Influence of native endophytic bacteria on the growth and bacterial crown rot tolerance of papaya (Carica papaya)

The native plant microbiome is composed of diverse microbial communities that influence overall plant health, with some species known to promote plant growth and pathogen resistance. Here, we show the antibacterial and growth promoting activities of autoclaved culture metabolites (ACM) from native endophytic bacteria (NEB). These NEB were isolated from a papaya cultivar (var. Cariflora) that is tolerant to bacterial crown rot (BCR) caused by Erwinia mallotivora. In this cultivar, bacterial colonization in tissues recovering from the disease was observed before onset of tissue regeneration or ‘regrowth’. We further isolated and characterized these bacteria and were able to identify two culturable stem NEB related to plant endophytic genera Kosakonia sp. (ex. Enterobacter sp., isolate EBW), and to Sphingomonas sp. (isolate EBY). We also identified root NEB under genus Bacillus (isolates BN, BS, and BT). Inhibition assays indicated that ACM from these NEB promptly (within 18-30 h) and efficiently inhibited (60–65% reduction) E. mallotivora proliferation in vitro. When surface-sterilized papaya seeds were soaked in ACM from isolates EBY and EBW, germination was variably retarded (20–60% reduction) depending on plant genotype, but plant biomass accumulation was significantly stimulated, at around two-fold increase. Moreover, greenhouse experiments show that ACM from all isolates, especially isolate EBW, significantly reduced BCR incidence and severity in a susceptible genotype (var. Solo), at around two-fold. In general, our observations of pathogen antagonism and plant growth promotion leading to disease reduction, suggested the influence of native endophytic bacteria to increased fitness in plants, and tolerance against the re-emerging crown rot disease of papaya.

     

Anti-oxidant enzyme responses during in vitro embryogenesis in Catharanthus roseus

Summary

The present study was carried out to analyse the activities of several anti-oxidant enzymes at various stages of somatic embryogenesis in Catharanthus roseus. The hypothesis was that anti-oxidant enzymes accumulated as part of a cellular defence mechanism in response to stress. We therefore measured superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities in various in vitro-grown tissues such as embryogenic and non-embryogenic calli, and in embryos at various stages. SOD activity increased gradually from the early embryogenic stage to heart-shaped stage embryos, but declined in the later stages (i.e., torpedo-shaped and cotyledonary embryos). In contrast, APX activity was high in non-embryogenic callus and decreased rapidly during the stage of embryo initiation. This pattern was the same for CAT. The maximum CAT activity was observed in non-embryogenic callus, then it declined almost linearly at the embryonic and post-embryonic developmental stages. The effect of exogenous hydrogen peroxide (H₂O₂) on in vitro embryogenesis was also evaluated. Lower H₂O₂ levels (0.025 mM) promoted embryo formation, whereas higher levels (0.10 mM) inhibited embryogenesis in C. roseus. Finally, higher soluble protein, free amino acid, and proline contents were found in embryogenic calli compared to non-embryogenic calli.     

Assessment of Fulvic Acid-Like Fractions during Tannery Waste Composting

Changes in the structural composition of fulvic acids were followed during composting of tannery solid waste after neutralization of its acidity by ammonium or by lime. Different techniques (elemental analysis, Fourier transform infrared (FTIR), ¹³C-NMR spectroscopy) were applied. During both trials of composting, a decrease of carbon and increase of oxygen occurred, which originated from strong microbial oxidation and preservation of some structures during composting. In fact, Nuclear Magnetic Resonance (NMR) spectra showed the preservation of anomeric or tannin structures around 105 ppm. The infrared (IR) spectral data showed a decrease in the intensity of COO^? group bands (1623 and 1399.5 cm^?1); this is correlated with a decrease of fulvic acid levels. The variations observed in NMR spectra could be explained by the involvement of COO^? groups of certain structures in polycondensing to form humic acids. The fulvic acids remain composed of less polycondensed structures with a –COOH extremity, as supported by a decrease of the C/H ratio. In contrast, in the trial with addition of ammonia a slight increase in N content occurred, a decrease in absorbance in the 1730–1000 cm^?1 regions compared to the absorbance around 3400 cm^?1, and a strong decrease of carboxyl carbon in the ¹³C-NMR spectra.     

