فصلنامه مطالعات حفاظت گیاهان
سال سی و سوم شماره 4 (زمستان 1398)

Among crop culture, tomato (Lycopersicum esculentum L.) is an important vegetable crop that grown throughout the world in open as well as protected cultivation. Iran ranks sixth among tomato producing countries. One of the biggest challenges in modern agriculture worldwide, is the management of soil-borne plant pathogens, including plant-parasitic nematodes. Among plant parasite nematodes, root-knot nematode genus Meloidogyne spp. (RKN) is one of the most important nematodes in a wide spectrum of crops that causes serious damage in most agricultural crops worldwide. The eggshell of root-knot nematode is containing 50% protein, 30% chitin and 20% lipid and Species of Trichoderma due to the production of the high level of many hydrolytic enzymes, are used as \ biocontrol agents of plant pathogens.

In the current study, extracellular protease and lipase activity of 15 isolates of four species of Trichoderma spp. including T. harzianum, T. virens, T. konigii and T. saturnisporum were investigated to their biocontrol effects on tomato root-knot nematode in the greenhouse. These Trichoderma isolates were cultured on Potato Dextrose Agar (PDA) media for 7 days and were used to prepare inoculation of Trichoderma. In order to prepare Trichoderma inoculum, we used sterilized wheat as the substrate contains Trichoderma fresh culture and after that incubated in 28ºC for 12 days. The Meloidogyne javanica pure population was prepared and tomato seedlings were inoculated with 2000 of the fresh egg of nematode and 1×107 different Trichoderma strain conidia and were kept in greenhouse conditions. The enzyme activity was assessed based on the colorimetric method using a special substrate as the only energy source for Trichoderma isolates. We used casein as the substrate for protease and extra-pure olive oil as the substrate for lipase activity assessment.

According to the enzyme activity results, the highest protease activity was in the isolates T. harzianum BI, T. virens T65 and T. virens T64 and the lowest protease activity was in isolates T. harzianum T16A, T. saturnisporum T12 and T. saturnisporum T12N, respectively. The highest lipase activity was in T. harzianum T19, T. virens T6 and T. virens T65 and the lowest lipase activity were in T. harzianum T14N, T. harzianum T16A and T. harzianum T16. Based on the greenhouse results, T.BI, T65 and T6 isolates were the highest effective isolates and T12N, T12 and T16 reported as the lowest effective isolates in the biocontrol of root-knot nematode on infected tomato plants. Also, according to the results of correlation between protease and lipase activity and nematode reproduction factor, the correlation coefficient between enzyme activity and nematode reproduction factor for protease activity measured R2=0.83 and for lipase activity measured R2=0.42 which given the constituents of the root-knot eggshell and larvae cuticle that contains high amounts of protein, this is understandable. There are many reports about the effects of protease and chitinase on the induction of resistance against plant pathogens in plants. An investigation on the effect of Trichoderma isolates extracellular protease level on the biocontrol ability of these isolates against tomato root-knot nematode showed that the higher number of protease-encoding genes copies increases the biocontrol ability of these isolates.

Root-knot nematode is one of the most important damaging agents on tomato plants. It is difficult to control this endo-parasite nematode because of its wide host range, short life cycle, and high reproductive potential. The activation of the plant's own defense system through biotic and abiotic agents, called elicitors, has been considered as a focus of research only in recent years for the control of plant pathogens. The resulting elevated resistance due to an inducing agent upon infection by a pathogen is called induced systemic resistance (ISR) or systemic acquired resistance (SAR). Several abiotic and biotic agents have been reported to induce resistance against plant-parasitic nematodes. So far, many pieces of research have done on the use of different species of Trichoderma as biological control agents of plant pathogens. The ability to produce high amounts of chitinase, protease and glucanase enzymes made this isolates as a biocontrol agent of a wide range of plant pathogens. Overall, there is no sure whether or not a biocontrol agent is successful in controlling a particular pathogen, and many variables influence the success rate of biocontrol agents in natural environments. 

Wheat take-all caused by Gaeumannomyces tritici fungus is one of the most destructive diseases in the world. The disease is common in alkaline to natural, non-fertile and low-drainage soils. Thereby, wheat take-all can be suppressed by reducing soil pH. In recent years, sulfate-containing fertilizers had been substituted with new sulfur-free fertilizers which decrease soil content of sulfur and sulfur-oxidizing bacteria, significantly. So, soil amendment with mineral sulfur or Thiobacillus spp. could be reconsidered to reduce soil pH. However, soil amendment with mineral sulfur seems to be more effective when the rhizosphere is colonized by sulfur-oxidizing bacteria. This study aimed was to investigate the effect of mineral sulfur and Thiobacillus sp. on take-all disease and wheat growth.

