Iran Agricultural Research
Year:2018 | Volume:37 | Issue:1|Papers Count:11

Different soil potassium (K) pools including soluble, exchangeable and non-exchangeable in surface and subsurface soils may be totally used by canola roots at different growth stages under drought conditions. A field experiment was conducted for one growing season (2013-2014) to study K pools changes during growth stages of two rapeseed cultivars under drought. The experiment was arranged in a randomized complete block design with four factors including different stages of rapeseed growth (before planting, seedling, stem elongation, flowering, grain filling and harvesting), drought (full irrigation, drought from flowering and silique formation), rapeseed cultivars (Sarigol and RGS) and soil depths (0-15 and 15-30 cm). Soil samples were collected and soluble, exchangeable and non-exchangeable K were determined. Results showed that the contents of soluble and non-exchangeable K (NEK) decreased during the growth stages (22 and 198 mg kg-1, respectively) while the contents of exchangeable K increased until stem elongation (57 mg kg-1) and then remained constant. Decrease in the contents of HNO3-extractable K (sum of soluble, exchangeable and non-exchangeable K) in the topsoils was significantly more than that in the subsoils (198 vs. 142 mg kg-1). Drought also had a significant effect on K pools distribution. Drought from flowering decreased the contents of NEK and HNO3-extractable K; however, drought from silique formation had no significant effect on the contents of the different K forms. Type of rapeseed cultivar had no significant effect on K pools distribution. It is concluded that a severe decrease in HNO3-extractable K occurs at the flowering stage (170 mg kg-1) and it must be considered for K fertilizers management. Decrease in NEK during the rapeseed growth supports the hypothesis that this form of K may be released during a growth season and this large pool of K may be considered in K fertility management and fertilizer recommendations. Generally, K uptake by Sarigol cultivar was significantly higher than that by RGS cultivar (177. 7 vs. 129. 4 kg ha-1). Potassium uptake by rapeseed decreased by drought and this decrease was more pronounced by drought from silique formation (more than 40% decrease in K uptake).

The effects of inoculum density and temperature on the disease intensity of Phytophthora parsiana on almond seedlings were investigated. Almond seeds (Rabie and Kaghazi cultivars) were placed in moist vermiculite at 4° C for 45 days. Germinated seeds were sown in a soil: sand mixture (2: 1 v/v) and grown in greenhouse (18° C-25° C). One-month-old seedlings were transferred from the greenhouse to the growth chambers set at 15, 18, 20, 25, 30 and 32° C. The seedlings were subsequently inoculated either with mycelium of P. parsiana grown for 4-6 weeks on vermiculite amended with hemp seed extract or with zoospore (103, 104, 105 and 106 ml-1) by root dip method. The effect of temperature, inoculum density and their interaction on seedling mortality was measured. The results indicated that all three factors had significant effects on seedling mortality. While the highest disease incidence (100% mortality in almond seedlings) occurred at 30° C and 32° C, no mortality was observed at 15° C and18° C. Increasing temperature from 20° C to 30° C and inoculum rate from 103 to 106 zoospores ml-1 increased disease incidence significantly. Higher temperatures and inoculum densities also caused significant increases in the colonization level of the crown, main and lateral roots as well as reductions in the fresh and dry root weights of the seedlings.

Many fruits, vegetables and ornamental crops of tropical origin experience physiological damage when subjected to low temperatures. Protection of plants from the effects of lethally low temperatures is important in agriculture, especially in horticultural production of high value fruits and vegetables. The objective of this study was to develop a simple model to predict the daily minimum air temperature for prediction of frost occurrence in Bajgah and Kooshkak semi-arid areas, Fars province. Initially, the relationship between the minimum temperature of the early morning of a day with some meteorological parameters of the previous day was developed. Meteorological parameters used in this analysis are daily relative humidity, wind speed, pan evaporation, rainfall, sunshine hours, and estimated dew-point temperature. Dewpoint is an important parameter which is related to the minimum temperature in different months with low temperature in Bajgah and Kooshkak areas. Many daily weather parameters used in the regression analysis showed no significant relationship with the daily early morning minimum temperature, except the dew-point and relative humidity. The regression equation between the differences between dew-point and minimum temperature with relative humidity as a simple model was proposed to be used to predict the minimum temperature and subsequently frost occurrence in the study regions. This model was validated by independent data set with an acceptable accuracy for the study regions.

