Assessment of the preventive effect of vermicompost on salinity resistance in tomato (<Emphasis Type="Italic">Solanum lycopersicum</Emphasis> cv. Ailsa Craig)

To determine the effects of vermicompost leachate (VCL) on resistance to salt stress in plants, young tomato seedlings (Solanum lycopersicum, cv. Ailsa Craig) were exposed to salinity (150 mM NaCl addition to nutrient solution) for 7 days after or during 6 mL L^??1 VCL application. Salt stress significantly decreased leaf fresh and dry weights, reduced leaf water content, significantly increased root and leaf Na⁺ concentrations, and decreased K⁺ concentrations. Salt stress decreased stomatal conductance (g_s), net photosynthesis (A), instantaneous transpiration (E), maximal efficiency of PSII photochemistry in the dark-adapted state (F_v/F_m), photochemical quenching (qP), and actual PSII photochemical efficiency (ΦPSII). VCL applied during salt stress increased leaf fresh weight and g_s, but did not reduce leaf osmotic potential, despite increased proline content in salt-treated plants. VCL reduced Na⁺ concentrations in leaves (by 21.4%), but increased them in roots (by 16.9%). VCL pre-treatment followed by salt stress was more efficient than VCL concomitant to salt stress, since VCL pre-treatment provided the greatest osmotic adjustment recorded, with maintenance of net photosynthesis and K⁺/Na⁺ ratios following salt stress. VCL pre-treatment also led to the highest proline content in leaves (50 µmol g^??1 FW) and the highest sugar content in roots (9.2 µmol g^??1 FW). Fluorescence-related parameters confirmed that VCL pre-treatment of salt-stressed plants showed higher PSII stability and efficiency compared to plants under concomitant VCL and salt stress. Therefore, VCL represents an efficient protective agent for improvement of salt-stress resistance in tomato.     

Homoeologous recombination in the presence of <Emphasis Type="Italic">Ph1</Emphasis> gene in wheat

A crossover (CO) and its cytological signature, the chiasma, are major features of eukaryotic meiosis. The formation of at least one CO/chiasma between homologous chromosome pairs is essential for accurate chromosome segregation at the first meiotic division and genetic recombination. Polyploid organisms with multiple sets of homoeologous chromosomes have evolved additional mechanisms for the regulation of CO/chiasma. In hexaploid wheat (2n = 6× = 42), this is accomplished by pairing homoeologous (Ph) genes, with Ph1 having the strongest effect on suppressing homoeologous recombination and homoeologous COs. In this study, we observed homoeologous COs between chromosome 5M^g of Aegilops geniculata and 5D of wheat in plants where Ph1 was fully active, indicating that chromosome 5M^g harbors a homoeologous recombination promoter factor(s). Further cytogenetic analysis, with different 5M^g/5D recombinants, showed that the homoeologous recombination promoting factor(s) may be located in proximal regions of 5M^g. In addition, we observed a higher frequency of homoeologous COs in the pericentromeric region between chromosome combination of rec5M^g#2S·5M^g#2L and 5D compared to 5M^g#1/5D, which may be caused by a small terminal region of 5DL homology present in chromosome rec5M^g#2. The genetic stocks reported here will be useful for analyzing the mechanism of Ph1 action and the nature of homoeologous COs.     

Assessment of photosynthetic potential of indoor plants under cold stress

Photosynthetic parameters including net photosynthetic rate (P_N), transpiration rate (E), water-use efficiency (WUE), and stomatal conductance (g_s) were studied in indoor C₃ plants Philodendron domesticum (Pd), Dracaena fragans (Df), Peperomia obtussifolia (Po), Chlorophytum comosum (Cc), and in a CAM plant, Sansevieria trifasciata (St), exposed to various low temperatures (0, 5, 10, 15, 20, and 25°C). All studied plants survived up to 0°C, but only St and Cc endured, while other plants wilted, when the temperature increased back to room temperature (25°C). The P_N declined rapidly with the decrease of temperature in all studied plants. St showed the maximum P_N of 11.9 μmol m^?2 s^?1 at 25°C followed by Cc, Po, Pd, and Df. E also followed a trend almost similar to that of P_N. St showed minimum E (0.1 mmol m^?2 s^?1) as compared to other studied C₃ plants at 25°C. The E decreased up to ≈4-fold at 5 and 0°C. Furthermore, a considerable decline in WUE was observed under cold stress in all C₃ plants, while St showed maximum WUE. Similarly, the g_s also declined gradually with the decrease in the temperature in all plants. Among C₃ plants, Pd and Po showed the maximum g_s of 0.07 mol m^?2 s^?1 at 25°C followed by Df and Cc. However, St showed the minimum g_s that further decreased up to ～4-fold at 0°C. In addition, the content of photosynthetic pigments [chlorophyll a, b, (a+b), and carotenoids] was varying in all studied plants at 0°C. Our findings clearly indicated the best photosynthetic potential of St compared to other studied plants. This species might be recommended for improving air quality in high-altitude closed environments.     

