فصلنامه مطالعات حفاظت گیاهان
سال سی و چهارم شماره 4 (زمستان 1399)

Garlic (Allium sativum L.) is one of the medicinal and economically important crop plants belongings to the Amaryllidaceae and is well known for its worldwide applications. It is widely used as a vegetable. In Iran despite the agricultural potential, we are still facing a garlic shortage in the market, mainly due to the high prevalence of plant diseases particularly viral infections. Most garlic plants are infected by several viruses belonging to different taxonomic groups known as “garlic viral complex”. However, Onion yellow dwarf virus (OYDV) acts as a major element of this complex. This virus is an important and damaging potyvirus in garlic which causes mild chlorotic to bright yellow stripes on infected leaves. OYDV survives in bulbs and sets and therefore can be transmitted during vegetative reproduction. Also, the green peach aphid, Myzus persicae, as well as other aphids, spreads the virus from plant to plant in a nonpersistent manner.  OYDV, RT-PCR technique is an effective analytical tool for this purpose. In Iran, for the first time, Shahraeen et al. (2008) were reported OYDV by the serological method in garlic. Afterward, Baghalian et al. (2010), studied the molecular structure of Iranian OYDV based on the coat protein gene analysis. The current study was intended to investigate the partial spreading, genetic diversity and phylogenetic analysis of the different OYDV isolates from garlic and comparing them with other sources of OYDV isolates available in the GenBank. In this study, we present for the first time the genome sequence of Iranian isolates of OYDV based on the CI gene. Besides, the recombination pattern of the CI gene in Iranian isolates was analyzed.

During two consecutive growing seasons of 2016-2017 and 2017-2018, a survey was conducted in some of the major areas under the cultivation of garlic in Iran (Khorasan Razavi: Mashhad, Golbahar and kadcan, Mazandaran: Sari and Babolsar, Kerman: Jiroft, Lorestan: Aleshtar and Khuzestan: Shoshtar). Leave samples with yellow striping; crinkling; dwarfing and mosaic symptoms were collected and taken to the laboratory for both sap (mechanical) and molecular tests (RT-PCR/PCR), to identify the disease cause. Total RNA was extracted from the symptomatic leaf samples using the RNeasy Mini Kit (Qiagen, Germany) and used for the reverse transcription (RT-PCR) test. Primary detection was done by RT-PCR using degenerate primer pairs (CIF/R). After performing PCR, products with 700 bp length, separated by electrophoresis in 1% agarose gel extracted and purified with the Qiaquick Gel Extraction Kit (Qiagen, Germany). Then PCR products were cloned in pTG19-T Vector (Vivantis, Malaysia). The recombinant plasmids were extracted using the plasmid DNA isolation kit (Denazist, Iran) followed by sequencing (Macrogene, South Korea). Nucleotide sequence data were analyzed using Clustal Omega, MEGA 6, and RDP 4 software.

Among Iranian OYDV garlic isolates which detected in this study, seven isolates from Golbahar, kadcan, Sari, Jiroft, Aleshtar and Shoshtar with severe mosaic symptom and dwarfing were selected for sequencing and determination of their molecular and biological characteristics. Comparative analyses of the partial CI gene sequences showed that seven Iranian isolates shared 75.04-99.86% and 90.22-100% sequence identities at the nucleotide and amino acid level respectively, with different OYDV isolates available in the GenBank. Phylogenetic tree based on partial CI gene placed Iranian OYDV isolates in two varying evolutionary groups; I and II. Group, I consisted of OYDV isolates from Argentina (KF632714/KF632715), Japan (AB219833/AB219834), Australia (HQ258894/JN127342), China (AJ510223), Spain (JX429964), India (KJ451436) alongside Iranian isolates. This group is geographically heterogeneous. All these isolates in group I are isolated from the garlic host. Three Iranian isolates, IR-Kh1, IR-Kh2, and IR-Kh16, which isolated from garlic placed in subgroup I-II, along with isolates from Spain (JX429964), Australia (HQ258894), and India (KJ451436). It indicates the high degree of genetic relationship among Iranian isolates in this subgroup. However, group II, which is also divided into two subgroups, includes four Iranian garlic isolates, IR-Kh33, IR-Kh54, IR-Kh23, and IR-Kh48, and are closely related to the German (JX433020)  and Argentine (JX433019) onion isolates. Recombination analysis among Iranian and other isolates in the CI gene showed that there was no recombination in this part of the genome.

Based on the results of this study, the presence of OYDV isolates from some garlic areas of Iran was confirmed and for the first time, the molecular characteristics of the virus based on CI gene were determined. Results showed that OYDV is a dominant pathogen in the garlic field, which is highly prevalent in most sampled areas. Considering the importance of garlic in the food, pharmaceutical, and medical industries, determining the molecular characteristics of its viruses is highly important to determine an efficient control program.

