Phylogenetic relationships of fluorescent <Emphasis Type="Italic">Pseudomonad</Emphasis> isolates associated with bacterial canker of stone fruit trees in Kurdistan province,Iran

Bacterial canker is one of the most important diseases of stone fruit trees in various locations of Kurdistan province, Iran. Genetic diversity and evolutionary relationships among 20 fluorescent pseudomonads isolated from stone fruit trees with symptoms similar to bacterial canker were investigated using a polyphasic approach by means of phenotypic characterizations, repetitive PCR using the REP and ERIC primers and multilocus sequence typing (MLST) of four housekeeping genes (gapA, rpoD, gyrB and gltA). The pathogenicity of strains was carried out under greenhouse conditions. Twelve strains produced an expected amplified DNA fragment of about 752-bp which indicated the presence of the syrB gene. Based on MLST, these strains belonged to P. syringae species complex and included in the genomospecies 1, phylogroup 2b and 2d. Phylogenetic analysis of the other eight fluorescent pseudomonad strains by using gyrB and rpoD sequences allowed the identification of strains into P. fluorescens, P. putida and P. lutea groups. Unweighted pair group method analysis (UPGMA) of genomic fingerprints obtained by rep-PCR revealed 17 different patterns which grouped P. syringae strains into three clusters clearly separated from other fluorescent pseudomonads. MLST confirmed the genetic variability among strains obtained by rep-PCR. Grouping identified of P. syringae strains by both rep-PCR and MLST was related to geographic locations of strains.     

Biological characteristics of Orius similis Zheng (Heteroptera,Anthocoridae) by feeding on different aphid species as prey

Journal of Plant Diseases and Protection - The predatory flower bug Orius similis Zheng (Heteroptera, Anthocoridae) which originated in China is a polyphagous predator that feeds on a wide range of...     

The effect of water salinity on growth and physiological stages of eight Canola (Brassica napus) cultivars

Laboratory/greenhouse and field experiments were conducted to evaluate the effects of salinity levels ranging from 1 to 12 dS/m on germination rate, 8 leaf seedling dry matter, seed yield, and seed oil content of the 8 Canola (Brassica napus) cultivars: ACSN1, Falcon, Shirali, Ceres, Tower, Cobra, Global, and Oyerka. Statistical results revealed that the factors: salinity, cultivar, and their interaction had significant (P<0.01) effect on germination rate and 8 leaf seedling dry matter. Based on statistical analysis seed yield was significantly influenced by both salinity and cultivar at the 5% significance level; while the cultivar factor had a significant effect on seed oil content, salinity did not show any effect on seed oil content. Analytical results, using the well-known sigmoid or S-shape salinity response function gave reliable results for determining tolerant and sensitive cultivars to salinity. Applying an existing model on canola response to salinity levels in different growth stages, the values of C ₅₀ and P parameters were developed for local canola cultivars. Results showed that the response of cultivars to salinity levels vary in different growth stages. While a cultivar is tolerant in a growth stage, it may be sensitive to salinity in another growth stage. Based on observed data and ANOVA analysis, we concluded that ACSN1, Shiraly, and Falcon can be ranked as salt-tolerant, and Global and Oyerka as the salt-sensitive cultivars.     

Planning and management modeling for treated wastewater usage

Due to urban growth, some agricultural lands have been replaced by residential, municipal, and industrial areas. In some cases the remaining agricultural land will not have enough water because of transfers from agriculture to M&I (municipal and industrial) users. Therefore, in many places, especially in arid and semi-arid regions, the use of treated wastewater as a reliable source of irrigation water has already been, or will be, considered in the future. Due to its unique characteristics, this new resource has many challenges that cannot be ignored, such as health issues, water quality, and long- and short-term effects on soils and crops. The study described herein considered the development of a new GIS-based model for planning and managing the reuse of treated wastewater for the irrigation of agricultural and green lands, considering various factors such as population and urban growth. The model is composed of several different modules, including an urban growth model. These modules are designed to help in the decision-making process for allocations of water resources to agricultural areas, considering factors such as crop types, crop pattern, water salinity, soil characteristics, pumping and conveyance costs, and also by comparing different management scenarios. Appropriate crops that can be grown with a specific water salinity and soil characteristics, proper water resources for each farm (according to pumping and conveyance costs, and analysis of water demand, and water supply) can be determined through the application of this model. The model can also rank agricultural areas and open spaces in and near an urban area according to their suitability for irrigated agriculture.     

