Temperature and seedling age affect susceptibility of perennial ryegrass seedlings to pathogenic fungi

Summary Effects of temperature and seedling age on survival of perennial ryegrass (Lolium perenne L.) seedlings grown on sand-wheat wholemeal cultures of different isolates ofFusarium spp. (9 isolates),Pythium spp. (9 isolates), andChaetomium spp. (1 isolate) are reported. Some isolates were virulent over the whole range of temperatures tested (7.5–27.5°C). The virulence of others depended on temperature. Most isolates were less virulent at intermediate temperatures (12.5–22.5°C) than at higher or lower temperatures. At 25°C ryegrass seedlings were susceptible to fungal attack for only a limited period after germination commenced. This period differed for different fungi, but for most isolates tested, seedlings were resistant after 2–3 days.     

Fungi pathogenic to ryegrass seedlings

Summary Fungi borne on or in ryegrass (Lolium spp.) seeds or invading ryegrass seedlings grown on field soils were isolated and identified. Selected isolates were tested to determine their pathogenicity to ryegrass seedlings. Seed-borne fungi were generally weakly virulent or non-pathogenic to ryegrass seedlings. Pathogenic seed-borne fungi includedChaetomium globosum Kunze: Fr.,Curvularia trifolii (Kauffm.) Boedijn, and species ofPenicillium Link andAspergillus Mich. ex Link. Species of fungi isolated from seedlings grown on field soils de pended on soil and temperature. Soil-borne fungi pathogenic to seedlings includedFusarium avenaceum (Fr.) Sacc.,F. culmorum (W. G. Smith) Sacc.,F. equiseti (Corda) Sacc.,F. oxysporum Schlecht.: Fr.,F. solani (Mart.) Sacc.,Pythium afertile Kanouse and Humphrey,P. debaryanum auct. non Hesse,P. irregulare Buisman,P. ultimum Trow, a sphaerosporangiatePythium sp.,Chaetomium globosum, Thanatephorus cucumeris (Frank) Donk,Trichoderma koningii Oudem., and aPhomopsis sp. Individual isolates of fungi differed in virulence to ryegrass seedlings, and ryegrass cultivars differed in susceptibility to seedling pathogens.     

Studies in parasitic watermolds of Kumaun Himalayas: The host range of five species of olpidiopsis

The host range of five species of Olpidiopsis in some species of Achlya, Aphanomyces, Brevilegnia, Isoachlya, Saprolegnia, Thraustotheca and Pythium was studied. Species were different in their host range.     

Replant problems in South Tyrol: role of fungal pathogens and microbial population in conventional and organic apple orchards

The South Tyrol, the main apple-growing area in Italy, is characterised by intensive soil cultivation. Previous investigations have revealed the existence of replant disorders although the main causes of these have not been evaluated. A survey was carried out in this area with two main aims: to evaluate the role of soil-borne pathogens in apple replant disease and to compare the impact of organic and conventional management on replant diseases caused by soil-borne pathogens. The experimental sites were chosen to obtain three pairs of contiguous conventional and organic apple orchards. There was a high level of organic matter in both the organic and the conventional apple orchards with no appreciable differences in humic fractions. The soil sickness test with apple seedlings revealed a significant reduction in growth for all soil samples as compared to the peat control. The growth score on soil samples from organic orchards was significantly higher than that obtained on conventional soil. Total fungal population in soil samples was positively correlated to the apple seedlings growth score and negatively correlated to the frequency of root colonisation. Most of the root-colonising pathogens belonged to the well-known root rot complex, Rhizoctonia solani and Pythium spp. being the most pathogenic on apple seedlings.     

Effect of temperature,hydrogen ion concentration and osmotic potential on zoospore production by threePythium species isolated from pond water

Pythium fluminum produced zoospores most abundantly at 15°C, whereas the optima forPythium group F andP. marsipium were 20 and 25°C, respectively. Increasing the incubation temperature above the optimum resulted in the decrease of the duration of zoospore production. InPythium group F the ability to produce zoospores was not lost even after incubation at 40°C for 24 h. On the other hand,P. marsipium andP. fluminum lost the ability under these conditions. Zoospore production was inhibited at pH 4.5 and 10.5 in all the species tested.Pythium fluminum andP. marsipium were found to have two pH optima for zoospore production (7.5 and 9.5 for the former and 5.5 and 8.5 for the latter). The optimum pH for zoospore production byPythium group F was 6.5–7.5. Moderate osmotic potentials (–0.27–0.47 MPa) appeared to favor zoospore production by the pythia tested. The effect of temperature, pH and osmotic potential on zoospore production was discussed in relation to pollution of pond water.     