Cucumber, Cucumis sativus is a widely cultivated plant in the Cucurbitaceae family, which is used as a vegetable. Various pests at different stages of growth cause economic damage to it. Lesser pumpkin fly, Dacus ciliatus Loew (Diptera: Tephritidae) could be considered as one of the most important pests of cucurbits worldwide, which direct feeding of larva on fruit making it unusable. Farmers often spray their fields with various pesticides and in some cases is not very effective. Owing to many problems in the chemical control of fruit flies, using resistant plants is one of the most important components in integrated pest management. Host plant resistance is an important component for the management of lesser pumpkin fly, due to difficulties associated with its chemical and biological control. Resistant genotypes can be used to manage this pest.

Seeds were sown in 2018 with ten replicates (blocks) for each genotype following a completely randomized block design. The area of each bed was 4 m × 4 m and the plant-to-plant distance was maintained at 50 cm with a drip irrigation system. All the recommended agronomic practices (e.g. weeding, fertilization, hoeing, etc.) were performed equally in each experimental bed. The infested fruits were sorted and the percent fruit infestation was calculated. Different genotypes by degree of infection into completely resistant (no contamination), very resistant (1-10%), resistant (11-20%), relatively resistant (21-50%), susceptible (51-75%) and high susceptible (100-75%) were sorted. In this experiment, morphological and biochemical characteristics related to resistance were measured in six different genotypes of cucumber (Hayek, Surina, Maximus, Kish, Armenian cucumber, and a local genotype of Kermanshah). The effect of these traits on fruit infestation and larval density was determined. Ten fresh fruits were selected from each genotype and fruit length, fruit diameter, fruit rind thickness, and rind trichomes density were measured and recorded. To measure biochemical traits two fresh fruits from each genotype were selected and the number of chemical compounds such as phenols, flavonoids, tannins, and total alkaloids was measured.  Percentage of fruit infestation, larval density, biophysical, and biochemical traits values were analyzed by Two-way analysis of variance using SPSS 24 software. The means of significant parameters, among tested genotypes were compared using Tukey’s tests for paired comparisons at the probability level of 5%. Correlations between biophysical and biochemical fruit traits and fruit fly parameters (percent fruit infestation and larval density per fruit) were determined using correlation analysis at the 95% significance level.

The larval density per fruit increased with an increase in percentage of fruit infestation and there was a significant positive correlation between percent fruit infestation and larval density per fruit. Among the studied genotypes, Hayek resistant, Surina, Maximus, and Kish moderately resistant, Armenian cucumber susceptible and local genotype was highly susceptible. Phenol content (r = 0.77), tannin (r = 0.89), total alkaloids (r = 0.93) and flavonoids (r = 0.87) were statistically correlated with the percentage of fruit infestation. The percent fruit infestation had significant positive correlation with fruit length (r = 0.55), fruit diameter (r = 0.48), fruit rind trichomes density (r = 0.81) and rind thickness (r = 0.87). Maximum variation in fruit infestation (86.50%) and larval density (63.70%) was explained by the alkaloids. Stepwise regression analysis of our data showed that the highest variation in fruit infestation (75.30) and larval density (61.40) was explained by the trichomes density. Therefore, it can be argued that the reduction of fruit fly infestation on resistant cultivars could be due to physical and biochemical characteristics.

Reduction of fruit fly infestations on resistant genotypes could be due to antibiosis (adverse effect of host plant on the development and reproduction of insect pests, which feed on the resistant plant) and antixenosis (operates by disrupting normal arthropod behavior). Our results suggest that biochemical and biophysical fruit traits could contribute to these mechanisms of resistance. Rind thickness, rind trichomes density, total alkaloids, and tannin were playing an important role in pest resistance. In summary, certain biochemical (tannins, phenols, alkaloids, flavonoid) and biophysical (rind thickness, fruit rind trichomes density, fruit length, fruit diameter) traits were linked to the resistance of cucumber against D. ciliatus and therefore can be used as marker traits in plant breeding programs to select resistant genotypes. By using Hayek genotypes, which have less susceptibility to the lesser pumpkin fly, farmers can produce safe products with less residual insecticides.

Weeds are among the major constraints to crops growth that can affect yield based on their species composition and density. Weed competition reduces yield and consequently farm income. Weeds infestation also encourages disease problems, serves alternate host for deleterious insects and diseases, slows down harvesting, restricts operations, increases the cost of production and reduces the market value of crops. Weed flora composition is strongly associated with regional climate, soil and irrigation water characteristics, and management methods. Weeds dispersal power is amongst the major factors affecting the agricultural plants success. Diversity reflects the complexity of a system and can maintain its sustainability. Higher diversity results in higher inherent complexity of agro-ecosystems and strengthens their processes. It is necessary to realize the spatial distribution and temporal properties of the biodiversity components in agro-ecosystems, for the conservation and optimal utilization. Since weeds as complementary components of agro-ecosystems are inseparable, studying species and their functional and structural diversity plays an important role in weed management and balance of ecological systems. Weeds are highly problematic in agricultural systems in Bardaskan county reducing yield quality and quality. However, the first step in weed management is identifying the flora. Therefore, this study was conducted to determine the flora and structure of weed communities of agricultural and horticultural products in Bardaskan-Iran.

