Crassulacean Acid Metabolism in Two Species of Orchids Infected by Tobacco Mosaic Virus-orchid Strain and/or Cymbidium Mosaic Virus

The effect of viral infections on the Crassulacean Acid Metabohsm (CAM) was determined in two orchid species. Plants of a Sophrolaeliocattleya (SLC) commercial hybrid were inoculated with either the orchid strain of the Tabacco Mosaic Virus (TMV-O), with Cymbidium Mosaic Virus (CybMV) or with a mixture of both viruses. Plants of Epidendrum elongatum, a wild terrestrial orchid, were inoculated either with TMV-O or with TMV-O and CybMV simultaneously. Virus infected plants started to show a systemic mosaic on the leaves 3 to 4 years after inoculation, the symptoms being more appreciable in SLC than in E. elongatum. Double inoculation with TMV-O and CybMV proved to the lethal for the SLC plants. TMV-O infection caused 58 % and 24 % reduction in nocturnal leaf titratable acidity (TA) in SLC and E. elongatum, respectively. TMV-O also changed the daily pattern of leaf nonstructural carbohydrates typical of CAM plants. A 50 % decrease in TA at dawn and a mid-morning peak of sugar accumulation were measured in leaves of doubly inoculated E. elongatum plants. In SLC CybMV infection inhibited CAM and induced an accumulation of glucans in the leaves. Cytoplasmic agglomerations of CybMV, but not of TMV-O, were detected in SLC mfected cells, whereas TMV-O particles were clearly observed in the cytoplasm of E. elongatum. Infection by TMV-O or CybMV in SLC caused an increase in chloroplasts volume and distortion of the grana due to high glucan accumulation. In contrast, TMV-O infection in E. elongatum induced a lesser degree of damage in the cell ultrastructure.     

INFECTIOUS DISEASES OF MAZZAELLA LAMINARIOIDES (RHODOPHYTA): CHANGES IN INFECTION PREVALENCE AND DISEASE EXPRESSION ASSOCIATED WITH SEASON,LOCALITY, AND WITHIN-SITE LOCATION1

This study addresses the issues of infection prevalence and disease expression in two wild populations of the red algal host Mazzaella laminarioides and their variability associated with locality, season, and spatial location of the host in the intertidal zone. Our results demonstrated that Endophyton ramosum is the most frequent infective pathogen affecting M. laminarioides in Matanzas and Pucatrihue. This situation prevailed through the year and across the high-to-low intertidal gradient. Although there was a general trend for lower levels of infection in late winter and early spring, only in a few, cases was well-defined seasonality detected. Furthermore, clear seasonal patterns, as displayed by deformative disease in the high intertidal zone of Pucatrihue, were attenuated in the middle and lower intertidal zones. Differences in levels of infection in M. laminarioides between the high intertidal zones of Matanzas and Pucatrihue diminished toward the low intertidal zone. Thus, effects of seasonality and locality on infection prevalence may be influenced, at least in part, by the position of the hosts an the intertidal zone. Spatial distribution of the diseased individuals also varied along the beach. This pattern was consistent between the two sites and seemed related to wave exposure and the specific pathogen. Comparisons of the size distribution of noninfected fronds with their infected counterparts showed that infections by Endophyton ramosum and Pleurocapsa sp. more frequently affected medium-and large-sized fronds. This pattern was consistent temporally and similar in the two localities. Finally, a clear association between maturity and prevalence of infection was detected. This association resulted in most fronds of the noninfected segment of the host population being immature, whereas most mature fronds were infected. In conclusion, infectious diseases affecting the red alga Mazzaella laminarioides are a persistent phenomenon in wild populations of the host, although only a small segment of the infected populations displays the full expression of the disease. In spite of the suggested role of factors such as season, latitude, and spatial location of the host on disease prevalence and expression, additional studies are needed to understand fully the dynamics of infectious diseases in wild populations of algal hosts.     

Plasmodium relictum (lineage P-SGS1): effects on experimentally infected passerine birds

We evaluated the effects of Plasmodium relictum (lineage P-SGS1), which is a host generalist, to five species of passerine birds. Light infection of P. relictum was isolated from a naturally infected adult reed warbler Acrocephalus scirpaceus. The parasites were inoculated to naive juveniles of the chaffinch Fringilla coelebs, common crossbill Loxia curvirostra, house sparrow Passer domesticus, siskin Spinus spinus and starling Sturnus vulgaris. Susceptibility of these birds to the infection of P. relictum was markedly different. This parasite developed in birds belonging to the Fringillidae and Passeridae but the starlings (Sturnidae) were resistant. Only 50% of experimental house sparrows were susceptible to the infection. The intensity of parasitemia varied markedly inside and between different susceptible bird species. There were no effects of the infection on body mass or temperature of experimentally infected birds. Infection of P. relictum leads to the significant decrease of haematocrit value and hypertrophy of spleen and liver in heavily infected common crossbills and siskins. This study shows that infection of the same lineage of P. relictum causes diseases of different severity in different avian hosts; that might have different evolutionary consequences and should be taken in consideration in conservation projects.     