Phycoremediation potential,physiological, and biochemical response of <Emphasis Type="Italic">Amphora subtropica</Emphasis> and <Emphasis Type="Italic">Dunaliella</Emphasis> sp. to nickel pollution

Metal pollution can produce many biological effects on aquatic environments. The marine diatom Amphora subtropica and the green alga Dunaliella sp. possess a high metal absorption capacity. Nickel (Ni) removal by living cells of A. subtropica and Dunaliella sp. was tested in cultures exposed to different Ni concentrations (100, 200, 300, and 500 mg L^?1). The amount of Ni removed by the microalgae increased with the time of exposure and the initial Ni concentration in the medium. The metal, which was mainly removed by bioadsorption to Dunaliella sp. cell surfaces (93.63% of total Ni (for 500 mg Ni L^?1) and by bioaccumulation (80.82% of total Ni (for 300 mg Ni L^?1) into Amphora subtropica cells, also inhibited growth. Exposure to Ni drastically reduced the carbohydrate and protein concentrations and increased total lipids from 6.3 to 43.1 pg cell^?1, phenolics 0.092 to 0.257 mg GAE g^?1 (Fw), and carotenoid content, from 0.08 to 0.59 mg g^?1 (Fw), in A. subtropica. In Dunaliella sp., total lipids increased from 26.1 to 65.3 pg cell^?1, phenolics from 0.084 to 0.289 mg GAE g^?1 (Fw), and carotenoid content from 0.41 to 0.97 mg g^?1 (Fw). These compounds had an important role in protecting the algae against ROS generated by Ni. In order to cope with Ni stress shown by the increase of TBARS level, enzymatic (SOD, CAT, and GPx) ROS scavenging mechanisms were induced.     

Induced Homoeologous Pairing for Transfer of Useful Variability for High Grain Fe and Zn from <Emphasis Type="Italic">Aegilops kotschyi</Emphasis> into Wheat

Biofortification of bread wheat by the transfer of useful variability of high grain Fe and Zn from Aegilops kotschyi through induced homoeologous pairing is the most feasible approach to alleviate micronutrient malnutrition worldwide. Deficiency of chromosome 5B in interspecific hybrids allows homoeologous pairing and recombination of chromosomes of wheat with those of the related species. The interspecific hybrid plants without 5B chromosome showed much higher chromosome pairing than did the plants with 5B. The F₁ plants without 5B chromosome were selected and repeatedly backcrossed with wheat cultivar PBW343. The chromosome number of BC₂F₁ plants ranged from 43 to 60 with several univalents and multivalents. Molecular markers and GISH analysis confirmed the introgression of U/S chromosomes of Ae. kotschyi and their fragments in wheat. The BC₂F₂ plants showed up to 125 % increase in Fe and 158 % increase in Zn compared to PBW343 with Lr24 and Yr36. Induced homoeologous pairing in the absence of 5B was found to be an effective approach for transfer of useful variability for enhanced grain Fe and Zn content for biofortification of wheat for high grain micronutrient content.     