In order to study flora and structure of weed communities of fields and orchards in Bardaskan county, this research was conducted on wheat, rapeseed, autumn sugarbeet, cotton, cumin, melon, pistachia, vineyard, pomegranate and saffron during 2016. Sampling was performed using the W systematic method proposed by Thomas (1985) and McCauley et al. (1991) by using 0.5×0.5-meter quadrate with a slight modification (random systemic method of W instead of systemic of W method). The basis of sampling was systematic, but after determining the main sampling points with intervals of 20 steps on the W system as the main sampling points, other sampling points were randomly selected as sub-sampling points within a radius of 5 to 10 m from the main sampling points to increase the sampling accuracy. Sampling was not performed to remove the marginal effects depending on the farm and garden up to 20 meters from the farm margin. The weeds in each quadrat were counted and their genera and species were identified and weed population indices including mean relative density, relative uniformity and frequently were calculated.

In this study, 106 weed species belonging to 30 families were identified which the most species were from Poaceae with 22 species, Brassicaceae with 15 species and Asteraceae with 13 species. From the 106 identified weed species, 80 species (75.47%) were broad-leaf and 26 species (24.53%) were grassy weeds. In terms of life cycle, 82 weed species (77.36%) were annual and 24 species were perennial. Based on photosynthetic pathway, 82 species (77.36%) had C3 photosynthetic pathway, 23 species (21.7%) C4 and one species (0.94%) was CAM photosynthetic pathway. Among the studied crops, the largest number of weed species were observed for saffron (61 species) and pistachia (55 species) and the lowest species were found for cotton (26 species) and rapeseed (28 species). The broadleaf species of Russian knapweed, hoary cress, African rocket, lambsquarters, camel thorn, mesquite, prostrate knotweed, field bindweed, Russian thistle, common orach and the grassy weed species of mouse barley, wild barley, ryegrass, wild oat, bermudagrass and lesser canarygrass had the highest relative dominance, frequency and density (plant m-2).

In general, a wide range of broadleaf and grassy weeds especially Poaceae and Brassicaceae families was found in the studied area. Overall, the results showed that most weeds identified in this study can grow in different environmental conditions and their growth is less dependent on growth condition. Therefore, presence of some weed species in all studied fields and orchards indicates the possibility of their growth under different environments and managements. Therefore, difference in management strategies and climates can be considered as one of the important factors of differences in the flora and population structure of weed communities in Bardaskan. It seems that weed management in Bardaskan county is inappropriate for various reasons including farmers' lack of knowledge on weeds control, application of inappropriate chemical technologies, and the lack of specific herbicides in some products.

Contamination of wheat seeds in southern Golestan province (Shahkooh village) with rye has rendered it a weed in wheat fields. Due to the lack of suitable herbicides, it is very difficult for farmers to control weed-rye. According to observations, many farmers use rye-infected self-consumed wheat seeds for cultivation. Separation of rye seeds from wheat seeds is very difficult due to their similarity in appearance, and farmers are not aware of the possibility of seed separation. Therefore, this study was conducted to compare the physical properties of rye and wheat seeds to improve seed separation.

Rye seeds were collected from wheat fields in Shahkooh village. The seeds of Alvand wheat cultivar, which is a common cultivar in Shahkooh region, were also obtained from Shahkooh Rural. The studied physical properties included seed size (seed length, width and thickness), seed surface area, seed weight, spherical percentage, bulk density, true density, porosity percentage, angle of repose and coefficient of friction. Physical properties of the seeds were studied at five seed moisture levels including 10, 15, 20, 25 and 30%.

Based on the results, the length, width and surface area of both wheat and rye seeds were not affected by seed moisture. Only in wheat, seed thickness increased with increasing seed moisture content. Since these properties determine the final seed size, it can be said that the seed size remained almost constant by increasing the percentage of seed moisture in these two plants. On the other hand, in all moisture levels, the width, thickness and surface area of wheat seeds were higher than those of rye seeds. In contrast, seeds length of rye was longer than wheat seeds. In wheat seeds, the spherical percentage increased linearly by increasing seed moisture content, but its amount was constant in rye at different seed moisture content. The significant difference between the spherical percentage of wheat and rye seeds also indicates that the wheat seed is more spherical compared to rye at all moisture levels. The seed weight increased linearly with increasing seed moisture content in both wheat and rye plants, with a higher slope in wheat than rye. In addition, wheat seed weight was higher than rye seed weight in all moisture levels. The existence of these differences in the dimensions, the shape and weight of wheat and rye seeds can be considered as the basis for their separation. In wheat and rye plants, the bulk density, true density and percentage of seed porosity decreased linearly by increasing seed moisture content. Also, the bulk density and true density in wheat was higher than in rye at all moisture levels. With an increase in seed moisture from 10 to 30 percent, the porosity percentage in both wheat and rye plants decreased by about 14 percent on average, and there was no significant difference between them in terms of the percentage of porosity at different moisture levels. An increase in the percentage of seed moisture caused a linear increase in the angle of repose. In other words, the ability of seeds to move was reduced by increasing the moisture content in two wheat and rye plant. There was no significant difference in the angle of repose between wheat and rye at any of the moisture levels. In this study, the coefficient of friction in wheat and rye seeds linearly increased on different materials by increasing seed moisture content. There was no significant difference in the coefficient of friction on galvanized iron and cement surfaces at different moisture levels between wheat and rye. However, the coefficient of friction in wheat was always higher than rye on plastic, wood and rubber surfaces. Due to these differences, it is easy to remove rye seeds from wheat seed lots and prevent rye from re-entering the wheat fields during planting.

