Biochemical indices (RNA/DNA ratio and protein content) in studying the nutritional status of Ruditapes decussatus (Linnaeus 1758) juveniles

In this work, we investigated the nutritional status of Ruditapes decussatus juveniles under different rearing conditions, using biochemical indices (RNA/DNA ratio and protein content) and the linear instantaneous growth rate (IGR). Two experiments were conducted to study the effect of starvation, addition of substrate (sand) as rearing support and diet composition on somatic growth and biochemical indices. Results show that biochemical indices of fed juveniles were significantly (P<0.05) higher. Highest RNA/DNA values and protein content were recorded in fed juveniles reared with substrate (P<0.05); conversely, lowest values were recorded in starved ones reared without substrate. In the second experiment, the highest RNA/DNA ratio was recorded in juveniles fed with control algal mixture composed of species commonly used in bivalve nurseries [Isochrysis galbana (clone T-Iso), Chaetoceros calcitrans and Tetraselmis suecica] and lowest in those fed with algal species isolated from Tunisian coasts. This confirms the usefulness of the RNA/DNA ratio and protein content in the clam's nutritional status evaluation. This assay is useful to provide information about the nutritional status and health of the clam in field conditions.     

Biological study of Plutella xylostella (L.) (Lep: Plutellidae) and it's solitary endoparasitoid, Cotesia vestalis (Haliday) (Hym. Braconidae) under laboratory conditions

Plutella xylostella (L.) (Lep: Plutellidae), is a destructive pest of brassicaceous crops in the world. Cotesia vestalis (Haliday) is one of most important biological control agents of P. xylostella in the world and Iran. Both of P. xylostella and C. vestalis biology were carried out in laboratory condition. Results showed that development time of immature stages of P. xylostella including egg, Instar I, Instar II, Instar III, Instar IV, prepupa, pupa were 2.39 +/- 0.17, 2.18 +/- 0.17, 2.06 +/- 0.28, 2.14 +/- 0.14, 2.54 +/- 0.12, 0.40 +/- 0.12 and 4.23 +/- 0.23 days, respectively. Longevity of female and male were 28.26 +/- 0.05 and 30.22 +/- 0.05 days. By dissecting the parasitized larvae, the egg incubation period of C. vestalis was recorded 1.73 +/- 0.06 days. In long-term oviposition trials, females laid eggs on P. xylostella larvae for up to 10 days. Larval development of the parasitoid in host only required 6.47 days: the first instar larva required 3.25 +/- 0.047 days; the second instar larva needed 2.78 +/- 0.1 days and the third instar larvae exited the host and pupated in, 0.4 +/- 0.07 days. Prepupal and pupal period of wasp were 1.9 +/- 0.06 and 2.13 +/- 0.09 day, respectively. Unmated female and male longevity of wasp were 16.83 +/- 0.37, 16.25 +/- 0.17 and sex ratio is male-biased. When a mixed group and isolated of instars were presented for parasitoid, the 2nd and 3rd instar larvae were so preferred and the 4th instar was less attractive for selection. In choice experiment, the percentage parasitism of 2nd, 3rd and 4th instars was 78.58, 69.94 and 4.36%, respectively. The rapid oviposition rate, short life duration and high percentage parasitism increases parasitoid potential for suppression of host population. Present results suggest that C. vestalis has considerable potential as a biological control agent for P. xylostella.     

The Relationship Between Developmental Accumulation of Leaf Soluble Proteins and Vernalization Response of Wheat （Triticum aestivum L.em. Thell）

The relationship between vernalization requirement and quantitative and qualitative changes in total leaf soluble proteins were determined in one spring （cv. Kohdasht） and two winter （cvs. Sardari and Norstar） cultivars of wheat （Triticum aestivum L.） exposed to 4℃. Plants were sampled on days 2, 14, 21 and 35 of exposure to 4℃. The final leaf number （FLN） was determined throughout the vernalization periods （0, 7, 14, 24, and 35 d） at 4℃. The final leaf number decreased until days 24 and 35 in Sardari and Norstar eultivars, respectively, indicating the vernalization saturation at these times. No clear changes were detected in the final leaf number of Kohdash cultivar, verifying no vernalization requirement for this spring wheat cultivar. Comparing with control, clear cold-induced 2-fold increases in proteins quantity occurred after 48 h following the 4℃-treatment in the leaves of the both winter wheat cultivars but, such response was not detected in the spring cultivar. However, the electrophoretic protein patterns showed between-cultivar and between-temperature treatment differences. With increasing exposure time to 4℃, the winter cultivars tended to produce more HMW polypeptides than the spring cultivar. Similar proteins were induced in both Sardari and Norstar winter wheat cultivars, however, the long vernalization requirement in Norstar resulted in high level and longer duration of expression of cold-induced proteins compared to Sardari with a short vernalization requirement. These observations indicate that vernalization response regulates the expression of low temperature （LT） tolerance proteins and determines the duration of expression of LT- induced proteins.     

