فصلنامه مطالعات حفاظت گیاهان
سال سی و دوم شماره 4 (زمستان 1397)

Maize (Zea mays L.) is one of the most widely cultivated crops worldwide. More than 40 viruses can infect sweet corn. Maize dwarf mosaic virus (MDMV) is a positive-sense single strand RNA potyviruses that cause significant crop yield loss in susceptible sweet corn varieties. Infected young leaves by MDMV show chlorotic spotting which may eventually turn into a mosaic or mottled pattern. Approximately two-thirds of maize varieties are susceptible to MDMV infection, and even young resistant plants may be infected to the virus at 2-3 leaf stage. These symptoms vary greatly depending on the host genotype, time of infection, and on the strain causing the injection. However, the precise molecular details of maize responses to MDMV infection are largely unknown. In sensitive and tolerant plants during viral infection, the expression level of defense -related genes are altered based on plants ability to recognize pathogen attack. The elevated expression of defense-related genes such as SAMS and G-box factor 14-6 (GF146) leads to production of resistance proteins which are considered as molecular response of maize to variety of biotic stresses. The production of resistance proteins and the enhanced expressions of Peroredoxin, SAMS, G-box factor 14-6 (GF14- 6), and other genes are considered as typical responses in maize varieties. Proteomic analysis in susceptible and tolerant maize seedlings infected by sugarcane mosaic virus showed a high expression of 96 different proteins. In this study, the expression level of some defense genes including Germin like protein (GLP), Peroxiredoxin (Prx), GF14-6 and Sadenosylmethionine synthase (SAMS) was investigated in both susceptible and tolerant maize genotypes against MDMV at different times after inoculation by qRT-PCR. The seed of SC705 cultivar and the number of hybrid number 8 (KLM75010/4-4-1-2-1- 1-1×MO17) were used as susceptible and tolerant cultivar to MDMV, respectively. All the seeds were sterilized with chloramine T (3%), washed three times with distilled water and then grown in a greenhouse under controlled conditions at 25°C. Leaves of infected plants by MDMV showing macroscopic symptoms were homogenized in phosphate buffer (pH 7.2, 0.06 M) and were used for inoculation using carborundum. The leaves of mock-plants were mechanically injured and infected with phosphate buffer. Sampling was done at 5-time intervals including 0, 1, 9, 24 and 72 hours after plant viral infection. Total RNA was extracted from the leaf tissue and further treated with RNase free DNaseI to eliminate any DNA contamination. Reverse transcription reaction was performed using M-MuLV reverse transcriptase. Gene expression analysis was done using qRT-PCR method by an iCycler instrument (iQ5, BioRad, USA) using SYBR Green PCR MasterMix and the relative gene expression was calculated according to ΔΔCT method according to the Pfaffl method. The reaction of PCR was carried out at 50 °C for 2 min, 95 °C for 10 min, followed by 40 cycles of 95 °C for 15 s, 59 ºC for 20 s, and 72 ºC for 20 s. Reactions were finished with a dissociation step, starting at 55°C to 95 °C by increasing 0.5°C per cycle for 80 cycles. Symptoms of infected susceptible and tolerant plants were monitored for 20 days post inoculation (dpi). The success of infection was verified using the ELISA technique. All the susceptible SC705 cultivars showed visible mosaic symptoms at 16 dpi to MDMV while 8-hybrid plants showed mild mosaic symptoms at 19 dpi. Gene expression analysis showed that the expression level of all tested genes was significantly increased in tolerant maize in comparing with susceptible maize plants. One hour after maize inoculation an increase of expression level was seen for all tested genes. Peroxiredoxin and GLP were up-regulated at 1 hpi and then decreased over time. SAM and GF14-6 were up-regulated in the all-time intervals but the highest expression level was noted at 24 hpi. The lowest expression level for all tested genes was observed at 72 hpi. In the other word, the expression levels of SAM and GF14- 6 genes were elevated in a moderate rate with a continuous increase in the infected maize from first time point after inoculation until last time point of sampling. The rapid induction of defense-related genes is required to activate defense mechanisms and respond to against pathogens attacks. In this research, we tested the expression profile of four genes which have been defined as important proteins related to disease and stress signals. Based on these results, we can conclude that tested genes in this research could be suitable as biomarkers for the selection of tolerant or relatively tolerant maize cultivars against MDMV. Among them, GLP gene was more efficient as a screen able marker.

The plant parasitic nematodes are among the most important agents causing losses in agricultural crops (Nicol et al. 2013). The golden cyst nematode, Globodera rostochiensis (Wollenweber, 1923; Behrens, 1975) is the most destructive nematode of potato in the world (Brodie, 1984). Chitin is the most abundant polymer in structure of nematode eggshell. Chitinases are widely distributed in fungi and play important roles in degradation of chitin. The aim of this study was to assay chitinase activity in 16 isolates of various species of Fusarium obtained from golden potato cyst nematode, Globodera rostochiensis. In the current study, 16 Fusarium isolates were recovered from infected eggs of the golden potato cyst nematode, G. rostochiensis. These isolates were identified based on morphological (Seifert, 1996) and molecular features including internal transcribed spacer (ITS) regions (ITS1, ITS2 and 5.8S gene) of ribosomal DNA. Total genomic DNA was extracted from lyophilized mycelia with a QIAGEN DNeasy Plant Mini Kit (Germany). ITS regions of ribosomal DNA were amplified with the ITS1 (forward primer) and ITS4 (reverse primer) primers. PCR amplifications were performed with total reaction volume of 25 μl using a Takara EmeraldAmp GT PCR Master Mix. PCR products were separated by electrophoresis technique using 1% agarose gel in 1X Tris-Borate-EDTA (TBE) buffer by adding 12 μl SYBR-safe 10,000X concentrate DNA stain to melted agarose before running the gel and finally visualized under ultraviolet illuminator. The ITS1, ITS2 and 5.8S sequences were obtained by sequencing both strands in opposite directions using the PCR amplification primers, ITS1 and ITS4 in genomics resource laboratory at Massachusetts University, USA. Colloidal chitin was prepared using the procedure of Tikhonov et al. (2002). For enzyme assay in liquid media, the 16 isolates were grown in minimal synthetic medium (MSM) containing colloidal chitin (1 g l-1) based on the method described by Zeilinger et al. (1999). The culture medium was filtered through Whatman paper No. 3 filter followed by filtration