IRANIAN JOURNAL OF AGRICULTURAL SCIENCES (JOURNAL OF AGRICULTURE)
Year:2006 | Volume:37 | Issue:5|Papers Count:24

To study the flowering time and period, as well as the self- and cross-compatibility, some Asian pear cultivars, namely KS6, KS8, KS9, KS11, KS13 and KS14, were employed. Two branches on each of four trees in each cultivar were selected for controlled pollination. To prevent either undesired pollen contamination or pollination by insects, selected shoots were protected using cotton tissue bags. For controlled cross- pollination, flowers were emasculated and protected before anthesis, hand pollination being carried out two days after anthesis. In order to monitor pollen tube growth in the style, samples were taken 44, 72 and 96'hours after pollination, and fixed in FAA solution. The percentages of initial and final fruit set after self and cross-pollination were recorded and monitored 15, 35 and 75 days after full bloom (OAFS). A study of flowering time showed that there were some differences in the flowering period and time of bloom in the studied cultivars, the best coincidence being observed between KS11 and KS13. Microscopic examination of pollen tube growth showed that pollen grains were alive after pollination and the pollen tube grew within the style following germination. Results from self pollinated trees (75 OAFS) indicated that KSg had the lowest fruit set, with 2.92%, while the other cultivars KS13, KS6, KS8, KS14, and KS11 showed 4.16, 5.44, 7.03, 10.33, and 14.65% fruit set respectively. In addition, results from cross- pollination revealed that the highest fruit set (34.34%) was obtained from cross-pollination of KS11 (seed parent = ♀) with KS8 (pollen parent = ♂) while KS13 (♀) pollinated with KS8(♂) ended up with the lowest fruit set (4.15%).

Packaging is one of the main steps in food processing which extends the shelf life of fruit through controlling factors that affect fruit quality. Optimization of effective factors in packaging of Golden Delicious apple is an important issue in it's storage as well as in its exporting conditions. In this study the effect of temperature (1, 6 and 10oC) on respiration rate of Golden delicious apple was studied through measuring CO2 content, using gas chromatography. also, the effect of packaging materials (wooden, cellophane and polyethylene films) in different storage temperatures (1, 6 and 10oC) was studied during a period of five months of storage. Qualitative factors including dry matter, firmness, pH, titrable acidity and total soluble solids (TSS) were measured every 3 week interval. Results indicated that the climactric peak occured at 1,6 and 10oC in 100 th, 45 th and 20 th day respectively. Fruits stored at ]. and 6oC, and packaged in cellphane benefited from a better quality, followed by wooden and polyethylen. At 10°C and of higher temperatures and also for freshly consumed apples, polymeric packaging (cellophane and polyethylen films) resulted better than the wooden type. Different packaging materials had no significant effect on either pH or titrable acidity.

Erosion has been divided into interrill, rill, and gully components. Interrill erosion consists of soil particle detachment by raindrop impact and particle transport by splash and shallow overland flow. Interrill erosion and runoff rates were measured from one square-meter drainable flume filled with disturbed soil under simulated rainfall at different slopes ranging from 1.5 to 20%. Three contrasting soil types were used in the study. Rainfall was applied using a rainfall simulator with a single sweeping nozzle located 4 meters above the soil surface that sprayed drops with mean diameter of 1.5 mm. Results indicated that the effect of slope on interrill erosion depends on the soil type and rainfall rate. In other words, there is an interaction between slope, soil type and rainfall rate. Measured interrill erosion rates were compared to soil loss predicted by the proposed equations in WEPP model. Results revealed that the model tends to over-predict the values on the lower end, while under-predicting the values on the upper end of the scale.

Cadmium is one of the most important heavy metals that enters soil from various sources particularly from phosphorous fertilizers and causes soil pollution. This metal adversely affects nodulation and symbiotic nitrogen fixation, due to its deleterious effects on rhizobia and on their host plants. This research was undertaken to investigate the tolerance degree of lranian strains of Sinorhizobium meliloti (S.m.) to different levels of Cadmium (Cd). In order to prepare native strains of S.m. root nodules were obtained from provinces important for alfalfa cropping. Following isolation of the root nodules bacteria, pure culture of each isolate was prepared. Plant infection test with each isolate was performed, and after omission of the isolates with no symbiotic potential, 57 effective strains were selected. Tolerance potential of strains to different levels of Cd were assessed by using H.M. media of different amounts of Cd (0, 5, 10...70 mgl-1). The results showed that on the basis of Cd tolerance, there is a significant difference (p<0.05) among various strains of S.m. to the extent that they were classified into sensitive, partially sensitive and resistant groups. Ahigh percentage of studied strains (approximately 70%) were sensitive to Cd that had visible growth in Cd concentration range only of 5-10 (mg-1) Only 3.8% could tolerate high concentration levels of Cd (60-70 mgl-1). Therefore, these were introduced as resistant strains.