Isolation and identification of mycorrhizal fungi associating with an achlorophyllous plant, Epipogium roseum (Orchidaceae)

The identity of mycorrhizal fungi associated with the achlorophyllous orchid Epipogium roseum was investigated by DNA analysis. The fungi were isolated from each coiled hypha (peloton), and the ITS region of nuclear rDNA was sequenced. Phylogenetic analysis based on the neighbor-joining method showed that all the isolates clustered with fungi belonging to Psathyrella or Coprinus in Coprinaceae. Those fungi are known as saprobes, using dead organic materials for a nutritive source. Large colonies of this orchid were frequently found around tree stumps or fallen logs. In such colonies, these decaying wood materials would be used as a large and persistent carbon source for the growth of this orchid. This is the first report of Coprinaceae as an orchid mycorrhizal fungi.     

Relationships between phenolics-conjugated polyamines and sensitivity of sugarcane to smut (Ustilago scitaminea)

Infection of sugarcane buds (var. Barbados 42231) with teliospores of Ustilago scitaminea changes the pattern of polyamine conjugation in several organs of 2-month-old plants. Stalks of infected plants contain SH-spermidine that does not occur in the healthy organ. Similar results have been obtained for SH-spermine in the first expanded leaf and in the stem. The amount of SH-cadaverine in the first expanded leaf, roots and stem of infected plants is always higher than that found for healthy plants. Some phenolics are also associated with different polyamine fractions. So, the amount of p-hydroxybenzoic acid in both SH and PH fractions of polyamines extracted from the root increases after infection. Syringic acid is the main phenol associated with the PH fraction in the first expanded leaf of infected plants, whereas this phenol is mainly associated with both SH and PH fractions isolated from the stem and the whip. Infection enhances conjugation of p-courmaric acid to PH polyamines, whereas caffeic acid appears in the SH fraction in leaf, root and stem. However, ferulic acid seems to be the main hydroxycinnamic acid derivative in the whip. Chlorogenic acid is associated with the SH fraction from the stem of healthy plants although this changes to free phenolics after infection.Key words:Saccharum officinarum, Ustilago sciaminea, phenolics, polyamines.      

Entomophthora species infecting pea aphis

• 1 Three species of Entomophthora infected the pea aphis, Acyrthosiphon pisum, on lucerne at Rothamsted Experimental Station, Harpenden, Hertfordshire, between 1967 and 1972 and caused a maximum mortality of 83% in July 1968.
• 2 E.thaxteriana, the commonest species, occurred each year and frequently infected aphids during cool weather in spring and autumn. E.aphidis and E.planchoniana were absent in some years and were most common during warm weather in midsummer.
• 3 The incidence of infection by the three species was correlated with the density of conidia in the air above the crop, host density and rainfall, but not with any other weather factor considered.
• 4 Infection at any time was much more closely related to environmental factors during the preceding 12 than 3 days. The regressions, however, were weak and the relative importance of different environmental factors for the spread of infection can probably only be determined under controlled conditions in the laboratory.

     

A microsporidian pathogen of the poroporo stem borer,Sceliodes cordalis (Dbld) (Lepidoptera: Pyralidae): Effects on adult reproductive success

Larvae of Sceliodes cordalis were infected over a range of ages and doses with Nosema sp. (NSC). The resulting spore loads in adults ranged from 9.3 × 10⁵ to 8.9 × 10⁷ spores and varied with the age of the larva at infection and with the dose ingested. Infection caused small reductions in female weight, mating success, potential fecundity, longevity, and egg viability. The magnitude of spore loads in female moths was not found to influence any of these factors apart from potential fecundity in very low weight moths. The cumulative effects of infection reduced natality in the laboratory colony from 11,400 to 6000 hatching eggs per 100 females. Laboratory reared, infected females were smaller, had a lower longevity, a reduced spore load, and were more fecund (eggs per milligram adult weight) than infected females from a field population. Manipulation of NSC in a biological control program is not considered to be of any value.     

