Positive effects of Penconazole on growth of Brassica napus under drought stress

The aim of the present study was to compare the effects of drought on some physiological and biochemical parameters and to assess the inducing effects of Penconazole (PEN) on drought tolerance in two cultivars (RGS003 as a drought tolerant and Sarigol as a drought sensitive) of canola. Plants were treated with various PEG concentrations (0, 5, 10, and 15%) without or with PEN (15 mg l^?1). Decrease in fresh weight (FW) and dry weight (DW) in Sarigol under drought was higher than that of RGS003. Surprisingly, PEN reversed prominently the negative effects of drought on FW and DW in RGS003. Concomitantly, PEN treatment decreased malondialdehyde content in RGS003 under drought. Moreover, higher content of proline in RGS003 under all drought levels could be considered as a factor for drought tolerance of this cultivar. Superoxide dismutase (SOD), catalase (CAT) and Polyphenol oxidase (PPO) activities were induced by PEN in both cultivars under drought. Inducing effects of PEN on phenylalanine ammonia lyase and thyrosine ammonia lyase activities decreased by increasing of drought levels in both cultivars. In summary, PEN alleviated the negative effects of drought in RGS003 cultivar by inducing activities of SOD, CAT and PPO and proline content comparing to Sarigol.     

Inorganic and organic ligands induced changes in Pb sorption of arid ‎clay and calcareous loamy sand soils

The objective of this study was to investigate sorption, desorption, and immobilization of Pb in the clay and calcareous loamy sand soils treated with inorganic ligands (NO₃^?, Cl^? and H₂PO₄^?). Pb sorption was also determined in the presence of oxalate and citrate. The maximum Pb sorption capacities (q) ranged from 42.2 to 47.1 mmol kg^?1 for the clay soil, and from 45.2 to 47.0 mmol kg^?1 for loamy sand soil. It was observed that the binding energy constant (k) for Pb sorbed onto loamy sand soil (528–1061) is higher than that for clay soil (24.38–55.29). The loamy sand soil-sorbed greater quantities of Pb compared to the clay soil when initial pH was ≥ 3. However, it had lower sorption capacity at the lowest initial pH of 2. Additionally, the greatest Pb sorption and immobilization occurred in the soil treated with H₂PO₄. In the clay soil, the sorption of Pb was depressed at 0.1 mol kg^?1 of Cl^?, as compared with other ligands. Concerning organic acids, citrate ligand showed the highest decrease in Pb sorption. It could be concluded that the nature of Pb sorption can depend on the type and quantity of ligands present, as well as the soil type.     

Spatial distribution of wind-driven sediment transport rate in a fallow plot in Central Anatolia,Turkey

Wind erosion is a serious land degradation phenomenon in semi-arid parts of Turkey. It is even becoming more critical problem considering the current effects of global warming and climate change in the region. The objectives of this study are to model spatial variation of aeolian sediment transport and to map Sediment Transport Rate (STR) by geostatistics in a fallow plot in the Central Anatolia. STRs for four consecutive wind cases with different vegetation cover rates were determined using the cyclone BEST sediment traps. Plant cover ratio and height changed between 8 and 25% and 3–12?cm throughout the research period, respectively, and soil moistures ranged between 10.9 and 12.7%. The windstorms lasted for 400, 835, 1240, and 50 minutes with the mean wind velocities of 8.6, 7.7, 7.7, and 6.3?m?s^?1, respectively, for cases 1, 2, 3, and 4. The calculated STRs varied between 0.0248?±?0.0170?kg?m^?1?h^?1 and 0.190?±?0.084?kg?m^?1?h^?1. Spatial analysis revealed that the spatial correlations were between 19 and 48?m and different spatial patterns occurred from one case to another. The study results indicated that the amount of transported sediment and its spatial variation were mostly related to velocity and duration of erosive wind in the fallow area of the arid region.     

