فصلنامه مطالعات حفاظت گیاهان
سال سی و سوم شماره 3 (پاییز 1398)

Soil-borne sugar beet viruses are responsible for the destructive diseases of sugar beet. They can cause significant yield losses worldwide. Four of the soil-borne sugar beet viruses consisted of Beet necrotic yellow vein virus (BNYVV), Beet soil-borne mosaic virus (BSBMV), Beet soil-borne virus (BSBV) and Beet virus Q (BVQ) are transmitted by the protis Polymyxa betae, a common root infecting parasite which ensures the long-term persistence of the viruses in the soils and one consisted of Beet black scorch virus (BBSV), is transmitting by Olpidium brassicae. So far, four out of five aforementioned viruses have been reported (except for BSBMV) in Iran. BNYVV is the causal agent of the rhizomania disease which has been reported in mixed-infections with BSBV, BVQ and/or BBSV. In previous studies, BSBV, BVQ and BBSV have been found alongside the BNYVV in some root samples. Nevertheless, up to now, no field has been spotted with black scorch symptoms of sugar beet leaves. Recently, we observed symptoms of burns on leaves and similar signs of rhizomania disease in the roots of some sugar beet cultivars in the fields of Khorasan Razavi province. The purpose of this study was to detect soil-borne viruses of sugar beet and determine some of their molecular aspects.

In this study, sugar beet with bearded roots and black scorching of leaves symptoms were collected from Mashhad, Fariman, Chenaran, Jolge-Rokh, and Jovein sugar beet fields. Total RNA was extracted from 100 mg of rootlets using RNeasy Mini Kit (Qiagen-Germany) based on the manufacturer's protocol. The presence of three viruses of BSBV, BVQ and BNYVV were analyzed by multiplex reverse transcription-polymerase chain reaction (mRT-PCR). However, For BBSV detection, simplex RT-PCR was used to detect of the 3′-UTR of the genomic RNA. For the molecular characterization of the BNYVV isolates, the BNYVV type (A or B) was determined with duplex RT-PCR (dRT-PCR), using A/B-type-specific primers pairs for the triple gene block (TGB) gene in RNA-2 and the partial p25 gene of the RNA-3 segment of the virus. RT-PCR was done using the PrimeScript™ Reverse Transcriptase kits and the PrimeSTAR GXL DNA Polymerase (Takara, Japan). The PCR products were cloned in pGEM®-T Easy Vector (Promega-USA). The recombinant plasmids were extracted using PrimPrep Plasmid DNA isolation kit (GenetBio-Korea) and then sequenced (Macrogene, South Korea). Nucleotide sequences data were analyzed using Chromas (version 1.45) and MEGA7 softwares.

The results showed that in the three samples with bearded root symptoms (Mashhad, Jovein, and Jolge-rokh), only BNYVV (A-type) was present and there were no BSBV and BVQ in the tested samples. In addition, in the two samples (Fariman and Chenaran), none of the three viruses was detected. The results showed that the two BNYVV isolates had ‘ACHG’ (Mashhad and Jolge-Rokh isolates) or ‘AHHG’ (Jovein isolate) residues in the tetrad position. So that the amino acid cysteine (C) in a68 position was converted to histidine (H). Although this A-type tetrad has been previously reported by Mehrvar et al. (2009) in Khorasan Razavi and Northern Khorasan, Semnan, Qazvin, Zanjan, Ilam, Hamedan, and West Azarbaijan provinces. In this study, BBSV was detected in all samples. In Mashhad, Jolge-rokh, and Jovein samples, BNYVV was present accompanied by BBSV. However, BBSV was detected alone from Fariman (holding black scorching of the leaves and vascular necrosis of root symptoms) and Chenaran (black scorching of the leaves) samples. These results are consistent with the results of other researchers from Spain and the United States who reported the presence of rhizomnia symptoms in the BBSV infected roots.

While most of  the farmers in Khorasan province cultivate resistant cultivars of sugar beet carrying the Rz1 gene for successive years in a field, the breakdown of the resistance and emerging of new resistance breaking (RB) variant of the virus have occurred via amino acid changes. However, more research on BNYVV pathogenicity by the use of additional sources of resistance and alternative disease control majors is needed to have a suitable conclusion. In addition, the results of this study showed that the presence of both viruses (BBSV and BNYVV) together could exacerbate the Rhizomania syndrome symptoms while single infection by BBSV could just cause vascular necrosis in the root and black scorching symptoms of the leaves. This could be very important in symptoms based diagnosing of the disease and preventing errors in evaluating the resistance of sugar beet cultivars in the field.