Infection of Spathoglottis plicata (Orchidaceae) seeds by mycorrhizal fungus

Spathoglottis plicata seeds were encapsulated in 4-mm-diameter capsules of alginate-chitosan or alginate-gelatin and infected with the mycorrhizal fungus Rhizoctonia AM9. The encapsulated seeds were placed directly on Rhizoctonia culture. About 66% of the seeds encapsulated in sucrose-free chitosan-alginate established a symbiotic relationship with the mycorrhizal fungus after co-culturing for 2 weeks. The highest percentage of infection observed was about 84%. Addition of sucrose or using gelatin-alginate for encapsulation reduced the percentage of infection by about half. The growth of Rhizoctonia AM9 in sucrose-free alginate, chitosan and gelatin was found to be minimal. The advantages of germinating orchid seeds, encapsulated in sucrose-free polymers, through mycorrhizal infection is discussed. Received: 19 February 1998 / Revision received: 8 May 1998 / Accepted: 20 May 1998     

Infection experiments reveal broad host ranges of Eurychasma dicksonii (Oomycota) and Chytridium polysiphoniae (Chytridiomycota), two eukaryotic parasites in marine brown algae (Phaeophyceae)

Unialgal cultures of the brown alga Pylaiella littoralis (L.) Kjellman infected by either Eurychasma dicksonii (Wright) Magnus (Oomycota) or Chytridium polysiphoniae (Cohn) H. E. Petersen (Chytridiomycota) were used to elaborate the host ranges of these pathogens. Infection experiments with 48 host species covering 13 orders of the Phaeophyceae showed that 45 species were susceptible to attack by Eurychasma and 23 to Chytridium. The two pathogens showed host-specific differences in generation times: while in Pylaiella the shortest cycles were 16 days for Eurychasma and 6 days for Chytridium, one and five days more, respectively, were required in Acinetospora. Heavy parasite attack on the microscopic stages of host species with heteromorphic life histories, like kelps (Laminariales), is documented and discussed as a potential regulatory factor for the population dynamics of macroalgae.     

The haematozoan parasites of Common Blackbirds Turdus merula: associations with host condition

A population of Common Blackbirds Turdus merula was studied to investigate the relationships between the presence of blood parasites and host morphometrics, a putative sexually selected trait (bill colour), and reproductive parameters. Haematozoa of four genera were detected and their prevalence was high. Infection was negatively associated with adult morphometrics: adults infected with Leucocytozoon were in relatively poor body condition and had shorter wings than uninfected birds. The bill colour of males infected with Plasmodium tended to be duller than that of uninfected males, and in females Haemoproteus infection was significantly positively associated with bill coloration. Haematozoan infection of females was unrelated to measured reproductive parameters, and there was no relationship between blood parasite infection and the provision of parental care.     

Effects of Malaria (Plasmodium berghei) on the Maternal-Fetal Relationship in Mice

Plasmodium berghei infection was more severe in pregnant than in nonpregnant mice. Infection initiated on gestation day 7 resulted in rapidly increasing parasitemia and deaths of all pregnant mice within 12 days, while some nonpregnant mice survived until day 21 postinfection. When mice were infected on gestation day 12 or 14, a proportion of mice died before parturition; but some animals survived to deliver living pups. Reduced birthweights and increased spleen weight to body weight ratios were seen in pups from infected mice as compared with pups from uninfected animals. Histopathological abnormalities of placentae from infected animals included degeneration of the normal labyrinthine architecture and thickening of the trophobast separating maternal and fetal blood vessels.     

Diverse non-mycorrhizal fungal endophytes inhabiting an epiphytic,medicinal orchid (<Emphasis Type="Italic">Dendrobium nobile</Emphasis>): estimation and characterization

Although the terrestrial and temperate orchids–fungal biology have been largely explored, knowledge of tropical epiphytic orchids–fungus relationships, especially on the ecological roles imparted by non-mycorrhizal fungal endophytes, is less known. Exploitation of the endophytic fungal mycobiota residing in epiphytic orchid plants may be of great importance to further elucidate the fungal ecology in this special habitat as well as developing new approaches for orchid conversations. The composition of fungal endophytes associated with leaves, stems and roots of an epiphytic orchid (Dendrobium nobile), a famous Chinese traditional medicinal plant, was investigated. Microscopic imaging, culture-dependant method and molecular phylogeny were used to estimate their entity and diversity. Totally, there were 172 isolates, at least 14 fungal genera and 33 different morphospecies recovered from 288 samples. Ascomycetes, coelomycetes and hyphomycetes were three major fungal groups. There were higher overall colonization and isolation rates of endophytic fungi from leaves than from other tissues. Guignardia mangiferae was the dominant fungal species within leaves; while the endophytic Xylariaceae were frequently observed in all plant tissues; Colletotrichum, Phomopsis and Fusarium were also frequently observed. Phylogenetic analysis based on ITS gene revealed the high diversity of Xylariacea fungi and relatively diverse of non-Xylariacea fungi. Some potentially promising beneficial fungi such as Clonostachys rosea and Trichoderma chlorosporum were found in roots. This is the first report concerning above-ground and below-ground endophytic fungi community of an epiphytic medicinal orchid, suggesting the ubiquitous distribution of non-mycorrhizal fungal endophytes in orchid plants together with heterogeneity and tissue specificity of the endophyte assemblage. Possible physiological functions played by these fungal endophytes and their potential applications are also discussed briefly. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Hepatic lesions associated with Cooperioides hepaticae (Nematoda: Trichostrongyloidea) infection in impala (Aepyceros melampus) of the Kruger National Park

