JOURNAL OF AGRICULTURAL SCIENCE AND SUSTAINABLE PRODUCTION
Year:2001 | Volume:11 | Issue:2|Papers Count:11

During recent years, Strawberry production has been developed in different areas of Iran. The total production of strawberry in Iran was 17095 tons in 1996. Strawberry was produced more than 16000 tons in Kordestan province and 18tons in Khorasan province, in the same year. A lot of strawberries are destroyed due to sensibility and perishable characteristics, also insufficient and incorrect preservation methods. The amount of losses will be decreased if strawberry is converted to different products as jam, juice, concentrate or powder. In this research, the effect of pH, SO2 and SnCl2. 2H2O on colour stability of strawberry during juice concentration processing was studied. A factorial complete randomized design was used in order to determine the effect of pH, SO2 and SnO2. 2H2O. The factors under consideration were four levels of pH (3.5, 3.25,3 and 2.75), three, levels of SO2 (0, 20 and 40 mg/400ml) and two levels of SnCl2. 2H2O (0 and 0.2 percent). Results showed that the Sample with pH=3 which contained 40 mg/400ml of SO2 and 0.2 percents of SnO2. 2H2O had the most amount of under graded anthocyanin. The sample with pH=3.25 which contained 40 mg/400ml of SO2 and 0.2 percent of SnCl2.2H2O protected the most amount of ascorbic acid within itself. The sample with pH=2.75 which contained 40 mg/400ml of SO2 and 0.2 percent SnCl2. 2H2O had the most acidity.

During 1996, in a potato field at Bojnoord region, some potato plants showing stunting, pale and mild mosaic symptoms were marked. At harvest, a few tubers of each plant were randomly chosen and stored at a dark refrigerator at 4°C until the end of dormancy period Host range, direct double -antibody sandwich enzyme - linked immunosorbent assay (DAS- ELISA), dot immunobinding assay and electron microscopy tests showed that plants which grown from such tubers were infected with Potato Virus X (PVX). Inoculation of indicator plants caused systemic symptoms on Datura stramonium, Lycopersicon esculentum, Nicotiana glutinosa, N.debneyi, N.tabacum cv. Xanthi, N.tabacum cv.Samsun, N.tabacum cv. Turkish and Capsicum frutescent, and local lesion symptoms on Chenopodium amaranticolor, c.quinoa and Gomphrena globosa and did not induce any symptoms on Cucumis satius. The virus was propagated on N.glutinosa for purification and then antiserum was prepared against the purified virus. To determine the distribution of the virus in North of Khorasan, from 26 fields of Bojnoord, Chenaran, Shirvan, Toos, Farooj and Ghochan regions, 247 plants were randomly sampled and DAS -ELISA test was used for detection of PVX. The results showed that the percent of PVX infection in the above regions were 50, 63.6, 34.7, 53.3, 62.8 and 37.2 respectively.

The walnut aphid is regarded as a main pest of walnut trees throughout the world including Iran. The population fluctuations and identification of it's natural enemies was studied in Khalatpoushan Agricultural Research Station and a region of Oskou during year 1997 and 1998. Population samplings in two regions were made at weekly intervals when 50 leaflets were randomly taken from 10 selected trees at 4 directions and from internal parts of the tree canopies. The exact number of lavae, adults and existing natural enemies were determined later on the laboratory. Counts of the actively moving predators were made in situ using a hand lens before removing the leaflets. Samplings for recognition of predators and parasitoids were also done at 3-day intervals, twice during the day in the morning and afternoon using forceps, aspirator and brushes and/or by means of beating method. It was revealed that the aphid populations reached higher densties in Khalatpoushan on 2nd of July in 1997 and 25th. of June in 1998, being 49±4.7 and 8.4±1 aphids per leaflet, respectively. Also, high density aphid populations in Oskou reached on 19th. of June in 1997 and 28th. of May in 1998, with a mean density of 21±3.1 and 25.52±3.06 aphids per leaflet, respectively. However, the results showed significant differences between population densities in Khalatpoushan in contrary to Oskou region for the two successive years. The natural enemies population were also at higher densities in 1997 and the difference appeared to be significant (P <0.01). Natural enemies at both regions during the two years, were identified to be 4 Coleopteran, 1 Neuropteran, 2 Hemipteran and 1 Dipteran species and some species of spiders in 2 families. Also, in Hymenoptera 1 parasitoid and 2 hyperparasitoids were determined.