Aphids are small insects which are famous as pests in agriculture, horticulture and forestry. They cause economic damages directly by feeding plants’ sap and indirectly by transmitting plant viruses. Sitobion avenae (F.) is one the important pests in the United States, Europe and Asia. In Iran, it has been reported on wheat, barley, and the other cereals from the different provinces including Kermanshah. Investigating on the population dynamics of pests is a major factor in evaluation of the pest management. The aim of the present study was to determine the most appropriate life stage of S. avenae for sampling to investigate its population dynamics and identify natural enemies of S. avenae in Sar-Pole Zahab region in Kermanshah province.

This study was conducted in a wheat field in Sar-Pole Zahab region in Kermanshah province during years 2015 and 2016. None of pesticides were used to control the insect pests during experiments.  Population survey and sampling were began each year in the middle of February and continued weekly until the end of wheat growth season in the middle of June. Sampling pattern was X-shaped and totally 30 samples were collected from the field. The selected plants were separately put in plastic bags and transferred to the laboratory for counting the number of nymphs, winged and wingless adults. To examine probable emergence of parasitoids, the aphids were kept in Petri-dishes in laboratory for two weeks and the results were recorded. A standard insect collecting net was used for sampling of the predators. The collected predators were transferred to the laboratory in glass jars for identification. The aphids and collected natural enemies were sent to Plant Protection Research institution in Tehran for confirmation.

At the first sampling date in 2015, there were a few adult aphids in the field. However, the population of adults and nymphs were gradually increased and the highest population of aphids was observed between March 12th 2015 and April 30th 2015.The peak density of adult aphids was on April 9th 2015 (9.5 aphids per spike) and for nymphs, it occurred a week earlier, on April 2nd 2015. In the second year, however, the population fluctuation pattern was very different. Although some aphid colonies were seen in the field from 25th of February, 2016, the number of aphids was decreased due to severe cold happened in March, thus no aphids was found in the samples in the next two weeks. The peak population of adult aphids was observed on 14th of April 2016 (36.9 aphids in spike) and then gradually decreased during the next weeks. Coccinella septempunctata L. (Coleoptera: Coccinellidae), Eupeodes corolla (Fabricius) (Diptera: Syrphidae) and Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) were reported as aphid’s predators in the field. All predators were present at the field from the first sampling date. In the first year, E. corolla showed two distinct peak in its population during sampling including 19th of March 2015 and 16th of April 2015. In the second year, there were 17 adult flies per net in the first day of sampling, but the number of flies was increased gradually and reached to a maximum of 35.5 flies per net on 14th April 2016. C. septempunctata and C. carnea populations’ dynamics also followed the same patterns and showed two peaks in the first year and one peak in the second year of studies. No parasitoid was emerged from the aphids in Petri dishes

Due to presence of active predators in the wheat fields of Sar-Pole Zahab region and their high population, using of chemical pesticide should be restricted. Thus, if spray of pesticides is essential, the most appropriate time is when it has the least detrimental effects on natural enemies.

The citrus mealy bug,  Planococcus citri (Risso) is one of the major pests of citrus and many other orchards crops, as well as ornamental plants in subtropical and tropical regions of the world, including Iran. Due to the harmful effects of chemical pesticides on biological control agents and non-target organisms, along with developing resistance to various pesticides by the pests, there has been an increasing interest in integrating biological control methods in the pest management programs. The predatory ladybird, Cryptolaemus montrouzieri Mulsant is one of the most widely used biological control agents. It is an important natural enemy of many species of mealybugs such as P. citri. Functional response of a predator that refers to the number of prey consumed per predator as a function of a prey density is the important characteristic of predator–prey interactions. Temperature can affects the consumption behaviour of the predators. The aim of the present study is to evaluate the effects of temperature on the functional response of C. montrouzieri to different densities of P. citri. Improving our understanding about predator-prey interactions between C. montrouzieri and P. citri may be helpful to optimize biological control of the mealy bug.

The colony of P. citri was collected from bitter orange in Mehmansara region, Ghaemshahr, Mazandaran province, and was reared on pumpkin, Cucurbita maxima. The laboratory colony of C. montrouzieri was obtained from Baharan Dasht Sahel insectarium in Sari, Mazandaran province, and was reared on P. citri. The functional response experiments were performed with fourth instar larvae and adult females of C. montrouzieri to the adult female of P. citri. The experiments were conducted at the temperatures of 18, 23, 27, 32 and 37±1 °C, 60±10% RH and L16:D8 h. Prey in densities of 3, 5, 7, 10, 15 and 30 was offered to the predators. The predators used for the experiments were < 48 h old and were starved for 24 h before starting the tests. A single bitter orange leaf disc (3 cm2) was centred upside down in each ventilated Petri dish (10 cm diameter). Ten replicates were conducted for each prey density. After 24 h, the predators were removed from the experimental arena and the number of consumed prey was recorded and they were not replaced during the functional response tests. The type of the functional response was determined by logistic regression analysis (SAS/STAT, CATMOD-procedure) of the proportion of prey killed in relation to prey offered. To determine the type of functional response, the sign of the linear coefficient was estimated by the logistic regression. The negative sign is evident to a functional response type II, whereas a positive sign reveals a type III functional response. Parameters of attack rate and handling time were estimated using the PROC NLIN procedure of SAS and compared through the indicator variable method. 