Intrahepatic biliary lesions were observed in two of 12 lambs, seven of 12 yearlings and 10 of 25 adult impala (Aepyceros melampus) surveyed in the Kruger National Park, Republic of South Africa. Lesions were associated with the nematode Cooperioides hepaticae, a trichostrongyloid parasite that inhabits the bile ducts of impala, and ranged from a mild chronic-eosinophilic cholangitis to foci of florid hyperplastic cholangitis with duct ectasia. The latter almost always contained viable worms and, after the worms died, the lesions appeared as foreign-body granulomas. Infection was acquired early in life; severe lesions were seen most frequently in yearlings. Adults were less severely infected, which suggested an acquired immunity. Although the incidence of infection was high, cooperiiasis did not appear to be a serious herd-health problem at the time of this study.     

The effects of a rust infection on fitness components in a natural population of Tolumnia variegata (Orchidaceae)

The effects of a rust infection (Sphenosphora saphena, Basidiomycetes) on several fitness components of the orchid Tolumnia (Oncidium) variegata were quantified in a subtropical moist forest of Puerto Rico. Infected and uninfected plants of two size categories were observed and manipulated by increasing natural levels of fruit production to determine the effects of infection on short and long-term sexual reproduction, subsequent vegetative and reproductive growth, and mortality. Under artificially high levels of fruit production, infection had no effect on short or long-term reproduction through male or female function except for a modest decline in seed viability in small plants. Under natural levels of fruit production, infection was only related to a reduction in the number of leaves per shoot. At artificially high levels of fruit production, infection reduced leaf length, leaf width, and the number of live shoots. Survival was not associated with rust occurrence. The rust appears to have minor ecological impact on this orchid population.     

Interactions between Oncopera alboguttata (Lepidoptera: Hepialidae) and its microsporidan pathogen, Pleistophora oncoperae (Protozoa: Microsporida)

Infection by Pleistophora oncoperae is widespread in populations of Oncopera alboguttata. Detailed study of insects from one site indicated that 85% of the 131 pupae and 65% of the 403 adults were infected. The infection did not adversely affect duration of larval and pupal development, adult life span, the number of eggs laid, or fecundity. Infected females were able to transmit the disease to their progeny, though the degree of transmission ranged from 0 to 92%, depending on the severity of the parental infection. Transmission of the disease by infected males could not be detected. It was estimated that 49% of the progeny from this site would have been infected by transovum transmission. Details of the incidence of P. oncoperae infection from this area during the period 1972 to 1979 are given to emphasise the possible role of this disease in O. alboguttata population dynamics.     

Agrobacterium-mediated transformation of cotyledonary explants of Chinese cabbage (Brassica campestris L. ssp. pekinensis)

 A procedure for producing transgenic Chinese cabbage plants by inoculating cotyledonary explants with Agrobacterium tumefaciens strain EHA101 carrying a binary vector pIG121Hm, which contains kanamycin-resistance and hygromycin-resistance genes and the GUS reporter gene, is described. Infection was most effective (highest infection frequency) when explants were infected with Agrobacterium for 15 min and co-cultivated for 3 days in co-cultivation medium at pH 5.2 supplemented with 10 mg/l acetosyringone. Transgenic plants of all three cultivars used were obtained with frequencies of 1.6–2.7% when the explants were regenerated in shoot regeneration medium solidified with 1.6% agar. A histochemical GUS assay and PCR and Southern blot analyses confirmed that transformation had occurred. Genetic analysis of T1 progeny showed that the transgenes were inherited in a Mendelian fashion. Received: 15 December 1998 / Revision received: 2 July 1999 · Accepted: 8 July 1999     

Distribution of Nosema meligethi (Microsporida) in populations of Meligethes aeneus (Coleoptera: Nitidulidae) in Turkey