According to the results of this study, there is a significant difference between wheat and rye seeds in terms of physical characteristics. These differences facilitate separation of rye seeds and avoid entry into wheat seed lots. The difference in the length, width, thickness and density of the seeds in these plants makes it possible to use length or width based separators, air screen machines and gravity separators.

Cumin (Cuminum cyminum L.) is one of the most important domestic medicinal plants in the country. Currently Iran is one of the most important producers of cumin. Features such as short growing season, low water requirement, lack of interference with other crops, high economic justification for other crops and exportability, make this plant a special place in the pattern of cultivated area This plant has a special place in the cultivation pattern of arid and semi-arid regions, including Khorasan. Given that cumin is a delicate plant with low weed competitiveness and on the other hand because it leaves cover the ground as much as possible, it provides a suitable environment for weed growth and development. Although cumin growers are currently struggling with weeding the fields mechanically, this method is costly and damages to the cushion bushes, identifying the herbicide of choice for combating weeds. The weeds of this plant will be a great step towards reducing the cost of its production. Therefore, the purpose of this study was to evaluate the chemical control of weeds and to evaluate the cumin tolerance to herbicides and to select herbicides for this important medicinal plant.

In order to evaluate the efficacy of herbicides from cell division inhibitor and photosystem II inhibitor groups, an experiment was conducted as a randomized complete block design with 6 treatments and 3 replications in Agricultural Research Farm at University of Birjand 2017. In this research herbicides from cell division inhibitors group including trifluralin pre-plant incorporated (2 L.ha-1), pendimethalin pre-plant incorporated (3 L.ha-1), pendimethalin preemergence (3 L.ha-1) as well as herbicides from photosystem II inhibitors group including prometryn preemergence (2 Kg.h-1), metribuzin preemergence (1 Kg.h-1) and a weeding treatment was also added. The measured traits for weeds included: height, density, dry weight, leaf area and for cumin included: seed yield and biological yield.

According to the results of analysis of variance, herbicide treatments had a significant effect on density, height, dry weight and leaf area at different stages of weed sampling. Comparison of mean data on total weed density showed that after weeding treatment, application of pendimethalin preemergence caused an almost 100% reduction in total weed density, which was not statistically significantly different from pre-plant incorporated trifluralin. Concerning weed height, the results showed a significant decrease in the effect of herbicides on weed height. Comparison of means showed that preemergence and pre-plant pendimethalin had a great impact on weed leaf area reduction. Experimental treatments had a significant effect on weed dry weight. Results showed that pendimethalin herbicide had the greatest percentage of reduction in total weed dry weight after weeding treatment. The results of visual assessment also indicated the greater impact of cell division inhibitor herbicides on weed control at all three sampling stages. Preemergence pendimethalin had the greatest efficiency in weed control, whereas metribuzin and prometryn had the least efficiency in this regard. Moreover, the results of visual assessment of herbicide effects on cumin showed that pendimaline had no significant effects on cumin either in pre-plant or pre-emergence applications, probably due to the rapid metabolism of this herbicide in the plant and its low mobility in the soil. The greatest damage to cumin was related to metribuzin. The results showed that the greatest seed yield was related to full-season weeding treatment, followed by pendimethalin herbicide application which caused a 204% increase in the crop seed yield and the lowest seed yield was related to metribuzin with 63% reduction in crop seed yield. It seems that due to relatively long survival of metribuzin in the soil (30-60 days) and the high susceptibility of cumin to this herbicide, it caused severe damage to the crop.

All herbicides applied in this study showed an acceptable level of control over weeds in terms of percentage of density reduction, dry weight, height, and leaf area of ​​weeds. Pendimethalin herbicide after weeding all season had the highest percentage of grain yield and biological yield enhancement, while the least performance was related to metribuzin. According to the results of the visual assessment, the greatest and least impacts of herbicides on weeds was occurred with pendimethalin and metribuzin, respectively. In general, according to the results of this study, pendimethalin herbicide can be effective in controlling weeds and enhancing the yield of cumin because of its greater inhibitory effect on weeds as well as its safety for cumin.

Wild mustard (Sinapis arvensis L.) is a very common weed within cereal and rapeseed fields in Iran and many other countries. This weed is usually controlled by tribenuron-methyl in wheat fields of Iran. However, due to consecutive application of tribenuron-methyl for the last 27 years in wheat fields, control failures were reported by farmers. Resistance to ALS inhibiting herbicides is the most common form of herbicide resistance in the world. So far, 165 resistant biotypes to this family have been reported. Therefore, present study was carried out to survey suspected of resistance wild mustard accessions to tribenuron-methyl in wheat fields of Ramhormoz and preparing distribution map of resistant fields.

