S. A. Haroun

Bio: S. A. Haroun is an academic researcher from Mansoura University. The author has contributed to research in topics: Shoot & Kinetin. The author has an hindex of 10, co-authored 30 publications receiving 224 citations.

Dual inoculation of Bradyrhizobium and Enterobacter alleviates the adverse effect of salinity on Glycine max seedling

Abstract: The aid of beneficial microbes, which is a well-accepted strategy, may improve plant salt tolerance. However, the mechanisms that underpin it are unclear. In this study, seedling experiments were carried out to assess the effect of Bradyrhizobium and Enterobacter on the germination, growth, nonenzymatic and enzymatic content in soybean (Glycine max L.) under salt stress. Water was sprayed on the seeds as a control, and with 75 mM, 150 mM NaCl as salt stress. The findings demonstrate that salt stress (75, 150 mM) caused a significant decrease in germination, morphological criteria, and membrane stability index (MSI) when compared to control seeds but increased lipid peroxidation (MDA), electrolyte leakage (EL), osmotic pressure, proline, citric acid, sugar content, antioxidant enzymes. Furthermore, endophytic Bradyrhizobium and Enterobacter inoculation resulted in a significant rise in all of the above metrics.; however, these treatments resulted in significant reductions in ROS, EL, and MDA in stressed plants. Finally, the findings showed that combining Bradyrhizobium and Enterobacter was the most efficient in reducing the harmful effects of salt on soybean plants by boosting antioxidant up-regulation and lowering membrane leakage and ROS.

Application of actinomycetes as biocontrol agents in the management of onion bacterial rot diseases

Abstract: This study was conducted to achieve biological control for the post-harvest onion bacterial rot diseases with the aid of Egyptian isolates of actinomycetes. In this respect, 45 actinomycetes strains were isolated from Egyptian soils and screened for their antagonistic effect against onion bacterial rot pathogens; Erwinia carotovora subsp. carotovora and Burkholderia cepacia. The most two active strains were identified based on their cultural, morphological and molecular properties as Streptomyces lavendulae HHFA1 and Streptomyces coelicolor HHFA2, the latter was most potent and so was used in vivo (pots and field) for controlling onion bacterial rot. S. coelicolor HHFA2 application resulted in enhancement in the photosynthetic pigments and some foliar growth parameters of onion plants confirming its growth promoting effect. The results of the post-harvest estimation of the disease incidence (DI) of the onion bacterial rot throughout storage revealed that, the application of S. coelicolor HHFA2 reduced the...

Identification of Newly Isolated Talaromyces pinophilus and Statistical Optimization of β-Glucosidase Production Under Solid-State Fermentation

Abstract: Fungi able to degrade agriculture wastes were isolated from different soil samples, rice straw, and compost; these isolates were screened for their ability to produce β-glucosidase. The most active fungal isolate was identified as Talaromyces pinophilus strain EMOO 13-3. The Plackett-Burman design is used for identifying the significant variables that influence β-glucosidase production under solid-state fermentation. Fifteen variables were examined for their significances on the production of β-glucosidase in 20 experimental runs. Among the variables screened, moisture content, Tween 80, and (NH4)2SO4 had significant effects on β-glucosidase production with confidence levels above 90% (p < 0.1). The optimal levels of these variables were further optimized using Box-Behnken statical design. As a result, the maximal β-glucosidase activity is 3648.519 U g(-1), which is achieved at the following fermentation conditions: substrate amount 0.5 (g/250 mL flask), NaNO3 0.5 (%), KH2PO4 0.3 (%), KCl 0.02 (%), MgSO4 · 7H2O 0.01 (%), CaCl2 0.01 (%), yeast extract 0.07 (%), FeSO4 · 7H2O 0.0002 (%), Tween 80 0.02 (%), (NH4)2SO4 0.3 (%), pH 6.5, temperature 25°C, moisture content 1 (mL/g dry substrate), inoculum size 0.5 (mL/g dry substrate), and incubation period 5 days.

Plant Growth Promoting and Biocontrol Activity of Streptomyces spp. as Endophytes.

Abstract: There has been many recent studies on the use of microbial antagonists to control diseases incited by soilborne and airborne plant pathogenic bacteria and fungi, in an attempt to replace existing methods of chemical control and avoid extensive use of fungicides, which often lead to resistance in plant pathogens. In agriculture, plant growth-promoting and biocontrol microorganisms have emerged as safe alternatives to chemical pesticides. Streptomyces spp. and their metabolites may have great potential as excellent agents for controlling various fungal and bacterial phytopathogens. Streptomycetes belong to the rhizosoil microbial communities and are efficient colonizers of plant tissues, from roots to the aerial parts. They are active producers of antibiotics and volatile organic compounds, both in soil and in planta, and this feature is helpful for identifying active antagonists of plant pathogens and can be used in several cropping systems as biocontrol agents. Additionally, their ability to promote plant growth has been demonstrated in a number of crops, thus inspiring the wide application of streptomycetes as biofertilizers to increase plant productivity. The present review highlights Streptomyces spp.-mediated functional traits, such as enhancement of plant growth and biocontrol of phytopathogens.