Despite the benefits of herbicides, their persistence in soil can harm other plants in next rotations and contaminate ground water. The main purpose of this research is to simulate 2, 4-dichlorophenoxyaceticacid(2, 4-D) movement in silty clay loam soil using HYDRUS-1D model in a corn root zone. The maximum contaminant level goal, MCLG, of 2, 4-D in water resources is 10 ppb. The 3. 5 kg a. i ha-1 of 2, 4-D was applied to the experimental field under two irrigation treatments including normal and deficit irrigation. The presence of 2, 4-D along with soil water content was measured in soil profile at different depths during the growing season at 8, 13, 23, 30, 37 and 57 days after application. Both measured and simulated data showed that 2, 4-D concentrations reduced from top to bottom of soil profile, maximum 40 cm in both irrigation treatments. The 2, 4-D residues in normal and deficit irrigation were used for calibration and validation of HYDRUS-1D model, respectively. In general, total measured and simulated 2, 4-D concentration in normal irrigation treatment were 68. 94 and 64. 96 mg kg-1and in deficit irrigation treatment were 74. 3 and 74. 0 mg kg-1, respectively. Statistical parameters including NRMSE, CRM and d were used for comparison of measured and simulated data. These parameters were 0. 267, 0. 77 and 0. 846 for normal irrigation and 0. 189,-0. 02 and 0. 937 for deficit regime, respectively. Therefore, the results showed a good agreement between measured values of herbicide residue and the values simulated using HYDRUS 1D model. The numerical simulations for deficit irrigation regime were more precise than normal irrigation because of less microbial activity due to less soil moisture. The numerical models could not simulate microbial activity with acceptable accuracy.

To compare the effects of six types of non-living mulches (wheat straw, sawdust, coco peat, peat moss, transparent and black plastic) with metribuzin on yield and yield components of tomato cv "CH" and the weed control efficiency, a study was conducted in a randomized complete block design with three replications at School of Agriculture, Shiraz University in 2012. Plots without mulch (weedy and weed free) were considered as control. The highest and the lowest tomato dry weight accumulation was observed in the black plastic mulch (728. 98 g m-2) and weedy treatment (126. 22 g m-2), respectively. The highest number of fruits (marketable plus unmarketable fruits) per plant (208. 33) under black plastic mulch treatment was observed at harvest time. Tomato yield in plots covered with transparent plastic and black plastic were 20. 93, 8. 31 kg m-2, respectively and were significantly different from those treated with herbicide (6. 06 kg m-2). Weed control efficacy evaluation showed that black (82. 23%) and transparent (86. 23%) plastic were not significantly different from metribuzin (84. 59%). Application of nonliving mulches produced tomatoes of higher quality and quantity.

For most fruit types, including apples, bruising is the most common type of postharvest mechanical injury. Bruise susceptibility was investigated in 3 commercial cultivars (‘ JazzTM’ , ‘ Granny Smith’ and ‘ Fuji’ ) and among a range of 4 different fruit sizes (commercial counts of 135, 120, 100, and 88) in each cultivar. Bruising was carried out by dropping a uniform round steel ball (110g) from a height of 30 cm through a vertical hollow PVC pipe onto the apples. Fruit physical properties and bruise assessments were evaluated. The results showed that ‘ JazzTM’ and‘ Granny Smith’ apples had the lowest and highest bruise susceptibility, respectively, indicating that ‘ Granny Smith’ apple would be more likely to be bruised during harvest and post-harvest handling. Results also showed that smaller fruits were less susceptible to bruising. There was a positive significant correlation between fruit bruising and fruit volume; but, there were significant negative correlations between fruit bruising and fruit density, fruit firmness and fruit dry mater. These findings will be very useful to reduce the incidence of fruit damage of studied apple cultivars, which is of interest to both growers and operators of postharvest handling and marketing facilities.

Bromus danthoniae Trin. is an annual grass species which grows mainly on dry grassy rocky mountain slopes and grassy steppe, and is grazed by many herbivores and recognized as a useful pasture plant. The chromosome number, morphological and anatomical traits of 82 genotypes of B. danthoniae belonging to three sub-taxa were investigated. Twenty-seven quantitative and 20 qualitative morphological traits were evaluated. The results of analysis of variance showed that B. danthoniae genotypes varied significantly for all quantitatively tested traits. Based on cluster analysis, the genotypes were divided into four groups which mostly corresponded to their subspecies identities. According to correlation analysis, lemma length had strong positive correlations with other traits such as awn length (r=0. 55**), lemma width (r=0. 72**) and caryopsis length (r=0. 84**). In addition, lemma width was significantly correlated with the traits like floret number per spikelet (r=0. 47**) and caryopsis length (r=0. 58**). Based on factor analysis, the first three factors encompass about 51% of total variation. Overall, lemma length and lemma width were the two reliable traits for morphological investigations in this species. The results of chromosome counting showed that B. danthoniae subsp. danthoniae and B. danthoniae var. lanuginusos Roshev. were diploid (2n=2x=14) whereas B. danthoniae subsp. pseudodanthoniae (Drobov) H. Scholz was tetraploid (2n=4x=28). The results of leaf surface anatomy showed that tetraploid genotypes had larger stomata but lower stomatal density than the diploid ones, thus a comprehensive relationship between genome size and guard cell size cannot be ruled out as a plausible explanation for differentiating the ploidy levels. The high morphological variations among the B. danthoniae genotypes explain the habitat distribution of this species and enable us to incorporate this knowledge into practice by exploiting the variation for improvement of pasture production.

