Journal of Agricultural Science and Technology
Volume:11 Issue: 5, Oct 2009

Population dynamics of three main alfalfa aphids, namely: pea aphid, Acyrthosiphon pisum (Harris), spotted alfalfa aphid, Therioaphis trifolii forma maculata (Buckton), black alfalfa aphid, Aphis craccivora Koch, and their most abundant predators and parasitoids in three sites and in two subsequent years in Isfahan, Iran, were investigated. The results revealed that frequency and temporal occurrence of alfalfa aphids and their natural enemies in different regions were varied, but aphid natural enemy populations were more or less coincident with aphid populations. Populations of aphids were mainly affected by alfalfa harvesting, ambient temperature, and coccinellid predators. Hemipterous predators in contrast with coccinellids, had little effect on aphid populations. Parasitoids seem to be effective on low populations of alfalfa aphids. Air humidity and rainfall had no effect on populations of alfalfa aphids.

A faunistic list of Syrphidae sampled in the agroecosystems of Neyshabur (Khorasan-Razavi Province) through Malaise, yellow water traps and hand net is hereby presented for the first time. A total of 22 species were collected, including 13 species through Malaise trap, 5 through yellow water trap as well as representatives of all species sampled through hand net. Among the species collected, 8 including phytophagous ones were exclusively sampled through hand net. In the case of Malaise trap the hover fly population was strongly dominated (73%) by 3 common species of: Sphaerophoria scripta, Episyrphus balteatus, and Eupeodes corollae while, in the yellow water trap, Episyrphus balteatus was the key species representing about 45% of all specimens. Shannon-Weiner index of biodiversity found out for Malaise trap (H= 1.86) was higher than that calculated for yellow water trap (H= 1.39). The relative efficiency of the three collection methods is discussed.

A thin layer solar drying method was compared with a traditional method (sun drying) of paddy drying, with their effects on quality characteristics of two varieties of Iranian rice (Kamphiroozi and Sazandegi) studied. Solar drying process was conducted in a passive, mixed mode type solar dryer at about 50ºC for 90 minutes. In sun drying method this process took 8-10 hours at a mean temperature of about 26ºC. Samples were milled and polished. Quality factors including trade quality (head rice yield percent and whiteness), cooking quality (amylose content, gelatinization temperature, gel consistency, aroma and flavor) as well as nutritional quality (thiamine and lysine contents) were evaluated. For a determination of head rice yield, the percentages of de-husked and broken kernels were determined by hand-sorting of broken kernels, the calculation being done through the pertaining formula. Gel consistency was determined according to the method of Cagampang et al. (the consistency of milled rice paste that has been gelatinized by being boiled in dilute alkali and then cooled to room temperature). Amylose content was determined through the simplified assay method of Juliano (setting standard curve by spectrophotometer and comparing the adsorption with the sample’s). Gelatinization temperature was estimated by the extent of alkali spreading and clearing of milled rice soaked in 1.7% KOH for 23 hours at room temperature. Organoleptic characteristics of cooked rice (iflavor, aroma) and apparent whiteness were judged by the taste panel using sensory evaluation method in triplicate. With respect to nutritional value, lysine amino acid was determined by using biological assay and applying Lactobacilllus delbrueckii while thiamine being measured through thiochrome fluorescence technique. The objective of this study was to examine the influence of solar drying process on the final quality of rice kernels and to compare the effects of this method with those in the traditional method of drying (natural sun drying). Results indicated that under the conditions prevailing in solar dryer, quality factors weren''t affected except for whiteness of rice that too was better than that for sun dried samples. All other quality characteristics of the final product were acceptable in comparison with those in sun drying method.

Intra-specific variation in responses of diurnal and long-term photosynthesis, stomatal conductance, chlorophyll fluorescence, and respiration in spring wheat (Triticum aestivum L.) to salinity was investigated using two tolerant cultivars (CR and Kharchia-65) and a sensitive one (Ghods). Plants were grown in sand culture in controlled environment at selected levels of salinity (5 as control, 100, 200, and 300 mol m-3 NaCl and CaCl2 in 5:1 molar ratios). Photosynthesis was markedly reduced in the saline conditions, but there were no significant differences observed amongst cultivars. Stomatal conductance of both upper and lower leaf surfaces was the main factor limiting photosynthesis in the presence of salinity. However, non-stomatal limitations as indicated by reduction in variable to maximum fluorescence (Fv/Fm) showed that plants might experience some degree of photoinhibition at the highest level of salinity. Gas exchange in control and 100 mol m-3 did not change throughout the day in either the salt-sensitive or the salt tolerant cultivars but in the last hours of the day photosynthesis in the sensitive cultivar was markedly reduced. Respiration remained unchanged up to 200 mol m-3 salinity but at 300 mol m-3 it decreased as compared with the lower salinity levels. The most remarkable change in respiration rate was that at seven hours after light when CO2 production was much higher than at the other times of the day. The results indicated that although photosynthesis is well correlated with stomatal conductance, wheat genotypes show different responses as regards other such aspects of photosynthesis, in different salt concentrations, as growth stage, time of the day and duration of salt exposure.

