)

The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), is a pest of various fruit, vegetable, fiber, and seed crops; including cotton. Lygus spp. populations often build on alternate host plants before moving to cotton, and in the midsouthern U.S. wild host plants, such as pigweed (Amaranthus spp.), play a major role in L. lineolaris population development. Three isolates of the entomopathogenic fungus Beauveria bassiana (Balsamo) were evaluated for L. lineolaris control in redroot pigweed (Amaranthus retroflexus L.): one from L. lineolaris in Mississippi (TPB3); one from Lygus hesperus (Knight) in California (WTPB2); and one commercial isolate from Mycotrol^® (GHA). Fungal applications resulted in moderate to high mycosis in adults (33 to 80%) and moderate mycosis in nymphs (36 to 53%) that were collected from field plots at 2 days post-treatment and incubated under laboratory conditions. Although TPB3 was previously found to be more pathogenic in laboratory bioassays, there was not a consistent separation of this isolate from the other two isolates in field trials. Where differences in adult mycosis or mortality were observed, TPB3 was the most pathogenic. However, in one field trial 7 day mortality for nymphs treated with GHA was higher than those treated with TPB3 or WTPB2. Infection rates at 2, 7, and 14 days post-treatment from caged and non-caged adults suggested that movement of adults among plots occurred, which could have masked some treatment effects. Fungal treatments did not significantly reduce populations relative to controls. This may have been caused by delayed mortality rates under field conditions and/or difficulties with estimating population change under field conditions characteristic of wild host plant populations (e.g., heterogeneous populations, adult movement, and small plot size). Further work evaluating time–dose–mortality over dynamic temperatures, spring and fall field trials on this and other wild hosts, and improved methods for estimating populations on wild hosts are needed.     

Bacterial Antagonist as Seed Treatment to Control Leaf Blight Disease of Bambara Groundnut (Vigna subterranea)

Summay Soil samples were taken from 48 fields in the southern part of Thailand in which either bambara groundnut (Vigna subterranea) or groundnut (Arachis hypogeae) had been planted. Bacillus spp. were isolated using soil dilution plates and heat treatment to screen for endospore-producing bacteria. Among 342 Bacillus spp. isolates tested, 168 isolates were not antagonistic to Bradyrhizobium sp. strain NC-92 using dual culture technique. Further testing found 16 isolates of Bacillus spp. had the ability to inhibit mycelial growth of Rhizoctonia solani, a causal agent of leaf blight of bambara groundnut. Among these isolates, Bacillus spp. isolate TRV 9-5-2 had the greatest activity in anti-microbial tests against R. solani. This isolate was later identified as B. firmus. A powder formulation of B. firmus was developed by mixing bacterial endospores, talcum, sodium carboxymethylcellulose (SCMC) and polyvinylpyrolidone (PVP). The formulations contained bacterial levels ranging from 10⁸ to 10¹⁰ c.f.u./g and the viability of bacteria in all formulations remained high after 1 year storage at room temperature (26–32 °C). All formulations showed satisfactory effectiveness in vitro in suppressing mycelial growth of R. solani using dual culture technique. The application of formulations as seed treatment showed that these formulations did not cause abnormality of seedling shape and had no effect on the germination of bambara groundnut seeds.     

Abundance and Spread of the Invasive Red Algae, <Emphasis Type="Italic">Kappaphycus</Emphasis> spp., in Kane’ohe Bay,Hawai’i and an Experimental Assessment of Management Options