In this study, the effect of planting date of sunflower, Helianthus annus, on population density of broomrape, Orobanche cemua, an important flowering plant parasite was investigated in Urmia region using a RCB design with 4 treatments (4th and 19th April, and 5th and 20th of May) and 5 replications. Sunflower yield in each plot was measured and recorded and the data were submitted to statistical analysis. The different growth stages of broomrape were also studied. The results revealed that there were significant differences in infestation between all treatments. According to the results, planting sunflowers on May 20th as well as April 4th resulted in a lower infestation rate. Consequently, the number of broomrape plants and total dry matter was reduced by 72 and 72.8 percent, respectively. On the other hand, the differences in sunflower seed yield found to be insignificant between different treatments. It is concluded that, with regard to the significant reduction in population density of broomrape obtained in this study, mid-Maycan be considered a suitable time for planting sunflower in Urmia region.

In order to determine of the best type and concentration of auxin and cytokinin to get the highest efficiency in carnation plantlet production from shoot tip explants, an experiment carried out in the form of factorial experiment by using a completely randomized design and a modified MS medium.Different auxins and cytokinins were used in various concentrations. The percent of regeneration, the number of regenerates per explants, the percent of callus and root production, the number of grown leaves and the percent of vitrified explants were measured and analyzed. In the most of the media plants were developed into regeneration. With media supplemented by Kinetin, Zeatin and IBA, no regeneration was observed. The best regeneration percent and the number of regenerates per explants were obtained in the modified MS medium supplemented by 0.3 mg/L NAA and 1 mg/L BAP.

The various methods of estimating evapotranspiration have been developed for different areas with various climates. With regard to special environmental characteristics one or several factors have been considered in each method. Therefore, calibration and correction of these methods for the region of under investigation could be helpful in carrying out irrigation design in order to determine consumptive use of water for plants and water balance as well as other agricultural studies. Since evaporation pan method is a simple and suitable method in estimating evapotranspiration, other methods were compared and modified based on the comparison with pan method for Tabriz region for a 20 - year data in this study. The results showed that the Christiansen-Hargreaves (RA) method showed better correlation with evaporation pan method than the others. Regression and correlation coefficients for each method both in linear and power forms are provided.

Among the secondary tillage implements, tandem disk is used more than others. In this study the effect of two parameters including: Soil moisture content at three levels (10-12%,13-15%and 16-18%) and travel speed at three levels of 5, 6.5 and 8 Km/h on draft, drawbar power, degree of soil pulverization, cone index and wheel slip in a clayloam soil were investigated. A randomized complete block design in factorial experiment with 9 treatments and 4 replications was used, and statistical analysis was conducted for obtaining the results. Effects of speed and soil moisture content on draft and drawbar power were significant at 1 and 5% probability levels, respectively, but no significant effect on slippage was noticed. Different levels of soil moisture content had significant effect on soil cone index, but for various speeds, no significant effect was found in secondary tillage with tandem disk, different moisture levels had significant effect on size reduction of MWD, but speed variations had no significant effect on MWD. Evaluation of MWD after disk operation showed that, the effect of soil moisture content at 1% probability levels were significant, but not for travel speed. The overall results indicated that, at soil moisture content ranges of 13-18 percent at the time of primary tillage, the total draft and required drawbar power were decreased, and tillage operations ended up to a finer soil surface with smaller clod sizeson seed bed. Results also showed that, when the drawbar power is not a timiting speeds factor, ranging of 6-8 km/h can be recommended or disk operations.

