Storability of onion bulbs contaminated by<Emphasis Type="Italic">Aspergillus niger</Emphasis> mold

In the course of pre- and postharvest epidemiological studies on bulbs contamination byAspergillus niger, two Sudanese onion cultivars were tested: ‘Saggai Red’ and ‘El-Hilo White’.A. niger spores, whether seedborne, soilborne or airborne, were avirulent to the healthy growing onion plants. The fungus heavily contaminated the dead onion tissues, mainly the dead leaves followed by the dry scales, the dead roots and, to a lesser extent, the bulb necks, preferring the red-skinned cultivar to the white one. The initial spores carried from naturally contaminated field soil on the dead tissues could germinate and produce massive numbers of new spores on bulbs stored at average climatic conditions of Sudan (23–39°C, 29–93% relative humidity). Under laboratory-controlled conditions, optimal growth occurred at 75–85% r.h. on bulbs with dry scales and maximum losses occurred at 100% r.h. and ambient temperature. Underin vitro conditions, the optimal growth and sporulation temperature forA. niger was in the range of 30–35°C. Early harvesting and removal of the dead onion tissues improved bulb storability in aseptic stores under low temperature and relative humidity conditions. http://www.phytoparasitica.org posting Oct. 20, 2003.     

Resistance to fusarium basal rot of onion in greenhouse and field and associated expression of antifungal compounds

Greenhouse and field evaluations of onion for resistance to Fusarium basal rot caused byFusarium oxysporum f.sp.cepae were conducted on cultivars ‘Akgün 12’ and ‘Rossa Savonese’ previously described as resistant at the seedling stage. In the greenhouse experiments inoculations were carried out on seeds or soil; in the field experiments evaluation was performed on onion sets from plants grown in naturally infested soils. Akgün 12 and to a lesser extent Rossa Savonese were resistant to the disease at the bulb stage in all experiments. Results were also consistent with those obtained from a previous screening at the seedling stage. Onion sets were also extracted and fractionated by thin layer chromatography to determine their content of antifungal compounds. Extracts were characterized by the expression of distinct antifungal components, which may be involved in resistance to the pathogen. http://www.phytoparasitica.org posting July 14, 2004.     

Sarcocystosis of chital-dhole: conditions for evolutionary stability of a predator parasite mutualism

Background  

For parasites with a predator-prey life cycle, the completion of the life cycle often depends on consumption of parasitized prey by the predator. In the case of such parasite species the predator and the parasite have common interests and therefore a mutualistic relationship is possible. Some evidence of a predator-parasite mutualism was reported from spotted deer or chital (Axix axis) as a prey species, dhole or Indian wild-dog (Cuon alpinus) as the predator and a protozoan (Sarcocystis axicuonis) as the parasite. We examine here, with the help of a model, the ecological conditions necessary for the evolution and stability of such a mutualistic relationship. A two – level game theory model was designed in which the payoff of a parasite is decided not only by alternative parasite strategies but also by alternative host strategies and vice versa. Conditions for ESS were examined.     

Photosynthetic ability of Horse gram [<Emphasis Type="Italic">Macrotyloma uniflorum</Emphasis> (Lam.) Verdc] plants in response to metal stress

The effects of heavy metals' stress like aluminium (Al), bismuth (Bi), lithium (Li) and nickel (Ni) on photosynthetic ability of Horse gram plants inoculated with the four metal tolerant rhizobial strains were studied. Horse gram plants can grow in Al contaminated soils up to 400 μg g^–1, at this concentration also they have shown maximum PS ability than in uninoculated plants when they were inoculated with the strain HGR-13. In soils containing Bi, the rate of PS increased up to 200 μg g^–1 with the strain HGR-13 and 400 μg g^–1 with the strain HGR-25. Li has shown significant changes on PS ability of horse gram plants. The PS ability of these plants increased with the strain HGR-6 up to 30 μg g^–1 only. The plants inoculated with the strains HGR-4, 6 and 25 along with uninoculated plants have shown their maximum PS ability at 80 μg g^–1 of Ni. The net PS ability of HGR-4 and HGR-6 was maximum than uninoculated plants. In conclusion, these plants were able to grow in Al, Bi, Li and Ni contaminated soils. The metal tolerant rhizobial strains enhanced the PS ability of horse gram plants when they were inoculated in metal contaminated soils. Horse gram plants and the rhizobia associated with it besides having the nitrogen fixing ability, also have heavy metal tolerance. So, it is concluded that horse gram plants can be used as reclamation agents and phytoremediation.     