Effects of silicon on the growth of maize seedlings under normal,aluminum, and salinity stress conditions

The effects of silicon on seed germination and growth parameters of maize seedlings under normal, aluminum (Al), and sodium chloride (NaCl) stress conditions were investigated. The results indicated a dose-dependent relationship between silicon and growth parameters, except for germination attributes.Application of silicon (2 mM) accelerated amylase activity, decreased abscisic acid content, and increased indoleacetic acid and gibberellic acid contents of seedling, The results suggest that the beneficial effects of silicon, at least in part, are mediated by the balance of phytohormones. Exposure to Al (10 mM) significantly decreased all growth parameters of maize seedlings. Application of 2 mM silicon, however, alleviated Al stress and restored almost all growth attributes. Decrease of Al absorption, increase of fructan content, and improvement of amylase activity were considered as the mechanisms of ameliorative function of silicon in Al-stressed maize seedlings. Exposure to silicon, however, did not show beneficial effects on growth parameters of maize seedlings under salt stress conditions.     

Root water uptake of pepper plants (Capsicum annuum L.) under deficit irrigation system

Root water uptake is a component of water balance that has not been clearly understood. This study was carried out in a completely randomized design with three replications under the greenhouse condition at Shahrekord University, Shahrekord, Iran. In this study, the root water uptake (RWU) by pepper plant under various irrigation water levels was investigated. Irrigation treatments included control (full irrigation level, FI) and three deficit irrigation levels, 80%, 60% and 40% of the plant's water requirement called DI₈₀, DI₆₀ and DI₄₀, respectively. A no-plant cover treatment with three replications was also used to measure evaporation from the soil surface. Daily measurements of volumetric soil moisture (VSM) were made at 10 cm intervals of the soil column. The differences between the measured VSM and the VSM in the next day, and evaporation rate at the soil surface at the same layer of the no-plant cover treatment were calculated and, eventually, the RWU in each layer per day was estimated. The results showed that the maximum and minimum RWUs were found in the FI and DI₄₀ treatments, respectively. The averages of root water uptakes in the DI₈₀, DI₆₀, and DI₄₀ treatments were reduced by 17.08%, 48.72% and 68.25%, respectively. Furthermore, in the DI₈₀ treatment, the reduced rate of water uptake was less than the reduced rate of water applied to the plants.     

Influence of mycorrhizal fungi on growth,chlorophyll content,and potassium and magnesium uptake in maize

Mycorrhizal fungi affect growth and nutrition of host plants positively. In this research, influence of vesicular-arbuscular mycorrhiza (VAM) ongrowth, chlorophyll content, and potassium (K) and magnesium (Mg) uptake in maize seedlings in pot culture was studied. This experiment was performed using natural soil containing a mixture of spores of Glomus spp. Mycorrhizal spores were exposed to four concentrations of K solution, i.e. 0.61 (soil K content), 0.92, and 1.23 meq/L and three concentrations of Mg, i.e. 4.8 (soil Mg content), 7.2, and 9.6 meq/L concurrently. Plants were watered every 4 days for 16 days with 50 mL distilled water. A pot with sterilized soil was used as negative control. For study of mycorrhizal colonization, very thin manually prepared longitudinal sections of plant roots (>1 mm in diameter) were stained with lactophenol-cottonblue and examined microscopically. Percentage of mycorrhizal colonization was determined using the grid-line intersect method. Samples from root and shoot of maize were collected for further analysis. Results showed mycorrhizal plants had significantly higher dry and fresh weight and chlorophyll content than plants grown in sterilized soil (p ≤ 0.05). Treatments with concentrations of 7.2 meq/L of magnesium alone and in combination with 0.92 meq/L of potassium with7.2 meq/L of Mg had better effect on morphological characters (dry and fresh weight of root and shoot). Mycorrhizal colonization increased Mg uptake but decreased K uptake.     

Low phosphorus and competition affect Chinese fir cutting growth and root organic acid content: does neighboring root activity aggravate P nutrient deficiency?

Purpose

In order to manage Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) plantations over the long term, it is critical to understand the species’ response to intraspecific competition at sites with low phosphorus (P). The objective of the present study was to investigate the effects of neighbor competition on the growth of Chinese fir under low P conditions, as well as on the morphology and organic acid content of the root tissues.

Materials and methods

We investigated the growth, dry matter accumulation, and organic acid content and type in root tips of Chinese fir cuttings in a greenhouse experiment, which was a design with three factors including competition intensity (single, mild, moderate, and severe), P supply level (0, 6, and 12 mg kg^?1 KH₂PO₄), and competition time (50, 100, and 150 days).