through 0.2-mm Millipore polydifluoropropilene membranes. The filtrate obtained was analyzed for chitinolytic activity. Chitinase activity was determined by measuring the release of reducing saccharides from colloidal chitin by the N-acetyl-glucosamine-dinitrosalicylate method according to the method described by Monreal and Reese (1969). Protein concentration was determined according to Bradford (1976) with bovine serum albumin (Sigma) as the standard. Chitinase specific activity was obtained by dividing the enzyme activity rate by total protein mass. Enzyme assay was done to determine the most promising isolates for biological control of G. rostochiensis in 24 and 96 h after fungal growth. The chitinase specific activity data was subjected to analysis of variance (ANOVA) using software SAS, version 9.0 (Statistical Analysis System Institute Inc., USA) in a CRD (completely randomized design) with three replicates. Two selected isolates were assayed using a chitinase assay, fluorimetric kit-CS1030 (Sigma). The assay included three substrates, 4-Methylumbelliferyl N,N′-diacetyl-β-D-chitobioside, 4-Methylumbelliferyl N-acetyl-β-Dglucosaminide and 4-Methylumbelliferyl β-D-N,N′,N′′-triacetylchitotriose for the detection of the chitinolytic isozymes Chitobiosidase, β-N-acetylglucosaminidase and Endochitinase. The experiment was a randomized complete block design (RCB) with three replicates. Chitinase activity was subjected to analysis of variance using software SAS, version 9.0. Enzyme activity was expressed over time using the Logistic-Peak, software Slide Write, version 2.0. Two isolates (the strongest and weakest ones) were selected to determine the optimum conditions for chitinase production. The measured conditions were pH, temperature and reaction time between enzyme and substrate in a N-acetyl-glucosaminedinitrosalicylate method. According to measurements taken by an enzyme activity assay kit, the fourth day (96 h) showed the highest activity for the two selected isolates. We then tested our two isolates at pHs of 3, 4, 5, 6, 7, 8 and 9, temperatures of 22°C, 25°C, 28°C, 31°C for differing periods of time (1 h, 6 h, and 24 h). The experiment was based on factorial experiment in a completely randomized design with three replicates. Analysis of variance chitinase activity was performed using SAS 9.0 software. Among 16 isolates, F12 (1/02 U/mg) and F15 (0/04 U/mg) had the maximum and minimum amount of specific activity, respectively. According to morphological features and sequencing of ITS regions (ITS1, ITS2 and 5.8S gene) of ribosomal DNA, these 16 isolates were classified in three species i.e. F. solani, F. oxysporum and F. equiseti. The optimum conditions to produce chitinase in isolates of F12 and F15 were pH=6, 96 hours after fungal growth in 25°C and the reaction between the enzyme and substrate during one hour achieved by the N-acetyl-glucosamine-dinitrosalicylate method. As a producer of various chitinase enzymes, the filamentous fungus, Fusarium spp. seems to be recommendable to biologically control Globodera rostochiensis.

Tan spot (Pyrenophora tritici-repentis) is one of the most destructive leaf diseases that causes significant damages to wheat during epidemic periods. The application of fungicides is a rapid control practice of the disease during epidemic periods. Under the Integrated Management of Diseases (IDM), fungicides application for controlling leaf diseases is recommended based on disease level (disease pressure), plant growth stages, and only for susceptible cultivars. Several fungicides have been proposed for controlling tan spot, but the efficiency of recommended fungicides is effective when they are used to reduce the disease pressure on important plant leaves especially flag leaf. According to growth stages, four timing have been recommended to fungicides application including, T0 (early stem elongation to node forming 1), T1 (node formation 2-3), T2 (the full flag leaf emergence) and T3 (flowering). The results of fungicides application at different growth stages of wheat are inconsistent and also there is no comprehensive study about the timing of fungicides application for controlling this disease in Iran. Therefore, the present study was carried out to determine the appropriate timing of fungicides application at four wheat growth stages. A field experiment was conducted in a split plot design with four replications. The main and sub-main factors of the experiment were cultivars (Karim and Koohdasht) and the spraying treatments, respectively, and common fungicides (such as Tilte, Folicur, Falcon, and Rexduo) were sprayed at four timings including, T0 (early stem elongation to node forming 1), T1 (node formation 2-3), T2 (the full flag leaf emergence) and T3 (flowering). The spraying treatments were as follows: one, two, three and four spraying times. The efficiency of spraying treatments was evaluated one week after the last spraying by determining the disease index (incidence, severity and area under the disease progress curve; AUDPC) and also comparing the yield and yield components. The results showed that spraying treatments from the full flag leaf emergence to flowering stages (Tr3, Tr5, Tr6, Tr8 and Tr9) decreased the values of AUDPC-I by 42.1 to 80.5% and 33 to 76.6% for Koohdasht and Karim cultivars, respectively, whereas the values of AUDPC-S decreased by 30.7 to 47% and 33 to 58% in Koohdasht and Karim cultivars, respectively. The effect of spraying treatments on damage reduction showed that the damage reduction ranged between 1.4-30.8% and 1.1-29.7% in Koohdasht and Karim cultivars, respectively. The highest damage reduction was observed at the full flag leaf emergence to flowering stages. The highest yield increase was observed at the full flag leaf emergence to flowering stages, which was more than 36% (1071.2 to 1298.9 kg/ ha) and 34% (1054.5 to 1313.8 Kg/ ha) in Koohdasht and Karim cultivars, respectively. The spraying treatments at the node formation stages had the least effect on the yield improvement, which were, respectively, 2.1-7.1% and 1.5-5% in Koohdasht and Karim cultivars. In both cultivars, the comparison of economic profit showed that treatment of Tr3 (flag leaf emergence stage), in addition to decreasing the disease severity and yield increase, and reduction of spraying costs had the highest economic profit compared to other spraying treatments (Tr6, Tr8 and Tr9). Spraying prior to the appearance of flag leaf stage (node formation) was not effective for reducing tan spot severity. The treatment of Tr3 (spraying once at the full flag leaf emergence stage), was the best timing of fungicide application for the disease pressure reduction, and the yield and economic profit increase. In addition to the timing and spraying frequency, the disease pressure reduction rate and yield enhancement, economic profit should be also considered to decide on spraying application.