The logistic regression for fourth instar larvae and adult females of C. montrouzieri to P. citri at all temperatures showed a negative linear parameter and the proportion of prey eaten by the predators declined with increasing prey density. This suggested that fourth instar larvae and females of C. montrouzieri exhibited a type II functional response to change in P. citri density at all tested temperatures. The highest attack rate and lowest handling time of fourth instar larvae were estimated at 37 and 27 °C, respectively. Whereas the highest attack rate and lowest handling time of adult females were estimated at 37 and 32 °C, respectively. At the same temperature, the attack rate estimated for the adult female was higher than that of the larval instar of the predator, showing higher predation potential of adult female in compared to the fourth larval instar of the predator. Theoretical maximum attack rates (T/Th) for fourth larval instar of the predator at above-mentioned temperatures were respectively estimated 8.20, 28.81, 43.80, 19.82 and 14.44 and for adult female predator were 9.70, 9.17, 9.10, 18.47 and 17.92, respectively.          

Temperature affected significantly functional response parameters of fourth instar larvae and adult females of C. montrouzieri to P. citri densities. Although the last instar larvae and adult females of C. montrouzieri showed high predation potential at all temperatures, adult females of the predator was more voracious compared to the last instar larvae of the predator especially at higher temperatures.

Whitefly, Bemesia tabaci Bemisia (Gennadius) (Hemiptera: Aleyrodidae) is the key pest of many crops worldwide, directly damages the plant by feeding and indirectly by transmitting the virus. The Begomoviruses in the family Geminiviridae are transmitted by B. tabaci through a circulative and persistent manner. For some insect vectors of plant viruses like aphids, information has been collected regarding their digestive tract anatomy and cell structure in relation to the formation of virus receptor for successful transmission. In B. tabaci, such structural details are poorly understood. This study was performed to determine the details of the digestive organs of B. tabaci.

Ultrathin sections from important regions of the digestive tract of the insect were prepared and studied by electron microscopy according to a conventional procedure (Cristofoletti et al., 2003). After dissection of the alimentary tract, the tissue was fixed in Karnovsky solution and Osmium tetraoxide, 8 and 1.5 hours, respectively. After rinsing in sodium cacodylate buffer, the tissue was dehydrated in successive alcohols grades. Then the tissue was embedded in resin and ultrathin sections (50 nm) were prepared using a U3 ultra-microtome. These sections were stained in Uranyl acetate and Lead Citrate then were examined by a Philips CM10 electron microscope. Alimentary canal of B. tabaci was dissected in a few drops of 260 mM NaCl buffer located on a microscope slide on top of an ice block. Dissected tissues were homogenized in a motorized potter-elvehjem homogenizer (Teflon pestle, 0.1 mm clearance) for 3 minutes at 500 rpm. Enzyme assay methods were according to (Allahyari et al., 2010). Briefly, α and β-glucosidase activity were measured using 5 mM α and β-D, 4-nitrophenyl glucopyranoside in 50 mM citrate– phosphate buffer pH 5.0, respectively, based on the appearance of p-nitrophenol in the solution. Protein concentration was measured according to the method of Bradford (1976), using bovine serum albumin (Bio-Rad, Munchen, Germany) as a standard.

Observations showed that ascending and descending midgut are composed of thick epithelial cells with microvilli (MV) extending into the large lumen. These microvilli appeared to join each other and tighten by trabeculae. Furthermore, the Modified Premicrovillar Membranes (MDPMV) are sent into the lumen through the inter-lamellar space in the form of small vesicles between microvilli (fig. 2, A). These membranes are synthesized in Golgi cisternae and then fused whit with the microvillar membrane at the base of microvilli. Based on our knowledge this is the first report describing MPMV in B. tabaci. The receptor position for begomoviruses is probably on microvillar membrane as reported by other vectors however, MDPMV may have some roles in virus transmission processes. In order to study the possibility of isolating these membranes, we measured the activity of membrane-bound enzymes, α and β- glycosidase reported in other Hemipetran insects (Silva et al., 1996). Assessing specific activities of these enzymes showed that they were not present or active in B. tabaci gut. The specific activity of α and β- glycosidase in the gut homogenate of B. tabaci were 0.34 and 0.053 mU/mg protein whereas in Eurygaster integriceps first part of midgut homogenate mean specific activity of these enzymes were 316.97 and 27.93, respectively (Allahyari et al., 2010). Previous research also found that other enzymes may be involved in trehalose formation and decreasing osmotic pressure due to high sucrose concentration in phloem sap (Salvucci, 2000).