An experiment was conducted in Agricultural Sciences and Natural Resources University of Khuzestan during 2017-2018. 22 no. of the suspected resistance wild mustard accessions to tribenuron-methyl were gathered from wheat fields of the Ramhormoz. One susceptible accession was also gathered from a field with no history of spraying. Pot experiments were carried out in two stages including the initial screening with the recommended dose of tribenuron-methyl (15 g ai ha-1) and dose-response assay that accessions were investigated for the effect of tribenuron-methyl on dry weight and survival plant no. under outdoor conditions. The plants per pots were sprayed, based on tribenuron-methyl dose (0, 0.125, 0.25, 0.5, 1, 2, 4, 8, 16, and 32-fold of recommended dose). The shoot dry weight data were converted to a percentage based on control plants data within each accession. A log-logistic curve with three and four-parameters was used to describe dose–response relationships. Dry-weight data were fitted to a nonlinear log-logistic regression model using the package drc in the statistical program R (R Development Core Team, 2008). The distribution map of the resistant populations was plotted using ArcGIS 10.3 software.

Screening results showed that nine accessions (B, C, H, P, S, T, W, X, U) were strongly resistant (R) and 10 accessions (A, E, F, G, K, L, M, O, Q, R) were probably resistant (PR or RR), and three accessions (D, N and Y) were susceptible (S) or suspected resistance (SR) to tribenuron-methyl based on Adkins and Mo‘s 's ranking system. While, Screening results based on Mo‘s 's ranking system showed that nine accessions (B, C, H, P, S, T, W, X, U) were completely resistant (RRR) and 10 accessions (A, E, F, G, K, L, M, O, Q, R) were probably resistant (RR), and two accessions (D and N) were suspected resistance (SR) and one population (Y) was susceptible to tribenuron-methyl. With increasing doses of the herbicide tribenuron-methyl, the dry weight of susceptible and susceptible accessions decreased during the sigmoid process. Resistance factor of accessions (W, U, X, S, B, C, T, K, R, G, Q, O, E, A, P, M, F, H, and L) based on dry weight (% of control) and survival (% of control) ranged from 1.10- 8.17 and 2.08-7.60, respectively. A different resistance factor was observed between the accessions; thus, the W accession with the highest resistance factor of 8.17 and 7.60 and the L accession with the lowest resistance factor of 1.10 and 2.80 based on dry weight and survival (% of control) were resistant to the herbicide tribenuron-methyl. While 6.80 g ai ha-1 caused a 50% reduction in the dry weight of the susceptible Z accession, this reduction was calculated to be 60.55 g ai ha-1 for the most resistant accession (W), which differed significantly based on the calculated confidence limits. A map of the distribution of contaminated fields of resistant wild mustard accessions using GIS showed that most resistant accessions were observed in eastern and southeastern regions of Ramhormoz.

The results of this experiment confirmed the presence of resistance in wild mustard accessions to tribenuron-methyl. Repeated use of tribenuron-methyl in wheat fields of Ramhormoz is one of the most important reasons for resistance in these fields. Distribution map makes it possible to predict farms infected with resistant accessions and help prevent the recommendation and use of ALS inhibiting herbicides in these farms, so that in order to break the resistance in resistant accessions and it will be effective reduce the use of herbicides. Therefore, the use of distribution maps can be used to implement integrated weed management programs and to prevent the development of resistance accessions in other areas.

Plant Protection Organization (PPO) has registered seventeen commercial herbicides formulations for broadleaved weed control of wheat in Iran (Nourbakhsh, 2019). Among these herbicides, five herbicides contain one active ingredient and the others have two or three active ingredients including acetolactate synthase (ALS) enzyme inhibiting groups, synthetic-auxin groups, photosynthetic inhibitor of photosystem II, and pigment synthesis inhibitor groups, which are sometimes formulated with safeners (Tomlin, 2009). Previous studies show that existing weed species do not similarly respond to herbicides and therefore the percentage control of some of the weed species is lower than the other species (Ohadi, 2010). These hard-to-control weeds are naturally resistant to herbicides. Thus, new herbicides with several active ingredients are suggested to be used to suppress such weeds. The aim of this work was to find the best chemical treatments against weeds in wheat production based on using new herbicides bromoxynil+2,4-D and comparing their efficacy with the common registered herbicides in the major wheat growing areas of Iran.