Cotton whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) is one of the most critical pests of numerous agricultural crops including tomato especially under protected cultivation. The whitefly because of ingestion of phloem sap, secretion of massive honey dew that reduces both the quality of the tomato and the available leaf area for photosynthetic activities, and transmission of plant viruses is considered as destructive agent. Development of alternative methods for chemical compounds seems essential in pest management due to human health and environmental safety. Since plants are rich sources of active chemicals they may be a substitute for pesticides. Recent studies have shown that chemicals with insecticidal properties derived from plants are active against target specific species and are converted to non-toxic materials in environment. In the present study the effect of Calotropis procera (Willd.) R. Br. (Asclepiadaceae) extraction on demographic parameters of B. tabaci was evaluated. For this purpose four different extracts were prepared, using four different solvents (methanol, ethanol, acetone and hexan).The swallow wort plant, C. procera (Asclepiadaceae), is a shrub widely distributed in south of Iran (Haji Abad, Bandar Abbas, and Ourzoeiyh) and other parts of the tropics regions. The plant is erect, tall, large, branched and perennial with milky latex throughout. A large quantity of latex can be easily collected from its green parts. The essential oils and the extracts of this plant have insecticidal properties. Tomato seeds, Var. CH were planted directly in plastic pots filled with sterile plant growth media4 (BAGA; Dashte Sabz Atie Co. Iran). Cotton whitefly adults were collected from the Rafsanjan field and transferred onto 2-4 tomato leaves in a greenhouse. Adults of the same age were collected from red-eye pupae and moved to separate plant cages. These adults were used in all the experiments. The toxicity of C. procera for adults of cotton whitefly were assayed by the leaf-dip method. For bioassay, we applied five different concentrations in three replicates. Two clear plastic glasses (10 cm diameter, 15 cm height) were put together as a plant cage. The upper one was covered with a fine mesh and the lower one filled with distilled water. Two tomato leaves were dipped in the dilutions for 5s and put in each cage. After drying the treated leaflets, fifteen same age adults were released into the upper part of cage. Mortality was evaluated after 24 h and all of the experiments were carried out at 27±2 ºC, photoperiod of 16: 8 (L: D) and with the 50±5 % relative humidity. In this research, the effect of C. procera extraction with different solvents; acetone, ethanol, hexan, and methanol was studied on demographic parameters of B. tabaci on tomato. Data analyzed by Age-stage, two-sex life table analysis-MSChart software. The experiments were carried out in a completely randomized design (CRD) with at least four replications in controlled conditions. The collected data were analyzed by SPSS16 software and the means compared using Duncan’s test. The LC25 was estimated by probit analysis 2011 software. Graphs were drawn using SigmaPlot 11.0. Different biological parameters including pupa duration (F6,37= 4.49, P< 0.01) and female (F4,674= 23.649, P< 0.000) and male adult longevity (F4,575= 19.21, P< 0.000), sex ratio (male) (F4,10= 148.33, P< 0.000), sex ratio (female) (F4,10= 33.884, P< 0.000), oviposition period (F4,10= 13943.40, P< 0.000) and total fecundity/ female (F4,674= 31.450, P< 0.000),showed significant difference among extractions derived from various solvents of C. procera. The results showed that there are significant differences among treatments on net reproductive rate (R0 or NRR), intrinsic rates of increase (rm), finite rate of increase (λ), gross reproductive rate (GRR) and mean generation times (T) at the 5% probability level. The intrinsic rate of increase of the whitefly, in treatments control, and C. procera extraction by acetone, ethanol, hexan, and methanol solvents were 0.081, 0.030, 0.045, 0.054 and 0.043 respectively. All of the treatments compared with control reduced the oviposition period and the total number of eggs that laid each female. These two parameters were the least on acetone extraction of C. procera (0.59 and 3.093) and the highest on control (2.45 and 15.131) respectively. The results clearly indicate that the acetone and methanol extract of C. procera possesses many useful properties to control insect pests.

Bulb mites of genus Rhizoglyphus (Acari: Acaridae) have been identified as pest of many crops in storage, greenhouse, and field. The most important hosts are species of family Liliaceae (e.g. Allium spp.) Rhizoglyphus echinopus (Fumouze & Robin) (Astigmata: Acaridae) is one of the most important pest of gladiolus corms in Mahallat. The mites infest bulbs and corms by penetrating through the basal plate or outer skin layers. Bulb mites may establish in the inner layers, which makes control extremely difficult. Feeding wounds created by bulb mites provide entry sites for soil-borne fungal pathogens such as pythium, rhizoctonia and fusarium. Despite their economic importance and broad distribution, the control of R. echinopus remains in a state of confusion and needs a thorough evaluation. In addition, the field biology and ecology of this mite is not well studied, and methods for sampling, monitoring and assessment are limited. Management of bulb mites is complicated because of their short generation time, high reproductive potential, broad food niche, interactions with other pests and pathogens, and unique adaptations for dispersal. Historically, these pests have been controlled by synthetic acaricides and insecticides, which are now limited due to their resistance. Alternative control strategies, including cultural and biological control, have shown limited success, but need to be further developed and implemented. We evaluated the capacity of the soil-dwelling predatory mite, Hypoaspis (Geolaelaps) aculeifer (Canestrini) (Mesostigmata: Laelapidae), as well as disinfestations of corms to control attacking bulbs mite. The experiment was performed in 24 treatments and 3 replicates in randomized complete block design. Each plot was separated with plastic and its soil was sterilized by solarization. In addition, 30 gladiolus corms were cultivated in each plot. Disinfestations treatments (corms were soaked in poison solution for 25 minute) include: 1, 2 & 3- abamectin (0.4, 0.8, 1.2 ml/lit); 4, 5 & 6- ethion (1, 1.5, 2 ml/lit); 7, 8 & 9- fenazaquin (0.5, 1, 1.5 ml/lit); 10, 11 & 12- hot water (45°C for 25, 50 and 75 min); 13, 14 & 15- release of predator mite H. (Gaeolaelaps) aculeifer 10, 20 and 30 predator for every 100 Gladiolus bulb (previously infested with bulb mites); 16, 17 & 18- release of 100, 250 and 500 predator mites in square meter 15 days after planting; 19, 20 & 21- tap water as control treatments (30°C for 25, 50 and 75 min); 22- hot water (45°C for 25 min) and release 10 predator for every 100 gladiolus bulb; 23- hot water (45°C for 25 min) and release of 100 predator mites per square meter; 24- hot water (45°C for 25 min) and release 10 predator for every 100 gladiolus bulb and release of 100 predator mites per square meter 15 day after planting. Significant differences were found among treatments and with control (α= 0.5). In all cases, the population of predatory mites increased as long as bulb mite densities were not too low. Experiments in the greenhouse showed that in the absence of predatory mite, populations of the bulb mite, R. echinopus, on gladiolus corms increased, whereas population growth of bulb mite was slowed down as the predatory mite were released. The highest infestation severity was observed in treatments 19, 20 and 21 (control), while the lowest percentage of corms infestation were recorded in treatments 24, 23 and 22. The highest frequency of corms was produced in treatment 24, also the highest inflorescence length was found in treatments 13 and 24. The height length mean of gladiolus stem was observed in treatments 24, 23 and 13, respectively. The flowers in treatments 7, 14, 17 and 23 lived the greatest. The fastest germination rate was recorded in corms in treatments 24, 23, 22, 14, 15, 13 and 10, respectively. But the number of buds was statistically located in the same group and their differences were not significant. Based on the results and with respect to the gladiolus features, biological and integrated pest control methods could be recommended for reducing R. echinopus infestation.