Water relations in plants subjected to heavy metal stresses

Abstract: Concentrations of heavy metals in soil seldom reach a level sufficient to cause osmotic disturbances in plants. It is likely that water entry to the roots is indirectly governed by other factors which are themselves affected by metals. Decreased elongation of the primary root, impaired secondary growth, increased root dieback, or reduced root hair caused by toxic ions all exert a deleterious effect on the root-absorbing area and water uptake. Moreover, metals are able to decelerate short-distance water transfer both in symplast and apoplast, which in turn reduce the movement of water into the vascular system and affect water supply to the shoot. Long-distance transport is limited also due to decreased hydraulic conductivity in the root, stem and leaf midrib caused by a reduction in the size of vessels and tracheids, and partial blockage of xylem elements by cellular debris or gums. Heavy metals influence water delivery to the shoot due to inhibition of transpiration as they decrease the size of the leaves and the thickness of the lamina, reduce intercellular spaces, affect the density of stomata and decrease their aperture. Stomata closure is induced by direct interaction of toxic metals with guard cells and/or as a consequence of the early effects of metal toxicity on roots and stems. In metal-stressed plants, root-derived ABA or ABA-induced signals might play a role in stomatal movement. Disturbances in water relations trigger differential regulation of aquaporin gene expression, which may contribute to further reductions in water loss.

Effects of cyanobacterial extracellular products and gibberellic acid on salinity tolerance in Oryza sativa L

Abstract: Salt stress is one of the most serious factors limiting the productivity of rice, the staple diet in many countries. Gibberellic acid has been reported to reduce NaCl-induced growth inhibition in some plants including rice. Most paddy soils have a natural population of Cyanobacteria, prokaryotic photosynthethic microorganisms, which synthesize and liberate plant growth regulators such as gibberellins that could exert a natural beneficial effect on salt stressed rice plants. The aim of this work was to evaluate the effect of the cyanobacterium Scytonema hofmanni extracellular products on the growth of rice seedlings inhibited by NaCl and to compare it with the effect of the gibberellic acid in the same stress condition. Growth (length and weight of the seedlings) and biochemical parameters (5-aminolevulinate dehydratase activity, total free porphyrin and pigments content) were evaluated. Salt exposure negatively affected all parameters measured, with the exception of chlorophyll. Chlrorophyll concentrations nearly doubled upon exposure to high salt. Gibberellic acid counteracted the effect of salt on the length and dry weight of the shoot, and on carotenoid and chlorophyll b contents. Extracellular products nullified the salt effect on shoot dry weight and carotenoid content; partially counteracted the effect on shoot length (from 54% to 38% decrease), root dry weight (from 59% to 41% decrease) and total free porphyrin (from 31 to 13% decrease); reduced by 35% the salt increase of chlorophyll a; had no effect on root length and chlorophyll b. Gibberellic acid and extracellular products increased 5-aminolevulinate dehydratase activity over the control without salt. When coincident with high salinity, exposure to either EP or GA3, resulted in a reversal of shoot-related responses to salt stress. We propose that Scytonema hofmanni extracellular products may counteract altered hormone homeostasis of rice seedlings under salt stress by producing gibberellin-like plant growth regulators.

Effect of two species of cyanobacteria as biofertilizers on some metabolic activities, growth, and yield of pea plant

Abstract: Two cyanobacterial species (Nostoc entophytum and Oscillatoria angustissima) were tested as biofertilizers, substituting the normally used chemical fertilizer, for pea plant. Inoculation of soil with a suspension of each species or a combination of the two species significantly increased the germination percentage and stimulated the other measured growth parameters and photosynthetic pigment fractions of pea. However, the soil inoculation with one cyanobacterial species and the addition of the recommended dose or half the recommended dose of chemical fertilizer were usually more effective and also increased carbohydrate and protein contents of produced pea seeds. However, biofertilization combined with half the recommended dose of the chemical fertilizer was usually more effective than the addition of the full rate of the chemical fertilizer, and this may allow saving 50% of the used chemical fertilizer. The protein profile of the produced seeds showed appearance and disappearance of some protein bands in response to fertilization treatments compared to the control. Blue green algae analyses show that N. entophytum fixed more N, produced more exopolysaccharide, and contained more auxin and cytokinin than O. angustissima, the latter contained more gibberellins. These data may explain their different influences on growth and yield of pea.