A mini-survey of moulds and mycotoxins in locally grown and imported wheat grains in Nigeria

A preliminary survey involving limited sample size was conducted to determine the spectrum of moulds and mycotoxins in wheat grains from flour mills and local markets in Nigeria. Fourteen wheat samples were analyzed for moulds using standard mycological methods and for toxic fungal metabolites using a liquid chromatography-tandem mass spectrometric method. Fusarium (range of incidence 12.5–61.7%) dominated in the wheat grains though species of Aspergillus (range of incidence 2.24–3.86%) were also recovered from the samples. The identified fungal species were Aspergillus flavus (7.7%), Aspergillus niger clade (2.6%), Fusarium avenaceum (10.9%), Fusarium culmorum (22.4%) and Fusarium graminearum (56.4%). A total of 54 microbial metabolites were detected in the samples at concentration ranging between 0.01 μg/kg for macrosporin and 2560 μg/kg for deoxynivalenol. Among the four mycotoxins addressed by regulations in the European Union (EU) found in the samples, deoxynivalenol (incidence 100%) dominated in the samples and its levels exceeded the maximum acceptable EU limit (750 μg/kg) in 36% of the samples. This report underscores the need for more robust surveys with larger sample sizes and across several agro-ecologies in the country.     

Seaweed-Derived Biostimulant (Kelpak<Superscript>®</Superscript>) Influences Endogenous Cytokinins and Bioactive Compounds in Hydroponically Grown <Emphasis Type="Italic">Eucomis autumnalis</Emphasis>

The effect of a seaweed-derived biostimulant (Kelpak^® at 1, 2.5 and 5 % dilution; v/v) on the growth, endogenous cytokinin (CK) and phytochemical content in Eucomis autumnalis (Mill.) Chitt. under hydroponic conditions was evaluated. After 4 months, the stimulatory effect of Kelpak^® treatments was more noticeable in the underground organs than in the aerial organs. Total endogenous CK was also higher in plants treated with Kelpak^® (c.a. 1000–1200 pmol g^?1 DW) compared to control plants (860 pmol g^?1 DW). Isoprenoid CKs (which mainly accumulated in the aerial organs) were more dominant than aromatic-type CKs across all the treatments. A total of 11 bioactive chemicals (8 phenolic acids and 3 flavonoids) and eucomic acid known for their diverse biological activities were quantified in the samples. The most abundant compound was p-coumaric acid (6.5 µg g^?1 DW) and it was approximately sevenfold higher in 2.5 % Kelpak^®-treated plants than in the control. It was also noteworthy that syringic acid only occurred in the underground organs of 5 % Kelpak^®-treated plants. Eucomic acid which is a major bioactive compound in E. autumnalis was significantly enhanced in Kelpak^® treatments, and the leaves accounted for more than 70 % of the overall content. Thus, Kelpak^® elicited a significant influence on the growth, endogenous CK and phytochemical content in E. autumnalis. These findings provide additional evidence of the enormous potential of Kelpak^® as a useful biostimulant with practical applications in various agricultural endeavours.     

Oxygen transfer as a tool for fine-tuning recombinant protein production by <Emphasis Type="Italic">Pichia pastoris</Emphasis> under glyceraldehyde-3-phosphate dehydrogenase promoter

Effects of oxygen transfer on recombinant protein production by Pichia pastoris under glyceraldehyde-3-phosphate dehydrogenase promoter were investigated. Recombinant glucose isomerase was chosen as the model protein. Two groups of oxygen transfer strategies were applied, one of which was based on constant oxygen transfer rate where aeration rate was Q _O/V = 3 and 10 vvm, and agitation rate was N = 900 min^?1; while the other one was based on constant dissolved oxygen concentrations, C _DO = 5, 10, 15, 20 and 40 % in the fermentation broth, by using predetermined exponential glucose feeding with μ _o = 0.15 h^?1. The highest cell concentration was obtained as 44 g L^?1 at t = 9 h of the glucose fed-batch phase at C _DO = 20 % operation while the highest volumetric and specific enzyme activities were obtained as 4440 U L^?1 and 126 U g^?1 cell, respectively at C _DO = 15 % operation. Investigation of specific enzyme activities revealed that keeping C _DO at 15 % was more advantageous with an expense of relatively higher by-product formation and lower specific cell growth rate. For this strategy, the highest oxygen transfer coefficient and oxygen uptake rate were K _L a = 0.045 s^?1 and OUR = 8.91 mmol m^?3 s^?1, respectively.     