Several species of Kappaphycus were intentionally introduced into Kane’ohe Bay, Hawai’i in the 1970s. Subsequent research has demonstrated that these algae have spread rapidly throughout the bay and can be found in a variety of reef habitats overgrowing and killing corals. This study was conducted to (a) quantify Kappaphycus spp. abundance both spatially and temporally, and (b) investigate control options including manual removal and the use of biocontrol agents. Kappaphycus spp. distribution has increased in the bay over the period between surveys conducted in 1999 and 2002, with variation among reefs. The biomass of Kappaphycus spp. removed, and the amount of time required to manually remove them from the reef varied with habitat type, but in all cases amounted to at least 10 kg/m² requiring almost 2 person-hours to clear 1 m². Re-growth of the algae following their removal was rapid at most sites, likely due to the experimentally demonstrated ability of the algae to re-grow from minute attachment points and the low palatability of the algae to native herbivorous fishes. The native sea urchin, Tripneustes gratilla, reduced the biomass of Kappaphycus spp. in small experimental enclosures and may be a useful biocontrol agent. Because Kappaphycus spp. are still spreading in Kane’ohe Bay and can overgrow over 50% cover on some reefs, we recommend that rapid management action be taken to prevent further damage and spread to other Hawaiian coral reefs.     

Two heteropteran predators in relation to weed management in herbicide-tolerant corn

Deployment of genetically modified (GM), herbicide-tolerant corn may alter weed flora abundance and composition and may affect pests and their natural enemies. Among on-plant predators, Orius spp. are the prevalent group in Spain and were selected to study the impact of glyphosate use on predators. We also studied Nabis sp. which is commonly recorded on corn in the study area. For this, a 4-year study was conducted in NE Spain. Three different herbicide regimes were compared: two glyphosate (a broad-spectrum herbicide) treatments per season, no herbicide treatment, and one pre-emergence conventional treatment with selective herbicides against broadleaf and grassy weeds. Density of main arthropod herbivores and the above two predatory groups was recorded on plants. Differences between herbicide regimes were observed in the two functional groups studied, herbivores and heteropteran predators. The comparison of glyphosate-treated and untreated plots showed significant differences for both functional groups, but the differences between glyphosate-treated and conventionally treated plots for the two functional groups were lower. For Orius spp., annual density per plot was significantly correlated with annual density of leafhoppers and to a lesser extent, with aphids. Nabis sp. densities were never different between glyphosate-treated and conventionally treated plots, and Nabis sp. density showed no relation to any of the herbivores tested. We concluded that no significant changes in heteropteran predator densities may be expected from moderate alterations in weeds arising from the deployment of herbicide-tolerant corn varieties and that leafhoppers are probably the herbivore prey that most influences Orius spp. densities in corn in our study area.     

Pseudomonas aeruginosa, Candida albicans, and device-related nosocomial infections: implications, trends, and potential approaches for control

For many years, device-associated infections and particularly device-associated nosocomial infections have been of considerable concern. Recently, this concern was heightened as a result of increased antibiotic resistance among the common causal agents of nosocomial infections, the appearance of new strains which are intrinsically resistant to the antibiotics of choice, and the emerging understanding of the role biofilms may play in device-associated infections and the development of increased antibiotic resistance. Pseudomonas aeruginosa and Candida albicans are consistently identified as some of the more important agents of nosocomial infections. In light of the recent information regarding device-associated nosocomial infections, understanding the nature of P. aeruginosa and C. albicans infections is increasingly important. These two microorganisms demonstrate: (1) an ability to form biofilms on the majority of devices employed currently, (2) increased resistance/tolerance to antibiotics when associated with biofilms, (3) documented infections noted for virtually all indwelling devices, (4) opportunistic pathogenicity, and (5) persistence in the hospital environment. To these five demonstrated characteristics, two additional areas of interest are emerging: (a) the as yet unclear relationship of these two microorganisms to those species of highly resistant Pseudomonas spp and Candida spp that are of increasing concern with device-related infections, and (b) the recent research showing the dynamic interaction of P. aeruginosa and C. albicans in patients with cystic fibrosis. An understanding of these two opportunistic pathogens in the context of their ecosystems/biofilms also has significant potential for the development of novel and effective approaches for the control and treatment of device-associated infections.     