Virulence ofPythium spp. isolated from pond water

Pre-emergence damping-off tests indicate that Pythiumspp. from pond water can be divided into two categories: avirulent Pythium (P. diclinum, P. marsipium, P. middletonii, P. monospermum, P. pleroticum, P. undulatum)and weakly virulent Pythium (P. catenulatum, P. coloratum, P. dissotocum, P. papillatum, Pythium Group F, Pythium group HS, Pythium group P, Pythiumgroup T). Post-emergence damping-off tests indicate that the pythia tested can also be divided into three categories: avirulent Pythium (P. catenulatum, P. dissotocum, P. marsipium, P. monospermum, P, papillatum, P. pleroticum, P. undulatum, Pythium group F, Pythium group T),weakly virulent Pythium (P. coloratum, P. diclinum, P. middletonii, Pythiumgroup P and moderately virulent Pythium (Pythium group HS).     

Materials forPythium flora of Japan. X. Occurrence,identification and seasonality ofPythium spp. in three pond waters and mud soils in Osaka

Seasonal fluctuations ofPythium species in three pond waters and mud soils in Sakai, Osaka, were studied for periods of two years and 14 months, respectively. Thirteen species and four groups were isolated from the pond waters while nine species and three groups were obtained from the mud soils. The highest frequency and total number of species were recorded in the cold and moderately warm seasons and the lowest in summer. Most of the species isolated from the pond waters have been previously recorded from aquatic habitats.     

Alnus rubra nodulation capacity of soil under five species from harvested forest sites in coastal British Columbia

Nodulation of Alnus rubra seedlings after inoculation with soil from under A. rubra, Betula papyrifera. Rubus lacianutus, R. spectabilis, and R.ursinus on 2 recently harvested sites was compared. Nodulation capacity was low compared to other published reports, ranging from 0 to 18.9 infective units cm^-3 of soil and was significantly affected by the site and plant species. Nodulation capacity of soil under alder was significantly higher than under all other species except R. spectabilis, regardless of site. The lowest nodulation capacity was found in soil under B. papyrifera.Joint appointment with Dept. of Soil Science, Faculty of Agricultural Sciences     

Characterisation of Lysobacter enzymogenes (Christensen and Cook 1978) strain 3.1T8, a powerful antagonist of fungal diseases of cucumber

Isolate 3.1T8 of Lysobacter enzymogenes (Christensen and Cook 1978), originating from the rhizosphere of cucumber and shown to have the potential to control Pythium aphanidermatum, is described. The strain produces extracellular proteases and lipases and shows high levels of resistance against streptomycin, kanamycin and tetracycline, but not to chloramphenicol. It shows strong in vitro antibiosis against P. aphanidermatum and several other phytopathogenic fungi. In order to identify the isolate, a carbon substrate oxidation profile (Biolog) was generated, and fatty acid methyl ester (FAME) analysis was performed. Also, the 16S rRNA gene was cloned and sequenced. With Biolog and FAME analysis, no assignment to species level was possible, because the species was not in the respective databases. BLAST analysis of the obtained sequence, followed by phylogenetic analysis, using a number of related and unrelated sequences, showed that the isolate was most closely related to Lysobacter enzymogenes (Christensen and Cook 1978).     

田野菟丝子寄生对五种红树植物叶绿素荧光参数的影响

红树林由于受到入侵植物薇甘菊的危害发生大面积退化,而田野菟丝子寄生是防控薇甘菊的有效途径。为了探讨田野莬丝子寄生对红树植物的影响,该研究通过同质园控制试验,利用PAM-2100便携式调制叶绿素荧光仪,测定了三种真红树植物(老鼠簕、木榄、秋茄)和两种半红树植物(海芒果、银叶树)幼苗在田野菟丝子寄生及对照情况下的叶片叶绿素荧光参数。结果表明:田野菟丝子寄生对红树植物幼苗光系统Ⅱ(PSⅡ)最大光化学效率(F_v/F_m)没有显著影响;对更为敏感的红树植物幼苗PSⅡ潜在活性(F_v/F_o)同样也没有显著影响;试验后期发现田野菟丝子对红树植物幼苗无法成功寄生。由此可见,田野菟丝子用于红树林薇甘菊的防治是安全的。     