Sensors onboard meteorological satellites such as MODIS and AVHRR are able to collect information adequate in frequency but with low spatial resolution. The problem can be overcome, if one finds a way to increase the quality of the vegetation indices through searching in each individual pixel of the images, employing concurrent higher spatial resolution images. The objective of this study was to investigate the enhancement of MODIS NDVI products by using NDVI from the ASTER sensor onboard the same platform, as MODIS. The ASTER averaged NDVI values computed using only vegetated pixels were compared to unadjusted MODIS NDVI. Two approaches for the comparison are introduced in this work. In the first one, vegetated ASTER NDVI compared with MODIS NDVI (AMII Model), and in the second one the difference between vegetated ASTER NDVI and MODIS NDVI was modeled against a code representing percentage of vegetation cover (AMDI Model). It is found that the MODIS NDVI index always reads lower as compared to the vegetated ASTER NDVI. It was also found that the difference between vegetated ASTER NDVI and MODIS NDVI for vegetation covers of less than 20% was greater than 0.1 and for vegetation covers of more than 80% as low as 0.01. This could produce erroneous results when introducing uncorrected NDVI values into the climatological models especially in the arid and semi-arid climates where the vegetation covers are sparse. Both AMII and AMDI models produce NDVI values higher than those calculated from MODIS. These models were tested using 10 samples where a RMSE of about 0.028 for AMII and 0.018 for AMDI was found out. It is revealed that AMII model increases the NDVI values up to 87% for pixels containing less than 10% vegetation while 5% for pixels with more than 80% vegetation covers. These increases for AMDI model were 84% and 6%, respectively.

Important parameters on apple drying process are investigated experimentally and modeled employing artificial neural network and neuro-Taguchi''s method. Experimental results show that the apple drying curve stands in the falling rate period of drying. Temperature is the most important parameter that has a more pronounced effect on drying rate than the other two parameters i.e. air velocity and the thickness of apple slices. In order to model the drying process, a software was developed which uses the error back propagation algorithm for training. At first, the software was used to simulate the time-dependent variations of moisture content using neural network. Then in order to model the time derivation of moisture ratio in break point, the software was utilized in two ways. First, it was used with no use of any optimization method for modeling the process. In the other approach, the software in a hybrid fashion with Taguchi''s method as an optimization method is utilized to correct weight matrix entries. The results demonstrate that the use of neuro-Taguchi''s method can give some improvements over neural network accuracy as compared with conventional neural networks approach. By using neuro- Taguchi''s method, error is reduced by about 46.4%.

The estimation of velocity distribution plays a major role in the hydrodynamics of vegetated streams or rivers of extensive natural floodplains. The velocity profile in vegetated channels can be divided into three zones: uniform zone which is close to bed with uniform velocity distribution, logarithmic zone which involves the main channel with no vegetive cover and the transition zone that is affected by the upper zone flow. In order to arrive at an analytical solution to the force balance that governs the flow specific turbulence, characteristics of the flow through the vegetation are required. A new analytical model for the velocity distribution in the transition zone of vegetated (inflexible submerged vegetation) channels is hereby developed. The model is based on a force equilibrium equation and on Prandtl Mixing Length concept. Vegetation is treated as a homogeneous field of identical cylindrical stems and the flow field considered as uniform and steady. The proposed procedure is straightforward; it follows principles of fluid mechanics and shows good agreement with laboratory flume experiments. The new model can be employed for an exact estimation of discharge through naturally vegetated rivers. The model has been calibrated and verified. The results imply a desirable correlation between calculated and observed data.

The applicability of RAPDs, AFLPs, and SSRs to examine genetic relationships in 36 populations of Triticum boeoticum from West of Iran was investigated. A total of 224 (135 polymorphic), 979 (429 polymorphic) and 246 (145 polymorphic) bands/alleles were detected using 14 RAPD primers, 17 AFLP primer combinations and 17 well distributed, mapped SSR markers, respectively. The polymorphic information content (PIC) value was high for SSRs (0.81) but low for RAPDs (0.45) and AFLPs (0.56) reflecting the hypervariability of the first system. AFLPs carried the highest Marker Index (MI) value (14.19), reflecting the high multiplexity ratio of this system. The correlation coefficients of similarity were statistically significant for all the three marker systems employed. UPGMA cluster plots separated the 36 populations into three major groups based on their RAPD fragment similarities, and into two major groups based on their AFLP, SSR and RAPD+AFLP+SSR genotypic similarities. These different marker systems should provide different levels of information, important in the management of germplasm resources. A good level of genetic diversity observed in the populations of Kermanshah and Lorestan Provinces shows that T. boeoticum invades a wide range of agroecosystems in the West of Iran.