Physicochemical properties of soil were analyzed based on standard methods. Sulfur was mixed with soil in 0, 2, 4 and 8 g/kg of soil with three methods. In the first method, sulfur amended soil was inoculated with the pathogen and sown immediately. In the second method, amended soil was incubated for two months then inoculated and seeded with wheat. In the third method, sulfur amended soil was inoculated with Thiobacillus sp. bacteria and sown immediately. G. tritici inoculum was prepared on oat seeds and was placed in a layer under plant seeds. Disease severity was checked once plants seedling in control pots exhibited the disease symptoms. The experiments were carried out in a completely randomized design with four replicates. Analysis of variance was done by SAS 9.1.

Analysis of soil showed the examined soil was calcareous and moderately alkaline. It has appropriate nitrogen and zinc content but slightly Fe, Cu and P are deficient. Results exhibited that sulfur amended has no significant role on take-all disease neither with incubation nor without incubation. However, mixed treatment with sulfur and Thiobacillus sp. decreased disease severity in concentration depended on manner. The highest disease suppression achieved in 8 g /kg sulfur of soil which decreased disease severity up to 45%. Soil amendment with 2 g/kg sulfur of soil either incubated or not increased plant dry weight 20 and 25%, respectively. However, a further increase in sulfur concentration showed no more increase in plant growth. In a combination with sulfur and Thiobacillus sp., wheat aerial parts dry weight was increased paralleled with an increase in sulfur concentration and reach to 25% higher than control in 8 g /kg sulfur of soil. Calcareous soils are highly buffered and it is very difficult to change their pH. In our experiment, the Soil amendment with mineral sulfur was unable to reduce pH as much as necessary for Take-all suppression. However, sulfur had synergistic interaction with Thiobacillus sp.. Indeed, these bacteria can colonize the plant rhizosphere efficiently. Thereby, they can reduce the pH of the rhizosphere zone instead of whole balk soil. In this situation, G. tritici could not survive in an acidic condition of the rhizosphere. On the other hand, mineral sulfur improved plant growth in all concentrations. It should be considered that sulfur could be uptake by the plant as a nutrient element. However, sulfur-oxidizing bacteria will help the plant to uptake sulfur more efficiently. It should be considered that Thiobacillus is compatible with other biocontrol bacteria such as Bacillus and Pseudomonas. These bacteria are highly effective in Take-all disease but cannot survive well in calcareous soils. Co-inoculation of these bacteria with Thiobacillus sp. in the presence of sulfur seems to be a promising approach in biological control of Take-all disease.

Our results showed that a combination of sulfur with sulfur-oxidizing bacteria could be a promising approach in the suppression of Take-all in wheat. In recent years, integrated disease management and integrated crop management receive high attention in susceptible agriculture. In these strategies, agricultural practices such as plant nutrition are considered as multifaceted practice. This means that soil amended with specific fertilizer not only increases plant growth but it can increase or decrease specific plant disease. In the case of sulfur, this element not only decreases Take-all disease but also improves the availability of other nutrients such as Fe, Zn and Cu. Furthermore, it should be considered that soil amendment with a low amount of sulfur is not effective to reduce soil pH in buffered calcareous soils and we need to add sulfur-oxidizing bacteria to improve fertilizer efficiency. This combination is effective against Take-all disease.