Integrated use of GIS,remote sensing and multi-criteria decision analysis to assess ecological land suitability in multi-functional forestry

The Zagros forests are a treasure of valuable oak forests, but they have been severely degraded from long-term misuse. Geographic information systems (GIS) and multi-criteria decision analysis (MCDA) have been increasingly used to improve the management of vulnerable ecosystems to prevent further degradation and increase the sustainability of land use. This study presents a methodology to assess land suitability using remote sensing (RS) to obtain wall-to-wall data for the calculations, GIS to analyze the data, and MCDA to rank alternative land uses. The criteria and subcriteria affecting the suitability of land for different uses were identified and weighted using an analytic hierarchy process. Variables used as subcriteria were assessed using satellite data and other sources of information such as existing maps and field surveys. Numerical values for the subcriteria were classified, and each class was given a priority rating according to expert judgments. Based on the ratings and weights of the subcriteria, a priority map was created for each land use using the weighted linear combination method. The priority maps for different land uses were overlaid to obtain a preliminary land use map, which often indicated several simultaneous land uses for the same location. The preliminary map was further edited by removing unrealistic, mutually exclusive land-use combinations. The study tested and demonstrated the potential of integrating RS, GIS and MCDA techniques for solving complicated land allocation problems in forested regions using a scientifically sound and practical approach for efficient and sustainable allocation of forestland for different uses.     

Water Relations and Transpiration of Quinoa (Chenopodium quinoa Willd.) Under Salinity and Soil Drying

Drought and salinity are the two major factors limiting crop growth and production in arid and semi‐arid regions. The separate and combined effects of salinity and progressive drought in quinoa (Chenopodium quinoa Willd.) were studied in a greenhouse experiment. Stomatal conductance (g_s), leaf water potential (Ψ_l), shoot and root abscisic acid concentration ([ABA]) and transpiration rate were measured in full irrigation (FI; around 95 % of water holding capacity (WHC)) and progressive drought (PD) treatments using the irrigation water with five salinity levels (0, 10, 20, 30 and 40 dS m^?1); the treatments are referred to as FI₀, FI₁₀, FI₂₀, FI₃₀, FI₄₀; PD₀, PD₁₀, PD₂₀, PD₃₀, PD₄₀, respectively. The measurements were carried out over 9 days of continuous drought. The results showed that increasing salinity levels decreased the total soil water potential (Ψ_T) and consequently decreased g_s and Ψ_l values in both FI and PD. During the drought period, the xylem [ABA] extracted from the shoots increased faster than that extracted from the roots. A reduction in Ψ_T, caused by salinity and soil drying, reduced transpiration and increased apparent root resistance (R) to water uptake, especially in PD₀ and PD₄₀ during the last days of the drought period. The reasons for the increase in apparent root resistance are discussed. At the end of the drought period, the minimum value of relative available soil water (RAW) was reached in PD₀. Under non‐saline conditions, Ψ_l decreased sharply when RAW reached 0.42 or lower, but under the saline conditions of PD₁₀ and PD₂₀, the threshold values of RAW were 0.67 and 0.96, respectively. In conclusion, due to the additive effect of osmotic and matric potential during soil drying on soil water availability, quinoa should be re‐irrigated at higher RAW in salt‐affected soils, i.e. before the soil water content reaches the critical threshold level causing the drop in Ψ_l resulting in stomatal closure.     