Rice (Oryza sativa L.) is one of the most cultivated crop in northern Iran. The rice fields, is harbor a rich composition of insect fauna inhabiting vegetation, water and soil of the rice fields. The insects in this agro-ecosystems play different roles, some are herbivore and some other are natural enemies of herbivores. Ground beetles, Carabidae, are mainly predators and could effect on pest population as biological agent in different agro-ecosystems including rice fields. Since rice has been attacked by various pests, especially stem borer, Chilo suppressalis Walker (Lep.: Pyralidae), therefore identification and protection of the natural enemies in the field are important in reduction of pesticide applications. The Carabidae beetles as polypagous predators of many pests could also take attention in integrated pest management programs (IPM). Although this family is one of the largest family of beetles, it is studied very poorly in different agricultural ecosystems in Iran. Depending on crop and sequencing of growth stages of the crop in agricultural fields, ground beetles may vary among different species. Until 2015, 955 Carabidae species were recorded from different parts of Iran such as northern. For identification of active species of Carabidae in the rice field, present study was conducted. Several samplings were taken with pitfall traps at different growth stages of rice in a one-hectare rice field (Ahangarkola: a.s.l. 11 m, 36°, 30' N, 52°, 48' E) located in the Qaemshahr city (Mazandaran), in the 2015 -crop year. Every 10 days, the contents of pitfall traps were examined and transported to the laboratory and then, the number of the collected beetles were counted and recorded. The samplings were continued till two months after rice harvesting. Percentage of abundance and species diversity (Shannon-Weiner index) were calculated. The statistical tests were performed in Excel 2013. The Shannon-Weiner index was calculated by formula (Hʹ): Where pi is number of individuals of species i/total number of samples and Ln is natural basic logarithm. In sum, 16 species from 13 genera, nine tribes, and six subfamilies of Carabids beetles were collected and identified during crop seasons and two month after rice harvesting. The identified species were Acinopus (Acinopus) picipes (Olivier 1795) (1.18%), Bembidion (Trepanes) octomaculatum (Goeze 1777) (0.59%) and Elaphropus (Tachyura) lucasi (Jacquelin da Val 1852) (1.76%), from subfamily Trechinae, Brachinus psophia (Audinet-Serville 1821) (1.18%) from Brachininae, Pterostichus (Argutor) cursor (Dejean 1828) (11.76%), Pterostichus (Platysma) niger (Schaller 1783) (1.76%) and Poecilus cupreus (Linnaeus 1758) (25.88%) from Pterostichinae, Scarites (Parallelomorphus) subcylindricus (Chaudoir 1843) (0.59%), Clivina (Leucocara) laevifrons (Chaudoir 1842) (1.18%) from Scaritinae, Harpalus distinguendus (Duftschmid 1812) (0.59%), Harpalus (Pseudoophonus) rufipes (De Geer 1774) (27.65%) Anisodactylus (Pseudodichirius) intermedius (Dejean 1829) (0.59%), Acupalpus maculatus (Schaum 1860) (4.71%), Stenolophus abdominalis persicus (Mannerheim In Chaudoir 1844) (4.12%) from Harpalinae, Chlaenius (Epomis) amarae (Andrewes 1920) (11.76%) and Chlaenius (Amblygenius) dimidiatus (Chaudoir 1842) (5.29%) from Licininae. Among them H. rufipes with 27.65% and P. cupreus with 25.88% of all collected specimens were the most frequent species. They were present in all stages of plant growths in the rice field. The species of S. subcylindricus, B. octomaculatum, H. distinguendus, A. picipes and A. intermedius had the lowest frequency and seems to be occasional species in the rice field. Among 16 species, six species B. octomaculatum, C. amarae, P. cursor, E. lucasi, S. subcylindricus and A. intermedius were new for Mazandaran fauna. During the growing season until harvesting time, the highest number of insects and species were observed during reproductive growth and clustering stage in the field, although the comparison of Shannon-Weiner species diversity index did not show a significant difference for species diversity. The population of Carabidae was severely reduced one month after rice harvest, however their maximum abundance was observed two months after harvesting rice. The results of the present study indicates that due to the presence and appropriate diversity of the carabid species in the rice field as well as their predation activity, it is necessary to know more about the role of the carabid species in biological control of rice pests, specially rice stem borer, at future researches.