Evaluation of decay resistance of wood products made from borax-impregnated wood and bonded with a formaldehyde-free cornstarch and tannin adhesive

? At present, the production of wood composites mainly relies on the petrochemical-based and formaldehyde-based adhesives such as phenol-formaldehyde (PF) resins and urea-formaldehyde (UF) resins, which are non-renewable and therefore ultimately limited in supply.

? This paper concerns the decay resistance of wood products bonded with a new, environment-friendly adhesive derived from abundant and renewable cornstarch and tannin. To improve the total resistance of the composite against both Coriolus versicolor and Coniophora puteana rot fungi, borax (di-sodium tetraborate) was added in proportions of 0.5%, 1% and 2% (w/w) to the cornstarch-tannin adhesives.

? The results show that increasing the concentration of borax in the adhesive decreased the mechanical properties of the composite. The best way to avoid this problem was to use wood impregnated with borax.

? Biodegradation studies were conducted on new composites, first without any treatment, followed by borax at 0.5% aqueous solution treatment. The results show that wood impregnated with borax, in the presence of tannin and sodium hydroxide in the adhesive improves the total resistance of the wood composite against both Coriolus versicolor and Coniophora puteana rot fungi.

     

Germination,growth and ions uptake of moringa (Moringa oleifera L.) grown under saline condition

Salinity is the major environmental stress that affects the growth and productivity of plants. The present study was conducted to determine the effect of salinity on growth and ions uptake by moringa (Moringa oleifera L.) plant. The experiment was carried out in two phases. Initially, a germination test was conducted in the laboratory under the different salinity levels (control, 5, 10, 15, and 20 dS m^?1) and found that moringa seeds were germinated only at 5 and 10 dS m^?1 salinity levels, and no germination occurred at higher salinity levels (15 and 20 dS m^?1). The experiment was laid out in a completely randomized design (CRD) with five replications. In the second phase, three-week old nursery grown plants of moringa were shifted in pots under the five salinity levels (control, 5, 10, 15, and 20 dS m^?1). The experiment was laid out in CRD and replicated four times. In pot experiment, the root, shoot length, and dry weights were significantly affected by increasing the salinity levels. The uptake of K⁺ and Ca²⁺ was highly affected at different salinity levels as compared to control and Na⁺ ions accumulation was higher in roots rather than shoot. The results reveal that moringa plant can germinate, survive, and can be cultivated in areas with moderate saline condition.     

Antibody Prevalence and Risk Factors for Toxoplasma gondii Infection in Women from Multan,Pakistan

Toxoplasma gondii infections are prevalent in humans and warm‐blooded animals. Maternal infections during pregnancy may have devastating consequences for transplacentally infected neonates. This study was conducted to examine the seroprevalence of antibodies to T. gondii in pregnant women of childbearing age and determine risk factors associated with pregnancy history, pet ownership, social and cultural factors at Nishtar Hospital, Multan. Samples were collected from 403 women and examined using a commercially available enzyme‐linked immunosorbent assay (ELISA). The overall prevalence of antibodies to T. gondii was 17.6% (71) in the 403 samples collected from women. Antibodies to T. gondii were present in 19.4% (45) of 232 pregnant women and 15.2% (26) of the samples from 171 non‐pregnant women. This study identified miscarriage history, pet ownership, type of residence, marital status, source of drinking water and eating habits as significant (P < 0.05) risk factors associated with the presence of antibodies to T. gondii infection. Seroprevalence was not significantly different (P > 0.05) in women from different ethnic groups based upon lifestyle and culture.     

