JOURNAL OF AGRICULTURAL SCIENCE AND TECHNOLOGY (JAST)
Year:2011 | Volume:13 | Issue:6|Papers Count:17

The present study investigated the effect of Iranian university entrance examinations and the high school grade point average (HSGPA) on agriculture students' achievement. The population included 598 admitted students at the Faculties of Agriculture and Natural Resources, University of Tehran. The specific variables of the study included college grade point average (CGPA) and average of major field specialized courses (FSGPA) as dependent variables. Also, scores in mathematics, physics, biology, and chemistry at the university entrance examinations record (UEX), along with high school grade point average (HSGPA) were the independent variables of the study. The results indicated that high school grade point average (HSGPA) was a significant predictor of agriculture students’ academic achievement. With the exception of Food Sciences, there was no significant relationship between the scores in mathematics and students’ academic achievement in fields related to agriculture.

Diversity, accessibility and reliability are the three main factors governing the adoption of information sources by farmers in rural areas. Based on the research hypothesis, the existing knowledge and information delivery system in the agricultural sector, functions far below the ever changing nature and tangible needs of existing farming systems. The main objective in this study is to determine and prioritize farmers’ information channels and their communication networks within rural areas of 19 townships of Isfahan Province – the central part of Iran. After exploratory field visits of several villages, a questionnaire was designed and pre-tested for its validity and reliability (Alpha=82%). The statistical society included all farmers who had regular contacts with the local extension offices. The sample population was 228 farmers who were selected through a two-step random sampling method from the villages with an extension office. The results showed that extension system disregarded farmers’ local media and did not meet their actual needs. The extension system failed to build trust among the local communities. Moreover, farmers’ trust in one information source had a synergic effect on the others. The sources were categorized in three groups based on the farmers’ preferences. The printed materials did not play any significant role in the knowledge and information processes. There was also a significant correlation between dependent variables (determination of information source by farmers) and the independent variables (for example: farming land size and farmers educational level). Finally, most farmers claimed that visiting ‘local extension service offices’ was mainly in response to their urgent needs to acquire subsidized agricultural input such as fertilizer, rather than acquisition of information and were yet disappointed.

Storage of potatoes is very important because fresh potatoes are available only for a few months in a year. Thus, any treatment such as irradiation that controls sprout growth and extends shelf life of potatoes could be beneficial. In this study, potato sprout inhibition and tuber quality after treatment with various levels of Gamma Irradiation (0, 50, 100 and 150 Gy) on different dates (10, 30 and 50 days after harvest) were studied during prolonged storage at 8 and 16oC using tubers of Agria variety. A factorial experiment based on a randomized split plot design with three replications was carried out. There was minimum sprout development (4.83±0.01 g/3kg tuber) in tubers from early irradiation date (10 days after harvest). This study indicated that early irradiation and higher irradiation levels significantly decreased sprouting, percent weight loss and specific gravity of tubers. The loss of ascorbic acid and the contents of reducing and nonreducing sugars significantly increased by delay in irradiation whereas the content of sugars and ascorbic acid level decreased by irradiation. The loss of firmness became clearer during five months storage in non-irradiated tubers. Higher storage temperature (16oC) caused greater loss of ascorbic acid (20.34%). In other words, tubers stored at 16oC showed greater metabolic changes as indicated by sprouting, weight loss, and changes in sugars and ascorbic acid contents. The 50 Gy irradiation treatment on the 10th day after harvest resulted in complete sprout inhibition of tubers at 8oC storage and 150 Gy dose while inhibiting sprouting at 16oC, caused greater loss of ascorbic acid. Tubers irradiated with later after harvest were subject to greater loss of ascorbic acid in response to higher doses of irradiation and higher storage temperature. Consequently, to reduce undesirable changes in Agria potato tubers, delay in irradiation and storage at high temperature are not recommended.