Bifunctional recombinant cellulase–xylanase (rBhcell-xyl) from the polyextremophilic bacterium <Emphasis Type="Italic">Bacillus halodurans</Emphasis> TSLV1 and its utility in valorization of renewable agro-residues

The thermostable bifunctional CMCase and xylanase encoding gene (rBhcell-xyl) from Bacillus halodurans TSLV1 has been expressed in Escherichia coli. The recombinant E. coli produced rBhcell-xyl (CMCase 2272 and 910 U L^?1 xylanase). The rBhcell-xyl is a ~62-kDa monomeric protein with temperature and pH optima of 60 °C and 6.0 with T_1/2 of 7.0 and 3.5 h at 80 °C for CMCase and xylanase, respectively. The apparent K _m values (CMC and Birchwood xylan) are 3.8 and 3.2 mg mL^?1. The catalytic efficiency (k _cat/K _m ) values of xylanase and CMCase are 657 and 171 mL mg^?1 min^?1, respectively. End-product analysis confirmed that rBhcell-xyl is a unique endo-acting enzyme with exoglucanase activity. The rBhcell-xyl is a GH5 family enzyme possessing single catalytic module and carbohydrate binding module. The action of rBhcell-xyl on corn cobs and wheat bran liberated reducing sugars, which can be fermented to bioethanol and fine biochemicals.     

Growth kinetics and scale-up of <Emphasis Type="Italic">Agrobacterium tumefaciens</Emphasis>

Production of recombinant proteins in plants through Agrobacterium-mediated transient expression is a promising method of producing human therapeutic proteins, vaccines, and commercial enzymes. This process has been shown to be viable at a large scale and involves growing large quantities of wild-type plants and infiltrating the leaf tissue with a suspension of Agrobacterium tumefaciens bearing the genes of interest. This study examined one of the steps in this process that had not yet been optimized: the scale-up of Agrobacterium production to sufficient volumes for large-scale plant infiltration. Production of Agrobacterium strain C58C1 pTFS40 was scaled up from shake flasks (50–100 mL) to benchtop (5 L) scale with three types of media: Lysogeny broth (LB), yeast extract peptone (YEP) media, and a sucrose-based defined media. The maximum specific growth rate (μ _max) of the strain in the three types of media was 0.46 ± 0.04 h^?1 in LB media, 0.43 ± 0.03 h^?1 in YEP media, and 0.27 ± 0.01 h^?1 in defined media. The maximum biomass concentration reached at this scale was 2.0 ± 0.1, 2.8 ± 0.1, and 2.6 ± 0.1 g dry cell weight (DCW)/L for the three media types. Production was successfully scaled up to a 100-L working volume reactor with YEP media, using k _L a as the scale-up parameter.     

Nitrogen-induced variations in leaf gas exchange of spring triticale under field conditions

Nitrogen (N) is the key factor limiting photosynthetic processes and crop yield. Little is known about the response of leaf gas exchange of spring triticale (Triticosecale Wittm.) to N supply. The effect of N fertilizers on different gas exchange variables, i.e., photosynthetic rate (A), transpiration rate (E), stomatal conductance (g _s), instantaneous water use efficiency (WUE) and maximum quantum yield of photosystem II (PSII) (F _v/F _m), chlorophyll index (SPAD, soil–plant analysis development), and the relationship of these variables with yield were studied in spring triticale grown under field conditions. Six treatments of N—0, 90, 180, 90 + 30, 90 + 30 + 30 kg ha^?1 (applied as ammonium nitrate, AN) and one treatment of N 90 + 30 + 30 kg ha^?1 (applied as urea ammonium nitrate solution, UAN) were compared. The analysis of variance showed that throughout the triticale growing season, N fertilization had significant effects on A, WUE, g _s and SPAD. On average, N fertilizer application increased A values by 14–70%. E and F _v/F _m values were not influenced by N fertilization levels. The effect of growth stage and year on gas exchange variables and F _v/F _m and SPAD was found to be significant. At different growth stages, A values varied and maximum ones were reached at BBCH 31–33 (decimal code system of growth stages) and BBCH 59. With aging, values of A decreased independently of N fertilization level. The gas exchange variables were equally affected by both fertilizer forms. The interplay among grain yield, leaf gas exchange variables, F _v/F _m and SPAD of spring triticale was estimated. The statistical analysis showed that grain yield positively and significantly correlated with A and SPAD values throughout the growing season.     

<Emphasis Type="Italic">Pseudomonas</Emphasis> spp. increases root biomass and tropane alkaloid yields in transgenic hairy roots of <Emphasis Type="Italic">Datura</Emphasis> spp.