Pome fruits are affected by many viruses that cause diseases with adverse effects in orchards worldwide. Apple chlorotic leaf spot virus (ACLSV) is one of the most widespread and economically important latent viruses that naturally affect many Prunus species, apples (Malus domestica Borkh.), pears (Pyrus communis L.) and the other rosaceous species. ACLSV infection rates of up to 80–100% in many commercial apple cultivars with yield losses of the order of 30–40% have been reported. In most commercial apple cultivars, the infection generally is latent, but insensitive cultivars, such as apple trees grown on Marubakaido (Malus prunifolia cv. Ringo) rootstocks, malformation and reduction in leaf size and chlorotic rings or line patterns are common. The severity of symptoms induced by ACLSV depends largely on the plant species and virus strains. Some virus isolates induce a severe disease in apricot and plum characterized by depressions and protuberances that deform the fruit, often confused with the “sharka” disease due to Plum pox virus (PPV), and named for this reason as “pseudopox.” ACLSV is a filamentous virus, 680–780 nm long and 12 nm in width as the type species of the genus Trichovirus in the family Betaflexiviridae. ACLSV contains a single-stranded, positive-sense RNA about 7.5–8 kb in size, with a polyadenylated 3" terminus and a cap at its5"-end, and also contain multiple copies of a single coat protein (CP) of 21–24 kDa. The economic importance of ACLSV is largely due to its worldwide distribution and its capacity to induce severe graft incompatibilities in some Prunus combinations, causing major problems in nurseries. In apple trees, ACLSV frequently is detected in coinfection with Apple stem grooving virus and Apple stem pitting virus. ACLSV is mainly transmitted by grafting. No natural virus vectors are known for this virus and are not known to be seed or pollen transmitted. The older National Apple Collection of Native and Imported apple cultivars in Kamalshahr Horticulture Research Station located in Karaj includes 85 cultivars and promising genotypes on seed stocks benefit a high genetic variability. Though the cultivars were screened for more biotic and abiotic factors, but no screening has been achieved yet for virus diseases, while this valuable germplasm comprises a wide range of newly released cultivars or in releasing procedure, high yield natives and those imported selected as adapt to Iranian climate, so a great need of healthy primary nucleus to establish mother orchards for certified plant material. As this valuable germplasm is very important in providing healthy primary nucleus to establish mother orchards for certified plant material so the aim of this research was an evaluation of native and imported apple tree cultivars of this Collection to ACLSV infection.

To assess the occurrence and the prevalence of this virus in the collection, a total of fifty accessions were collected. The sample collection was carried out in summer (2016) and spring (2017). The collecting method consisted of sampling leaves homogeneously distributed around the canopy of the plant. All samples were screened for the presence of ACLSV by DAS-ELISA using the ACLSV specific polyclonal antibody using commercial kits purchased from Bioreba Company, Switzerland. To confirm ELISA results some cultivars were subjected to reverse transcription-polymerase chain reaction. Total RNA was isolated from some apple cultivars using CTAB RNA extraction method and was used as a template for RT-PCR. Specific oligonucleotide primers corresponding to a region of the ACLSV genome that encodes part of the CP, were used in RT-PCR. The amplified PCR products were analyzed in 1% agarose gel stained by ethidium-bromide and visualized under UV light after electrophoresis.

The ELISA results showed that 39 out of 50 cultivars were infected by ACLSV. RT-PCR on total RNA from the ELISA positive samples resulted in the amplification of an expected 358 bp DNA fragment. In RT-PCR out of 18 tested cultivars, five were infected. Some cultivars including Makintash, Red Rome Beauty, Starking, Ardebil1, Nayan Arangeh, Khorsijan, Red spur cooper, Yellow transparent 1, IR6-1 and Ardebil2 recognized ACLSV free in ELISA and RT-PCR, so could be used in the production and employment of virus-free propagating material program after infection testing to the other three important viruses Apple stem pitting virus, Apple stem grooving virus and Tomato ringspot virus. The results showed a high rate of ACLSV infection of native and imported apple cultivars in the older National Apple Collection in Kamalshahr Horticulture Research Station. Previous studies, in apple gardens and nurseries of Iran, have shown a high percentage of ACLSV infection too. Similar results have also been obtained on the percentage of infection with this virus in the Czech Republic, Romania, Albania, and Bosnia and Herzegovina. As germplasm exchanges are the main source of transmission of new viruses to countries, one of the most important strategies to control viruses in fruit trees is to prevent the introduction of virus-infected germplasm into the country.

Root-knot nematodes (Meloidogyne spp.) are among the most dangerous herbal parasites which destroy 8.8 to 14.6 percent of agricultural products annually. In vegetables, 50 to 80 percent damage caused by nematodes is normal. It is unavoidable to use safe methods for controlling root-knot nematodes. Plant parasitic nematodes can be inhibited using chemical fertilizers, which reduce the losses induced by plant parasites and increase total products. The aim of this study was to evaluate the effect of different levels of two macronutrients including nitrogen and phosphorous on the infection of M. javanica on eggplant (cv. Black Beauty) under greenhouse conditions.