It is suggested that cultivars of wheat (Triticum aestivum L.) with regulated growth and development would be able to produce higher yields under water-limited conditions, which is crucial in future food production. Water use efficiency (WUE) is worthy of exploration in this regard. In this study, the effects of nitrogen fertilizer levels (0, 40 and 80 kg Nha-1) and a plant growth retardant (Chlormequat Chloride=CCC) on WUE of four dryland wheat cultivars (Agosta, Nicknejad, Azar-2 and Fin-15) were examined in a field experiment during 2006-07 and 2007-08 growing seasons at College of Agriculture, Shiraz University, Iran. The results showed that there existed significant differences between cultivars for grain yield, biomass and WUE. In the first season, the highest grain yield and biomass production (192.4 and 431.2 gm-2, respectively) were obtained from Nicknejad cultivar, CCC application and using 80 kg Nha-1, and in the second season, from Azar-2 cultivar (121.5 and 333.5 gm-2, respectively). CCC and nitrogen had significant effects on photosynthesis rate and WUE in both seasons. Interaction of CCC and 80 kg Nha-1 on WUE were significant in both seasons (1.24 and 2.72 gm-2mm-1, respectively). It is suggested that interactive application of CCC and nitrogen fertilizer could have beneficial effects on wheat grain yield under similar agro-climatic conditions.

This study was carried out to evaluate the effects of red onion (Allium cepa L.) juice and green tea (Camellia sinenses) extract on lipid oxidation and sensory characteristics of refrigerated (4oC) sturgeon fillets (Acipenser persicus). Fresh fillets were tumbled in 1%, 2.5%, and 5% (v/v) aqueous solutions of onion Juice (OJ) and tea extract (TE), and then stored for up to 8 days at 4oC in a refrigerator. Chemical indices of lipid oxidation as assayed by heme iron, thiobarbituric acid and free fatty acid contents indicated much more reduction in 2.5%TE, 5%TE and 5%OJ-treated samples relative to the other samples (P<0.05). Significant (P<0.05) differences in pH values of treatments and the control were observed during the first 2 days of storage time. For 5%OJ treatment, the pH remained constant during refrigerated storage (P>0.05) whereas gradual changes were detected in pH values of the others. Generally, the order of effectiveness for inhibiting oxidation in sturgeon fillets was found to be: 5% TE or OJ=2.5% TE>2.5 % OJ>1% TE=1% OJ. Based on sensory scores, higher amounts of onion juice (>1%) were more effective to improve attributive characteristics of the fillets.

This study was carried out to investigate the effects of salinity levels (0, 2, 4, 7 and 10 ppt) on growth indices, blood biochemical parameters, and body composition in Rutilus frisii kutum fingerlings (initial weight 1.33±0.02 g) during 60 days. Results indicated that the highest rates of daily growth, specific growth and weight gain per fish were obtained at the levels of 4 and 2 ppt (P<0.05). The lowest rates of these indices were observed at 10 ppt (P<0.05). FCR (food conversion ratio) and CF (condition factor) showed no significant difference among various treatments (P>0.05). Findings of blood biochemical factors at the end of the study (hematocrit, total protein, glucose, cholesterol, calcium, sodium, potassium and magnesium) revealed no significant variation in different salinities (P>0.05). Changes in protein, moisture, fat and ash content were not significant at the end of the experimental period (P>0.05).

The influence of maleic anhydride-polypropylene (MAPP) (0, 2, 3 and 5%) as a compatibilizer on the wettability of polypropylene/wood flour/glass fiber hybrid composites was studied by using the contact angle determination technique. Sample slats with a cross section of 10×70 mm were made by a twin screw extruder. Specimens were conditioned at room temperature and the angles between the water droplets and surfaces of the hybrid composites were measured. Results revealed that the wettability of the composites was significantly decreased as the MAPP was increased to 3%. However, no significant decreasing effect was observed at MAPP contents above 3%.

This study was carried out in order to determine the leave characteristics of some chestnut genotypes in the Central Black Sea Region of Turkey and also to determine whether the leaf morphometric characteristics could be used for differentiation of genotypes. In this study, seven chestnut (Castanea sativa Mill.) genotypes (SA5-1, SE 3-12, SE 21-2, SE 21-9, 552-8, 556-7 and 556-8) and one cultivar (Sariaslama) were used. Some leaf parameters such as lamina length, lamina width, leaf length, leaf area, petiole length, teeth width, teeth length, stomatal density, stomata width, stomata length, lamina width/lamina length, lamina width/leaf length, petiole length/lamina length, stomatal index, distance between the lateral veins and teeth width/teeth length were measured. Most of the chestnut genotypes could be differentiated easily by using leaf morphometric characteristics. The lamina width, lamina length, leaf length, distance between the lateral veins, leaf area, stomata width, stomata length and the ratios of teeth width/teeth length, lamina width/lamina length and lamina width/leaf length were better discriminators for chestnut genotypes.

