Pesticides to control ostracods grazing on blue-green algae

Means to control ostracods grazing on blue-green algae (cyanobacteria) important in fixing nitrogen in flooded rice soils were studied. The relative acute lethal toxicity (LC₅₀⁴⁸) to the ostracods Cyprinotus carolinensis and Heterocypris luzonensis grazing on Tolypothrix tenuis was 0.4 and 2.4 μg ml^?1 for carbofuran and 4.5 and more than 56.0 μ g ml^?1 for lindane. Complete inhibition of grazing was achieved with 1.0 and 25 μ g carbofuran ml^?1 and 0.1 and 5.6μ g lindane ml^?1 for C. carolinensis and H. luzonensis, respectively. Lindane at concentrations below 0.02 μ g ml^?1 stimulated feeding by C. carolinensis on the alga. Breakdown of carbofuran markedly reduced its effectiveness as a measure to control grazing, but lindane did not rapidly lose its effectiveness. The toxicity of carbofuran to C. carolinensis feeding on T. tenuis was not affected by pH. The difference in ostracod responses to the pesticides, which may be associated with resistance acquired through previous exposure, is an important consideration in designing practical means to reduce grazing in paddy fields.     

Epibiotic bacteria associated with microcrustaceans in the overlying water of paddy fields

The surface of micro crustaceans collected from the overlying water of a submerged paddy soil was observed in detail by scanning electron microscopy. Epibiotic bacteria were less diverse compared to free-living bacteria in the overlying water. Specific bacteria appeared to preferentially colonize certain parts of microcrustaceans. The epibiotic bacteria, the sites they colonized and their density depended on the kinds of microcrustaceans (Moina macrocopa, Cyclopidae, Cypretta sp., and Tanycypris sp.). These results suggested the presence of significant associations in the overlying water between specific groups of bacteria and microcrustaceans.     

The abundance of heterocystous blue-green algae in rice soils and inocula used for application in rice fields

Summary Algal populations were quantified (as colony-forming units [CFU] per square centimetre) in 102 samples of rice soils from the Philippines, India, Malaysia and Portugal, and in 22 samples of soil-based inocula from four countries. Heterocystous blue-green algae (BGA) were present in all samples. Nostoc was the dominant genus in most samples, followed by Anabaena and Calothrix. In soils, heterocystous BGA occurred at densities ranging from 1.0 × 10² to 8.0 × 10⁶ CFU/cm² (median 6.4 × 10⁴) and comprised, on average, 9% of the total CFU of algae. Their abundance was positively correlated with the pH and the available P content of the soils. In soil-based inocula, heterocystous BGA occurred at densities ranging from 4.6 × 10⁴ to 2.8 × 10⁷ CFU/g dw (dry weight), comprising only a moderate fraction (average 13%) of the total algae. In most soils, the density of indigenous N₂-fixing BGA was usually higher than that attained by applying recommended rates of soil-based inoculum. Whereas research on the practical utilization of BGA has been mostly directed towards inoculation with foreign strains, our results suggest that attention should also be given to agricultural practices that enhance the growth of indigenous strains already adapted to local environmental conditions.Maître de Recherches ORSTOM (France), Visiting Scientist at IRRI     

Molecular characterization of the wild relatives of safflower (Carthamus tinctorius L.) in Turkey as revealed by ISSRs

In the present study, we used 39 plant samples representing six Carthamus taxa collected from different regions of Turkey: 11 of C. dentatus, 5 of C. glaucus, 18 of C. lanatus, 3 of C. persicus, 1 of C. tenuis subsp. tenuis and 1 of C. tenuis subsp. gracillimus. On these samples, we screened nine ISSR markers for polymorphic products. We generated 151 polymorphic bands. In a dendrogram based on these ISSR bands, the first branch was C. tenuis subsp. gracillimus, then C. persicus formed the second group. The rest of the taxa were grouped in two clusters: the first included C. lanatus, C. tenuis subsp. tenuis and C. glaucus, and the second included C. dentatus. Within the first cluster, C. tenuis subsp. tenuis and C. glaucus grouped together and then united to C. lanatus. Representatives of the same taxa consistently clustered together. Also within species, the groupings were generally concordant with their geographical distributions.     