An Evaluation of the Rust FungusGymnoconia nitensas a Potential Biological Control Agent for AlienRubusSpecies in Hawaii

The rust fungusGymnoconia nitensinfects blackberry (Rubus argutus) systemically in regions of the continental United States, producing bright yellow–orange masses of spores on newly developing floricanes during springtime. In tests to determine the suitability of this rust as a biological control agent forR. penetransin Hawaii, a species now thought to be conspecific withR. argutus,rooted cuttings of the Hawaiian plants were grown at North Carolina State University, inoculated, and observed. Other introduced weedyRubusspp. in Hawaii, includingR. ellipticus, R. rosifolius,andR. glaucus,as well as the two endemic speciesR. hawaiensisandR. macraei,also were inoculated. No species ofRubusare of commercial importance in Hawaii, but the protection of the native species, of whichR. macraeiis rare, was of utmost concern. The native Hawaiian species did not survive well in North Carolina in this study, however. Later availability of a plant pathogen containment laboratory in Hawaii enabled similar tests to be conducted at that facility. In addition to the above species,R. spectabilis(salmonberry), a species native to the Pacific Northwest with which the HawaiianRubusspp. are thought to share a common ancestor, was inoculated in Hawaii. Infection withG. nitensunder natural field conditions becomes apparent only when sporulation occurs on floricanes the second year following infection. However, experimental inoculation led to early responses of chlorotic leaf flecking and puckering, leaf and stem contortion, and stem gall formation, indicating the sensitivity ofR. penetrans(=R. argutus),R. hawaiensis,andR. macraeito this rust. Apparent systemic infection also resulted in sporulation on one plant ofR. macraei.Ability to attack the endemic species suggests thatG. nitenswould not be suitable for release in Hawaii as a biological control agent, at least on the islands with populations of the native species.     

Ultrastructure of the spermatozoa of<Emphasis Type="Italic"> Parenterodrilus taenioides</Emphasis> (Protodrilida: “Polychaeta”) and its phylogenetic significance

The interstitial annelid Parenterodrilus taenioides from coral sands of the island of Moorea (French Polynesia) is a mouthless species characterized by a vestigial non-functioning alimentary canal and a distinctive body shape. It is the only known annelid that has a non-functioning gut and no symbiotic bacteria. Parenterodrilus is thought to represent the sister group of the well-known taxon Protodrilus, generally recognized as Protodrilidae. An ultrastructural study revealed that, as in Protodrilus spp., the males of P. taenioides have lateral organs, i.e. paired epidermal, glandular and ciliated grooves, in the anterior body region where the sperm ducts are located. As in Protodrilus two types of spermatozoa were found, commonly called euspermatozoa and paraspermatozoa. Both types are filiform and the euspermatozoa, like those in Protodrilus spp., have a characteristic midpiece reinforced by symmetrically arranged supporting structures and reduced mitochondria. The ultrastructure of the spermatozoa in P. taenioides and Protodrilus spp. is basically the same but the species can be distinguished from each other on the basis of particular structural details of spermatozoa and the pattern of lateral organs. The two types of spermatozoa and the epidermal lateral organs are unique features of these two taxa; as they are not present in any other potentially related taxon, such as Saccocirrus and Protodriloides, they very likely represent autapomorphies of Protodrilidae. In Protodrilus spp. spermatophores are deposited on the epidermis of the females, whereupon sperm are released and penetrate the body wall. Since in polychaetes the structure of the sperm is correlated with the fertilization biology, the similar structure of sperm suggests that sperm transfer and fertilization are very probably the same in P. taenioides as in Protodrilus.This paper was presented at the symposium Morphology, molecules, evolution and phylogeny in Polychaeta and related taxa held in Haus Ohrbeck, Osnabrück, in September 2002, and is dedicated to Prof. Dr. Wilfried Westheide on the occasion of his 65th birthday     

Rhizobacteria and their potential to control <Emphasis Type="Italic">Fusarium verticillioides</Emphasis>: effect of maize bacterisation and inoculum density