Binding sites of the virus particles on an inner surface of the alimentary canal, which most probably has a role in the absorbing region of this organ, the midgut and the inner surface of the midgut are covered by microvilli. Thus the virus particles firstly must be bind to the microvillar membrane. Glycoproteins and other transmembrane proteins are possible binding sites. Modified perimicrovillar membranes also may have an important role in virus transmission and digestion. In the process of digestion free amino acids that are abundant in phloem sap are trapped in the MDPMV and in this way making amino acid absorption easier by increasing the concentration of amino acids (Cristofoletti et al., 2003). In order to study the physiology of virus interaction with midgut, it is necessary to isolating microvillar and perimicrovillar membrane. Investigations using other candidate enzymes like aminopeptidase and also lectin binding properties are powerful markers to isolate these membranes for future studies.

Herbicides that persist in soil are of benefit to farmers seeking to control late emerging weeds in cultivated crops, and to managers looking for long-term vegetation control on rights-of-ways and industrial sites. Herbicides that persist in soil can also create problems for farmers who want to diversify their rotation into subsequent crops which may be sensitive to certain herbicide residues. Several factors mainly soil factors, climatic conditions, and herbicide properties determine the herbicides persistence in soil. Trifluralin is one of the important soil applied selective, pre-sowing or pre-emergence herbicide used to control many annual grasses and broadleaf weeds in a large variety of crops. It is a generally regarded as a moderately persistence herbicide with a half-life time of 1.5 to 6.5 months. Some studies, however, have reported higher half-life times varying from 7.5 to longer than 12 months. These results have been generally obtained at sites with very dry or very cold climates in which soil is frozen over winter. Normally Residual herbicides extend the period of weed control, increasing the efficiency of weed management practices. However, they may persist longer than desired and injure or kill subsequent rotational crops. Thus, most herbicide labels include crop rotation guidelines, but rotational restrictions are often not listed for many crops. This experiment was carried out to determine trifluralin soil persistence affected by its dose and application some organic and biofertilizers.

In order to study the effect of some organic and biofertilizers on trifluralin herbicide persistence in soil, an experiment was conducted as a factorial arrangement in completely randomized block design with three replications in a cotton field at Ferdowsi University of Mashhad. Experimental factors included trifluralin (EC 48 %) dose at two levels (480 and 960 g a.i. ha-1), application of organic fertilizers at two levels (Humic acid (85 %) and folic acid (12 %) and biofertilizers application at two levels (Nitroxin and fertile phosphate2). To determine the trifluralin soil residue, soil samples were taken from 0 to 10 cm soil depth during 3, 7, 15, 30, 60, 90 and 120 days after herbicide application and were kept in a freezer (-18 oC). For trifluralin soil residue, gas chromatography technique was used. The trifluralin value recovered from soil at different time intervals for each treatment was fitted in the first order kinetic equation according to:C = C0e–kt                                                                                                                                                     (1)
Where C denotes the amount of trifluralin recovered from soil at time t, C0 is the amount of trifluralin recovered at t = 0 interval; λ represents the degradation constant, and t is time in days. The DT50 (half-life) and DT90 (the time required to disappear 90 % of herbicide) were calculated as follows:                                                                                                                      (2)
                                                                                                                    (3)

Results showed that application of organic and biofertilizers significantly reduced trifluraline persistence in soil. The lowest trifluralin half-life time was observed for organic and bio-fertilizer application equal to 55.26 and 41.26 days, respectively, at the dose of 480 g a.i ha-1 of trifluralin. The highest half-life times equal to 106.64 and 78.77 days were observed in control treatment without application of fertilizers for the trifluralin dose of 960 and 480 g. a.i ha-1, respectively. Application of organic and biofertilizers plays important role in reducing of trifluralin soil residue and persistence. Therefore, the mentioned fertilizers have positive effects in fields where there is a risk of damage of trifluralin residue for rotational crops.

Onion (Allium cepa L.) is a monocot and bulbous perennial plant belongs to the Amaryllidaceae family. It is one of the most important crops in Iran and Southern Kerman. The total area cultivation of this crop is about 63 thousand hectares in Iran and 7.5 thousand hectares in Southern Kerman. Weeds are one of the greatest limiting factors in crop production. Onion is more susceptibility to weed competition in compared to many crops due to its inherent characteristics such as slow germination, extremely slow growth in the early stage, non-branching habit, sparse foliage and shallow root system. Weed competition can reduce average onion yield by 46- 86% compared to weed-free control. The most important weeds of onion fields in Iran are Alopecurus spp, Avena fatua L., Bromus spp., Dactyloctenium aegypticum (L.) P.Beauv, Echinochloa colonum. (L.) Link, Cyperus esculentus L., Cynodon dactylon L. Pers., Hordeum spp., Lolium spp., Setaria viridis L. Application of herbicides is the most prevalent method of weed control in onion fields. Oxyfluorfen, oxadiazon, ioxynil, clethodium, haloxyfop-r-methyl ester, sethoxydim, and cycloxydim are the commonly used herbicides for weed control in onion fields in Iran.