Interaction among free-living N-fixing bacteria isolated from Drosera villosa var. villosa and AM fungi (Glomus clarum) in rice (Oryza sativa)

Rice is usually grown in N-deficient soils, demanding that the element be supplied to the field by commercially available N fertilizers. Unfortunately, a substantial amount of the urea-N or NO₃-N applied as fertilizers is lost through different mechanisms, causing environmental pollution problems. Utilization of biological N₂ fixation (BNF) technology can decrease the application of N fertilizers, reducing environmental risks. This study evaluated the effects of four free-living N-fixing bacterial species, isolated from oligotrophic soil conditions, as single inoculants or combined with arbuscular mycorrhizal fungi (Glomus clarum), on the development of rice plants grown as flooded or upland rice, in the greenhouse. Upland rice roots were inoculated with Methylobacterium sp., Burkholderia sp. and Sphingomonas sp., whereas the species Burkholderia sp., Pseudomonas sp. and Sphingomonas sp., were inoculated on flooded rice. Inoculants consisted of individual bacterial species or their mixtures, with or without G. clarum. Controls included non-bacteria/non-AM fungi, and AM fungi alone. Experiments were carried out in five replicates. The presence of G. clarum decreased or did not significantly affect plant growth under the different culture conditions. The presence of AM fungi stimulated the N-fixing bacterial population of upland rice. Bacterial species had different effects, under both culture conditions, and some genera of N-fixing bacteria increased root and shoot growth at different plant growth stages. The level of mycorrhiza colonization had no influence on plant growth     

Effect of grazer regulation and algal inoculation on photodependent nitrogen fixation in a wetland rice field

Summary A dry season field experiment conducted for two consecutive years highlighted problems of achieving increased populations of N₂-fixing blue-green algae (BGA) in wetland rice fields. Inoculation of non-indigenous BGA strains, either dried or as fresh viable inocula even at high levels of application, was unsuccessful. A limiting effect of grazing invertebrate populations on BGA establishment was evident, but other factors were involved. Reducing grazer pressure did not permit establishment of inoculated BGA; interspecific competition and environmental factors may explain the inoculation failure. Grazer regulation permitted the establishment of a fast-growing indigenous N₂-fixing Anabaena and the doubling of N₂-fixing activity over a control. Neither inoculation nor grazer control affected grain yields significantly.     

Plant and soil responses to a commercial blue-green algae inoculant

A commercial blue-green algae inoculant (Genesis II) for improving the N content of soils was applied to basalt and pumice soils in a greenhouse pot test with orchardgrass, pinegrass, Douglasfir, and ponderosa pine. Treatments were control (deionized water), live algae, killed algae, live algae plus P, K and S and P, K and S only. Plant biomass yields with live inoculant generally were significantly greater than with the control treatment but were the same as with killed inoculant. Live algae plus P, K and S further enhanced productivity. P, K and S alone produced no increase over the control treatment. Response to the inoculant compared to the control appears to be a result of addition of nutrients present in the inoculant stock solution. Further biomass increases with the P, K and S plus live algae treatment compared to live and dead algae treatments occurred because these nutrients became limiting as N was added. Total organic-N and total C in surface soils were similar in all treatments.When the stock solution was sampled via culture methods, the most prominent species found was Chlorella, a green alga. Anabaena, an N₂ fixing blue-green alga, produced less than one colony per plate on the average. Phormidium, a blue-green alga not found in the inoculant, was dominant on the soil surface at the end of the test suggesting a soil origin for this species. Results indicate that Genesis II probably has very limited potential to enhance blue-green algal populations and, consequently, N of the forest soils used in this test.     

Epibiotic microorganisms associated with microcrustaceans in overlying water of Philippine paddy fields

Epibiotic microorganisms associated with micro crustaceans in the overlying water of Philippine paddy fields were examined by scanning electron microscopy, and their associations were compared with those observed in Japanese paddy fields (Soil Sci. Plant Nutr., 43, 633-641, 651-664, 1997). Various types of microorganisms, including bacteria, protozoa, and algae, colonized microcrustaceans and their kinds and colonizing patterns varied depending on the kinds of microcrustaceans. Common associations between epibionts and respective micro crustaceans were observed in the Philippines and in Japan: e.g., rodshaped bacteria on Cyclopidae and Cypridopsidae; no microorganisms on Simocephalus spp.     

Blue-green algae in soils of specially protected natural territories in the Cis-Ural and Southern Ural regions

Blue-green algae (Òyanobacteria) have been studied in soils of specially protected natural territories of the Cis-Ural and Southern Ural regions. The species composition of the algae has been determined in water and dish cultures with fouling glasses. The investigated soils are characterized by the rich flora of bluegreen algae comprising 79 species and intraspecies taxa. Recreation loads on the territory have resulted in a drop in the species diversity and numbers of algae; their taxonomic structure is becoming simplified. Active development of algae from the Oscillatoriales order assigned to the P-form and to the typical xerophytes (species of the Oscillatoria, Phormidium, and Plectonema genera) has been registered in some anthropogenically disturbed areas.     