Transgenic hairy roots of Datura spp., established using strain A4 of Agrobacterium rhizogenes, are genetically stable and produce high levels of tropane alkaloids. To increase biomass and tropane alkaloid content of this plant tissue, four Pseudomonas strains, Pseudomonas fluorescens P64, P66, C7R12, and Pseudomonas putida PP01 were assayed as biotic elicitors on transgenic hairy roots of Datura stramonium, Datura tatula, and Datura innoxia. Alkaloids were extracted from dried biomass, and hyoscyamine and scopolamine were quantified using liquid chromatography-tandem mass spectrometry analysis. D. stramonium and D. innoxia biomass production was stimulated by all Pseudomonas spp. strains after a 5-d treatment. All strains of P. fluorescens increased hyoscyamine yields compared to untreated cultures after both 5 and 10 d of treatment. Hyoscyamine yields were highest in D. tatula cultures exposed to a 5-d treatment with C7R12 (16.633 + 0.456 mg g^?1 dry weight, a 431% increase) although the highest yield increases compared to the control were observed in D. stramonium cultures exposed to strains P64 (511% increase) and C7R12 (583% increase) for 10 d. D. innoxia showed the highest scopolamine yields after elicitation with P. fluorescens strains P64 for 5 d (0.653 + 0.021 mg g^?1 dry weight, a 265% increase) and P66 for 5 and 10 d (5 d, 0.754 + 0.0.031 mg g^?1 dry weight, a 321% increase; 10 d 0.634 + 0.046 mg g^?1 dry weight, a 277% increase). These results show that the Pseudomonas strains studied here can positively and significantly affect biomass and the yields of hyoscyamine and scopolamine from transgenic roots of the three Datura species.     

Uptake and biotransformation of pure commercial microcystin-LR versus microcystin-LR from a natural cyanobacterial bloom extract in the aquatic fungus <Emphasis Type="Italic">Mucor hiemalis</Emphasis>

Objectives

To evaluate the remediation efficiency of Mucor hiemalis by comparing media elimination, uptake, and biotransformation of microcystin-LR with exposure to pure toxin versus a crude bloom extract.

Results

With exposure to the extract, the elimination rate of microcystin-LR from the media, which was 0.28 ng MC-LR l^?1 h^?1, was significantly higher compared to that achieved with exposure to the pure toxin (0.16 ng MC-LR l^?1 h^?1) after 24 h. However, intracellular breakdown of microcystin-LR was significantly lower in the extract exposed pellets compared to the pure toxin treated fungal pellets over time. This coincided with reduced intracellular glutathione S-transferase activity with crude extract exposure which could be responsible for the detection of only the glutathione conjugate of microcystin-LR.

Conclusion

This paper signifies the importance of using laboratory exposure scenarios which resemble conditions in nature to fully understand and evaluate remediation efficiency. There is merit in using M. hiemalis for mycoremediation of cyanotoxins in surface waters.

     

Verrucarin A and roridin E produced on spinach by <Emphasis Type="Italic">Myrothecium verrucaria</Emphasis> under different temperatures and CO<Subscript>2</Subscript> levels

The behavior of Myrothecium verrucaria, artificially inoculated on spinach, was studied under seven different temperature conditions (from 5 to 35 °C) and under eight different combinations of temperature and CO₂ concentration (14–30 °C and 775–870 or 1550–1650 mg/m³). The isolate used for this study was growing well on spinach, and the mycotoxins verrucarin A and roridin E were produced under all tested temperature and CO₂ conditions. The maximum levels of verrucarin A (18.59 ng/g) and roridin E (49.62 ng/g) were found at a temperature of 26–30 °C and a CO₂ level of 1550–1650 mg/m³. Rises in temperature as well as in temperature and CO₂ concentrations had a significant effect by increasing Myrothecium leaf spots on spinach. The biosynthesis of verrucarin A was significantly increased at the highest temperature (35 °C), while roridin E was influenced by the CO₂ concentration. These results show that a positive correlation between climate condition and macrocyclic trichothecene production is possible. However, because of the ability of M. verrucaria to produce mycotoxins, an increase in temperature could induce the spread of M. verrucaria in temperate regions; this pathogen may gain importance in the future.     