A Nondestructive,Remote Sensing-Based Estimation of the Economic Value of Aboveground Temperate Forest Biomass (Case Study: Hyrcanian Forests,Nowshahr-Iran)

ABSTRACT

Background: Traditional field-based methods of measurement of biomass and carbon storage face difficulty in collecting time-consuming and expensive, suggests the use of remote sensing-based techniques. It estimates the economic value of the aboveground biomass (AGB) using satellite remote sensing across the Hyrcanian forests of Iran. Methods: The Landsat-8 OLI sensor data were combined with field-based allometric information of 186 circular sample plots. The AGB was calculated at the plot level using the collected data and specific volumetric mass for species in the studied area. It was followed by calculating the carbon storage using a 50% carbon coefficient and the photosynthesis equation at the forest parcel level. Model results using the random forest and support vector machines. The carbon sequestration value was calculated with USD 25.3 as a shadow value of carbon in 2014 and using the replacement cost approach. Results: The highest performances achieved by RF for biomass, carbon storage and the carbon storage value (Iranian Rials of 0.67% and 16%, respectively). The value was derived once at the plot level of 12.22 million IRR (370.43 USD) per ha. In addition, at the parcel level, which resulted in an estimated value of 12.87 million IRR (390.24 USD) per ha.     

Spatial patchiness and association of pests and natural enemies in agro-ecosystems and their application in precision pest management: a review

Natural enemies can effectively reduce pest populations when they coincide spatially and temporally with those populations. Therefore, along with temporal synchronization, the spatial association of pests and natural enemies is also necessary to increase the efficiency of biological control. The aims of this review were to assess the current state of knowledge concerning the spatial association of pests and their natural enemies in agro-ecosystems, evaluate its application in precision pest management programs and highlight the relevant gaps in the existing literature. Spatial analysis by distance indices (SADIE) and geostatistics are adequate sets of statistical tools used to study spatial patchiness and association of pests and natural enemies, especially in field crops. Spatial association between pests and natural enemies is dynamic and many biotic and abiotic factors can influence it. According to the literature, there are important gaps in the research about the spatial association of pests and natural enemies in orchards and stored products, as well as about the effects of environmental factors on the spatial association between these organisms. Mapping the spatial distribution and association of pests and natural enemies’ populations has not been used in precision biological control until recently. Precision applications focus on the targeted application of agricultural inputs in management zones rather than whole-field treatments. Information about spatial distribution and association of pests and natural enemies can be used to improve pest management practices through precision or site-specific applications of chemical and biological control measures.

     

The potential of soya oil industry products as oil alternatives in rainbow trout (Oncorhynchus mykiss) diet

This study investigated the effects of different soya oil products on growth, nutrient digestibility, and fatty acid composition of muscle in rainbow trout. The products’ ingredients were soap stock, fat powder, crude oil, and refined soya oil as a control. Four experimental diets were formulated by addition of 12 % of each of the four ingredients to a basal diet. Replacement of refined soya oil by the soya oil products did not influence growth performance until 8 weeks (P > 0.05). This replacement, however, reduced fat digestibility in rainbow trout (83.7 vs. 73.3–79.8 %; P < 0.05). Dietary inclusions of fat powder and crude oil led to larger values of protein digestibility than those of refined soya oil and soap stock (P < 0.05). The compositions of saturated and monounsaturated fatty acids of the muscle were similar, but linoleic acid concentration (LA, 18: 2n-6) increased in fish muscle fed refined soya oil compared to the other diets (37 vs. 30–31 %; P < 0.05). Arachidonic acid (ArA, 20: 4n-6) concentration was higher (P < 0.05) in fish fed both fat powder and soap stock than those fed the other diets. In conclusion, refined soya oil can be replaced by soya oil products in rainbow trout diet with no negative impacts on the growth. However, fish fed on diet containing refined soya oil had higher concentration of LA and lower density of ArA. It appears that rainbow trout is capable of digesting soya oil products though the digestibility rate reduced slightly with an increase in saturated fatty acid content.     

Effects of coated and non-coated ZnO nano particles on cucumber seedlings grown in gel chamber

Zinc oxide-engineered nanoparticles (ZnO ENPs) have received the most attention in recent years. This increasing interest has been directed towards studying the environmental fate and effects of ZnO ENPs on ecological terrestrial species. In this study, ZnO NPs were synthesized by atmospheric pressure solution evaporation method and were coated or uncoated with humic acid (HA). The root uptakes of uncoated and HA-coated ZnO NPs and zinc (Zn) were investigated by gel-grown cucumber. Two ZnO levels (1 and 200 µM) were applied in the form of coated (T₃) and non-coated (T₂) NPs or bulk particles (T₁). The results showed that coating NPs by HA increases zeta potential of NPs and decreases their aggregation size due to the increase in the repulsion forces among the particles. Addition of 1 mgL^?1 ZnO into gel chamber enhanced root and shoot biomass; however, the shoot growth was higher in the presence of NPs compared to its bulk counterpart. Moreover, greater phytotoxicity of ZnO from the source of NPs than bulk particles in shoot was observed. Scanning electron microscopy results showed a clear evidence of the penetration of NPs into root cells.     