受固氮活性制约的蓝藻固氮去铵阻抑及其与生理条件的关系

在不同气体环境中培养的蓝藻Ａｎａｂａｅｎａ７１２０固氮活性各异，Ａｒ＋ＣＯ２中最大，空气中次之，Ａｒ中最小。固氮活性高者去铵阻抑速率大，反之则小。它们对各种生理条件的反应不一样，固氮活性高者，其去铵阻抑速率受氧和氮的抑制小。在氢和氧加合条件下，三种活性的蓝藻去铵阻抑均加快，但活性低者慢而小些。光强减弱或加光合抑制剂时，固氮活性低者去铵阻抑速率显著小于活性高者，而添加外源的蔗糖或丙酮酸时，也是固氮活     

The effect of surface growth of blue-green algae and bryophytes on some microbiological,biochemical, and physical soil properties

Summary The influence of surface growth of inoculated cyanobacteria (blue-green algae) on subsurface properties of a brown earth, silt loam soil was studied in reconstituted flooded soil columns. One blue-green algae species, Nostoc muscorum, become dominant within the first 7 days of inoculation. In light control columns (not inoculated) a bryophyte, Barbula recurvirostra, was dominant although significant growth of indigenous blue-green algae occurred. The blue-green algae counts were in the range of 1×10⁶ g^-1 dry soil in the surface layer (0–0.7 cm) in both columns. Any effect of surface phototrophic growth on soil properties was restricted to the surface layer. In inoculated columns there was a twofold increase in microbial biomass and an eightfold increase in bacterial numbers by week 13. However, bacterial numbers declined so that there was only a 2.8-fold increase by week 21. Dehydrogenase (x2.1), urease (x2.8) and phosphatase (x3.1) activities and polysaccharides (+69%) increased by week 21 as a result of the blue-green algae inoculation along with a significant improvement in soil aggregation. However, similar increases occurred in the light control columns, indicating that given appropriate conditions of light and moisture indigenous species may be ultimately as effective as introduced species in bringing about biochemical and microbiological changes to soil.     

Structure and productivity of epiphytic algal communities onLobelia dortmanna L. in acidified and limed lakes

The epiphytic algal community growing onLobelia dortmanna L. was studied in two acidified lakes in southwestern Sweden from May through October 1980; Lake Gårdsjön (pH 4.3 to 4.7) and L. Högsjön (pH 6.3 to 6.7 after liming in 1978/79). In both lakes a layer of firmly attached diatoms,Eunotia veneris andE. rhomboidea, covered theLobelia leaves. Scanning electron microscope study revealed a mucoid matrix, and in L. Gårdsjön, heavy cover of detritus. The spring period in L. Gårdsjön was characterized by red algaBatrachospermum sp., which was followed by the appearance ofBinuclearia sp., andMougeotia spp. Blue-green algae appeared during the warmer period of the year. The spring period in L. Högsjön was characterized by the development of desmids. Diatoms dominated the community in the summer while green algae appeared in autumn. The biomass in L. Gårdsjön showed spring and late summer maxima, while in L. Högsjön it increased gradually reaching a maximum in autumn. Chlorophylla concentration was highest in L. Gårdsjön in late summer. Primary productivity rates calculated per unit substrate surface area at 1.0 m depth were highest in early summer and decreased in late summer. The results suggest that the liming of L. Högsjön caused significant structural changes in the epiphytic community, favoring diatoms and green algae, especially desmids. Blue-green algae were characteristic for L. Gårdsjön despite that lake's low pH. Productivity rates at 1.0 m depth show similar trends in both lakes.     

Multivariate correlation of water quality,sediment and benthic bio-community components in Ell-Ren river system,Taiwan

The distribution and correlation of benthic bio-community, water and sediment pollutants were evaluated with multivariate analysis from data collected over six samplings at 12 sites in the Ell-Ren river system, Taiwan. A total of 41 benthic algae species, 8 aquatic insect species and 2 annelid species were collected. On the basis of both principal component and correlation matrix analyses, we defined six water and sediment pollutant components to reveal common behaviour. Metrioenemus sp., Tubifex sp., Bacillariophyceae and Cyanophyceae could tolerate the environment at highly polluted sites. Caenis sp., Rhithrogena sp. and Baetis sp. preferred sites that were aerobic, and their populations were negatively correlated (52–56%) with detrital heavy metals in sediment. The population of benthic algae was positively variated with lead of the “bound to organic matters and sulphides” fraction, but negatively with copper in the detrital pattern. Results suggested that benthic bio-community demonstrated measurable relationships with water and sediment pollutants in Ell-Ren river system, and could be used as indicators to assess the water quality of river over a longer period.     