Ecology of Hymexazol-Insensitive Pythium Species in Field Soils

Soils from 100 irrigated fields (95 under vegetables, 5 under citrus) in different geographical locations in the West Bank (Palestinian Autonomous Territory) were surveyed for hymexazol-insensitive (HIS) Pythium species using the surface soil dilution plate (SSDP) method with the VP3 medium amended with 50 mg/L hymexazol (HMI) (VP3H50), over a period of 12 months. HIS Pythium species were isolated from 37% of the soils surveyed, with mean population levels ranging from 4.3-1422 CFU g(-1) dry weight. Eight HIS Pythium taxa were recovered on the VP3H50 medium, the most abundant of which was P. vexans (found in 29% of field soils surveyed). Seasonal variations in population levels of HIS Pythium species were studied in four fields over a period of 12 months. Significant seasonal variations in HIS population levels were detected in the four fields, with the highest population levels of HIS Pythium spp. encountered in spring and the lowest population levels in winter in three of the fields surveyed. Effects of HMI on linear growth and colony morphology of 149 Pythium ssp. isolates were examined on CMA amended with HMI at five concentrations. Pythium vexans isolates responded differently from those of the other Pythium species. Isolates of this important pathogen were more insensitive to HMI at high concentrations than the other main species tested. A large proportion of the P. ultimum isolates was either insensitive or weakly sensitive to HMI. Furthermore, a few isolates of other Pythium species were insensitive to the fungicide at various concentrations. The colony morphology of P. vexans isolates was not affected by HMI, whereas colonies of the other species showed sparse growth on the HMI amended medium relative to the control. The pathogenicity of P. vexans and P. ultimum isolates to cucumber seedlings was examined in growth chambers. Insensitive isolates of both species were found to be more virulent damping-off pathogens than the sensitive isolates. The present study demonstrates that HMI can not be used effectively in controlling Pythium spp. in soil inhabited with high densities of HIS Pythium spp. pathogens.     

Effect of beetle size on predation of cabbage root fly eggs by ground beetles

Laboratory studies were done to determine the numbers of cabbage root fly (Delia radicum L.) (Diptera: Anthomyiidae) eggs eaten by sixty species of ground beetles (Coleoptera: Carabidae) collected from a range of habitats. For 35 species that were between 2.7 mm and 10 mm long, there was a linear relationship between the numbers of eggs eaten and beetle length. For each 1 mm increase in length above 2.7 mm, an additional 18 eggs were eaten/beetle/day. Eight further species within the above size range did not eat any fly eggs, as these species are known to be either phytophagous or to feed on moving prey. Large numbers of eggs were eaten by beetles in 13 of the 25 genera tested. Based on size, maximum numbers of eggs were eaten by 7 species of Agonum Bonelli, 5 species of Amara Bonelli and seven species of Bembidion Latreille. Only one of the 6 species of Pterostichus Bonelli tested, P. strenuus (Panz.), ate the expected numbers of eggs, the other species being too large to feed from such small prey items as cabbage root fly eggs. The numbers of beetles larger than 10 mm that ate eggs was highly variable and so 10 mm was considered the upper size limit of carabid predators of cabbage root fly eggs.     

Variations in total phenolics during ontogenetic, morphogenetic, and diurnal cycles inHypericum species from Turkey

Several species ofHypericum are used in traditional Turkish folk medicine. Their most medicinally important secondary metabolites are the hypericins, hyperforins, and phenolics. Here, we determined the ontogenetic, morphogenetic, and diurnal variations in total phenolics contents fromH. aviculariifolium subsp.depilatum var.depilatum (endemic),H. perforation, andH. pruinatum. Plants of wild-growingH. aviculariifolium subsp.depilatum var.depilatum andH. perforatum, and greenhouse-grownH. pruinatum were harvested four times per day during their vegetative, floral-budding, full-flowering, fresh-fruiting, and mature-fruiting stages. They were then dissected into stem, leaf, and reproductive tissues to be dried separately and assayed. The highest level of phenolics inH. aviculariifolium subsp.depilatum var.depilatum andH. pruinatum was found in the leaves, whereas the floral buds produced the greatest amount inH. perforatum. Variations in contents from whole plants fluctuated diurnally, differing among species over the course of ontogenesis, reaching the highest level at floral-budding and tending to increase at mid-day inH. aviculariifolium subsp.depilatum var.depilatum. ForH. perforatum andH. pruinatum, contents also were the highest during floral development, although no diurnal fluctuations were observed in those species.     