Weed management is a key topic in many farming systems. Nowadays, application of herbicides is the most common method to control wheat weeds and maximize yield. Modification of sprayer such as adjusting sprayer for producing droplet with suitable size and uniform can be considered to reduce herbicides usage. For this purpose, the volume median diameter (VMD), numerical median diameter (NMD) and uniform spraying ratio (VMD/NMD) = QC are the common factors. Other method to decrease herbicide usage in field is applying appropriate sprayer. Electrostatic, lance tractor, microner, atomizer and boom sprayer tractor are the common sprayer applying for controlling weeds in wheat fields. Among them, lance tractor sprayer is used at more than 70% of farms in the country. Tribenuron-methyl is a selective post-emergence herbicide for controlling broad leaved weeds in wheat fields. The product is absorbed and transferred by weeds stems and leaves to prevent cell division and kill weeds. Application should be carried out in early spring when weeds are actively growing. Tribenuron-methyl mode of action is inhibiting biosynthesis of the essential amino acids valine and isoleucine, hence stopping cell division and plant growth. Selectivity derives from rapid crop metabolism. Mode of action is rapidly absorbed by foliage and roots and translocated throughout plant. Susceptible plants cease to grow almost immediately after post-emergence treatment and are killed in 7-21 days. To evaluate common sprayer and different doses of tribenuron-methyl herbicide on broadleaf weeds of irrigated wheat, an experiment was carried out in field (with an area of 1200 m2) located in Hakimabad, Mashhad, Iran (latitude 58° 53' N, longitude 36° 46' E) during spring of 2014. The experimental design was split plots based on randomized completed blocks with four replications undertaken in plots with 50 m2 (5 × 10) area. The experimental treatments included the main factor with five types of sprayer (Electrostatic, Lance tractor, Microner, Atomizer and Boom sprayer tractor) and sub factor with applying tribenuron-Methyl herbicide (Giahstar, 75% DF, Ariashimi, Iran) at dosage of 15, 20 and 25 gr. ha-1. Broadleaf weeds were sampled in middle of the plots using 1 × 1 quadrate 10 and 20 days after spraying. The weeds biomass and density and wheat yield loss were then assessed. Samples were oven-dried at 75 °C for 72 h and then weighed. Final data were analyzed by SAS 9.1 and EXCEL. The results of experiment showed that both weeds density and weight were sigificantly reduced by boom sprayer, whreras the lowest efficiency was found for atomizer and lance sprayers. Further, wheat broadleaf weeds were better controlled by boom sprayer with 25 gr/ha tribenuron-methyl application resulting in an increase to 5050 kg/ha for wheat yield. As for solution consumption rate in one hectare, the difference between spraying methods was significant at level of 1%. The highest and lowest herbicide solution rates were found for tractor lance sprayer and microner with 732.8 and 34.9 l.ha-1, respectively. Quality coefficient (VMD/NMD) also was significant at 1% probability level. The best quality coefficients were obtained for tractor boom sprayer (VMD/NMD = 1.8) followed by microner (VMD/NMD = 3). In other words, the tractor boom sprayer had more uniform spray quality than the microner sprayer. Moreover, both sprayers displayed better performance as compared with other sprayers tested. The largest (14.5 %) and lowest (2.8 %) crop losses were determined for tractor boom and microner sprayer, respectively. The highest (3.2 ha-1.h ) and lowest (1.1 ha-1.h ) field capacities were also obtained for tractor boom and microner sprayer, respectively. The microner sprayer was the best sprayer in terms of solution consumption rate with an efficacy rate of 96 %. The greatest wheat yield (4830 kg.ha-1) was observed for tractor boom sprayer with applying 25 kg.ha-1 herbicide. Using tractor lance sprayer applying 15 kg.ha-1 herbicide, however, resulted in the lowest wheat yield (4615 kg.ha-1). The greatest and lowest weeds controls were also found for tractor boom and tractor lance sprayer, atomizer sprayer tractor, respectively. Tribenuron-methyl application with dosage of 25 kg.ha-1 was the suitable dose for controlling prennial weeds such as bindweed, knotweed, knapweed and rhubarb.

Japanese brome (Bromus japonicus Thunb.) is one of the most important annual narrow leaf weeds in wheat fields of Sistan and Baluchistan province. About 2 to 22 percent of yield loss depends on density and wheat cultivar. Fresh seeds of B. japonicus are classified on non-dormant or non-deep physiological dormant seeds. Treating by gibberellic acid is highly effective in both the embryo growth and seed germination processes in this type of dormancy. One of the important goals of germination and emergence studies in weed science is prediction of the dormancy longevity and germination time in field conditions. Therefore, the aim of this study was to evaluate germination properties of seeds at different times after physiological examination under the effect of gibberellic acid. An experiment was carried out as factorial based on randomized complete block design in 2013. Experimental factors were included six levels of 1- period of after ripening (immediately after harvest, 2, 4, 6, 9 and 12 months after harvest) and 2- pre-treatment by gibberellic acid for 48 hours in four concentrates (0, 100, 200, 300 mg lit-1). The effect of these factors was evaluated for two types of Japanese brome seeds; glumelle and nonglumelle. Samples placed into the incubator and temperature was kept on 20◦C in dark condition. Germination percentage, germination rate and mean germination time were recorded in every 48 hours. Analysis of data was performed using PROC GLM procedure of SAS (Version 9.2; SAS Institute, Cary, NC, USA). A three parameter sigmoidal model was fitted to the data using PROC NLIN of SAS to find the relationship between germination percentage and gibberellic acid concentration. The results showed that the effect of all experimental factors on germination properties was significant (P <0.01). Removal of glumelle, increasing the concentration of gibberellic acid and keeping more time after harvesting significantly increased germination percentage. The fitted model showed that the time to reach 50% of maximum germination in non-glumelle seeds was less than one month (T0> 1). In glumelle seeds, it takes about 6 months to reach 50% of its maximum (63%) in the 12th month after harvest. Germination rate increased from 1.7% per day in glumelle seeds to 15.5% per day in non- glumelle seeds. The duration of seed storage had a significant effect on its germination rate, so that at 12 months after harvest, it was approximately 15 times higher than harvest time. For the first three times after harvest; 0, 2 and 4 months after harvest, non-glumelle seeds showed a higher mean germination time than intact seeds, and vice versa, for the second three times; 6, 9 and 12 months after harvest. In this study, although the effect of gibberellic acid on enhancing germination was positive and there was significant differences among the four levels of this hormone, but its effect on glumelle seeds was higher than nonglumelle seeds. In other words, by removing glumelle, the effect of seed germination is reduced by the use of gibberellic acid. This experiment showed that removing glumelle and keeping seeds of the Japanese for 2 months and more have the greatest contribution to reduce non-deep physiological dormancy of this weed.