Brent geese Branta bernicla bernicla and their food in the solent,Southern England

The Solent, a large estuarine system on the central south coast of England, is an important wintering ground for the dark-bellied brent goose Branta bernicla bernicla: peak winter counts there rose from 300 in 1951–1952 to 23 000 in 1979–1980. Until 1973–1974 the geese remained in the intertidal zone, where they fed on eelgrass Zostera and green algae Enteromorpha and Ulva lactuca. The increase in goose number coincided with the spread of these plants in parts of the Solent. The spread of algae has been linked with increased discharges of sewage. However, only part of the annual production of Zostera and algae is available to geese because of autumn and winter die-back, storm damage and other factors.From 1973 to 1974 geese fed on permanent pasture, playing fields and autumnsown cereals, the last being especially important in 1978–1979 and 1979–1980. The evidence suggests that in some estuaries terrestrial feeding is increasingly attractive even though the intertidal zone could still sustain most of the goose-days spent in the area. The habit appears to be stimulated by large numbers of first winter birds in the population.The geese have evoked great public interest and generated concern for estuarine conservation. However, terrestrial feeding conflicts with farming. Nature conservation organisations have encouraged a policy of scaring from valuable crops by proven methods, whilst seeking to provide alternative terrestrial refuges.     

Hyperparasitism of oospores of Phytophthora megasperma var. sojae

Hyperparasites of oospores of Phytophthora megasperma Drechs. var. sojae Hildb. were present in each of 15 field soils tested. Maximum numbers of oospores parasitized ranged from 42.5 to 87.5% for flooded soils, and from 25.5 to 73.0% for soils adjusted to 50% water holding capacity; the mean for all soils was 51.5%. The frequency of hyperparasitism was not correlated with the disease potential soils for Phytophthora root-rot of soybean as determined in seedling tests on flooded soil samples. Of eight isolated hyperparasitic fungi tested in steamed soil, the most efficient parasites were Hyphochytrium catenoides, Humicola fuscoatra, and Pythium monospermum, each of which parasitized at least 76% of oospores during 3 weeks. Hyphae were not parasitized by any of the eight fungi. Parasitism by H. catenoides in sterilized soil increased as soil temperature increased from 16° to 28°C. Parasitism by P. monospermum was maximum at 20°–24°C. Oospores of P. meyasperma var. sojae race 7 were more resistant to infection by hyperparasites than were oospores of races 1 and 3. Oospores produced in culture were slightly more susceptible to hyperparasitism in soils than were oospores produced in soybean seedlings.     

Wood, nematodes, and the nematode-trapping fungus Arthrobotrys oligospora

Researchers have proposed that Arthrobotrys oligospora and related fungi trap soil nematodes to obtain nitrogen and thereby compete saprophytically for carbon and energy in nitrogen-poor environments, including litter and wood. The current study tested two hypotheses concerning this model. The first was that wood decomposition would be enhanced if both large numbers of nematodes (a potential nitrogen supply) and A. oligospora (a cellulolytic organism that can use that N supply) were present. The second was that A. oligospora trapping activity would increase if large numbers of nematodes were added to soil containing abundant carbon (a wood dowel or chip). Although the first hypothesis was supported by an in vitro experiment on agar (A. oligospora degraded much more wood when nematodes were present), neither hypothesis was supported by an experiment in vials containing field soil. In soil, wood decomposition was unaffected by the addition of A. oligospora or large numbers of nematodes. Whereas A. oligospora trapped virtually all nematodes added to agar cultures, it trapped few or no nematodes added to soil. Given that the fungal isolate was obtained from the same soil and that the fungus increased to large numbers (>1×10³ propagules g⁻¹ soil), the failure of A. oligospora to trap nematodes in soil is difficult to explain. Soil nitrate levels, however, were high (71 mg kg⁻¹), and it is possible that with lower nitrate levels, trapping in soil might be stimulated by wood and nematodes.     