A field study was conducted in four regions of Iran, including Karaj, Shahryar, Kermanshah and Shiraz during 2017-2018 growing season. The statistical layout was a completely randomized block design with four replicates. Eight herbicides in 13 treatments were 2,4-D+MCPA (U46-Cambi fluid® 67.5%SL, 1.5 1 L ha-1), Mecoprop-p + Dichloprop-p + MCPA (Duplosan super® 60% SL , 1 L ha-1), Bromoxynil + MCPA (Bromicide® 40% EC, 1.5 L ha-1), Tribenuron-methyl (Granstar® 75% DF, 20 gr ha-1), Mesosulfuron-methyl + Iodosulfuron-methyl sodium+ Diflufenican+Mefenpyre-diethyl (Othello® 75% WG, 1.6 L ha-1), 2,4-D + Dicamba (Dialant super® 46.4 SL, 0.8 L ha-1), Triasulfuron + Dicamba (Lintur® 70% WG, 165 gr ha-1), and the new herbicide Bromoxynil + 2,4-D with six recommended doses (Buctrile Univeral® 56% EC, 0.75, 1,1.25, 1.5, 1.75 and 2 L ha-1).  A hand-weeded treatment and an unweeded treatment served as controls. Weed density and weed dry weight for each plot were measured four weeks after the last application the herbicides.  Wheat was harvested from six m2 of each plot after removing border plots. Wheat grain yield was determined after adjusting the moisture level of grain to 14 %. Data from each region were subjected to statistical analysis using SAS/STAT® statistical software and the means were separated by Duncan (α=5%).

The results showed a diverse spectrum of weeds (18 species) at the experimental locations. Descuriania Sophia was dominant in three tested locations except Kermanshah. The next dominant weed species were Galium aparine L. and Centaurea depressa M.B. were present dominantly in Kermanshah and Shiraz. Lepyrodiclis holosteoides and Convolvulus arvensis as noxious weeds, respectively were dominant in Shahryar and Kermanashah. Malcolmia africana and Sinapis arvensis were present in Karaj. Across the experimental locations, Bromoxynil + 2,4-D was efficient at 1.5-2 L ha-1 concentrations for total weed control (85.7 to 91.47%). However, when applied at dosage of under 1.5 L ha-1, its weed control efficiency was lower (63 to 80%). Mecoprop-p + Dichloprop-p + MCPA and Bromoxynil + MCPA with 82% average efficiency in controlling weeds in all the locations, which was in agreement with the findings of some previous studies (Minbashi and Saeedi, 2019). 2,4-D + Dicamba and Triasulfuron + Dicamba were inefficient in weed control (68-72%) across all locations. Bromoxynil + 2,4-D (1.5 L ha-1 and upper doses), Mecoprop-p + Dichloprop-p + MCPA, and Bromoxynil + MCPA  were the most efficient to control Lepyrodiclis holosteoides with 86.99 to 99.19% of weed density.This weed beside C. arvensis and G. aparine were identified as difficult-to-control weeds. None of herbicides showed visual injury symptoms on wheat.

According to these experiments, we found that the Bromoxynil + 2,4-D (1.5 L ha-1 and upper doses) as new candidate herbicide showed good to excellent (85%-100%) weed control efficiency averaged in the all experimental locations and it could be recommended to be used in wheat field after registration process. Due to environmental concern, it should be applied at lower doses. Mecoprop-p + Dichloprop-p + MCPA and Bromoxynil + MCPA were found to be the next two efficient herbicides. C. arvensis, was the most difficult-to-control weed that there was not controlled by new herbicides. L. holosteoides and G. aparine were difficult-to-control weed species.

Weeds are the most important limiting factor in agricultural systems and if they are not controlled, crop yields can be reduced up to 90% depending on the competitiveness of weeds and between 10 and 100% according to some literatures. One of the benefits of green manures is their ability to suppress weeds. Also, a higher crop density can reduce the biomass of weeds by reducing the amount of available light. Green fertilizers are plants cultivated in order to improve physical, chemical and biological soil properties and provide the necessary nutrients for the optimal crop growth. The use of different types of green manure is a suitable management for sustainable production in all agricultural ecosystems. In this way, the highest amount of light reaches to the crop and the least amount reaches to the competing weed. Increasing crop density can be an effective way to increase crop share of total source inventory and reduce weed dry weight. Rapeseed plant with allopathic substances in addition to food and medicinal uses, is also known as a weed controller providing a suitable environment for growing other plants by controlling weeds. This experiment was, therefore, performed to investigate the effect of canola green manure and planting density on weed control and sunflower yield.

the present study was conducted as split-plot design based on randomized complete block with three replications at the Research Farm of the Bu-Ali Sina University in 2015-2016 growing season, to evaluate the effect of canola green manure and crop density on weeds dynamic and sunflower yield. Weed free, using and non-using canola green manure were set as main-plots and sunflower densities (6, 8 and 10 plants.m-2) were considered as sub-plots. Rapeseed was mixed with soil at the beginning of flowering stage and after two weeks, sunflower was planted in the main plots with the desired planting densities. The amount of rapeseed biomass at the time of return to the soil was about 6250 kg of shoot dry matter per hectare. In each sub-plot, six rows with five meters long were planted. Weeds were sampled to determine their density and dry weight in three stages (three weeks after emergence, flowering and physiological maturation of sunflower) with three replications by 1 × 1 m2 quadrat. Weeds were counted by species and their biomass was measured after drying for 72 hours in an oven at 80 °C. Also, two square meters were taken from each experimental plot after applying the margin effect (one row on both sides and half a meter from the top and bottom of the planting row) so as to measure the yield of sunflower seeds. Weed control efficiency index was used to evaluate the ability of green manure and plant density in controlling weed of sunflower field. Data analysis was done by SAS ver. 9.1 and comparison of means was performed using LSD test at the significance level of 95%.