In order to introduce best chemical treatment and preservation method for cut chrysanthemuma factorial experiment of completely randomized design was carried out. The chemical treatments were: citric acid, hydroxyquinoline citrate, ethanol, benzyl adenine, cobalt chloride and aluminum sulfate all of which included sucrose while distilled water was used as control. The experiment was carried out using cold storage long with, pulse and continuous methods of application. The vase life of cut flowers, chlorophyll content, fresh weight, ethylene production and water uptake were evaluated for treatments. Results indicated that no ethylene was produced by flowers. Longevity was promoted in cold storage. Continuous method of application was a better method than pulse method. All chemical treatments increased longevity of cut flowers among them hydroxyquinoline citrate was shown to be the best treatment.

To develop a disease forecasting system for effectively controlling wheat fusarium head blight caused by Fusarium graminearum, some epidemiological studies were conducted for two consecutive growing seasons in 2001-02 and 2002-03.On the basis of field experiments, the disease progress was determined on three wheat cultivars, namely Falat, Tajan, Zagros and one resistant line at Araghi-Mahalle Research Station in Gorgan. Disease index (DI) and various epidemiological models were employed to evaluate disease progress. The appropriateness for each model was evaluated by calculating Coefficient of determination (R2), and parameters of residual errors, including ME, CD, RMSE, EF and CRM. The Log-Logistic model, considered being the most appropriate model to describe disease progress on Falat, Tajan and Zagros under moist conditions. The resistant line did not show appreciable disease. However, under non moist conditions but artificial inoculation, Logistic was the most suitable model on Falat and Zagros with R2 of 0.86 and 0.91, respectively, while on Tajan, Log-Logistic (R2=0.79) was the most applicable model. Logistic and Log-Logistic were prefered as the most appropriate models to describe disease progress for FHB. This is the first report in which the above statistical parameters are collectively employed in describing temporal progress of a disease, as well as their importance in identifying the most appropriately fitted model.

Strawberries (Fragaria x ananssa Dutch.) cv. 'Aliso', Selva', 'Gaviota' and 'Camarosa') were grown hydroponically with five ratios of NH4/N03 (0/6 (S1), 0.25/6(S2), 0.5/6(S3), 1/6(S4), 2/6(S5)) and constant total N in three replicates for two seasons (summer: July- November, and winter: December-June) to determine the relationship between the rate of NH4/N03 and nitrate accumulation in different plant organs. Leaf and petiole nitrate contents were measured three times each season (summer: August, September and November and winter: April, May and June). Leaf nitrate percent increased gradually. Petiole and root nitrate contents were dramatically higher than content in leaf and crown. In leaf and petiole, nitrate content increased as NH4-N increased in nutrient solution. Nitrate percent in crown and root were highest with NH4-N increasing from 0.25 to 0.5 mM were constant in the remainder solutions. Aliso had the highest crown and root nitrate. Gaviota had the highest leaf nitrate while Camarosa the highest petiole nitrate content. S2, S4 and SS nutrient solutions resulted in highest nitrate content in petiole. Crown, root and fruit nitrate contents were highest in 0.25 mM NH4- N; increasing ammonium in solutions caused a decreasing nitrate in these organs. Nitrate content in fruit, leaf, crown and root, were highest in Gaviota. Nitrate in leaf, root, petiole, and crown, were significantly higher in summer than in winter. Based on these results, solution S5 and cv. Aliso ore suggested for commercial use both because of bearing low nitrate containing fruit.

This study was carried out to determine the reproductive performance of Tehran Province Holstein dairy cows and some factors affectingit, while using 30678recordsfrom6913cows. At estimation of means and standard deviation of calving interval, days open, calving to first service interval, and first service to conception interval were 397.50±60.50, 122.10±62.45, 93.20±41.00 and 24.60±12.00 days, respectively. Effects of herd, calving season, lactation number and milk yield on reproductive performance were significant (P<0.001). Effect of sex of calf on calving to first service interval was significant (P<0.01).The results suggest that, the most and the least days open pertained to spring and autumn calving respectively. Days open increased from the fifth lactation number. The reproductive performance decreased with increasing milk yield.