The present research was carried out under hydroponic culture to evaluate the interaction between salicylic acid (SA), nickel (Ni) on vegetative and reproductive growth of strawberry plants as a factorial experiment in a completely randomized design. Well-rooted daughter plants of Pajaro cultivar, were potted in 3 L plastic pots and were sprayed with SA at concentrations of 0, 1, 2 and 3 mM and NiSO4 at 0, 150 and 300 mg.L-1, after establishment. Results indicated that SA at 2 mM increased root and shoot fresh weight, number of inflorescences and fruits, fruit nitrogen concentration and yield. The effect of Ni was promoting too, as 150 mg.L-1 of Ni led to significant increments of fruit number, inflorescences, leaf area per plant and yield.However, the best results were found when SA was applied accompanied by Ni.

Comparative assessment of genetic diversity of 122 durum wheat genotypes (Triticum turgidum L. var. durum) was performed using 73 SSAP polymorphic fragments, 123 AFLP polymorphic loci and 104 SSR alleles. SSAP and AFLP data showed a clear demarcation between the cultivars and landraces and SSR data classified cultivars and landraces according to their origin. Furthermore, the estimated genetic diversity of Iranian landraces was higher compared to the foreign entries and a loss of genetic diversity was observed from landraces to cultivars. This study determined that differences in genetic relationships revealed by SSAP, AFLP and SSR distances could not be attributed solely to differences in the level of polymorphism detected by each marker system. The molecular evidence of genetic diversity decrease of the durum wheat gene pool further strengthens the strategic relevance of undertaking appropriate genetic conservation measures for food security.

The use of healthy planting material is an important prerequisite for controlling destructive viral diseases in potato production. Virus elimination methods such as meristem culture and thermotherapy are usually used to produce the nucleus stock of healthy planting material. Here, we report a new technique of electrotherapy for elimination of two potyviruses, Potato virus A (PVA), and Potato virus Y (PVY), from potato plants. Electric currents of 15, 25 and 35 mili Ampers for 10 to 20 minutes were used for eliminating the combination of PVA and PVY in six potato cultivars. An electric current of 35 mili Ampers for 20 minutes was the most effective electrotherapy treatment for eliminating these two viruses. Responses of potato genotypes to electrotherapy were significantly different. Regenerations of electrotherapy treated plantlets in cultivars Lady Roseta and Banaba were 70.8 and 66.6 percent respectively, while these were approximately 54 to 58 percent for cultivars Olimpia, Agria, Desirea and Clone 69. Virus free plantlets were successfully produced in the potato cultivar Lady Roseta. However, in other cultivars examined in this study, electrotherapy resulted in drastic reduction of virus concentration but not total eradication of the virus infection from plant tissues.

In order to assess drought tolerance of mycorrhizal petunia plants (Petunia hybrida cv. Mix), a greenhouse experiment was carried out with two different mycorrhizae species (Glomus mosseae and Glomus intraradices) applied singly or in combination at two phosphorous (P) levels (0 and 100 mg kg-1 dry soil) and three irrigation regimes (100% field capacity (FC) as control, 75% FC producing moderate water stress and 50% FC producing severe water stress). Both mycorrhizal endophytes established well on roots of the petunia plants with higher colonization values at lower P concentration and lower colonization rate at increasing water stress. Mycorrhizal colonization generally enhanced plant vegetative and reproductive growth, both under full and reduced field capacities and with and without P fertilization. The content of soluble sugar in AMF-inoculated leaves was higher than that in non-AMF-inoculated plant leaves in response to drought treatments but proline level did not show any significant increase in mycorrhizal treatments at the same conditions. This study confirms that mycorrhizal colonization can mitigate the adverse effects of water stress on treated plants restoring most of the key growth parameters to levels similar or close to those in unstressed plants.