In order to study the efficacy of herbicides to control narrow leaf weeds of onion fields, an experiment was conducted at South Kerman Agricultural and Natural Resources Research and Education Center, Jiroft, during 2016- 2017 growing season. Plots were located on a sandy loam soil with pH 7.4. Experiment was carried out in randomized complete block design with 4 replications. Treatments included clethodium (Elective 24% EC) at 1.2 lit ha-1 equivalent 288 g a.i. ha-1, clethodium (Superpower 12% EC), at 1.2 lit ha-1 equivalent 144 g a.i. ha-1, clethodium (Select 24% EC), at 1.2 lit ha-1 equivalent 288 g a.i. ha-1, haloxyfop-r-methyl ester (Gallant-Super 10.8% EC) at 750 ml ha-1 equivalent 81 g a.i. ha-1, sethoxydim (Nabu-S 12.5% EC) at 2 lit ha-1 equivalent 375 g a.i. ha-1, cycloxydim (Focus 10% EC) at 2 lit ha-1 equivalent 200 g a.i. ha-1 ,and hand weeded as control treatment. Broadleaf weeds were hand removed during the season. The herbicides were applied 30 days after planting of onion transplants when onion plants were at the 3–4 leaf stage and weeds were at 5–10 cm in height. The herbicides were applied using a Matabi sprayer equipped with an 8002 flat fan nozzle tip delivering 350 L ha-1 at 2 bar spray pressure. Weed density and dry weight were determined in a 0.70-m2 quadrate per each plot randomly. Fresh weight of onion bulbs was recorded for a 2.5-m2 quadrate per each plot. Statistical analysis of data were done by SAS ver.9 and comparison of means were tested using the LSD test at 95% level of significant.

Dominated narrow-leaf weeds were Polypogon monspeliensis L., B. tectorum L., Phalaris brachystachys L., L. perenne L., Lophochloa phleoides (Vill.) Reichb, E. colonum (L.) Link, H. murinum L., A. fatua L. Visual observation confirmed that the most of the weeds were effectively controlled by herbicide treatments. The statistical analysis of the data on the weed density and biomass indicated that herbicides in onion significantly decreased the weed density and biomass. Results also showed that application of Focus, Select and Gallant-super provided excellent control of the dominant weeds. These treatments reduced biomass of P. monspeliensis, B. tectorum, P. brachystachy, L. perenne and total weeds more than 94%. Application of Superpower and Elective reduced weed biomass in B. tectorum about 75% and 68%, respectively. The results also showed that the weed biomass of P. monspeliensis were decreased about 80% and 79% using Superpower and Elective, respectively. The decreasing effect for Superpower and Elective on weed biomass of L. perenne and P. brachystachy were about 79 and 75%, respectively. The effect of Superpower and Elective on total weed biomass were approximately 80 and 71%, respectively. Onion yield in the plots treated by Focus, Select and Gallant-super increased about 250%. Onion yield for Superpower and Elective treatments was 55 and 46 ton ha-1, respectively, that showed an increasing in yield approximately 201% and 162%, respectively.

Results showed that the best herbicide treatments were Focus, Select and Gallant-super. These treatments decreased density and biomass of weeds and increased onion yield. In general, Superpower was superior to Elective in control of the dominant weeds and increased onion yield.

Tillage is one of the most important causes of soil erosion in croplands that affects productivity and inflates the cost of production. Recently, in order to enhance sustainability without compromising land productivity, there has been a growing trend toward conservation agriculture. No-tillage (NT) as one of the components of conservation agriculture is a planting system in which soil  dose not disturb and mulch cover remain from previous crop at least in 30%. It has revolutionized agricultural systems because it allows farmers to manage greater amounts of land with reduced energy, labor, and machinery inputs. Minimum tillage systems, such as shallow or surface tillage and direct drilling or no-tillage (NT), increase the degree of soil cover and increase organic matter at the soil surface over time. In specific soil types and climates, this can lead to an improvement of the soil physical condition. Improvement of the biological and physical quality of the surface soil can also help to protect the soil resource against redistribution and erosion. NT cropping systems frequently suffer from weed infestations, especially those of weedy annual grasses. The timing of competition in NT systems may differ from that in conventional systems. Rottenly, a combination of relative crop yield and specific input costs (i.e., fertilizer and pesticide) are considered as key determinants to the profitability of adopting minimum tillage systems. Our understanding of weed community dynamics and suppression in NT systems is limited, particularly in long-term rotations. Winter annuals, biennials, and perennials are typically associated with NT systems because of their affinity for non-disturbed soil environments. The vertical distribution of viable weed seeds in the soil profile is shallower in NT systems than in intensive-tillage systems. Weed seeds remaining at or near the surface are more susceptible to predation and disease, which may deplete the seed bank over time. NT is dependent on herbicides because of the elimination of tillage for control of weeds.