An experiment was conducted for two consecutive years (2000-2001) to study the effect of manganese (Mn) fertilizer on soybean yield and to determine critical level of the soil Mn. Twenty soybean farms were selected from a soybean growing area in the eastern part of Mazandaran province. The soils had a wide range of CaCo3 (5-39 %) and DTPA extractable Mn of 1.56 to 9.10 mg/kg. The experiment on each farm was a randomized complete block, one with three replications and two treatments, 20 soils and two levels of manganese sulfate (0 and 40 kg manganese sulfate per hectare). Each experimental plot was 49 m2 , planted with Pershing variety of soybean. The aerial parts of plants were harvested at the end of growth period. The results indicated that manganese sulfate application significantly increased the seed yield, Mn concentration and Mn uptake by 24, 10.3 and 37 percent, respectively, and also increased thousand kernel weight, number of seed per plant and seed protein content by 6.5, 10 and 5.1 percent, respectively. Based on farm experiments for obtaining 85% relative yield, manganese critical levels in these soils were calculated to be 3.54 and 4.40 mg/kg, while with 90% relative yield they were found to be 5.10 and 6.20 mg/kg, using Mitcherlich-Bray and Cate-Nelson methods, respectively.

During the years2001to 2004, samples of mulberry leaves were collected from different mulberry orchads in Guilan province to identify the causalagent(s) of mulberry leaf blight. Symptoms of diseased plants consisted of formation of irregular necrotic lesions on leaves surrounded by yellow chlorotic halo. Under favorable conditions, these lesions gradually expanded and leaves became blighted. In attempts to investigate the causalagent, two types of gram-negative bacteria with raised fluorescent colonies on King's B medium were isolated. Based on morphological, physiological, biochemical, pathogenicity properties, and total cellular protein profiles (SDS-PAGE), while employing PCR method with specific primers, the predominant pathogenic type was identified as Rseudomonas syringae pv.mori. However, the other type on some mulberry orchads was identified as P.s.pv. syringae.

Fecundity, development period, percent emergence, longevity, sex ratio and hind tibia length of Trichogramma brassicae Bezd. (Hym.: Trichogrammatidae) were evaluated in five consecutive rearing generations on the eggs of Sitotroga cerealella Oliv. (Lep.: Gelechiidae) & Plodia interpunctella Hub. (Lep.: Pyralidae) in 24±1oC, 60±5% RH and 14:10(L:D).The means figures for the mentioned characters (for wasps reared on the eggs of S. cerealella and P. interpunctella)were obtainedas fallows:fecundity:34.55 and 21.65 eggs per female, development period: 11.60 and 11.41 days, percent of emergence: 93.52 and 77.01; longevity: 3.04 and 2.44 days, the sex ratio: 64.55 and 60.01 and the hind tibia lenght: 158.08 and 146.45 microns. The means of fecoundity, longevity, sex ratio and hind tibia lenght of wasps reared on either host indicated significant differences, increasing until 3rd generationthen decreasing in the next generations, while the means for development period and percent of emergence exhibited no significant difference in any five rearing generations. Also strong positive correlations among the hind tibia length, fecundity, and longevity of the wasps reared on either host were observed. According to the obtained results non continual rearing of this wasp on one host is suggested in its mass production.

Iran is in possession of the richest gene pool of pomegranate, with an amazing diversity and number of genotypes, in the world. In this study RAPD markers were mployed to determine the level of diversity, and phylogenetic relationships among 24 Iranian pomegranate genotypes. Genomic DNA extracted from leaves, and its quantity as well as quality were determined by use of spectrophotometry and agarose gel electrophoresis to be used for PCR after being adjusted for the concentrations. In total 113 primers were used for PCR reactions on the template DNAs among which 27 showed reasonable amplification and polymorphism. Bands with a acceptable resolution and high repeatability were selected for calculations. These 27 primers produced 257 bands, among them, 158 were polymorphic. Cluster analysis of the genotypes was performed based on the presence (1) or absence (0) of the bands, using Jaccard's similarity coefficient and UPGMA method. The highest and lowest observed genetic similarity between genotypes was 0.88 and 0.30 respectively. At a distance of 0.64 similarities on the dendrogram, the genotypes were divided into 8 sub.clusters. A Cophenetic coefficient of r=0.92 between similarity matrices and the dendrogram is an indication of the dendrogram properly fitting the similarity data. The examined genotypes were to relatively high diversity, implying the richness of pomegranate genetic resources in Iran. Furthermore, this study reflected the possibility of similar names \ having been given to different genotypesor the mistakes and mixes in either collection establishments or during translocation of genotypes. Besides, RAPD markers were shown to be a useful technique for studying the genetic diversity in pomegranate.