Prevalence of Fusarium species of the Liseola section on selected Colombian animal feedstuffs and their ability to produce fumonisins

A total of 57 samples of feedstuffs commonly used for animal nutrition in Colombia (corn, soybean, sorghum, cottonseed meal, sunflower seed meal, wheat middlings and rice) were analyzed for Fusarium contamination. Fusarium fungi were identified at species level by means of conventional methods and the ability to produce fumonisins of the most prevailing species was determined. A total of 41 of the feedstuffs analyzed (71.9%) were found to contain Fusarium spp. Most contaminated substrates were corn (100%), cottonseed meal (100%), sorghum (80%), and soybean (80%). Wheat middlings and rice showed lower levels of contamination (40% and 20%, respectively), while no Fusarium spp. could be isolated from sunflower seed meal. The most prevalent species of Fusarium isolated were F. verticilliodes (70.8%), F.␣proliferatum (25.0%), and F. subglutinans (4.2%). All of them correspond to section Liseola.Production of fumonisins on corn by the isolated Fusarium was screened through liquid chromatography. Almost all strains of F. verticilliodes (97.1%) produced FB1 (5.6–25,846.4 mg/kg) and FB2 (3.4–7507.5 mg/kg). Similarly, almost all strains of F.␣proliferatum (91.7%) produced fumonisins but at lower levels than F.␣verticilliodes (FB1 from 6.9 to 3885.0 mg/kg, and FB2 from 34.3 to 373.8 mg/kg), while F. subglutinans did not produce these toxins. This is the first study in Colombia describing toxigenic Fusarium isolates from␣animal feedstuffs.     

Immunological detection of the fungal parasite,Pythium sp.; the causative organism of red rot disease in Porphyra yezoensis

The red rot disease of Porphyra yezoensis Ueda (Rhodophyta) is caused by a parasitic fungus, Pythium sp. To facilitate the detection of this pathogen in infected thalli of P. yezoensis, polyclonal and monoclonal antibodies were prepared. Antibodies were raised against antigen prepared from an isolate of fungal hyphae obtained from red-rot infected thallus of P. yezoensis from Aichi Prefecture. Polyclonal antibody was obtained from the antisera of immunized rabbits. Monoclonal antibody was obtained from the culture supernatant of a hybridoma which had been established by cell fusion between a myeloma cell line and spleen cells of immunized mice. Hyphae were detected by means of indirect fluorescent antibody technique. Titers of polyclonal antibodies obtained were too low to recognize fungal hyphae that had penetrated the thalli of P. yezoensis; however, monoclonal antibody was useful for the detection of fungi that had penetrated algal thalli. The monoclonal antibody was specific for the Pythium sp. from red-rot infected thalli of P. yezoensis from Saga (western Japan) and from Aichi Prefectures (central Japan), but was ineffective for infections from Miyagi Prefecture (northern Japan). It is evident, therefore, that Pythium sp. can give rise to immunologically distinct groups of red rot disease. Based on chemical and enzymatic treatments, the antigenic determinant appeared to localize on the sugar chains of glycoconjugates or the polysaccharides of the hyphal cell wall.     

Effect of temperature,hydrogen ion concentration and osmotic potential on oospore germination of fivePythium spp. isolated from pond water

Oospore germination occurred over a temperature ranging of 15–35°C forPythium coloratum, 10–35°C forP. diclinum, 15–30°C forP. dissotocum, 7–30°C forP. monospermum, and 10–30°C forP. pleroticum. Optimum temperature was 25°C for all species tested. In case of pH, oospore germination occurred over a range of 4.76–8.55 with an optimum of 6.40–7.40. The least germination occurred at pH 4.76 forP. coloratum, P. diclinum, P. monospermum andP. pleroticum, whileP. dissotocum germinated from pH 5.02. Oospores of the all tested pythia were able to germinate at –0.13 to –1.65 MPa and could not germinate at –3.40 MPa, with the highest germination rate at –0.27 to –0.47 MPa. The effect of temperature, pH and osmotic potential on oospore germination was discussed in relation to pollution of pond water.     