Fusarium verticillioides is the most important seed transmitted pathogen that infects maize. It produces fumonisins, toxins that have potential toxicity for humans and animals. Control of F. verticillioides colonisation and systemic contamination of maize has become a priority area in food safety research. The aims of this research were (1) to characterise the maize endorhizosphere and rhizoplane inhabitant bacteria and Fusarium spp., (2) to select bacterial strains with impact on F. verticillioides growth and fumonisin B₁ production in vitro, (3) to examine the effects of bacterial inoculum levels on F. verticillioides root colonisation under greenhouse conditions. Arthrobacter spp. and Azotobacter spp. were the predominant genera isolated from maize endorhizosphere and rhizoplane at the first sampling period, whilst F. verticillioides strains showed the greatest counts at the same isolation period. All F. verticillioides strains were able to produce fumonisin B₁ in maize cultures. Arthrobacter globiformis RC5 and Azotobacter armeniacus RC2, used alone or in a mix, demonstrated important effects on F. verticillioides growth and fumonisin B₁ suppression in vitro. Only Azotobacter armeniacus RC2 significantly reduced the F. verticillioides root colonisation at 10⁶ and 10⁷ CFU g^–1 levels under greenhouse conditions.     

Role of symbiotic and non-symbiotic bacteria in carbon dioxide production from hosts infected with Steinernema riobrave

Entomopathogenic nematodes of the family Steinernematidae and their mutualistic bacteria (Xenorhabdus spp.) are lethal endoparasites of insects. We hypothesized that growth of the nematode’s mutualistic bacteria in the insect host may contribute to the production of cues used by the infective juveniles (IJs) in responding to potential hosts for infection. Specifically, we tested if patterns of bacterial growth could explain differences in CO₂ production over the course of host infection. Growth of Xenorhabdus cabanillasii isolated from Steinernema riobrave exhibited the characteristic exponential and stationary growth phases. Other non-nematode symbiotic bacteria were also found in infected hosts and exhibited similar growth patterns to X. cabanillasii. Galleria mellonella larvae infected with S. riobrave produced two distinct peaks of CO₂ occurring at 25.6–36 h and 105–161 h post-infection, whereas larvae injected with X. cabanillasii alone showed only one peak of CO₂, occurring at 22.8–36.2 h post-injection. Tenebrio molitor larvae infected with S. riobrave or injected with bacteria alone exhibited only one peak of CO₂ production, which occurred later during S. riobrave infection (41.4–64.4 h post-infection compared to 20.4–35.9 h post-injection). These results indicate a relationship between bacterial growth and the first peak of CO₂ in both host species, but not for the second peak exhibited in G. mellonella.     

Dominant fungi in the rhizosphere of established tea bushes and their interaction with the dominant bacteria under in situ conditions

Species of Penicillium and Trichoderma were found to dominate the rhizosphere of established tea bushes in a detailed study conducted from various tea growing locations in India. Penicillium erythromellis, P. janthinellum, P. raistrickii, Trichoderma pseudokoningii and T. koningii were found to be closely associated with tea roots. While seasonal fluctuation was observed in the case of Penicillium spp., the population of Trichoderma spp. showed less variation during the year. Both species were sensitive to low temperatures. In general, fungi associated with the tea rhizosphere were found to prefer a mesophillic temperature range (15 °C to 35 °C). The dominant species of Penicillium and Trichoderma also exhibited tolerance to lower temperatures, i.e., 5 to 10 °C on agar plates. Most fungi were able to grow in a wide range of pH (4 to 12). Lowering of soil pH in the rhizosphere of tea bushes was positively correlated with the age of the bush and may have affected the development of a specific microbial community in the rhizosphere.The populations of Penicillium and Trichoderma species were inversely correlated with the populations of two most dominant rhizosphere bacteria, Bacillus subtilis and B. mycoides. Both Bacillus species have been shown to have antagonistic activity against these two fungi under in vitro conditions. The present study demonstrates the existence of a similar antagonism under in situ conditions in the rhizosphere of established tea bushes.