System analysis helped to divide an economical system of dairy herd into two components of: revenues and costs, each of which could be sub-divided into other elements. In the next stage, use of models as well as computer programming led to simulation of a bio-economical situation. Based on such a simulation, revenues and costs of production system were related in a way that change in any factor led to change in other factors and finally to dynamic economical productivity index and vice versa. The sensitivity of system performance toward change in each factor was studied, taking into account different quantities of any of the parameters in the model. Among costs, any change in feed costs with priority given to the price of concentrate, was more important that any other factor in the productivityindex.83.81% increasein feed costs, 225.10% in roughage price and 133.84% in the price of concentrate, tend to decrease productivity index by 36.64% getting it close to 1. A 32.84% increase in milk production, 42.93% increase in basic price of milk, or 39.56% simultaneous increase in basic revenue of milk as well as extra payments due to any percentage of extra fat and protein, increases the productivity index by 36.64%, compensating the negative effect of above mentioned prices. Furthermore, the effect of change in replacement cost, sundry costs, total cost, milk revenue, calf revenue, manure revenue, total revenue, on productivity index was studied.

Adequate feeding of silkworm is a very important factor in cocoon production. In addition to feed quantity, the manner of feeding which can preserve the quality of mulberry leaves is also important in silkworm rearing. In order to study the role of feeding frequency on productive and nutritional behavior of commercial silkworm, four treatments namely one, two, three and four times of feeding per day were studied. The results revealed that increasing the frequency of feeding causes enhancement of cocoon shell weight, cocoon weight, shell percentage, amounts of ingestion and digestion, ingestibility and digestibility. But, the efficiency of conversion of ingested and digested food into cocoon shell weight, cocoon weight and shell percentage increased at lower feeding frequencies. The percentage of pupation and larval duration did not indicate any significant difference among treatments. Therefore it was concluded that an decrease in feeding frequency in mass production from 3 to 2 and from 3 to 1, in addition to more ease in work, it is commercially justified too.

The effects of cold and heat pretreatments on floral buds as well as on cultured anthers were examined in 4 tomato lines and their 6 hybrids in three different culture media. Temperature pretreatments included cold WC for 48h and 10oC for 10 days), heat (35oC for 4 d) and a combination of cold and heat pretreatments WC for 48h followed by 35oC for 4d and 35oC for 4 d, followed by 4oC for 48h). The control and pretreated cultures were Kept at 26oC throughout the experiments. Experimental design was based on a factorial arrangement of completely randomized design. Callus induction (Cl), callus diameter (CD) and shoot induction (SI) were recorded. Cl was not influenced by pretreatments on floral buds except for 4oC. However all pretreatments of anthers showed Cl except for 35oC followed by 4oC. Statistical analyses in the affected pretreatments were carried out. The results indicated that pretreatment, genotype, culture media as well as interaction among them had significant (p<0.01) effects on Cl, CD and SI. In anthers pretreated at 4oC followed by 35oC and control, SI was not observed. However, SI was seen in all the other pretreatments. The effects of pretreatment were different among genotypes and culture media. The hybrids Micro- Tina x Moneymaker and Micro- Tina x MSK8 exhibited the highest SI (22- 35.5 %) in all 3 culture media when their floral buds and cultured anthers pretreated at 4oC. However, SI for these hybrids was 14.5% and 18.9% at 10oC, 14.5% and 16.7% at 35oC respectively. Among the parents, SI for MSK8 at 4oC and Micro- Gemma at 35oC of a were more considerable SI (18.9% and 17.8% respectively). It can be deduced that application of cold and heat pretreatment of tomato anther culture will be helpful in production of haploid/doubled haploid population.

For determination of damages to potato crop through harvesting machinery in Ardebil area, three types of harvesters (Sabz Dashte Isfahan, American Design, and Russian Design) were tested and results analyzed through Nested Design with random samples in five replications. Data were analyzed with respect to standard factors in three damage levels of 1, 3 and 7 respectively for scuffed, peel, severe damage, and also total quality damage mean which was defined as the mean of those quality damages. Analysis of Variance indicated that, quality damage, at the three levels, was significant in the case of all three harvesters. According to mean comparison (Duncan Test), the highest quality damage come from Russian Design with total quality damage mean of 21.6 (p< 0.05), which was significantly different from other machines, damages (scuffed, peel and severe). But Sabz Dashte Isfahan with 10.26 and American Design with 12.73 total quality damage mean were not significantly different as regards scuffed and peel quality damages. At the end it was concluded that with respect to the available standards of PMB (Potato Marketing Board) and SIAE (Scottish Institute of Agricultural Engineering) the damage index of the three mentioned types of harvesting machines is in match with the standard range, and therefore their performances are acceptable.

