Effects of Elevated Ozone Concentration on Starch and Starch Synthesis Enzymes of Yangmai 16 Under Fully Open-Air Field Conditions

O3 is not only greenhouse gas but also a primary gaseous contaminant in the atmosphere.It has long-lasting effects on crop growth,yield and quality,and brings a series of ecological and environmental problems.A free-air controlled enrichment（FACE） system was applied to study the effect of elevated ozone concentration on activities of key enzymes of starch synthesis of Yangmai 16 in 2009-2010.The main-plot treatment had two levels of O 3 ：ambient level（A-O 3） and 50% higher than ambient level（E-O 3）.The main results were that accumulation rate of amylose,amylopectin and starch were represented in a single peak curve,and their content and accumulation amount rose gradually.The O 3 elevation decreased the accumulation rate of amylose,amylopectin and starch amylase,reduced the accumulation amount of amylopectin and starch,and decreased the content of amylopectin and starch,but increased the content of amylose.With the increase of O 3 concentration,the enzyme activity of grain granule-bound starch synthase（GBSS）,soluble starch synthase（SSS） and starch branching enzyme（SBE） decreased after anthesis.The activities of GBSS and SSS had highly significant correlations with amylose,amylopectin and starch accumulation rate,and the activity of SBE had significant correlations with these items.So the O 3 elevation decreased the activity of key enzymes of starch synthesis,which led to the variation of starch synthesis.     

Development of CAPS markers and their application in breeding for mango, Mangifera indica L.

To develop cleaved amplified polymorphic sequence (CAPS) markers for the identification of true hybrids in F1 progeny, we cloned sucrose synthase (SS) and sucrose phosphate synthase (SPS) genes from 19 mango cultivars. Through comparison of amino acid sequences in a BLASTX search, cloned SS and SPS genes were found to be homologs of Citrus unshiu CitSUS1 (AB022092) and CitSPS1 (O22060), respectively. Therefore, we designated the SS and SPS genes as MiSUS1 and MiSPS1, respectively. There were 11 genotypes in MiSUS1 and 10 in MiSPS1 sequences. In the MiSUS1 nucleotide sequences, 46 SNPs and 5 in/dels were detected. Twenty-six out of the 46 SNPs mapped on the restriction enzyme recognition sites were successfully converted to 25 CAPS markers. In the MiSPS1 nucleotide sequences, 99 SNPs and 6 in/dels were detected. Thirty out of 99 SNPs and 2 out of 6 in/dels mapped on the recognition sites were also converted to 32 CAPS markers. By using two CAPS markers, SS-2798 and SPS-5745, we identified 37 true hybrids that had different genotypes to ‘Irwin’ from 82 F1 progeny obtained through a cross between ‘Irwin’, the maternal parent, and paternal parents by using flies as pollinators. The method developed here to identify true hybrids is a simple, rapid and highly reliable tool for efficient mango breeding.     

Comparison of Ammonium Deposition Flux at Roadside and at an Agricultural Area for Long-Term Monitoring: Emission of Ammonia from Vehicles

To understand the effect of the NH₃ emissions from vehicles, the NH₄ ⁺ bulk deposition and concentrations of gaseous NH₃ and particulate NH₄ ⁺ were measured at two sites in Saitama prefecture, Japan, one at the roadside of an arterial road (Kounosu), and the other in an agricultural area (Kisai). We observed that the NH₄ ⁺ bulk deposition and NH₃ concentration were significantly increased in Kounosu; the effect of NH₃ emissions from vehicles was confirmed. NOx was a primary pollutant mainly emitted by vehicle exhaust in the vicinity of arterial roads, and the relationship between NO _x and sum of gaseous NH₃ and particulate NH₄ ⁺ (T-NH₄ ⁺) was examined. The [T-NH₄ ⁺/NO _x ] ratios in Kounosu ranged from 0.08 to 0.23 (average 0.15), and in Kisai they ranged from 0.16 to 0.67 (average 0.39). In Kounosu, the effect of vehicle exhaust was great, but seasonal variation was small. The contribution ratio of NH₃ from vehicle emissions increased at low temperatures, while that from the non-vehicle emissions increased at high temperatures.     