Wheat, as a strategic crop, has a special place in agricultural production of Iran and it has the highest cultivation area in the country. One of the most important limiting factors of wheat production in the world and in the country is weeds. Having comprehensive knowledge of the flora and species diversity of weeds is one of great importance for wheat management and it perceived as a primary need for production management and effective method of weed control in wheat farming program. In order to study of weed flora and evaluation of species, functional and structural diversity of weeds in wheat field of Golestan province, weeds population were surveyed at different cities during 2015 and the results were compared with the findings of last decade surveys. Randomized sampling method as W shape was conducted systematically using 0.5×0.5 m quadrate. All weeds in each quadrate were identified, counted and recorded for subsequent data entry and analysis. Mean density, frequency and uniformity percentage and relative abundance were calculated based on Thomas, 1985. Species Similarity index between different cities and Shannon and Simpson species diversity indices in each city were calculated based on available formula. Then cluster analysis based on average linkage method is carried out by SAS 9.2 for clustering different cities on basis of calculated traits that mentioned above. In this study, 51 plant species from 20 families were recorded. The most number of weeds were recorded in Poaceae, Fabaceae and Asteraceae families with 14, 7 and 6 weed species, respectively, but Poaceae, Polygonaceae and Brassicaceae were the most important weed families in wheat fields of Golestan provice, based on their relative abundance, respectively. The results showed that 78.43 % of recorded weeds were annual and the rest were perennial, 29.41 % of weeds were monocotyledons and 70.48% were dicotyledones. Avena ludoviciana and Phlaris minor with 40.21 and 37.11% relative abundance were the most important weed from narrow-leaved weeds and Sinapis arvensis with 32.42% relative abundance was the most important weed from broad-leaved weeds. P. minor, A. ludoviciana ،Veronica persica poir. and Stellaria media (L.) Vill. had the highest mean density in wheat fields of provice, respectively. The result of this study showed that the density of Avena ludoviciana, Sinapis arvensis, Phalaris minor, Lolium rigidum, Polygonum aviculare, Fumaria officinalis and Veronica persica has increased while the density of Polygonum convolvulus and Melilotus officinalis decreased over time gradually. Increase of narrow-leaved weeds than last decade may be related to continuous application of aryloxy phenoxy propionate herbicides for the years and resistance of weeds to this group of herbicides. Decrease of P. convolvulus density than last decade can be contributed to successful control of this weed by available herbicides such as tribenuron methyl, bromicid M.A. (bromoxinil+MCPA) and 2, 4, D. The most uniformity index was observed in A. ludoviciana (29.15), S. arvensis (26.57), P. minor (21.90) and V. persica (18.03), respectively. S. arvensis, A. ludoviciana, P. minor and V. persica with 42.55, 41.49, 41.49 and 30.85 % had the most frequency, respectively. The highest richness (the number of species) was observed in Khan Bebin (26 species) and the lowest (8 species) was in Kord Koy. Low richness in Kord Koy may be contributed to poor drainage of soil in this city that many of weed species cannnot adapt with this condition. The highest and Shannon diversity index was observed in Gonbad (2.48) and Khan Bebin (2.44) and the lowest value was observed in Kord Koy (1.18). The highest Simpson diversity index was observed in Kalaleh (0.43) and Minoo Dasht (0.4) and the lowest value was observed in Gonbad (0.11) and Khan Bebin (0.11). Different cities of Golestan Provience were grouped in 7 clusters for weed uniformity and weed abundance but for weed density they were grouped in 8 clusters. The most important weed in Aq qala, Bandargaz, Khan Bebin, Kord Koy, Kalaleh and Gorgan cities were Melilotus officinalis, P. minor, S. arvensis, Phalaris paradoxa, P.convolvulus, V. persica. A. ludoviciana was the most important weed in Ali Abad, Gonbad and Minoo Dasht cities. In general A. ludoviciana (40.21), P. minor (37.11), S. arvensis (32.42), and V. persica (27.96) had the most relative abundance in wheat fields and study of their control methods must be considered as research priorities in Golestan provice.

The genus Carthamus includes 25 species and subspecies in Iran, the two species C. oxycantha and C. lanatus have the most diversity, distribution and adaptation to the climatic conditions of Iran. C. oxycantha is a broadleaf weed and belongs to sunflower (Asteraceae) family. As seed germination is the beginning of the life cycle of plants, seedling emergence is critical for the establishment of plant populations. Germination and early seedling growth of many plants are the most sensitive stages to environmental stresses. Environmental factors, such as temperature, soil solution osmotic potential, solution pH, light quality, management practices and seed location in the soil seed bank, affect weed seed germination and emergence. Temperature is the most important environmental factors that control plant development, growth and yield. All biological processes respond to temperature, and all responses can be summarized in terms of three cardinal temperatures, namely the base or minimum (Tmin), the optimum (Topt), and the maximum (Tm) temperatures. Modeling of seed germination is considered an effective approach to determining cardinal temperatures for most plant species. Determination of cardinal temperatures could be a useful guidance to introduce new species in a new area or in selection of the sowing time. A clear understanding of cardinal temperatures could also be the first step for domestication of new species. There are various mathematical models describing seed germination responses to temperature, among which three have been used more often: intersected lines (ISL), quadratic polynomial (QPN) and five parameters beta (FPB). In order to investigate percentage and germination rate of C. oxycantha seeds, a laboratory experiment was conducted in complete randomized design (CRD) with four replications and under 7 constant temperatures 5, 10, 15, 20, 25, 30 and 35 ºC. Seeds were sterilized with 0.5% sodium hypochlorite solution for 1 min. Followed by washing with distilled water. Then, they were transferred to 9 cm diameter sterilized petri dish containing single layer of filter paper (Wathman #1). The germinated seeds were counted daily and continued until a cumulative germination reached a fixed amount (up to 14 days) or when 100% germination was achieved. Seeds were considered as germinated if the radicle was visible. To estimate the effects of temperature on germination rate of C. oxycantha seeds, three regression models included: Five-parameters Beta (FPB), Intersected-lines (ISL) and Quadratic Polynomial (QPN), were used. The germination data were tested for normality before analysis of variance. Data were analyzed using SAS 9.1 and Microsoft Excel 2007, and figures were designed by Sigmaplot 12.5. The results of the experiment showed that the temperature had a significant effect on the percentage and rate of germination. The lowest germination percentage was at 30°C (23%), while the lowest germination rate (0.62) occurred at 5°C. The highest germination percentage and germination rate occurred in 15-20 ºC. Generally, by increasing temperature from 5 °C to 20 °C, the percentage and germination rate increased and decreased after 20 °C, so that at 35 ºC, no seeds of wild safflower germinated. Based on the regression models the cardinal temperatures (Tbase, Topt and Tmax) were (4.4-5), (19.6-19.91) and (28.4-33.66) °C, respectively. ISL was the best model to estimate cardinal temperature of C. oxycantha based on the root-mean-square error, determination coefficient and residual values. According this model, the base, optimum and maximum temperatures were estimated as 4.41°C, 19.6°C and 33.3 °C. Khalaj et al (2015) modeled the germination rate of three medicinal plants, including wild oat (Avena fatua L.), wild mustard (Sinapis arvensis L.) and Descurania Sophia (L.). They showed that the segmented model was the best. But parmoon et al (2015) showed that the beta model was found to be the best model for predicting the germination rate and cardinal temperature of milk thistle (Silybum marianum L.). Soltani et al (2006) showed that the response of chickpea (Cicer arietinum L.) emergence to temperature is best described by a dent-like function. The result of this experiment showed the best model to estimate cardinal temperature of C. oxycantha was ISL. According this model Tb, To and Tm were estimated as1.4.41°C, 19.6°C and 33.3°C, respectively. It should be noted that although according to the results of this experiment, the optimum germination temperature in the wild safflower was about 20 °C and high temperatures were effective in reducing germination percentage and consequently inducing dormancy in the safflower seedlings, with climate change, plants such as wild safflower adapted to the new conditions, and the cardinal temperatures of this plant may also be changed in accordance with the new conditions.