Effects of rhizosphere of rice plant on the native inorganic phosphorus fractions in the paddy soils of north of Iran were investigated in a greenhouse experiment. The study was performed as a 14x2 factorial experiment in a randomized complete block design with 2 factors of soil (10 calcareous and 4 noncalcareous), and cultivation (cultivated and uncultivated), each level with 2 replicates. Bags of soil samples, buried in experimental pots (cultivated and uncultivated), were taken out simultaneously after a 3 month period, and their inorganic P fractions measured by the sequential extraction methods of Jiang and Gu (1989) in calcareous soils, and Kuo (1996) in noncalcareous soils. The available P in all soils was measured by Olsen method. In a different experiment, a special pot of 1 m2x 30 cm depth was designed to measure the variation in available P with distance from the plant stem. In this pot, the plant spacing was 25 cm, and bags of soil samples were buried in the soil at different distances from the plant stem. The results of these experiments are as follows: 1- In all 14 soils, the Olsen-P in the rhizosphere of rice was significantly lower than that in the uncultivated soils. 2- In calcareous soils, the dicalcium phosphates, the octacalcium phosphates, the AI-phosphates, the P in apatites, and the occluded-P in the rhizosphere of rice were significantly lower than those in the uncultivated soils; whereas the Fe-phosphates was not significantly different in the two conditions. 3- In noncalcareous soils, the readily soluble-P, the Fe-phosphates, and the AI-phosphates in the rhizosphere of rice were significantly lower than those in the uncultivated soils; whereas the occluded-P and the apatites were not significantly different in the two conditions 4- The Olsen-P of the soil between the two hills of rice plant in the special pot experiment, did not vary with the distance from the plant stem, whereas, the Olsen-P in the cultivated soil was significantly lower than that in the uncultivated soil. 5- In all soils, the pH of the water on the surface of the soils in the cultivated pots was significantly lower than that in the uncultivated pots at the end of the growth period.

Fungus, Verticillium lecanii as one of insect pathogens has a broad range of hosts. In this research, pathogenicity of hyphomycete, V. lecanii (DAOM 198499 isolate), was investigated with six different concentrations against third nymphal stage of the aphid, Myzuspersicae under laboratory conditions (23±1oC, 95±5% RH and 16L: 8D).Three days after inoculation, aphid mortality was initiated. Minimum and maximum mortality, achieved with fungul suspension of 104 and 108 conidia per ml were 51.1 and 100 percent (after 10 days) respectively. Analysis of lethal effect of various concentrations of V. lecanii against M. persicae, indicated that there were significant difference in aphid mortality. LC50 and LT50 values were estimated by probit analysis and life test on aphid mortality during 12 days after treatment. LC50 value was 1.4 x 104 conidia/ml-1. LT50 values for concentrations of 104, 105, 106, 107 and 108 conidia/ml-1 were 10, 10, 9, 8 and 6 days, respectively. The results showed that net reproduction rate of aphids (RO) decreased significantly when the concentration increased. Based on these results as well as results of other researchs,it is implied that V. lecanii (DAOM 198499 isolate) has the potential to be used as a biocontrol agent against aphids in greenhouse conditions.

Having in mind, achievement of self sufficiency in sugar, the land under cultivation of sugarcane, and as a result the use of chemical nitrogen fertilizer in Khuzestanprovince has been increased causing a pollution problem. Gluconacetobacter diazotrophicus is an associative endophyte nitrogen fixing bacteria in sugar cane which is entirely confined to the living plant tissue and does not survive in soil and therefore can only be isolated by tissue extraction. Five native isolates along with 3 imported species were employed in this study. This bacteria produces orange to red colonies on solid standard LGIP medium. The colonies turn brown in an old culture. White colonies are produced in solid PDA medium. They can turn dark brown after 10 days. The bacterium produces brown colonies along with water soluble brown pigment in GYC medium. It grows in high glucose (30%) concentrations producing acetic acid. This bacteria can be identified by negative oxidase and nitrate reductase and by positive catalase tests. It produces acid by oxidizing ethanol, however it does not complete the second stage of oxidation. The capability of the bacteria for biological nitrogen fixation(207-253 nmoles C2H4 h-1ml-1) was evaluated through ARA method.