Maximum weeds density and biomass were found at the treatment of 6 plants.m-2 under non-using green manure. In comparison with this treatment, cultivation of sunflower with 10 plants.m-2 under using green manure increased weed control efficiency (WCE) up to 79% and decreased biomass of Amaranthus retroflexus, Chenopodium album, Setaria viridis, Convolvulus arvensis and total weeds up to 70, 76, 99, 92 and 72 %, respectively. Sunflower yield at the 10 plants.m-2 density was the highest and the same under weed free and weed infested by using green manure. The interaction effect of treatments on density and biomass of sunflower field weeds was significant. The highest and lowest density and biomass of weeds were obtained from uncontrolled at a density of six plants and green manure at a density of 10 plants, respectively. Also, the highest yield of sunflower seeds (411 g.m-2) was attributed to the density of 10 plants in weed control treatment, which was insignificantly different with the density of 10 sunflower plants in the application of green manure, which had a yield of 379 g.m-2. This can be attributed to the role of green manure in controlling weeds, increasing microbial activity, increasing food mobility and better use of water and nutrients. It seems that at low densities, the absorption of solar radiation and dry matter production are lower due to the low leaf area. Other researchers have attributed increased corn yield at high densities to greater uptake of solar radiation by the canopy.

Since the goal of sustainable agriculture is applying minimum herbicides and alternative management methods to control weeds, application of green manure and normal crop density can be a good strategy in this regard. Therefore, sunflower cultivation with density of 10 plant.m-2 and using green manure suppressed weeds and produced the highest yield. Therefore, this treatment can help to reduce herbicide application, and it will be an effective step for promotion of sustainable agriculture.

Sugar beet competes with weeds for light, nutrients and water resources and is so sensitive especially at the early stages of growth. Weeds are the most important factors limiting sugar beet production in Iran. Although, about 20 herbicides were registered to control weeds, but their effectiveness would be high only if farmers use them properly. Due to sensitivity of weeds to herbicides at certain times, determination of the best herbicide application time is very important. Cloridazon is one of the selective herbicides registered for broadleaf weeds control of sugar beet. Both pre and post-emergence applications of this herbicide were recommended but the effectiveness of treatment should be evaluated. 

In order to determine the best application time of Cloridazon (Pyramin, WP 65%) to control broad leaf weeds in sugar beet field, an experiment was conducted in two locations i.e. Golestan province (Gonbad station) and Khozestan province (Safiabad, Dezful station), Iran, during 2018. Experiments were arranged as randomized complete block design with 4 replications. Treatments were: application of Cloridazon at 3, 4 & 5 kg/ha, and two different application times (i.e. pre-emerge and post-emerge at 4 leaf stages), application of Phenmedipham+Desmedipham+ Ethofumesate (Betanal Progress O.F. at 3 lit/ha at 2-4 leaf stages), and weed free as the check. Each experimental plots were divided into two parts including: uncontrolled part (as weedy control) and treatment part. Efficacy of the treatments on weed population and control was evaluated based on the percent of reduction in weeds density and dry weight and EWEC scoring system at 30 days after herbicides application. Root yield of sugar beet was also measured at the end of the growing season. The weed spectrum was not similar in both locations. Polygonum aviculare and Sonchus arvensis were dominant in Gonbad and Malva sylvestris and Sinapis arvensis were dominant in Dezful. Experimental data were analyzed by SAS (version 9.1) program and means were compared with the Duncan's multiple range test.

The results indicated that the effects of treatments on weeds were significant. Application of Cloridazon at 3 kg/ha controlled sinapis arvensis by 95 to 100% and Sonchus arvensis by 86 to 93%. In both locations, the difference between this treatment and Phenmedipham+ desmedipham+ ethofumesate (Betanal Progress OF) was not significant. Chloridazon (as pre-emergence treatment) performed better in controlling broad leaf weeds compared with post treatment. The pre-emergence application of Chloridazon (at 3 , kg/ha) was the best treatment (with more than 85% weed population control) in both studied areas. In addition, this treatment had no significant difference with Phenmedipham+ desmedipham+ ethofumesate (Betanal Progress OF). The results show the low efficacy of Pyramin on weeds when it was applied late (after 2 leaf stages). However, due to different germination time of weeds, single application of Pyramin is not enough to achieve the desired results. Application of post-treatments (like Betanal Progress OF) is necessary as complementary treatments. However, using 3 kg/ha of Pyramin, cannot control Malva sylvestris if this weed is dominant in the field, and the Pyramin dose should be increased to 4 kg/ha. Anyway, application of Chloridazon at more than 4 kg/ha is not recommended as it would have negative effects on sugar beet seed germination. It should be noted that both cultivars (Roza Gold and Silvetta) used in Gonbad and Dezful were monogrm and more sensitive to herbicides with respect to polygerms. The probability of seed damage on monogrm cultivars will be higher by pre emerge herbicide application. Based on our results, application of Chloridazon (at 3 kg/ha as pre-emerge treatment) was the best treatment for sugar beet root yield and showed no significant difference with the application of Phenmedipham+desmedipham+ ethofumesate (Betanal Progress OF).