Determination of neonicotinoid pesticide residues in vegetables and fruits with solid phase extraction and liquid chromatography mass spectrometry

A rapid and simple extraction method for the simultaneous analysis of five neonicotinoid insecticides has been developed. Twelve different fruit and vegetable matrixes were extracted with methanol and cleaned up using a graphitized carbon solid phase extraction cartridge loading with a 20% methanol solution. The concentrated eluate after methanol elution was then analyzed for pesticide residues by liquid chromatography/mass spectrometry in the APCI positive mode. The five pesticides including nitenpyram, thiamethoxam, imidacloprid, acetamiprid, and thiacloprid were recovered at 70-95% at spike levels of 0.1 and 1 mg/kg in bell pepper, cucumber, eggplant, grape, grapefruit, Japanese radish, peach, pear, potato, rice, and tomato. Relative standard deviations were less than 10% for all of the recovery tests. The proposed method is fast, easy to perform, and could be utilized for regular monitoring of pesticide residues.     

Receptor assay-guided isolation of anti-GABAergic insecticidal alkaloids from a fungal culture

The gamma-aminobutyric acid (GABA) receptor bears sites of action for insecticides. To discover GABA receptor-directed insecticides in natural products, fungal culture extracts were screened for their ability to inhibit specific binding of the radiolabeled noncompetitive antagonist [3H]1-(4-ethynylphenyl)-4-n-propyl-2,6,7-trioxabicyclo[2.2.2]octane to housefly head membranes. The screening efforts led to the isolation of two alkaloids from Aspergillus terreus: PF1198A (alantrypinone) and PF1198B (serantrypinone), which had IC50 values of 0.34 and 2.1 microM, respectively, in this assay. These compounds were ca. 47-61-fold selective for housefly vs rat GABA receptors. Both compounds showed insecticidal activity against Myzus persicae in the range of 100-500 ppm. Binding assay-guided screening should provide significant opportunities for the identification of novel and selective insecticides.     

Effects of elevated carbon dioxide concentration on biological nitrogen fixation, nitrogen mineralization and carbon decomposition in submerged rice soil

Controlled-environment chambers were used to study the effects of elevated CO₂ concentrations on biological N fixation, N mineralization and C decomposition in rice soil. In three chambers, CO₂ concentration was maintained at 353ᆣ/396ᆫ µmol mol^-1 (day/night; ambient CO₂), while in another three, CO₂ was maintained at 667ᆸ/700ᆽ µmol mol^-1 (day/night; elevated CO₂) throughout the growing season. Rice (var. Nipponbare) seedlings were grown under either ambient or elevated CO₂ concentrations, and then transplanted into the soils in the corresponding chambers. At different growth stages, soil samples were taken from surface (0-1cm) and sub-surface (1-10cm) layers at the centre of four hills, then sieved (<1 mm) to remove root residues. Fresh soil was used to measure N fixation activity (using the acetylene reduction assay), NH₄⁺ content and organic C. Separate sets of soil samples were transferred to serum bottles and anaerobically incubated at 30°C for 30 days to measure potential rates of N mineralization and C decomposition. Under an elevated atmospheric CO₂ concentration, acetylene reduction activity significantly increased in the surface soil layer during the early cultivation stages and in the sub-surface soil layer during the latter part of cultivation. There was no difference in the amount of NH₄⁺ in fresh soils between elevated and ambient CO₂ chambers, while the rate of N mineralization was increased by elevated CO₂ during the latter part of cultivation. Soils from the elevated CO₂ chambers had obviously higher rate of C decomposition than that from the ambient CO₂ chambers. CH₄ production gradually increased with the growth of rice plants. These results suggest that elevated CO₂ affected biological N fixation, N mineralization and C decomposition in submerged rice soil during the different growth stages of rice.     