The importance of temporal dynamics of edge effect in reedbed design: a 12-year study on five bird species

Although edge effect is a key topic of conservation biology, we have no data on the temporal dynamics of it. I investigated the distribution of five passerine bird species across reedbed (Phragmites australis) edges during large-scale construction work in the Kis-Balaton marshland, Hungary. The construction provided an experimental approach to study the effects of large timescale changes within a shorter period, because neither the locality nor the vegetation type changed. The water level was increased in the study area, which homogenised the internal structure of reedbed by declining the scattered small willow bushes (Salix) and the grass/sedge layer. The sedge (Acrocephalus schoenobaenus) and reed warblers (Acrocephalus scirpaceus) preferred edges. The sedge warbler, however, declined after inundation, while the reed warbler did not respond. Savis warbler (Locustella luscinioides) sharply declined during the study with changing edge effect. The number of great reed warblers (Acrocephalus arundinaceus) increased during the study, mainly in the reedbed interior, where the stands became patchy with open water. Reed bunting (Emberiza schoeniclus) avoided interiors, and declined over the study. Therefore, there were significant changes in the distribution of reedbed birds across the edge, although the location of edges and the basic habitat, reedbed, did not change. The results highlight the need to incorporate edge effect as a dynamic process in wetland planning.     

Experimental study on the impact of dinoflagellate Alexandrium species on populations of the rotifer Brachionus plicatilis

To investigate harmful effects of the dinoflagellate Alexandrium species on microzooplankton, the rotifer Brachionus plicatilis was chosen as an assay species, and tested with 10 strains of Alexandrium including one known non-PSP-producer (Alexandrium tamarense, AT-6). HPLC analysis confirmed the PSP-content of the various strains: Alexandrium lusitanicum, Alexandrium minutum and Alexandrium tamarense (ATHK, AT5-1, AT5-3, ATCI02, ATCI03) used in the experiment were PSP-producers. No PSP toxins were detected in the strains Alexandrium sp1, Alexandrium sp2.Exposing rotifer populations to the densities of 2000 cells ml⁻¹ of each of these 10 Alexandrium strains revealed that the (non-PSP) A. tamarense (AT-6) and two other PSP-producing algae: A. lusitanicum, A. minutum, did not appear to adversely impact rotifer populations. Rotifers exposed to these three strains were able to maintain their population numbers, and in some cases, increase them. Although some increases in rotifer population growth following exposures to these three algal species were noted, the rate was less than for the non-exposed control rotifer groups.In contrast, the remaining seven algal strains (A. tamarense ATHK, AT5-1, AT5-3, ATCI02, ATCI03; also Alexandrium sp1 and Alexandrium sp2) all have adverse effects on the rotifers. Dosing rotifers with respective algal cell densities of 2000 cells ml⁻¹ each, for Alexandrium sp1, Alexandrium sp2, and A. tamarense strains ATHK and ATCI03 showed mean lethal time (LT₅₀) on rotifer populations of 21, 28, 29, and 36h, respectively. The remaining three species (A. tamarense strains AT5-1, AT5-3, ATCI02) caused respective mean rotifer LT₅₀s of 56, 56, and 71 h, compared to 160 h for the unexposed “starved control” rotifers. Experiments to determine ingestion rates for the rotifers, based on changes in their Chlorophyll a content, showed that the rotifers could feed on A. lusitanicum, A. minutum and A. tamarense strain AT-6, but could graze to little or no extent upon algal cells of the other seven strains. The effects on rotifers exposed to different cell densities, fractions, and growth phases of A. tamarense algal culture were respectively compared. It was found that only the whole algal cells had lethal effects, with strongest impact being shown by the early exponential growth phase of A. tamarense. The results indicate that some toxic mechanism(s), other than PSP and present in whole algal cells, might be responsible for the adverse effects on the exposed rotifers.     

Hoarding behaviors of two wood mouse species: Different preference for acorns of two Fagaceae species

Two species of wood mouse, Apodemus argenteus and A. speciosus, were observed consuming and hoarding acorns of Quercus serrata and Castanopsis cuspidata. When each species of acorn was supplied individually, both species of mice used each species of acorn for eating and hoarding. When both species of acorn were supplied, A. argenteus consumed or hoarded only C. cuspidata, whereas A. speciosus tended to eat C. cuspidata acorns at the feeding site, and disperse or hoard Q. serrata acorns. Apodemus speciosus is unlikely to disperse C. cuspidata acorns (their utilization was biased towards consumption) when Q. serrata acorns are also available. Apodemus argenteus will make almost no contribution to the dispersal of Q. serrata when the two acorn species coexist.     

A technique for isolating bacteria-freePythium spp. from pond water

A special technique for isolating aquaticPythium spp. that are free from bacteria is presented and discussed by citing the disadvantages of the previous studies.