Results and discussion

There were no significant interaction effects between all three or any two factors on shoot growth (height or root collar diameter), biomass accumulation, or root:shoot ratio. However, the interactive effects between competition time and competition intensity on all root morphological traits were significant, as was the interaction between P supply and competition (e.g., intensity, time) on root organic acid concentration. The number of organic acid types gradually decreased from the first 50 to 150 days under no P supply and low P supply treatment. Interestingly, capric acid was detected in severe and moderate competition treatments, but not detected under mild competition or in single plant controls at low P. Also, citric acid was detected in P supply treatments (6 and 12 mg kg^?1), but not detected in the no P treatment.

Conclusions

Mild early-stage intraspecific competition somewhat alleviated the suppressive effect of low P supply on the height of Chinese fir. Seedlings adjusted their shoot and root growth separately to accommodate stress from low P or adjacent competition. Low P supply and competition intensity additively accelerated root volume proliferation, but interactively enhanced organic acid concentration in root tips.

     

Discovery and characterization of a molecular marker for <Emphasis Type="Italic">Sclerotinia minor</Emphasis> (Jagger) resistance in peanut

The production of cultivated peanut, an important agronomic crop throughout the United States and the world, is consistently threatened by various diseases and pests. Sclerotinia minor Jagger (S. minor), the causal agent of Sclerotinia blight, is a major threat to peanut production in the Southwestern US, Virginia and North Carolina. Although information on the variability of morphological traits associated with Sclerotinia blight resistance is plentiful, no molecular markers associated with resistance have been reported. The identification of markers would greatly assist peanut geneticists in selecting genotypes to be used in breeding programs. The main objective of this work was to use simple sequence repeat (SSR) primers previously reported for peanut to identify a molecular marker associated with resistance to S. minor. Out of 16 primer pairs used to examine peanut genomic DNA from 39 different genotypes, one pair produced bands at approximately 145 and 100 bp, consistent with either S. minor resistance or susceptibility, respectively. Cloning and sequencing of these bands revealed the region is well conserved among all genotypes tested with the exception of the length of the SSR region, which varies with disease resistance levels. This is the first report of a molecular marker associated with resistance to Sclerotinia blight in peanut. The identification of this marker and development of a PCR-based screening method will prove to be extremely useful to peanut breeders in screening germplasm collections and segregating populations as well as in pyramiding S. minor resistance with other desirable traits into superior peanut lines.     

Granular formulation of Fusarium oxysporum for biological control of faba bean and tomato Orobanche

BACKGROUND: Orobanche spp. represent a serious threat to a wide range of crops. They are difficult targets for herbicides, and biological control could provide a possible solution. This work therefore aimed to formulate mycoherbicides of Fusarium with adequate shelf life and virulence against Orobanche but safe to faba bean and tomato. RESULTS: Only two isolates of Fusarium oxysporum Schlecht. (Foxy I and Foxy II) obtained from diseased Orobanche shoots were found to be pathogenic to Orobanche crenata Forsk. and Orobanche ramosa L. Conidial suspension of both isolates significantly decreased germination, attachments and tubercles of Orobanche. Microconidia and chlamydospores of both isolates were formulated as mycoherbicides encapsulated in a wheat flour–kaolin matrix (four different formulations). All formulations greatly diminished Orobanche emerged shoots, total shoot number, shoot height, attachment of emerged shoots, the germinated seeds that succeeded in emerging above the soil surface and dry weight. Meanwhile, disease incidence and disease severity of emerged shoots were enhanced. The shelf life was adequate, particularly for coarse, freshly prepared, low‐temperature‐stored, microconidia‐rich formulations. The induced growth reduction of Orobanche‐infected host plants seemed to be nullified by formulations, particularly at the highest dose. CONCLUSION: These formulations seemed to destroy Orobanche but appeared harmless to host plants. Hence, they could be efficiently used as mycoherbicides for biological control of Orobanche in faba bean and tomato. Copyright © 2008 Society of Chemical Industry     

Enhanced control of bacterial wilt of tomato by DL-3-aminobutyric acid and the fluorescent Pseudomonas isolate CW2

Journal of Plant Diseases and Protection - Soil treatments with DL-3-aminobutyric acid (BABA) and the fluorescent Pseudomonas isolate CW2 significantly reduced bacterial wilt on tomato plants...