Removal of Cu<Superscript>2+</Superscript> ions from aqueous solution by amino-functionalized magnetic sawdust composites

In this study, amino-functionalized magnetic γ-Fe₂O₃/sawdust composites (MSC-NH₂) were investigated as biological absorption materials for removing Cu²⁺ ions from aqueous solution. These composites were fabricated by precipitated γ-Fe₂O₃ nanoparticles on sawdust substrate and then functionalized with 1,6-hexanediamine. Characterization of MSC-NH₂ was performed by means of SEM, TEM, XRD, FTIR, BET, MPMS and XPS analysis to discuss the uptake mechanism. As a result, the amino groups are grafted upon the sawdust surfaces. The MSC-NH₂ could be effectively used to remove Cu²⁺ from aqueous solution and be separated conveniently from the solution with the help of an external magnet. Batch experiments show that the adsorption equilibrium is achieved in 150 min, and the adsorption capacity is 7.55 mg/g at pH 6 and room temperature. The isotherm analysis indicates that the sorption data could be represented by Langmuir isotherm models. The kinetics is evaluated utilizing the Lagergren pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion models. Thermodynamic parameters reveal the spontaneous, endothermic and chemical nature of adsorption.     

Preparation of self-clustering highly oriented nanofibers by needleless electrospinning methods

Polyacrylonitrile (PAN) oriented nanofibers were produced by homemade needleless electrospinning device. Spiral coils were adopted to replace the traditional spinning needles in this equipment. The tracks of multi-jets were controlled by adjusting the microcurrent during the eletrospinning process. The microcurrent value and the motion track of the spinning jet during the spinning process were observed, the fiber morphology and the mechanical properties of fiber membranes were measured. The results revealed that the average diameters of the electrospun fibers were increased from 490 nm to 740 nm. with the addition of organic salt. Meanwhile, the self-clustering phenomenon was obviously observed, and the mechanical properties of obtained fibers were also altered, the tensile strength was improved from 3.63 MPa to 23.90 MPa, while the strain decreased from 74.6 % to 27.1 %.     

Development and application of a SRAP marker for the identification of sex in <Emphasis Type="Italic">Buchloe dactyloides</Emphasis>

Buffalograss, Buchloe dactyloides (Nutt.) Engelm, is a dioecious turfgrass native to the Great Plains of North America. Since its naturalization, it has become the most wildly cultivated warm-season turfgrass in northern China. While dioecious plants represent only a small proportion of all plant species, they are important models in the study of plant sex determination and evolution. The identification of the sexes is important in the theory and practice of breeding programs. At present, there is no effective method to determine the sex of early stage buffalograss. The objective of this study was to use sequence-related amplified polymorphism (SRAP) and integrated bulked segregant analysis (BSA) technology to find sex linked markers in B. dactyloides. A total of 228 primer combinations were screened and 2,690 SRAP bands examined. Only ME9/EM2 could generate a specific fragment (~240 bp) in all the female plants, which was absent in male plants. The methods described here provide a simple and reproducible means of early sex identification in B. dactyloides.     

Zinc fractions and solubility in a tropical semi-arid soil under long-term cultivation

There is an increasing incidence of Zn deficiency in savanna soil under intensive cultivation. The sizes of Zn pools and Zn²⁺ solubility were studied in a savanna soil under long-term cultivation and varying management practices which included fertilization with NPK, farmyard manure (FYM), NPK + FYM and a control which received neither NPK nor FYM for 50 years. An uncultivated natural site was sampled as a reference for assessing the effect of management history on Zn fractions and solubility. Total Zn ranged from 38 to 63 mg kg^-1 in the natural site, and from 28 to 57 mg kg^-1 in the cultivated fields. The FYM-fertilized field maintained total and extractable Zn on par with the natural site. Cultivation and management history did not affect the concentration of diethylenetriaminepentaacetic acid- (DTPA) extractable Zn, water-soluble Zn (SOL-Zn), exchangeable Zn (EXCH-Zn) and organically complexed Zn (OM-Zn). For the natural site, residual Zn (RES-Zn) accounted for 48% of total Zn, whereas Mn-oxide-bound Zn (MnOX-Zn) accounted for between 40% and 61% of total Zn in the cultivated fields. Cultivation caused the depletion of RES-Zn especially in FYM- and FYM + NPK-fertilized soils. Solubility studies indicated that some mechanism involving Zn and Fe, but independent of pH, appeared to control Zn²⁺ concentration in soil solution consistent with the reasonably constant values of pZn²⁺ + 2pFe³⁺ in soil solution.