A three-year field study was conducted to assess the efficacy of weed control in barley-cotton-wheat rotation under no-tillage system in the agricultural research station of Gonabad, Khorasan-Razavi province, Iran over 2014-2016 seasons. The experiment was arranged in a split plot design based on completely randomized block design with three replications. The main plot was crop residue (left on the ground from previous crop in rotation) in three levels;no residue, 30% residue (1200 kg ha-1) and 60% residue (2400 kg ha-1. The subplot was weed control methods in three levels; (weed infest control, weed free control and chemical control. In chemical control treatment, we applied 2,4-D+ MCPA  at dose of 1.0125 lit a.i. ha-1 for controlling broad-leaved weeds and pinoxaden (Axial® 10% EC) at dose of 67.5 g a.i. ha-1 for controlling narrow-leaved weeds in barley and wheat, and trifluxysulfuron-sodium (Envoke® 75% WG) at dose of 11.25 g a.i. ha-1 in cotton. For barley, the wheat residues were left from wheat planted a year before in rotation. Plots size were 3m×10m. Barley (var. Nosrat), cotton (var. Khordad) and wheat (var. Parsi) planted by direct seeding equipment with no tillage.

Cardaria draba and Malcolmia africana in barley, Acroptylon repense and Alhagi pseudalhagi in cotton and A. repense in wheat were dominant weed species from the beginning to the end of the study. Results showed a remarkable change in weed flora from mostly annual weeds (like M. africana) to perennials (like A. repense), because of the fact that no tillage system was deployed. For barley, application of 2, 4-D + MCPA significantly decreased weed dry weight and density compare to the weedy check. Residues showed no significant effect on biological and seed yield of barley. For cotton, the effect of trifluxysulfuron-sodium was significant on decreasing the density and dry weight of A. repense 30 days after spraying and in the end of the season as well. Effect of residue levels (30% or 60%) was not significant on the density and dry matter of A. repense in the early and at the end of the season as well. Trifluxysulfuron-sodium significantly increased cotton dry weight compare to the weedy control. Dry weight of cotton in hand weeding control and application of trifluxysulfuron-sodium treatments were significantly higher than that of weedy control. Residues showed no significant effect on cotton boll dry weight. For wheat, application of 2, 4-D + MCPA significantly decreased weed dry weight and density compared to the weedy control. Residues showed no significant effect on biological and seed yield of wheat.

No-tillage system by at least 30% (1200 kg ha-1) up to 60% (2400 kg ha-1) of residues spread on the soil surface can be recommended to be deployed besides a suitable chemical weed control management in barley-cotton-wheat rotation in semi-arid climate conditions to enjoy the benefits of no tillage system of agriculture.

Weed distribution studies are useful not only for increasing in herbicide application efficiency but also for evaluating and designing the agronomical approaches and weed management strategies. Community assembly theory provides a useful framework to assess the response of weed communities to agricultural management systems and to improve the predictive power of weed scientists. Under this framework, weed community assembly is constrained by abiotic and biotic ‘‘filters’’ that act on species traits to determine community composition. Weed management practices vary between conventionally and organically managed systems. The main filter in conventional systems likely would be herbicides, which are strong filters that select tolerant species against susceptible species. , Other filters like fertilizers also represent potential filters on weed community assembly. Therefore, this experiment performed in order to determine species and functional diversity and weed community structure in the soybean fields in two plain and mountain regions, which located in Neka and Galugah counties in the east of Mazandaran province.

In order to arrange the experiment, two Neka and Galugah counties were selected in the east of Mazandaran province. In Neka, all the experimental fields were in the plain but in Galugah some fields located in the plain and some in the mountain regions. According to the potential of selected field, sampling were done in five to nine points in each field. The total area sampled was 2820 ha and systematic sampling method was done at the stage of fourth growing nude (V4) in 2018. The size of quadrates was 0.5×0.5 m. For each species recorded in the quadrates, density, frequency and their evenness were measured. Shannon index was used to estimate of diversity. Sampled plants categorized on the four functional groups; life cycle, morph type, photosynthesis pathway and insistence degree. In some collections belongs to multivariate data, variables naturally divided in two groups. In this situation canonical correlation analysis (CCA) be used for determination relationships between them.