Competition with weeds is the most important factor that reduces agricultural crop yield worldwide. The magnitude of yield loss is affected by numerous agronomic and environmental factors, such as weed density, time of emergence, morphological characteristics of weed and crops and etc. Several studies have shown that the crop and weed growth parameters including height, total dry matter, leaf area index and its distribution in the canopy are major determinants of the capability of species competition under interference conditions. Asian spider flower (Cleome viscosa L.) is a summer annual weed of the Capparidaceae family. Currently, very high densities of this weed grow in the fields of eastern Golestan province. There is no report on the extent of damaging of this weed in this province. So, current study was conducted to achieve these goals: 1) Investigate the effect of different densities of Asian spider flower on growth characteristics of soybean. 2) Determine the soybean yield loss due to competition with different densities of this weed species. In order to investigate the soybean competitive ability (cultivar D P X) under interference condition with different densities of Asian spider flower (0, 3, 5, 10, 15, 20, 30, 45 plant m-2); an experiment was established based on randomized complete blocks design with three replications in Gorgan University of Agricultural Sciences and Natural Resources in 2015–2016 growing season. Sampling was done 25 days after planting in eight stages. In each sampling, leaf area, dry weight of soybean and Asian spider flower plants were measured. Vertical distribution of leaf area in canopy profiles of soybean and Asian spider flower was studied, too. For this purpose, plants were divided into segments in 20- cm interval and leaf area of each layer was measured separately. A two parameter rectangular hyperbolic function (Equation 1) used for estimating grain and biological crop yield loss. Finally the accuracy of the model was confirmed based on RMSE, r and the dispersion of the observed and predicted grain and biological yield loss of soybean around the one to one line. Equation (1) Where YL is percent yield loss, D is weed density (plants m-2), and I and A, are model parameters. Parameter I is the percent yield loss per unit weed as D → 0, and A is the asymptotic yield loss as D → ∞. The results showed that soybean height was not affected by interference with different densities of Asian spider flower. But maximum accumulation of dry matter of soybean and leaf area index were reduced under competition conditions. According to the fitted model, the maximum accumulation of the dry matter of Asian spider flower was obtained at 83 days after planting, while the maximum soybean dry matter accumulation, depending on the interference treatment, varied between 53 and 60 days after planting. The maximum leaf area index of soybean (in weed free treatment) and Asian spider flower were 6.41 and 0.96, and were obtained at 63 and 53 days after planting, respectively. Although Leaf area index of Asian spider flower was lower than soybean, but maximum percentage of leaf area of Asian spider flower was located at higher canopy layers than soybean (20-40 compare to 0-20 cm). The results showed that the maximum soybean grain and biological yield loss due to high densities of Asian spider flower were 60.42% and 54.52%, respectively. Also, soybean grain and biological yield reduction were 8.39 and 7.94, respectively, in case the first weed. Based on the results of this study (RMSE, r and correlation between observed and predicted grain and biological yield loss), it can be concluded that the present model has a good accuracy and its outputs can be cited. In general it can be said the competition effect of Asian spider flower on soybean biological yield was lower than grain yield. Overall our results showed that Asian spider flower weed could be considered as a strong competitor to soybean. According to the results, it seems that some characteristics of Asian spider flower including 1) representing greater height at the end of the growing season, 2) requiring a shorter time to reach maximum leaf area index and 3) arranging a greater part of plant leaf area at higher canopy layers compared to soybean, were the most important factors to increasing the competitive ability of this weed.