Effect of three slaughter weights (45, 52.5 and 60 kg) and two metabolizable energy levels (2.4 and 2.6 Mcal/kg) were studied on growth performance, average daily gain (ADG), feed conversion (FC) and some noncarcass traits of 53 Lori- Bakhtiari ram lambs. Levels of energy had a significant effect (P<0.05) on the final weights of the lambs but ADG and FC were not affected by the levels of energy. ADG and FC for lambs slaughtered at 45 kg were significantly lower (P<0.05) and higher comported to 52.5 and 60 kg, respectively. Levels of energy had no significant effect on the amount of fat deposited in different parts of the body except around scortum. The amounts of fat deposited around the kidney, scortum, omentum, and total internal fat for lambs slaughtered at 60 kg were significantly higher (P<0.05) than two other slaughter weights. The results indicated that the diet with 2.4 Mcal/kg performed as well as the 2.6 Mcal/kg diet, and 52.5 kg slaughter weight is the optimal slughter weight for Lori-Bakhtiariram lambs.

Changes in seed viability and vigour of two lentil genotypes (Ziba and Local-Abar) during seed development and maturation were evaluated under full irrigation (5 times) and limited irrigation (1 time) conditions at Research Farm of Faculty of Agriculture, Tabriz University, Tabriz, Iran. This experiment was conducted in 1995, using a factorial- split-plot design based on randomized complete blocks based on 4 replicates. Seeds were harvested at five day intervals from 16 to 61 days after flowering and seed moisture content and dry weight were determined. Subsequently, percent viable seeds, percent normal seedlings and seed germination rate of each seed sample were measured. Water limitation did not have significant effect on seed vigor and viability. However, mass maturity (end of seed- filling period, MM) and maximum seed vigor under limited irrigation (LI) occurred earlier than those under full irrigation (FI). Mass maturity for Ziba and Local-Ahar achieved at about 40 and 37 days after flowering (DAF) under FI, and 36 and 34DAF under LI, respectively. Maximum seed vigor for Ziba was achieved about 1-4 days after MM under FI, and up to 2 days after MM under LI. whereas, maximum seed viability and vigor for Local-Ahar was achieved 4-9 days and 2-7 days after MM under FI and LI, respectively. In Local-Ahar, percentage viable seeds, percentage normal seedling and seed germination rate, declined with delaying harvest. However, this trend did not occur in Ziba. In order to achieve a high vigor and optimum moisture content of seeds for harvest, 44 and 38 DAF in Ziba, and 44-48 and 38 DAF in Local-Abar were determined as the best stages for harvesting under FI and LI, respectively.

The Russian Wheat Aphid globally regarded as a serious pest of barley and wheat varieties, has been reported from Iran, (1954) and East Azarbaidjan province since 1971 with widespread distribution particularly in Tabriz, Ahar and Kaleybar wheat fields. Five Iranian wheat cultivars, namely Sardari, Sabalan, Alvand, Zarrin and Alamoot, the most extensively cultivated varieties in the province, were used in laboratory screening test for assessment of their antibiosis resistance to the aphid at the stem elongation growth stage. The resistance at the tillering growth stage of the same cultivars has been previously evaluated under separate experiments.This work was carried out under glasshouse conditions of 23.3±0.99°C Temp., 45-55% R.H. and 14:10 (L:D) light regime. Antibiosis was assessed by studying the developmental time, nymphal survival rate and adult fecundity (total no. of progeny / female produced within the first 10 and 15 days of reproductive stage), and by calculating the relevant intrinsic rate of natural population increase (rm value). The ANDVA of the data indicated that, regarding the two last characteristics, there was significant differences (P<0.05) between the varieties. The highest and the lowest mean number of progeny for 10 and 15 days of reproduction was obtained in rearing on Alvand (28.2±6.57 and 43.05±8.49) and Sardari (21.58±7.73 and 35.11±13.22), respectively. Also the highest mean (rm) value (0.2485±0.01 and 0.2553±0.01) was estimated for rearings on Zarrin with the lowest being 0.2224±0.03 and 0.2305±0.03 in rearings on Sardari variety. The results showed that Zarrin was more susceptible to the aphid than the other varieties with Sardari appearing sthe most resistant one. Alvand, Sabalan and Alamoot were regarded as intermediate among the others. Further experiments with later phonological stage of the cultivars and potential role of other resistance mechanisms are under way.