Overall, 47 weed species from 23 families were recognized. Asteraceae and Poaceae families each with eight species had the most species richness. The frequency of annual and perennial weed species were 33 and 13 plants, respectively. In mountain fields, broadleaf weed species was more because herbicide was not used. Because benefiting of low temperature in mountain fields, C3 plants had more share relative to C4 ones. Shannon index in the mountain region (Hm=1.13) was estimated more than the plain region (Hp=1.04), this subject related to further sustainability. Less weed density in the plain fields it seems arise from role of cultivation. The plain region had low species richness because agronomical managements possess intensive effects on the weed frequency and diversity. In this place, herbicides were the most important agents. The studies often have shown that perennial weeds are more in the fields in which they are applied minimum tillage or exist in cold places. This subject is caused from preservation food resources in the reserves organs. Johnson grass had more density in the plain relative to mountain regions, which its reason related to segment their rhizomes. Many species correlated with Min tillage have seeds which spread with wind. For example, Dandelion, Grinning swallow and Prickly lettuce observed only in the mountain. Using crop cultivars with high compatibility has a special role in reduction yield loss. So that characteristics such leaf area and plant height have straight link with competition ability. In this study cultivars such as 033 and JK were used (full leaf and tall). From 12 species that only observed in the plain, barnyard grass, goose grass, ground cherries, garden purslane and common heliotrope completely adapted to the warm and humidity conditions that existed in this region. Using CCA to analysis the relationship of site and functional groups confirmed that the majority species in the mountain regions were dicotyledonous, C3 and annual species.

Our conceptual framework proposes showed that weed community assembly in the soybean fields affected by a series of filters, such as herbicide, tillage, cultivars, fertilizer and temperature. Generally, different management in two regions for a long time as agronomy filters affected weed density and their composition. Our results suggest that the effects of crop management factors are more important than the environmental factors on soybean weed composition in a county-wide context even for intensified agriculture.

Weed management is one of the most important aspects of successful crop production for supplying food needed for the rising population. Johnsongrass (Sorghum halepense L.) is among the most noxious weeds in the world due to its superior biology and tremendous ecological adaptations. It causes substantial yield loss in different field crops including corn, soybean, wheat, and sorghum. Therefore, management of Johnsongrass is crucial for optimum crop production. Prevention by clean cultivation, cultural management by using weed-competitive, mechanical management by hand hoeing, biological management by applying pathogens, and eventually applying herbicide as chemical management can be used for controlling Johnsongrass. Chemical management is an effective method to control Johnsongrass. For decreasing adverse effects of herbicide and costs of production, optimizing herbicides performance is very essential. It appears that the use of adjuvants seems to be a best solution to achieve optimized herbicides performance. In spite of these advantages, some synthetic adjuvants have shown side effects on living organs. Therefore, using environmentally safe adjuvants is a key point for applying this technology. This study was conducted for evaluating vegetable oil effects on Johnsongrass control by sethoxydim herbicide.

To study the effects of vegetable oils on the performance of sethoxydim on Johnsongrass (Sorghum halepense L.) control, a factorial experiment based on completely randomized design including sethoxydim concentration at six levels (0, 46.875, 93.75, 187.5, 281.25 and 375 g ai ha-1) and vegetable oils at 8 levels (with and without corn, olive, grape seed, cumin, fennel flower, mint and sunflower oils) with four replications was conducted in the research greenhouse of college of agriculture Birjand university in 2017. For increasing seed germination and breaking seed dormancy of Johnsongrass, the seeds were treated by sulfuric acid for 3 min and then washed by tap water for 30 minutes. The seeds were then sown in potting trays (3 cm × 3 cm × 5 cm) filled with moistened peat. One week after sowing, at the one-leaf seedlings stages, they were transplanted to plastic pots with 2 liter volume and filled with a mixture of sand, clay loam soil, and peat (1:1:1; v/v/v). The pots were sub-irrigated every two days. The seedlings were thinned to four per pot at the two-leaf stage. Spraying was done at the four-leaf stage by using a chargeable sprayer equipped with an 8002 flat fan nozzle tip delivering 250 L ha-1 at 2 bar spray pressure. Four weeks after spraying, height of plant was measured and then the shoots and roots of plant were harvested and weighed immediately after the root volume was measured. The plant parts were oven-dried and reweighed.

When emulsified vegetable oils alone were sprayed against Johnsongrass, none of vegetable oils had phytotoxic effects on plant height, fresh and dry weight of shoot and root, root volume and root length of Johnsongrass (Table 2). This finding was similar to the results of Tworkoski (2002) (42) and Izadi darbandi et al (2013) (17). The ED50 parameter was estimated by dose response model based on Johnsongrass plant height, shoot and root dry and fresh weight, and root volume. All emulsifiable vegetable oils improved significantly the effectiveness of sethoxydim on Johnsongrass. Relative potency in the presence of corn, olive, grape seed, cumin, fennel flower, mint and sunflower oils was 1.30, 1.57, 1.18, 1.23, 1.27, 1.24, and 1.07 times for plant height, 3.75, 1.49, 1.59, 3.52, 2.93, 1.81, and 2.58 times for shoot fresh weight, 2.63, 1.30, 1.35, 2.57, 1.99, 1.48, and 1.86 times for shoot dry weight, 2.21, 1.27, 1.47, 2.09, 1.67, 1.82, and 1.71 times for root dry weight, and 1.74, 1.56, 1.55, 2.13, 1.58, 1.38, and 1.41 times for root volume, respectively, as compared to the condition without vegetable oils. Among emulsifiable vegetable oils, the highest effect on shoot and root dry weight was observed in corn and cumin oils while olive oil showed the lowest effect.