This is the first study on Nosema meligethi in populations of Meligethes aeneus in Turkey. In total, four of the 2020 beetles studied were infected with the parasite, giving an infection average of 0.2% in Turkey. Infection was observed in two of the eight localities investigated, and the infection rates in these localities were similar: 2.94 and 2.86%. N. meligethi infection was not observed in 1676 beetles (83% of the total studied) from five localities, including the main Brassica oleracea growing area, where chemical pesticides are commonly used. Three hundred and forty‐four beetles (17% of the total studied) were collected from three localities from uncultivated areas where there is no chemical pesticide application; infection was found in beetles from two of these localities. This study confirms that pesticide usage at sampling sites may play a role in the occurrence of N. meligethi, because the samples from which Nosema was detected originated from areas in which pesticides are not used.     

The control of apple canker (Nectria galligena) in a young orchard with established infections

In a factorial experiment on canker control the efficiency of phenylmercurie nitrate (PMN) applied at leaf fall, before bud burst or both was compared with the application of dodine, dithianon, triforine, thiabendazole, benomyl or carbendazim in May and June. Of the total number of cankers which developed in unsprayed trees 76–78% resulted from infections in April to August of each year of the experiment. Infection was reduced significantly by all of the fungicides applied in summer. Of these carbendazim was outstanding, controlling both summer and autumn infections. Sporulation throughout the summer was suppressed by carbendazim and to a lesser extent benomyl, but whereas the suppressant effect of carbendazim persisted until long after leaf fall that of benomyl was evident only until August. Dodine, dithianon, triforine and thiabendazole had no significant effect on spore production. Dithianon and dodine showed highest toxicity to the germination of Nectria galligena spores of all fungicides used in summer. All of the fungicides controlled apple scab (Venturia inaequalis) although thiabendazole was the least effective. Autumn applications of PMN reduced canker incidence but their value alone was not as great as carbendazim, dithianon, benomyl or dodine applied in summer. PMN applied in spring reduced the number of cankers in trees receiving no other fungicides but tended to increase the incidence of infections, particularly in autumn, when used in conjunction with fungicides applied in May and June. PMN applied before bud burst reduced sporulation of N. galligena for a few weeks, after which production resumed and in late summer and autumn actually exceeded the controls. None of the fungicides had any direct effect on leaf fall. Infection of the crotch and basal leaf scars was more common in summer than in autumn whereas infection of leaf scars above the basal region was more common in autumn than in summer. The rootstocks of many of the trees became infected via callus tissue associated with adventitious root development and this was controlled by the carbendazim treatment.     

The quantitative estimation of the infection of bean seed with Pseudomonas phaseolicola (Burkh.) Dowson

A routine laboratory method for the detection of Pseudomonas phaseolicola in bean seed is described. The method will detect low levels of seed-borne infection and has been used in a statistical procedure (the most probable number method) to give an estimate of percentage infection. Infection in seeds harvested from heavily infected crops varied from 10 to 1%, compared with from 1% to less than 0.1% in commercial seed stocks. A high proportion of infected seeds failed to produce infected plants and this may account for the very low levels of primary infection reported in the field. Removal of seeds showing possible ‘symptoms’ of disease reduced, but did not eliminate, infection from seed stocks.     

Phylogeny of subfamily Epidendroideae (Orchidaceae) inferred from ndhF chloroplast gene sequences

This project undertakes the first molecular-based phylogenetic study of subfamily Epidendroideae (Orchidaceae). Approximately 1200 nucleotides (from the 3' half of the chloroplast gene ndhF for 34 orchid taxa and a lilioid monocot, Clivia miniata (Amaryllidaceae), were subjected to phylogenetic analysis using parsimony and maximum likelihood methods. Oryza sativa (Poaceae), a nonlilioid monocot, was designated as outgroup. Trees from both parsimony and maximum likelihood methods suggest that subfamily Epidendroideae is monophyletic, with Listera (Neottieae) as sister. Although subtribal relationships are typically well resolved and have strong branch support, intertribal relationships are generally poorly resolved. Perhaps this general lack of resolution among tribes reflects a rapid species radiation that coincided with anatomical, physiological, and anatomical adaptations that initiated large-scale epiphytism in the ancestral Epidendroideae. Six taxa in this study exhibit deletions that are not evenly divisible by three and result in extensive sequence frameshifts. For example, one deletion is 227 bp in length and is flanked by the short direct repeat sequence; TCAATAGGAATTTCTTTT. Multiple deletions and frameshifts suggest that ndhF may be a pseudogene, in at least some orchid taxa.