Prediction of saturated hydraulic conductivity of compacted soils using empirical scaling factors

A new empirical-based scaling method is introduced to predict saturated hydraulic conductivity (K _s ) of compacted soils. This method is an improvement of the former non-similar media concept (NSMC) model that is generalized for tilled and untilled conditions. In this method, geometric mean particle size diameter (d_g ), geometric standard deviation (σ _g ) and saturated soil water content (total porosity) are successfully incorporated in the empirical-based scaling factor of K _s . Results showed that the scaled model overestimated K _s by ～18%, whereas the NSMC model underestimated K _s by ～21%. However, the scaled model based on the similar media concept (SMC) failed to predict K _s . Because of the complexity and high uncertainty in determining the shape factor parameter in the NSMC model, it is suggested that the new scaled model might be used reliably in practical cases to predict K _s in the various layers of compacted soils irrespective of the tillage condition. Further assessment of the new scaling model in other areas, in which new collected data are available, is recommended.     

Agricultural water management in the world during past half century

The present paper aims to estimate the areas equipped for irrigation and desirability of agricultural water management in the world. For this purpose, all necessary information was gathered from Food and Agriculture Organization and checked using World Bank Group. The selected 18 indices were analysed for all 26 regions in the area studied, and the extent of area equipped for irrigation to cultivated area was estimated by 2 different formulas and other 9 indices. In addition, an average index was calculated using various methods to assess region conditions for agricultural water management. The results show that Central Asia is the best region for agricultural water management and the value of relative error is less than 20%. The capability of irrigation and drainage systems was studied using other eight indices with more limited information. The results indicated that trial-and-error policies should be avoided and expert comments be applied to irrigation systems for any crop.     

Diachronic (1979–2003) analysis of rice genetic diversity in Guinea did not reveal genetic erosion

Greater insight into the dynamics of genetic resources of crop plants is needed in order to pinpoint detrimental evolutionary patterns and draw up conservation priorities. Temporal evolution of rice genetic diversity was monitored in Maritime Guinea where subsistence-oriented agriculture prevails. Diachronic comparison was performed between samples collected in six villages during the 1979/1982-period and in 2003, based on the names and number of varieties inventoried and the polymorphism of microsatellite markers. The number of varieties appeared not to be comparable between the two dates, due to differences in the collection methods. The varietal composition had evolved very substantially between the two collection dates. Many long-duration varieties present in 1979/1982 had been abandoned and several improved varieties had been introduced. The mean number of alleles per locus and per accession was significantly higher in accessions collected in 2003. Pairwise comparisons of the mean number of alleles per locus in 1979/1982–2003 homonymous accession pairs indicated higher intra-accession diversity for the 2003 collections. Genetic differentiation, measured with the F _ST values, was very high and significant for more than 80% of these pairs of accessions. The overall genetic differentiation between accessions from the two collections dates was also significant. Significant changes were also observed for allelic composition. However, alleles specific of each collection date had much lower frequency, compared to alleles common to the two collection dates. These results suggest that rice genetic diversity in Maritime Guinea has been maintained or even enhanced. Old collections of crop genetic resources are often not exhaustive enough to undertake perfect diachronic comparison. New methods to utilize this historical data for diversity monitoring are needed.     

Isolation and characterization of potassium solubilizing bacteria in some Iranian soils

The ability of a few soil bacteria to transform unavailable forms of potassium (K) to an available form is an important feature in plant growth-promoting bacteria for increasing plant yields of high-K-demand crops. In this research, isolation, screening, and characterization of six isolates of K solubilizing bacteria (KSB) from some Iranian soils were carried out. The ability of all isolates were tested in three treatments including acid-leached soil, biotite, and muscovite by analyzing the soluble K content after 5 days of incubation at 28 ± 2°C. Identification and phylogenetic analyses were also carried out by morphological, biochemical, and 16S rDNA analyses. Among the six efficient isolates, five isolates belonged to Bacillus megaterium (JK3, JK4, JK5, JK6, and JK7), while isolate JK2 belonged to Arthrobacter sp. The soluble K contents in all isolated-treatments were significantly (p < 0.01) higher than the contents in nonbacteria treatment. Herein, isolate JK2 had lower potential for K solubilization (910 mg kg^?1) compared with other isolates in acid-leached soils. The six bacterial strains showed higher solubilized K in biotite treatment than other two treatments. Overall, it can be concluded that the isolates belong to B. megaterium are the most efficient KSB under in vitro condition.