Our result showed that vegetable oil including corn, olive, grape seed, cumin, fennel flower, mint and sunflower oils had not only the phytotoxic effects on produced biomass by Johnsongrass, but also improved the performance of Sethoxydim for Johnsongrass control. Therefore, using vegetable oils mixed with sethoxydim can decrease the adverse impacts of this herbicide on the environment.

The light received by plants is composed of different types of wavelength, ranged from ultraviolet to infrared. The range between 400 nm and 700 nm is used by plants to drive photosynthesis and is typically referred as to Photosynthetically Active Radiation (PAR). Plants are very good filters of light. They absorb and use most of the R light available to them for photosynthesis, but reflect or transmit most of the FR light, since FR light is not useful in photosynthesis. As a result, the ratio of R: FR will be decreased. Red to far red ratio (R: FR) is considered as an indicator of the quality of light. Recent physiological studies indicate that plants can perceive the quality of light reflected from neighbors as an accurate predictor of future competition, and respond morphologically even before they are directly shaded. Understanding the loss of quality of light, and taking away red wavelengths, creates a series of reactions in the plant such as stem elongation, reduction in stem diameter, and a reduction in shoot and root biomass and so forth that are known as shade avoidance syndrome (SAS). In this study, we established a pot experiment to evaluate the effects of time, number and type of neighboring plants on shade avoidance mechanisms in red bean.

In order to investigate the effects of the neighboring plants consist of Phaseolus vulgaris, Zea maize, Amaranthus retroflexus and Chenopodium album with Phaseolus vulgaris (as target plant), a pot experiment was conducted in Ferdowsi University of Mashhad during spring and summer in 2016. The experiment was designed as a factorial with three factors and four replicates based on a randomized complete block design. The first, second, and third factors were, respectively, the duration of the neighboring period of the plants with red bean (15, 30 and 45 days), the number of plants neighbors with red bean (1, 2 and 3 plants), and the type of neighboring species with red bean, including Phaseolus vulgaris, Zea maize, Amaranthus retroflexus and Chenopodium album. The plants were planted, watered, fertilized and treated carefully. After completing the neighboring time for each treatment, all plants neighbored with target plant (central) were removed and the target plant remained to grow. This work was performed 15, 30 and 45 days after planting. At third stage (45 days of neighboring), after removing the third groups of neighboring plants, all target plants were harvested and some morphological traits such as plant height, number of branches, leaf dry mater, shoot dry mater were measured. Finally, all statistical analyses were performed using SAS 9.1 ((SAS Institute, Cary, NC)) with a type 1 error rate set at P ≤ 0.05.

The results of this experiment showed that among all the investigated factors, the duration of neighboring plants had a significant effect on most traits. Only leaf dry matter reacted to the number of neighboring species and also none of the traits was affected by the type of species. The comparison of means test related to the neighboring duration factor showed that among time of neighboring with central plant (15, 30 and 45 days), third treatment i.e. 45 days neighboring had the significant impact on most of the traits. The amount of plant height for time of 15, 30 and 45 of neighboring was 32.1, 35.2 and 41.2, respectively, demonstrating that time of neighboring is a vital factor in shade avoidance mechanism, regardless of type and number. In this experiment, neighboring did not affect lateral shoot. However, further assessment showed that the lateral shoot is a gene-based trait and the number of lateral shoot is constant. But neighboring time influenced the rate of lateral shoot number per height. The amount of that for the trait of 15, 30 and 45 days neighboring was 0.49, 0.46 and 0.38, respectively. In fact, the continuity of presence of neighboring plants besides the central plants is considered as an effective factor in the appearance of shade avoidance mechanisms. In this experiment, the presence of neighboring species type was one of the evaluated factors assumed to have different influences on shade avoidance mechanisms in beans. Considering that in shade avoidance mechanisms, the biomass volume produced by a plant is considered as reflection of farther red light with higher impact on neighboring plant, but the species treated has no effect on shade avoidance mechanism on red bean. Finally, the quality of light is more strongly affected, with increasing the number of neighboring species. This should be sensitive to the occurrence of shade avoidance mechanisms from the central plant, but number of species did not significantly impact trait.