H. Dashti

EFFECTS OF SALINITY AND SOIL ZINC APPLICATION ON GROWTH AND CHEMICAL COMPOSITION OF PISTACHIO SEEDLINGS

The effects of four salinity levels [0, 1000, 2000, and 3000 mg sodium chloride (NaCl) kg−1 soil] and three zinc (Zn) levels [0, 5, and 10 mg kg−1 soil as zinc sulfate (ZnSO4.7 H2O)] on growth and chemical composition of pistachio seedlings (Pistacia vera L.) cv. ‘Badami’ were studied in a calcareous soil under greenhouse conditions in a completely randomized design with three replications. After 26 weeks, the dry weights of leaves, stems and roots were measured and the total leaf area determined. Salinity decreased leaf, stem, and root dry weights and leaf area, while this effect diminished with increasing Zn levels. Zn fertilization increased leaf, stem and root Zn concentrations, leaf potassium (K) concentration, and stem and root sodium (Na) concentrations, while decreased leaf Na concentration, and stem and root K concentrations. Salinity stress decreased leaf, stem, and root Zn concentrations, and leaf K concentration, while salinity increased leaf, stem and root Na concentrations, and stem and root K concentrations. Proline accumulation increased with increasing salinity levels, whereas the reverse trend was observed for reducing sugar contents. Zn application decreased proline concentration but increased reducing sugar contents. These changes might have alleviated the adverse effects of salinity stress.

Introduced Pseudomonas fluorescens VUPf5 as an important biocontrol agent for controlling Gaeumannomyces graminis var. tritici the causal agent of take-all disease in wheat

About 900 bacterial strains obtained from plants rhizosphere from different areas of Iran and biocontrol ability were widely survey in vitro and greenhouse conditions against Gaeumannomyces graminis var. tritici the causal agent of take-all disease. Finally the best strain (VUPf5 strain) in the additional tests biocontrol ability in vitro and greenhouse conditions was selected for next studies. VUPf5 suppressed of take-all disease 85%. Based on biochemical and morphological tests, this isolate is belonging to the species Pseudomonas fluorescens. This isolate significantly produced the secondary metabolites such as siderophores, hydrogen cyanide, protease, phenazine and volatile metabolites.

Biocontrol performance evaluation of spontaneous mutants of Pseudomonas fluorescens VUPf5 generated during proliferation

VUPf5 genetic stability as a superior strain (of the 900 bacterial strains that were isolated from the rhizosphere of different regions of Iran) for the control of take-all disease of wheat was studied. The genetic stability of the strain in terms of, whether or not, the mass and reproduction of bacteria in liquid medium was determined. VUPf5 produces some secondary metabolites such as extracellular proteases, phenazine antibiotic, siderophore, hydrogen cyanide and volatile metabolites. The regulatory GacA/GacS system has involved as an important system in the production of secondary metabolites in the biocontrol fluorescent Pseudomonas spp. During proliferation, different colonies of bacteria were found in terms of morphology, such as colour (white instead of orange) and shape (approximately flat and larger) of the colony; and media pH that in the mutants was higher, and the production of some metabolites, such as protease, HCN and phenazine was surveyed. Also, mutants in the genetic comparison with the wild type were different. VUPf5 and different colonies were detected in gacA and gacS genes. This paper appears in colonies with low efficiency in the production of secondary metabolites is related to mutation in genes gacS and gacA.

Impact of Pistachio Residues on Compactibility, and Permeability for Water and Air of Two Aridic Soils from Southeast of Iran

So far no information is available on impacts of pistachio residues on physical and mechanical properties of aridic soils. The objective of this study was to assess the influence of pistachio residue amendments on soil compactibility, saturated hydraulic conductivity (Ks), and air permeability (ka) of two soils in Rafsanjan, Iran. Tests were set up as factorial experiments with two factors including: pistachio residue at four levels (0, 3, 6, and 9% dry basis) and two soil textures (silty clay loam and sand). The residue-treated soils were compacted using a modified Proctor test (5 blows per layer) to determine maximum dry bulk density (BDmax) and critical water content (θcritical). Soil samples with similar BD from the dry and wet limbs of the compaction curve were used to investigate the effect of dry and wet compactions on soil pore connectivity and continuity as quantified by Ks and ka. Residue applications decreased BDmax, but increased θcritical compared to the control; the effects were greater for larger residue rates. The impacts were more obvious for silty clay loam soil. Both Ks and ka of sandy soil were significantly different between the two samples with similar BD. However, such differences were not significant for the silty clay loam soil, indicating that effectiveness of pistachio residue amendments for improving soil structure depends on the soil texture. Moreover, deleterious effects of compaction on soil pore functions might not be described by bulk properties (e.g., BD) but could adequately be accounted for by intensity properties like Ks and ka.