Development of a powder formulation based on <Emphasis Type="Italic">Bacillus</Emphasis><Emphasis Type="Italic">cereus</Emphasis> sensu lato strain B25 spores for biological control of <Emphasis Type="Italic">Fusarium verticillioides</Emphasis> in maize plants

Maize is an economically important crop in northern Mexico. Different fungi cause ear and root rot in maize, including Fusarium verticillioides (Sacc.) Nirenberg. Crop management of this pathogen with chemical fungicides has been difficult. By contrast, the recent use of novel biocontrol strategies, such as seed bacterization with Bacillus cereus sensu lato strain B25, has been effective in field trials. These approaches are not without their problems, since insufficient formulation technology, between other factors, can limit success of biocontrol agents. In response to these drawbacks, we have developed a powder formulation based on Bacillus B25 spores and evaluated some of its characteristics, including shelf life and efficacy against F. verticillioides, in vitro and in maize plants. A talc-based powder formulation containing 1 × 10⁹ c.f.u. g^?1 was obtained and evaluated for seed adherence ability, seed germination effect, shelf life and antagonism against F. verticillioides in in vitro and in planta assays. Seed adherence of viable bacterial spores ranged from 1.0 to 1.41 × 10⁷ c.f.u. g^?1. Bacteria did not display negative effects on seed germination. Spore viability for the powder formulation slowly decreased over time, and was 53 % after 360 days of storage at room temperature. This formulation was capable of controlling F. verticillioides in greenhouse assays, as well as eight other maize phytopathogenic fungi in vitro. The results suggest that a talc-based powder formulation of Bacillus B25 spores may be sufficient to produce inoculum for biocontrol of maize ear and root rots caused by F. verticillioides.     

Colonization of sorghum and wheat by seed inoculation with <Emphasis Type="Italic">Gluconacetobacter diazotrophicus</Emphasis>

Colonization of sorghum and wheat after seed inoculation with Gluconacetobacter diazotrophicus strains PAL 5 and UAP 5541/pRGS561 (containing the marker gene gusA) was studied by colony counting and microscopic observation of plant tissues. Inoculum levels as low as 10² CFU per seed were enough for root colonization and further spreading in aerial tissues. Rhizoplane colonization was around 7 log CFU g^?1 (fresh weight). G. diazotrophicus was found inside sorghum and wheat roots with populations higher than 5 log CFU g^?1 (fresh weight). Stem colonization remained stable for 30 days post inoculation with endophyte concentrations from 4 to 5 log CFU g^?1 (fresh weight) (in both plants). Population in leaves decreased continuously being undetectable after 17 days post inoculation.     

The effect of chitin metabolic effectors on the population increase of stored product mites

The study tested the effect of the chitin metabolic effectors, teflubenzuron, diflubenzuron, and calcofluor, and a combination of a chitinase and soybean trypsin inhibitor (STI) on the population growth of eight species of stored product mites under laboratory conditions. The compounds were incorporated into the diets of the mites in concentrations ranging from 0.01 to 50 mg g^?1. The final populations of mites were observed after 21 days of growth in controlled conditions. Diflubenzuron and calcofluor suppressed the growth of all the tested species more effectively than the other compounds. The doses required to suppress the mite populations to 50% (rc₅₀) in comparison to the control ranged from 0.29 to 12.68 mg g^?1 for diflubenzuron and from 1.75 to 37.7 mg g^?1 for calcofluor, depending on the mite species. When tested at the highest concentration (10 mg g^?1), teflubenzuron also suppressed all of the tested mite species in comparison to the control. The addition of chitinase/STI into the diet influenced population growth in several ways. When the highest concentration of chitinase in a cocktail of chitinase and STI (12.5 mg g^?1 of diet) was compared to the control, populations of Acarus siro, Aleuroglyphus ovatus and Aëroglyphus robustus decreased significantly, whereas populations of Tyroborus lini and Sancassania rodionovi increased significantly. The sensitivity of species to the tested compounds differed among species. The most tolerant species was S. rodionovi, the most sensitive was A. ovatus. The results confirmed that calcofluor and diflubenzuron have a toxic effect on stored product mites.     