Considering health and economic issues, today, consumers have become more concerned with foods which contain natural ingredients. Hence, in this study, the effects of plum concentrate and puree which were incorporated into the Taftoon bread formulation at different levels on the rheological, baking properties and shelf life of bread were evaluated. Results showed that addition of plum concentrate and puree improved the quality and shelf life of Taftoon bread. Plum puree was effective in improving dough development time, mixing tolerance index and dough softening while concentrate affected stability and water absorption. Bread containing 4% plums puree had the lowest hardness compared with other samples. Image processing analyses showed that both concentrate and puree improved browning in Taftoon bread. Therefore, plum concentrate and puree can be used as a humectant to improve the quality and shelf life of Taftoon bread.

In order to produce transgenic rice lines lacking selectable marker gene, biolistic co-transformation technique using gold nanoparticles was adopted. In the first step, the efficiency of different sizes of gold particles was evaluated. The results showed that the efficiency of the nanoparticles in the transformation was comparable to that of the micro particles. Subsequently, two separate plasmids including p UBC harboring cry IA (c) gene and pTRA132 carrying hph gene as selectable marker gene were mixed and coated with gold nanoparticles. Embryo genic calli originated from mature rice seeds were targeted with plasmid-coated nan projectiles. Putative transgenic cells were selected from selection media after three subcultures in MS medium were supplemented with 50 mg hygromycine B l-1 in three weeks' intervals. The selected calli were then grown into putative transgenic plantlets. Molecular analysis performed on the regenerated lines showed that at least one copy of both genes was inserted into the genome of some transgenic lines. RT-PCR analysis also confirmed successful transcription of the cry IA (c) gene. Accordingly, it could be concluded that the biolistic co-transformation method using gold nanoparicles could be a successful method for gene delivery into rice varieties. Nevertheless, expression of cry IA (c) gene and loci of both genes should still be investigated in future studies.

Titanium is a beneficial element for plant since its promotive effect on plant metabolism has been well documented. However, the physiological role of this trace element in tomato is not clear. This experiment was conducted as a complete randomized design to study two concentrations of titanium (1 and 2 mg/L Ti) and 0 as control on physiological and nutrient properties of tomato cv. Foria with 4 replications. Plant growth (fresh and dry weight, root volume and flower number), greeness Index (SPAD value), photosynthesis and nutrient parameters of tomato were evaluated. The result of nutrient use efficacy (NUE) showed that NUE of K, Ca and Mn improved by Ti supplementation and Zn use efficiency decreased by increasing Ti concentration. The earliest flower induction was observed at 2 mg/L Ti. Root volume increased by both Ti concentration and root fresh weight increased at 2 mg/L Ti. Greeness Index (SPAD value) and PWUE were not influenced by Ti application. Results showed that photosynthesis rate increased by increasing Ti concentration. Transpiration was reduced at the highest Ti concentration. Based on the results, Ti increased plant growth and photosynthesis through increasing nutrient uptake and nutrient use efficiency.

Heat stress causes flower and fruit abscission in pepper. This study was conducted in the greenhouses of Isfahan University of Technology to evaluate the effect of foliar application of Benzyl adenine (BA) and potassium silicate (K2SiO3) under heat stress condition on bell pepper. Two factorial experiments based on completely randomized design with four concentrations of BA (0, 0. 06, 0. 6 and 6 ppm) and the second with two levels of K2SiO3 (0 and 5 Mm) both in two temperature treatments (25± 2 (optimum) 35± 2� (high temperature)) with six replicates were conducted. The results of the study indicated that the use of BA (especially 6 ppm) promoted growth parameters and increased proline, phenol and antioxidant content. Also, application of BA 6 ppm improved cell membrane stability assessed via decreasing electrolyte leakage (EL) and also reduced flower abscission in bell pepper. BA at 6 ppm increased plant height, shoot and root dry weight, proline and total phenol, root fresh weight, potassium (K) concentration and decreased flower abscission. Antioxidant content increased with heat stress in all BA levels. Results of the study indicated that fresh and dry weight of root and K concentration increased with 5 mM K2SiO3. Moreover, root fresh weight and K concentration and antioxidant content increased in 5 mM K2SiO3 under heat stress.