The response of five inbred sunflower seedling lines, including AC 4122, C, HA 89, HA 410, HA 411, to inoculation with Sclerotinia sclerotiorum culture filtrate containing endogenous oxalic acid was compared with the exogenous application of synthetic oxalic acid. The reaction of seedlings was evaluated in terms of dry and fresh plant weights and the total chlorophyll concentration relative to untreated controls. The expression of shikimate dehydrogenase in cotyledons was also assessed five days after treatment. The results indicated that exogenous oxalic acid inoculation caused more deleterious effects on stem rot, eliciting photosynthesis reduction and different isoenzyme patterns of shikimate dehydrogenase. A positive correlation was found between increased oxalic acid and shikimate dehydrogenase activity in both treatments. However, the excessive toxicity of the exogenously administrated acid suggests that Sclerotinia sclerotiorum infection triggers a more complex metabolic pathway involving oxalic acid secreted by the pathogen. These observations preclude the possibility of using the synthetic acid administration as a method of screening sunflower genotypes for resistance to Sclerotinia. In addition to these findings, the reactivation of shikimate dehydrogenase was observed in both treatments. In contrast to synthetic administration, expression during the first phase of growth may serve as a tool for rapid screening and selection of sunflower genotypes resistant to Sclerotinia sclerotiorum.

Carbon and sulfur isotopic data are helpful in understanding environmental conditions under which soils are formed. Soils from 18 sampling sites along a climotoposequence from higher Laleh Zar Mountains (4, 351 m above sea level with xeric-mesic soil moisturetemperature regimes) to Shahdad depression (250 m above sea level with aridhyperthermic soil moisture-temperature regimes) in Kerman Province, central Iran, were studied. d 13C values of the soil organic carbon varied between -20.6 ‰ and -26.9 ‰ PDB. d 13C values of pedogenic carbonates varied between -2.2 ‰ and+2.2 ‰ PDB and a decreasing trend was observed downward in the climotoposequence. A positive correlation (r=0.6) was found between d 13C and d 18O values in the lower arid landscape, but a different relationship (r=0.37) in the upper Mediterranean climatic positions was observed. It seems that the presence of more C3 plants under stress and more decomposition of organic matter in lower positions of the landscape has taken place. d 13C values of soil organic carbon and pedogenic carbonates and their trend along the gradient showed that higher proportion of C3 plants at lower elevations and presence of more C4 plants in the past history of upper landscape positions may have been experienced. Mean d 34S value of 11.3‰ showed that lower Cretaceous sea sulfate may have been the source of sulfur in the area. Mean d D and d 18O values of -51.2‰ and+6.0‰ in gypsum crystallization water showed that direct deposition from a solution saturated with gypsum is the only probable mechanism of gypsum formation in the area.

Biotic as well as abiotic factors may influence the biocontrol activity and population density of Pseudomonas fluorescens. However, limited studies have been carried out on the effects of extracellular metabolites of other competitor bacteria, especially on the biocontrol efficiency of P. fluorescens. A greenhouse experiment was conducted to evaluate the potential of the two P. fluorescens isolates UTPF68 & UTPF109 in the biocontrol of bean damping-off caused by Rhizoctonia solani (AG-4), when applied individually or in combination with the culture filtrates of five rhizobia isolates (RH3 to RH7). Although all treatments reduced bean damping-off severity in comparison with the untreated control, RH4+UTPF109 gave the lowest severity of damping-off (0.56,<1%). Beside the effect on disease control, seeds treatment with both P. fluorescens isolates individually or in combined treatments especially RH4+UTPF109 and RH6+UTPF68 significantly improved bean growth factors such as shoot and root fresh/dry weights. On the other hand, all tested rhizobia and P. fluorescens isolates especially, RH4, proved to be siderophore, HCN, IAA, and exopolysaccharide producers. Also, all tested bacteria except RH5 and RH7 produced chitinase. Furthermore, our in vitro studies demonstrated that the filtrates of tested rhizobia isolates can effectively increase the population density of both P. fluorescens isolates as a biotic factor. Thus, certain rhizobia seem to have a capacity to interact synergistically with P. fluorescens isolates having potential biocontrol activity.