Flooding responses of three earthworm species,Allolobophora chlorotica,Aporrectodea caliginosa and Lumbricus rubellus,in a laboratory-controlled environment

To get a better understanding of earthworm’ responses towards flooding, three laboratory experiments were performed with the species Allolobophora chlorotica, Aporrectodea caliginosa and Lumbricus rubellus.Flooding response was determined in a pot experiment, in which the earthworms were incubated for 42 days in flooded or non-flooded soil, with or without heavy metal pollution. To determine moisture preference, earthworms were incubated for 9 days in aquaria with five compartments, containing soil with a moisture gradient (%, w/w), ranging from 35%, 45% (field capacity), 55%, 65% (saturated) to 65%+ (saturated and an extra water layer). Effects on earthworm health were studied by incubating earthworms of each species for 42 days in soil with the same range of moisture contents and determining the dry/wet weight ratio and dry weight gain as an indication of earthworm health.A. chlorotica was tolerant to water, although the worms tended to escape from flooded soil. Their health was significantly lower in the flooded soils (P<0.05). A. caliginosa showed little response to flooding. This species, however, was affected by the heavy metal pollution in the pot experiment. L. rubellus was sensitive towards flooding, with escape and avoidance behaviour being the main mechanism of survival. This species was able to survive when forced to stay in flooded soil for at least 42 days, but this significantly reduced its health (P<0.05).These results suggest that earthworms are able to survive in inundated soils, but there are large differences between species in response to flooding conditions.     

Effects of root-associated N2-fixing cyanobacteria on the growth and nitrogen content of wheat (Triticum vulgare L.) seedlings

Summary Following co-cultivation of wheat with N₂-fixing cyanobacterial isolates capable of forming associations, Nostoc 2S6B, 2S9B or Anabaena C5, for 15 days in the presence or absence of combined N a large stimulation of root length was observed without any increase in root dry weight. Increases in the N concentrations of both roots and shoots occurred following co-cultivation with most cyanobacteria tested. The increase in plant N concentrations appeared to be dependent on the wheat cultivar and the cyanobacterial isolate used. Nostoc isolates had similar nitrogenase activities when associated with roots and when grown in shake-flask cultures. The nitrogenase activity of roots colonized by Anabaena C5 or Nostoc 2S6B was higher following removal of loosely associated cyanobacteria.     

Blue-green algae in rice soils of Jogjakarta,central Java

Preliminary studies were made to evaluate the role of the blue-green algae in flooded rice soils in the Jogjakarta district of central Java. They included identification of the components of the blue-green algal populations and the effects of fertilizers. The main findings were: (1) members of the families Nostocaceae (7 genera and 12 species recognized) and Oscillatoriaceae (8 genera and 18 species) were generally more abundant than other families; (2) application of nitrogen and phosphorus fertilizers affected the composition (reduction in numbers of nitrogen-fixing blue-green algae) and total size of the populations (increase in algal biomass); (3) a major role for blue-green algae in the N-economy of flooded soils was indicated.     

Colonization of sugarcane plantlets by mixed inoculations with diazotrophic bacteria

Micropropagated sugarcane plants have been used in Brazil for almost three decades. Besides the improvement in plant health, micropropagated sugarcane carries no endophytic plant growth-promoting bacteria. The Brazilian inoculation technology to reintroduce diazotrophic bacteria in micropropagated sugarcane plantlets revealed a synergistic-like effect in PGP-bacteria mixed inoculations. The infection model of single diazotrophic bacteria species in sugarcane was studied in detail, but still many questions remain open. In this study we used a combined fluorescence in situ hybridization (FISH) and a cultivation based approach (MPN) to evaluate the colonization of sugarcane plantlets by mixed inocula. The highest colonization for three out of the five species studied was obtained with a mixed inoculum, when the Azospirillum amazonense showed an increase by almost 100 times in colonization and Herbaspirillum spp. and Burkholderia tropica was determined at 10⁷ cells per gram root fresh weight. All of the inoculated bacterial species could be detected using the FISH probes 12 h after bacterial inoculation. The FISH results confirmed the MPN counts and showed differences in the population numbers and colonization behavior of particular bacterial inoculum strains in the different mixed inocula. A putative antagonistic effect among the inoculated H. seropedicae and H. rubrisubalbicans strains was observed using FISH, as well as the better competitiveness of B. tropica as compared to the A. amazonense strain. The observed data probably reflect also specific interactions with the sugarcane variety used in this particular inoculation system, and may not be generalized as a rule. This is the first study about the competition for sugarcane colonization in a mixed bacterial inoculum.