Industrial hemp (Cannabis sativa L.) is an annual herbaceous crop of Asian origin considered to be one of the oldest crops known to man and it is traditionally grown in many regions of Europe for its fiber production. In agricultural ecosystems, weeds known as a main factor that reduces quantity and quality of products. The competition of weeds with crop is always one of the most important problems in achieving maximum yield. Therefore, weed management is essential to increase production. Increasing plant density is one of the strategies to reduce weed damage. The critical period of weed control refers to a part of crop growing season in which weeds should be removed in order to prevent crop loss due to weed competition. Crop density may be shorten weed critical period. Therefore, this study was conducted for evaluating the impact of crop density on hemp weed critical period. A field experiment was conducted in 2016 at the Agricultural Research field of University of Birjand, Birjand. The experiment was conducted as a factorial design with the treatments arranged in a randomized complete block design with three replications. The experimental factors consisted of a quantitative series of both increasing duration of weed interference (WI) and length of weed-free (WF) periods, and hemp plant density at two levels, 8 and 16 plant m-2. Hemp seeds were planted on May 5, 2017. Each plot consisted of six rows spaced at 60 cm between rows and 10 cm (16 plant m-2) and 20 cm (8 plant m-2) inter row. Each plot consisted of 3 m wide and 6 m long (18 m2). Each plot divided two parts, one part used for measuring morphological traits, and the other part used for measuring final yield. 180 days after sowing the hemp plants was harvested. Equations describing crop yield response to weed interference were fitted to the hemp yield data using a nonlinear regression. The Gompertz equation was used to describe the effect of increasing duration of weed-free period and the logistic equation was used to describe the effect of increasing lengths of weed-infested period on the seeds yield of hemp. Analysis of variance results showed that grain yield per hectare was significantly affected by plant density and competition at 1% level, but the interaction effect of density in competition was not significant (Table 1). The highest grain yield was obtained from treatments that most of the growth was free of weeds. The highest grain yield was WI2, WFC, WF10 and WF8 treatments were respectively the highest yield. WF2, WIC, WI10 and WI8 treatments had the lowest yield due to more weed competition. WFC treatment increased the grain yield by 258.28% and WIC compared to WIC (Fig. 2). Martin et al. (21) reported a decrease or increase in grain yield due to the reduction or prolongation of the agronomic competition with weed. Density also had a significant effect on grain yield. The grain yield was 16 plants m-2, 56.57% higher than 8 plants density (Fig. 3). Martin et al. (21) reported that decrease or increase of grain yield by prolongation or reduction of the crop competition with weed. The grain yield of 16 plants m-2 was 56.57% higher than grain yield at 8 plants m-2 (Fig. 3). This increase in grain yield at 16 plants m-2 can be attributed to more plant number and more flower per square meter, which increases grain yield. Likewise results of this study, Mirzai and Madhajj (23) reported that decreasing the intervals between and within rows increases the grain yield per unit area and decreases in each plant. According to the results of analysis of variance, biological yield per plant (Table 2) had a significant effect on density and competition at 1% level (P <0.01), but the interaction between density and competition was not significant. Biological yield per plant at 8 plants m-2 density of was 14.86% higher than 16 plants m-2 (Fig. 5). The results of the present study indicated that to prevent yield losses higher than 5%, an “efficient” weed control for the hemp could be achieved by keeping the crop weed free between 616 and 988 GDD for 8 plant m-2 and 667.5-889 GDD for 16 plant m-2 , respectively. To prevent yield losses higher than 10%, an “efficient” weed control for the Hemp could be achieved by keeping the crop weed free between 547 and 1093 GDD for 8 plant m-2 and 616-935.5 GDD for 16 plant m-2 , respectively. According to the results of this study, grain yield per hectare was significantly affected by plant density and competition at 1% level, but the interaction effect of density in competition was not significant. The results of this study revealed that weed critical period was decreased in 5% yield losses from 38 days (8 plant m-2) to 31 (16 plant m-2) and in 10% yield losses from 29 days (8 plant m-2) to 19 (16 plant m-2). These finding support the early suppression of the weeds in order to avoid dramatic crop yield losses.

Conservation agriculture is an appropriate strategy for maintaining and improving agricultural resources which increases crop production and stability and also provides environmental protection. This attitude contributes to the conservation of natural resources (soil, water, and air) and it is one of the most effective ways to overcome the drought crisis, water management and compensation of soil organic matter in arid and semi-arid regions. Practicing the conservation agricultural systems, which requires an effective usage of previous crop residues and reduced tillage methods, is an irrefutable necessity for arid regions like South Khorasan with low soil organic matter. The addition of crop residues to the soil in conservation agricultural systems, however, might immobilize nitrogen as an important nutritional element affecting plant growth. The transition from traditional to conservation agricultural systems, nevertheless, would affect different constituents of agroecosystems including weeds dynamics and growth, which would eventually affect the crop production in these systems. Given that South Khorasan farmers still use traditional methods of cultivation and they do not return the previous crop residues to the soil in their farming systems, the aim of this study was to investigate the effect of crop residue management and nitrogen on dynamics and growth of weeds of cotton farm. In order to investigate the effect of crop residue management and nitrogen on the growth and dynamics of weeds of cotton farm, an experiment was carried out as split factorial design based on RCBD with three replications at the research field of Faculty of Agriculture, University of Birjand in 2013. In this experiment, the main plot was two tillage methods, including conventional tillage (moldboard plowing) and reduced tillage (disking) and the subplot consisted of a factorial combination of two nitrogen levels (50 and 150 kg ha-1) and five barley residue levels (0, 77, 154, 231 and 308 g m-2) which have been randomly distributed as a factorial in subplots. Weed samplings were performed at four stages including 30, 60, 90 days after planting and also at harvest time and after each sampling, weed density, dry matter and leaf area were measured. Results showed that plow type, residual amount levels and nitrogen fertilizer rate had significant effects on measured traits of weed species including density and dry matter of weeds as well as their leaf area. Increasing the residue amount significantly reduced weeds growth traits. The greatest density, dry matter and leaf area of weeds were observed with disk plow, while mouldboard plowing significantly reduced these traits. A lower disturbance of soil in conservation agricultural systems, which is the case with our study where disking was applied, often results in most weed seeds to accumulate on the upper soil layers and eventually might ends up with a higher weed density. The greater rate of nitrogen resulted in higher density, dry matter and leaf area of weeds. The stimulatory influence of nitrogen on weed emergence has been previously substantiated. Moreover, the interaction effects of studied factors were significant on weeds growth traits. The interaction effects of plow type by residue amount showed that the lowest weed densities were observed with mouldboard plow under all residue amount and the using greatest residue amount (308 g m-2) resulted in the lowest weed density under both tillage regimes. The control treatment (no residue) interestingly showed a lower amount of weed density compared with residue amounts of 77 and 154 g m-2. Weed control by crop residues is probably due to different factors like prevention of light penetration to the soil surface, exuding allelopathic substances, influencing soil nitrate content and moderating soil temperatures and improving crop growth. Our study, however, showed that lower amounts of residues on the soil surface cannot provide enough inhibitory effects to suppress weeds and might even stimulate weed emergence through maintaining more moisture under the residue layer at hot air of early summer. The results of this study revealed that although employment of conservation tillage systems is a suitable method to achieve sustainable agriculture, more extensive research studies are needed on the effects of these systems on weed density and their competition with crop plants. Thus, cover crops and conservation tillage systems can be used as a promising solution for the development of sustainable agriculture and protecting the health of ecosystems. Due to widespread cultivations of wheat and barley in our country, it seems that incorporating the cereal crop residues into the soil might inhibit weeds growth in cropping systems. Our study also showed that nitrogen management is very important strategy in regard to weeds growth in these systems.