In the current study, the levels of zero (N0), 50 (N1), 100 (N2), 200 (N3) mg nitrogen and zero (P0), 50 (P1), 100 (P2), 200 (P3) mg phosphorus per kg of soil were selected from nano-chelated nitrogen fertilizer and nano-chelated phosphorus fertilizer, respectively. The seeds of eggplant were planted in plastic pots containing 2 kg of culture media including equal amount of sand, farm soil and animal manure under greenhouse condition. The pots were irrigated daily and maintained at 27±4 °C with 16:8 h light: dark photoperiod. Four leaf stage seedlings were inoculated with five eggs and second stage juveniles of M. javanica per gram of soil, and 10 days after inoculation, different levels of fertilizers were added (100 ml per pot) to the pots through irrigation. Sixty days after inoculation, plant growth indices including shoot height, shoot fresh and dry weights and root fresh weight of the cultivated plants were recorded. Nematode population indices including number of galls and egg masses per root system, number of eggs in egg masses were also measured and finally the reproduction factor was calculated. The roots were gently washed with tap water and number of eggs in one gram of root were counted according to the procedure developed by Hussey and Barker (1973). One gram of root was stained with acid fuchsine according to the procedure developed by Byrd et al. (1983). The total number of eggs, galls and egg masses per plant root system was determined by multiplying with the root weight per plant. The final nematode population per pot was computed and finally, the reproductive factor (RF) of nematode was calculated by dividing the final nematode population by the initial nematode population (10000 eggs and second stage juveniles of M. javanica). Data on plant growth and nematode indices of the experiments were subjected to a factorial analysis of variance (Two-way ANOVA). Means were compared with least significant differences (LSDs) to identify significant difference at probability levels of P≤0.05 using SAS 9.1 software (Statistical Analysis System Institute Inc., USA) in a CRD (completely randomized design) with four replicates.

In nematode inoculated plants, the difference between shoot height and shoot fresh and dry weight of treated plants by phosphorus at the rate of 100 mg/kg soil and non-treated by nitrogen (N0P3) with control plants (N0P0) was significant. Similar results were observed in nematode inoculated plants treated by nitrogen and phosphorus at the rate of 50 and 100 mg/kg soil, respectively (N1P3), with nematode inoculated plants treated by nitrogen at the rate of 50 mg/kg soil and non-treated by phosphorus (N1P0), nematode inoculated plants treated by nitrogen and phosphorus at the rate of 100 and 100 mg/kg soil, respectively (N2P3), with nematode inoculated plants treated by nitrogen at the rate of 100 mg/kg soil and non-treated by phosphorus (N2P0) and also nematode inoculated plants treated by nitrogen and phosphorus at the rate of 200 and 100 mg/kg soil, respectively (N3P3), with nematode inoculated plants treated by nitrogen at the rate of 200 mg/kg soil and non-treated by phosphorus (N3P0) (P≤0.05). The results showed that using 100 mg nitrogen and 100 mg phosphorus per kg of soil from nano-chelated nitrogen fertilizer and nano-chelated phosphorus fertilizer, as the best treatment used in this experiment, decreased number of eggs, galls and egg masses per root system and reproduction factor of nematode by 53, 52, 62 and 55%, respectively. Therefore, nano-chelated nitrogen and phosphorus fertilizers, as two chelated fertilizers produced using nanotechnology, can decrease the population of M. javanica in eggplant cultivated in the greenhouse. Soil drenching of these water-soluble nano-fertilizers 10 days after infection of the eggplants by M. javanica can also reduce the population of nematode.

The Russian wheat aphid, Diuraphis noxia (Mordvilko), is an important pest of cereal, particularly wheat (Triticum eastivum L.) and barley (Hordeum vulgare L.) in many countries. It can also be damaging as a vector of plant pathogenic viruses including Barley Yellow Dwarf Virus (BYDV), Barley Mosaic Virus (BMV), and Sugarcane Mosaic Virus (SMV). Also, a yield loss of as much as 60% has been reported in wheat in years of heavy infestation. Utilization of synthetic pesticides is a common method for control of D. noxia, but the continuous application of such chemicals caused several side-effects such as environmental hazards, insect pest resistance and the outbreak of secondary pests. Therefore, other control methods need to be investigated for effective control of the pest. The use of resistant cultivar is an environmentally safe method of insect control and is also less expensive for growers resistance of host plants against herbivore insects may be due to antibiosis. The antibiosis properties of the host plant can reduce the amount of feeding, fecundity and size of the insect. They also can lengthen the development period, and increase the mortality rate. Therefore, the use of plant tolerance for managing D. noxia has received greater emphasis than in other systems. Wheat and triticale lines [×Triti- cosecale Wittmack, a hybrid between wheat and rye (Secale cereale L.)] with tolerant traits or tolerance combined with antibiotic, antixenotic and tolerance traits have been identified.