Contribution of Nitrogen Fixed by Mung Bean to the Following Wheat Crop

Crop rotation is a supportive management practice in which legumes greatly improve the growth and yield of subsequent cereal crops, particularly wheat. In this study, effects of mung bean (Vigna radiata)?? on the yield and quality of grains of following wheat crop were determined. An experiment was carried out with two sets of wheat (Triticum aestivum) crops: one grown following mung bean (Vigna radiata) crop and the other grown after a fallow period. Concentrations of macronutrients, sugar, protein, amino acids, and phytohormones of wheat were determined. The grain protein concentration of wheat was improved if cultivated after mung bean, and nitrogen and other macronutrients of wheat were increased significantly. In case of phytohormone contents in the wheat crop, abscisic acid concentration showed no change, but the concentrations of gibberellin increased significantly by 41% and indole acetic acid by 30% as a result of crop rotation. Sugar content in wheat cultivated after mung bean BRM-318 showed 10% increase and wheat protein content increased by 17% and 20%, respectively. The present study demonstrated that crop rotation simulated yield and improved the nutritional value of wheat grain compared to wheat which followed the fallow period.     

Resistance to <Emphasis Type="Italic">Meloidogyne incognita</Emphasis> expresses a hypersensitive-like response in <Emphasis Type="Italic">Coffea arabica</Emphasis>

Root-knot nematodes (RKN) are obligate parasite species of the genus Meloidogyne that cause great losses in Arabica coffee (Coffea arabica L.) plantations. Identification of resistant genotypes would facilitate the improvement of coffee varieties aiming at an environmental friendly and costless nematode control. In this work, the C. arabica genotype ‘UFV 408-28’ was found to be resistant to the most destructive RKN species M. incognita. Pathogenicity assays indicated that the highly aggressive populations of M. incognita races 1, 2 and 3 were not able to successfully reproduce on ‘UFV 408-28’ roots and displayed a low gall index (GI = 2). An average reduction of 87% reduction of the M. incognita population was observed on ‘UFV 408-28’ when compared to the susceptible cultivar ‘IAC 15’. By contrast, ‘UFV 408-28’ was susceptible to the related species M. exigua and M. paranaensis (GI = 5 and 4, respectively). Histological observations performed on sections of UFV408-28 roots infected with M. incognita race 1 showed that nematode infection could be blocked right after penetration or during migration and establishment stages, at 6 days, 7 days and 8 days after infection (DAI). Fluorescence and bright field microscopy observations showed that root cells surrounding the nematodes exhibited HR-like features such as accumulation of phenolic compounds and a necrotic cell aspect. In the susceptible ‘IAC 15’ roots, 6 DAI, feeding sites contained giant cells with a dense cytoplasm. Necrotic cells were never observed throughout the entire infection cycle. The HR-like phenotype observed in the ‘UFV 408-28’—M. incognita interaction suggests that the coffee resistance may be mediated by a R-gene based immunity system and may therefore provide new insights for understanding the molecular basis of RKN resistance in perennial crops.     

Fabrication and characterization of nanofibers based on poly(lactic acid)/chitosan blends by electrospinning and their functionalization with phospholipase A1

In this work, electrospinning of poly(lactic acid) (PLA), chitosan and their blends has been investigated, and nanofibers with a diameter ranging from 90 nm to 1.9 microns were produced and used as carriers for immobilization of the phospholipase A1. A strong influence of chitosan (CS) and the solvent trifluoroacetic acid (TFA) on the morphology, distribution of the nanofibers diameter and on their hydrophobicity was observed. The yield of phospholipase A1 (PLA1) on non-woven fibers was evaluated using the method of Bradford. Their activities and their reutilisability were assessed titrimetrically using soybean lecithin as substrate. The results showed that the degree of immobilization on the non-woven fibers of pure PLA and mixtures PLA/CS4 and PLA/SC6 are 73, 54, 45 % respectively and can be reused up to 4 cycles without significant loss of enzyme activity. Moreover, a remarkable improvement of the activity of phospholipase A1 on non-woven based on pure PLA fibers was observed, indicating that most of the enzymes were probably in their active form.