Survey of <Emphasis Type="Italic">Alternaria</Emphasis> toxin contamination in food from the German market,using a rapid HPLC-MS/MS approach

A HPLC-MS/MS-based method for the quantification of nine mycotoxins produced by fungi of the genus Alternaria in various food matrices was developed. The method relies on a single-step extraction, followed by dilution of the raw extract and direct analysis. In combination with an analysis time per sample of 12 min, the sample preparation is cost-effective and easy to handle. The method covers alternariol (AOH), alternariol monomethyl ether (AME), tenuazonic acid (TeA), altenuene (ALT), iso-altenuene (isoALT), tentoxin (TEN), altertoxin-I (ATX-I), and the AAL toxins TA₁ and TA₂. Some Alternaria toxins which are either not commercially available or very expensive, namely AOH, AME, ALT, isoALT, and ATX-I, were isolated as reference compounds from fungal cultures. The method was extensively validated for tomato products, bakery products, sunflower seeds, fruit juices, and vegetable oils. AOH, AME, TeA, and TEN were found in quantifiable amounts and 92.1 % of all analyzed samples (n?=?96) showed low level contamination with one or more Alternaria toxins. Based on the obtained results, the average daily exposure to Alternaria toxins in Germany was calculated.     

A saponin isolated from <Emphasis Type="Italic">Agapanthus africanus</Emphasis> differentially induces apoplastic peroxidase activity in wheat and displays fungicidal properties

A spirostane with an attached trisaccharide, (25R)-5α-spirostane-2α,3β,5α-triol 3-O-(O-α-l-rhamnopyranosyl-(1 → 2)-O-(β-d-galactopyranosyl-(1 → 3))-β-d-glucopyranoside), was isolated and identified from the aerial parts of Agapanthus africanus by activity-guided fractionation. Fungicidal properties of the crude extract, semi-purified fractions as well as the purified active saponin from A. africanus were screened in vitro against Fusarium oxysporum. At a concentration of 1 mg mL^?1, the crude extract and semi-purified ethyl acetate and dichloromethane fractions showed significant antifungal activity. The purified saponin inhibited the in vitro mycelial growth of F. oxysporum completely (100 %) at a concentration of 125 µg mL^?1. Furthermore, to verify previously observed induced resistance by crude extracts of A. africanus towards leaf rust, intercellular PR-protein activity was determined in wheat seedlings following foliar application of the purified saponin at 100 µg mL^?1. In vitro peroxidase enzyme activity increased significantly (60 %) in wheat seedlings 48 h after treatment with the purified saponin, demonstrating its role as an elicitor to activate a defence reaction in wheat.     

Unreduced gamete formation in wheat × <Emphasis Type="Italic">Aegilops</Emphasis> spp. hybrids is genotype specific and prevented by shared homologous subgenomes

Key message

The presence of homologous subgenomes inhibited unreduced gamete formation in wheat × Aegilops interspecific hybrids. Unreduced gamete rates were under the control of the wheat nuclear genome.

Abstract

Production of unreduced gametes is common among interspecific hybrids, and may be affected by parental genotypes and genomic similarity. In the present study, five cultivars of Triticum aestivum and two tetraploid Aegilops species (i.e. Ae. triuncialis and Ae. cylindrica) were reciprocally crossed to produce 20 interspecific hybrid combinations. These hybrids comprised two different types: T. aestivum × Aegilops triuncialis; 2n = ABDU^tC^t (which lack a common subgenome) and T. aestivum × Ae. cylindrica; 2n = ABDD^cC^c (which share a common subgenome). The frequency of unreduced gametes in F₁ hybrids was estimated in sporads from the frequency of dyads, and the frequency of viable pollen, germinated pollen and seed set were recorded. Different meiotic abnormalities recorded in the hybrids included precocious chromosome migration to the poles at metaphase I and II, laggards in anaphase I and II, micronuclei and chromosome stickiness, failure in cell wall formation, premature cytokinesis and microspore fusion. The mean frequency of restitution meiosis was 10.1 %, and the mean frequency of unreduced viable pollen was 4.84 % in T. aestivum × Ae. triuncialis hybrids. By contrast, in T. aestivum × Ae. cylindrica hybrids no meiotic restitution was observed, and a low rate of viable gametes (0.3 %) was recorded. This study present evidence that high levels of homologous pairing between the D and D^c subgenomes may interfere with meiotic restitution and the formation of unreduced gametes. Variation in unreduced gamete production was also observed between T. aestivum × Ae. triuncialis hybrid plants, suggesting genetic control of this trait.