Effect of Free-Air CO2 Enrichment (FACE) on the Community Structure of Aquatic Organisms in Floodwater of a Japanese Paddy Field during the Flooding Period of Rice Cultivation

In the present study, the effect of free-air CO₂ enrichment (FACE) on the diversity and the community structure of aquatic organisms in the floodwater of a paddy field in northern Japan was evaluated. The varieties and the number of aquatic organisms ranging from 30 μm to 2 cm were compared four times at intervals of 20 d between the FACE (599 ppm CO₂) and ambient air (384 ppm CO₂) plots during the flooding period of rice cultivation. Aquatic organisms were classified mainly at the order level. Twenty-eight taxonomical groups were detected, and the number of groups in the FACE plots was significantly lower than that in the ambient plots. Zygnematales and Chaetonotida were less frequently detected in the FACE plots. The population densities of Zygnematales, and Chaetonotida also tended to be lower in the FACE plots than in the ambient plots in the late flooding period (after 50 d of flooding). No groups showed a significantly higher population density and frequency of presence in the FACE plots than in the ambient plots. The seasonal variations in the number of taxonomical groups and the community structure of aquatic organisms were less conspicuous in the FACE plots than in the ambient plots. We concluded that the FACE conditions adversely affected the communities of aquatic organisms in paddy fields.     

Mild drying of sandy soil can physically limit the uptake of phosphorus by rainfed lowland rice in northeast Thailand

ABSTRACT

Poor response of rice to phosphorus (P) fertilization and low phytoavailability of soil P have been reported in sandy rainfed fields in northeast Thailand. In order to evaluate the effects of mild soil drying on the uptake of P by rainfed lowland rice, we carried out nutrient omission trials for nitrogen (N) and P at Ubon Ratchathani Rice Research Center under rainfed and flooded conditions. The surface soil was classified as sandy loam. To avoid severe soil drying and drought stress in the rainfed field, soil water potential at a depth of 20 cm was maintained at the field capacity (> ?20 kPa) by flush irrigation. The effects of flooding and drying on the soil properties were also evaluated in the laboratory using soils with diverse textures in and around the center. In the field experiments, the above-ground biomass of rice plants (RD6) did not respond significantly to P fertilization in the rainfed field, although it responded positively to N fertilization. Root length in the surface 10 cm under the rainfed condition was significantly smaller than that under the flooded condition due partly to the increased soil hardness upon drying, but this could not quantitatively explain the large discrepancy of P uptake observed between the rainfed and flooded conditions. Under the rainfed condition, the P uptake did not increase significantly, even when the concentration of soil Bray P was tripled by transferring the surface soil from the flooded to the rainfed field. From the laboratory experiments, it was further suggested that soil P was supplied mainly by diffusion and that the effective diffusion coefficient for P can become less than one-tenth of the value in the flooded field when the sandy soil with clay at around 10% dried to ?100 kPa. Our results suggest that the uptake of P by the rainfed lowland rice grown in sandy soil can be limited physically by mild soil drying that reduces the supply of P to roots by diffusion rather than the chemical extractability of soil P.     

Prenylated flavanones isolated from flowers of Azadirachta indica (the neem tree) as antimutagenic constituents against heterocyclic amines

Four prenylated flavanones were isolated from the methanol extract of the flowers of Azadirachta indica (the neem tree) as potent antimutagens against Trp-P-1 (3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole) in the Salmonella typhimurium TA98 assay by activity-guided fractionation. Spectroscopic properties revealed that those compounds were 5,7,4'-trihydroxy-8-prenylflavanone (1), 5,4'-dihydroxy-7-methoxy-8-prenylflavanone (2), 5,7,4'-trihydroxy-3',8-diprenylflavanone (3), and 5,7,4'-trihydroxy-3',5'-diprenylflavanone (4). All isolated compounds were found for the first time in this plant. The antimutagenic IC(50) values of compounds 1-4 were 2.7 +/- 0.1, 3.7 +/- 0.1, 11.1 +/- 0.1, and 18.6 +/- 0.1 microM in the preincubation mixture, respectively. These compounds also similarly inhibited the mutagenicity of Trp-P-2 (3-amino-1-methyl-5H-pyrido[4,3-b]indole) and PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine). All of the compounds 1-4 strongly inhibited ethoxyresorufin O-dealkylation activity of cytochrome P450 1A isoforms, which catalyze N-hydroxylation of heterocyclic amines. However, compounds 1-4 did not show significant inhibition against the direct-acting mutagen NaN(3). Thus, the antimutagenic effect of compounds 1-4 would be mainly based on the inhibition of the enzymatic activation of heterocyclic amines.