Application of herbicides in modern intensive agriculture to control weeds has increased dramatically, which leads to the serious environmental problems due to transferring and leaching of herbicides to non-target locations; and their negative effects on non-target organisms need to be reduced. In other words, leaching and transferring of herbicides not only reduce its efficiency but also leads to groundwater pollution. Among the herbicide transfer processes in the soil, leaching is the most important processes because of its potential to contaminate groundwater. Imazethapyr is extensively used in the country's arable lands, and the present experiment was conducted to investigate the effect of soil organic matter on the leaching depth of this herbicide.

A factorial pot experiment was conducted in 2017 based on a completely randomized design. The first factor was soil type (including 1- without adding organic matter and without herbicide application (S1), 2- without adding organic matter + herbicide (S2), 3- 10% organic matter + herbicide (S3), 4 - 25% organic matter + herbicide (S4) and 5-50% organic matter + herbicide (S5)), and leaching depths of 2, 4, 6, 8, 10, 12 and 14 centimeters was considered as the second factor. Imazethapyr herbicide was applied based on its recommended dose. After applying the herbicide in the soil columns, no cultivation operation was carried out for 48 hours so the herbicide had enough time to transfer to different depths of the soil. It was closed under each pot with a flat plate and then five cotton seeds were planted in each pot. After planting, the pots were not irrigated for 48 hours to absorb the herbicide by seeds and then irrigation was done according to the needs of the plant with a suitable sprinkler. All pots were cared for in the greenhouse for 30 days and then emergence percentage, stem height, root length, stem dry weight and root dry weight were measured and recorded. To measure the dry weight, a digital scale with an accuracy of one hundredth was used and to dry the plant components, all samples were placed in an oven at 75 ° C for 24 hours.

The results of analysis of variance related to the measured traits of cotton crop indicated that the simple and interaction effects of soil type treatments and leaching depth had a significant effect (p-value < 0.01) on stem length, root length, stem dry weight and weight dried cotton roots. Due to the significant interaction between soil type and leaching depth, physical cutting was performed based on the soil type. Emergence percentage trait was not affected by soil type but leaching depth treatments and the interaction of soil type leaching depth showed a significant effect on this trait (p-value < 0.05 and p-value < 0.01, respectively). Mean comparisons related to the emergence percentage of cotton seeds showed that in almost all soil treatments with increasing the leaching depth, the emergence percentage of cotton increased significantly, which indicates a decrease in the amount of imazethapyr herbicide leaching in more soil depths. In other words, with increasing soil depth, the amount of leached herbicide was also reduced. The average emergence percentage in each soil depth shows that the highest emergence percentage was obtained from a depth of 14 cm at 78.85 and the lowest was obtained from a depth of two centimeters at 42.66. The minimum stem length was obtained from depths of 2 and 4 cm. At depths of 6, 8, 10, 12, and 14 cm, stem length increased with increasing leaching depth and decreasing the concentration of imazethapyr herbicide. This could be due to the accumulation of washed herbicides at the bottom of the column, because after applying the herbicide, the soil columns were left standing for 48 hours to allow the herbicide to be transported deeper, and possibly after the herbicide reaches the end of the column and the drainage rate is low in this area, the accumulation of imazethapyr at low depths, especially at a depth of 14 cm, has reduced the stem length at this depth. In addition to the possibility of herbicide uptake by soil organic matter, plant growth may also be affected by more soil organic matter and be effective in compensating for the negative effect of herbicides. In herbicide treatments, the root length of cotton increased with increasing the leaching depth. Stem and root dry weight also increased significantly in S2, S3, S4, and S5 treatments with increasing the leaching depth. It seems that after absorption by cotton seedlings, imazethapyr stops the production of amino acids and reduces their levels such as valine, lysine and isoleucine, causing cell death and ultimately reducing the growth of cotton.

 The percentage of organic matter was effective on the penetration depth of the herbicide. In treatments with higher percentages of organic matter at depths greater than 4 cm, cotton traits were not zero and the presence of higher organic matter, in addition to helping plant growth, by absorbing more herbicides, caused its leaching damage. It is possible to consider a significant increase in the parameters studied in cotton crop by increasing the amount of organic matter at different depths of the leaching of imazethapyr herbicide from two aspects. First, an increase in organic matter is likely to increase the degradation of the imazethapyr herbicide. Second, the increase in organic matter has improved the metabolic reactions in the plant and therefore the increase in organic matter has been associated with the improvement of cotton growth indices.