The adoption of Integrated Pest Management (IPM) strategy by farmers of Bathinda cotton belt of Punjab, India resulted in reduction of insecticidal applications. There was 3-4 times reduction in insecticidal applications in IPM villages (4.86-5.33) over the non-IPM villages (15.16-18.12). A general trend of reduced insecticidal applications of both conventional as well as new insecticides, in IPM villages as compared to non-IPM ones, was observed. However, the use of endosulfan was significantly more in IPM villages (1.07 and 0.85 applications) over non-IPM ones (0.49 and 0.32 applications) in 2002 and 2003, respectively. The use of the remaining insecticides was significantly less in IPM than in non-IPM villages. There was no application of non-recommended insecticides and mixtures in IPM villages while it was observed in non-IPM ones only. Further, farmers in IPM villages showed increased preference for relatively new insecticides (imidacloprid, acetamiprid, thiamethoxam, indoxacarb and spinosad) over the conventional group of chemicals. The adoption of IPM strategies resulted in significantly reduced pest incidence (32-75%), reduced plant protection and total input costs (17-34 and 15-21%, respectively) and an increase in net profit (54-88%) in addition to conservation of natural enemies (0.8-1.0 natural enemies/ plant in IPM over 0.4-0.7/ plant in non-IPM villages).

Iron deficiency or lime induced chlorosis is a common problem in calcareous soils. Application of mineral iron fertilizer in these soils is not usually fully effective in curing iron deficiency as compared to organic chelates. Cow manure and iron refuse (oxides), a by-product of iron melting factories were mixed in different properties of: 0, 5, 10, and 20 % V/V to make mixtures which of after four months incubation were converted into iron-enriched vermicompost through the action of earthworms. In a greenhouse study, growth and nutrient uptake by tomato grown in pot soils treated with normal vermicompost and Fe-EDDHA (synthetic iron chelate) and compared with those in plants grown in soils receiving iron-enriched vermicompost. The study design was a randomized complete block one with three replications. Total and available forms of iron in iron-enriched vermicomposts as well as in tomato tissues increased by an increase in the proportion of iron refuse in vermicompost. Shoot dry matter of plants produced in soil treated with iron-enriched vermicompost (15-20% V/V), was significantly higher than that of plants produced in the other treatments. Iron uptake by tomatoes grown in Fe-EDDHA treated soil was higher than that in plants grown in vermicompost amended soil and that in control, but it was lower than the uptake by plants grown in iron-enriched growth media.

Cantaloupe (Cucumis melo) volume was measured using water displacement and image processing methods. The volume determined from image processing method was compared to the volume determined by the water displacement method using the paired samples t-test and the Bland-Altman approach. The paired samples t-test results showed that the volume determined by image processing method was not significantly (P> 0.05) different from the volume measured through water displacement method. The mean and standard deviation of the volume difference between the two methods were -81.1 cm3 and 237.4 cm3, respectively (95% confidence interval: -212.5 and 50.4 cm3, P= 0.207). The average percentage difference between the two methods was 7.60%. The Bland-Altman approach was also indicated to be a satisfactory, image processing method suitable for volume estimation of almost all size cantaloupe. Accordingly, image processing provides an accurate, simple, rapid and non-invasive method to estimate fruit volume and can be easily implemented in monitoring fruit growth as well as in sorting of fruits during postharvest processing.

Pomegranate, a small tree with potential human health benefits, is grown mainly in Iran, India and USA as well as in most Near and Far East countries. It has been used extensively in folk medicine for a number of therapeutic purposes. In the present study, the ferric reducing/antioxidant power assay (FRAP) was employed and the FRAP value of the seed fraction of six different cultivars of pomegranate in Iran was determined in an attempt to compare their differing antioxidant acitivity. The antioxidant activity of seed fraction of six different cultivars of pomegranate in water extracts showed that the Sour white peel cultivar has the highest FRAP value (3.45±0.85 mM) and the Agha Mohammad Ali cultivar has the lowest value (2.76±0.76 mM); ethanolic extract of the seeds showed that Sour white peel and Black peel cultivars have the highest (3.88±1.31 mM) and lowest (1.62±0.47 mM) antioxidant activity, respectively. Results indicated that the extracts obtained from pomegranate seeds using various solvents exhibited various degrees of antioxidant activity. Further, it was cleared that Sour white peel had the highest potent antioxidant activity among different pomegranate seed cultivars and, so might be useful for its health benefits.