Low back disorders in agriculture and the role of stooped work: scope, potential interventions, and research needs

Low back disorders (LBDs) continue to be a major occupational health problem facing the agricultural workforce. Working in a flexed or stooped posture is one of several workplace factors associated with occupationally related LBDs and is highly prevalent in many agricultural tasks. The purpose of this article is to evaluate the role of stooped work in the problem of LBDs among agricultural workers by examining the epidemiological literature, evaluating the scope of stooped work in agriculture, and examining current and potential intervention approaches. The literature review indicates that the prevalence of LBDs in agriculture worldwide is considerably high and substantially reported. Workers who are exposed to stooped work in agriculture are estimated to be in the 100s of millions worldwide. However, stooped work has not been specifically investigated as an independent LBD risk factor. Plausible biomechanical and physiological mechanisms of how stooped work may lead to damage to the spinal structures are discussed, and this complements the epidemiological evidence of high prevalence of LBDs in agriculture. However, this study also identifies the need to conduct more thorough epidemiological studies that utilize accurate quantitative exposure and outcome assessment techniques for developing more appropriate dose-response relationships in agricultural stooped work. This will provide better means for evaluating current and future interventions for jobs involving stooped work. Various intervention approaches are summarized to control and abate stooped work in agriculture; however, it must be emphasized that any development of ergonomic interventions for stooped work in agriculture must incorporate a participatory ergonomics approach that integrates the opinions and concerns of workers, managers, and ergonomists.     

Soil‐vegetation relationships of three arid land plant species and their use in rehabilitating degraded sites

It is essential to consider soil characteristics when establishing vegetation in arid lands. In this study, the redundancy analysis (RDA) ordination method was used in this study to evaluate the habitats of Halocnemum strobilaceum, Limonium iranicum and Tamarix passerinoides growing in the Sejzy region, east of Isfahan. The study area was stratified into six ecologic‐floristic complexes. Stratified random sampling was then employed to collect soil and vegetation data from 1‐ha quadrats on nine sites. The soil samples were analysed to determine the characteristics of the soil in which the three species grew and to examine the soil profiles up to a depth of 2 m. Soil analyses revealed that high amounts of gypsum, silt, clay, saline, alkali and sulphate in the soil constituted a favourable habitat for Halocnemum strobilaceum. However, the per cent of silt and sulphate concentration in deep layers were negatively correlated with the growth of this species. Evaluation of the L. iranicum habitat revealed that the amounts of carbonate and CCE in the topsoil were positively correlated with the establishment and growth of the species but salinity and alkalinity were negatively correlated. The primary soil characteristics that positively influenced T. passerinoides included the presence of organic matter and bicarbonate ions in the soil layers and the total Ca and Mg content of the topsoil. However, Na was negatively correlated with Tamarix species. Determination of the soil characteristics that are associated with each of these xerophytic species can be used to determine which species is suitable for rehabilitating degraded sites in the study area. Copyright © 2010 John Wiley & Sons, Ltd.     

Assessing the impact of site-specific spraying on control of <Emphasis Type="Italic">Eurygaster integriceps</Emphasis> (Hemiptera: Scutelleridae) damage and natural enemies

Sunn pest, Eurygaster integriceps Puton is a key pest of wheat and barley in Iran. In this study, the impact of site-specific spraying on control of sunn pest damage and densities of the natural enemies was compared with the whole-field spraying method in 2009 and 2010. Three plots were assigned to each spraying method and two others were left untreated as control. The plots were divided into 11 × 11 m grids. Adults of E. integriceps were sampled using the distance-walk method. Coccinellids, Chrysoperla carnea and nymphs of sunn pest were sampled using a sweep net. Spatial analysis of datasets was done using Geostatistical Analyst extension of ArcGIS 9.3. The spatial analysis indicated that the adults and nymphs of E. integriceps had aggregated distribution in space and that site-specific spraying was applicable. Whole-field spraying was carried out when the mean density of E. integriceps in plots exceeded the economic threshold. In the site-specific spraying method, decamethrin ([cyano-[3-(phenoxy) phenyl] methyl] 3-(2,2-dibromoethenyl)-2,2-dimethylcyclopropane-1-carboxylate) was applied to the grid cells with densities above the economic threshold. Site-specific application reduced the insecticide input by ca. 40–50%. The numbers of C. carnea and coccinellids were higher in site-specifically sprayed plots compared with whole-sprayed plots after treatment. The mean numbers of nymphs were not significantly different (P < 0.01) in whole-field and site-specifically sprayed plots. Percent damaged grain was below the economic damage threshold in all treated plots. It can be concluded that site-specific spraying has the potential to control E. integriceps at an acceptable level along with reducing the amount of insecticide used. It also conserved natural enemies in untreated refuges.