In the present study, the possibility of existence of resistance in thirty bread wheat genotypes (Tak Ab, Ryzhav, Oohadi, Gaspard, Say Sunz, Alvand, Phishgam, Azadi, Kras Sabalan, Omid, Navid, Sabalan, Mihan, Orum, Zare, SardariHoma, Rasad, Cascogen, Tos, Shahriar, Bezostiya, Azar 2, Bak Kras Roshan, MV17, C-89-7, C-89-12, C-89-15, Zarin and Almot, respectively) and one triticale cultivar that was evaluated at 12th growth stages of the plants. The experiments were carried out in the greenhouse (23±3˚C, 50±10% RH and a photoperiod of 14L: 10D h) and using a completely randomized design. The aphids used in the experiments were provided from the stock colony reared in Department of Plant Protection, University of Mohaghegh Ardebili, (originated from Namin city infested fields). Antixenosis was determined by counting the number of adult aphids attracted to each genotype potted plants at 24, 48 and 72 hours after release. Life tables were constructed based on the method described by Birch (1948) and Meyer et al. (1986). Differences in intrinsic rate of increase (rm) and other life table parameters were estimated by the jackknife method. Before analysis, all data were tested for normality by Kolmogorov-Smirnov method. Statistical differences among means were compared using the Tukey post hoc Honestly Significant Difference (HSD) and Student-Newman- Keuls (SNK) tests at α= 0.05 using the statistical software of SPSS ver. 19.0.

In summary, the analysis of variance of number attracted adult aphids to each genotype indicated that there were no significant differences among genotypes with respect to the number of aphids attracted to them. Antibiosis evaluated in two experiments. In the first experiment, the mean number of aphids among 31 genotypes was significantly lowest on triticale (Juanilo cultivar) (1 aphid) than resistance control (35.2 aphids). In the second experiment, D. noxia intrinsic rate of natural increase (rm) evaluated on four selected genotypes in the first experiment. The highest and lowest rm values were found on Alvand cultivar (0.273 day-1) and Bezostaya cultivar (0.214 day-1), respectively. Intolerance experiment, height and dry weight of seedling between control (no infested plants) and 14 aphids-day infested plants were measured. Proportional dry weight and height changes were significantly different among the genotypes. According to the results obtained in this research, to avoid hazardous chemicals against insect pests of such crops, certain protective or curative procedures could be implied using different non-chemical methods to reduce the pest population and resultant damage. Consequently, our results indicate Kaskogen and Juanilo cultivars had relatively tolerance and antibiotic resistance to Russian wheat aphid, respectively and so it can be used in the IPM of the aphid.

Further experiments under the field conditions will be needed to validate these findings. The study on chemical components of these cultivars which is unsuitable in our lab may further reveal the chemical base of the unsuitability of cultivars Kaskogen and Juanilo.

Alfalfa (Medicago sativa L.), also called lucerne, is the most important forage which cultivated in the most parts of the world. The main source of alfalfa is Southwest Asia, especially Iran. Alfalfa is a perennial forage legume which normally lives four to eight years, but can live more than 20 years, depending on type of its variety and climate. In the most regions, alfalfa is generally harvested three to four times and can be done up to 12 times per year. Many types of insects are found in alfalfa fields including beneficial, and harmful insects, which feed on the leaves, flowers, root and seeds. Amongst them, thrips are a group of insects belonging to the order Thysanoptera. Thrips have been considered in most areas. Different species of thrips have been recorded on alfalfa fields in western Iran i.e. Odontothrips confosus Priesner, Odontothrips iranensis Mirab-balou et Chen, Thrips tabaci, Frankliniella intonsa (Trybom), F. pallida (Uzel), Haplothrips reuteri (Karny) and Neohydatothrips gracilicornis (Williams).Therefore, it is critical to determine the biodiversity status of the thrips in order to manage its population.

To study the biodiversity of thrips species in different alfalfa cuttings, the sampling was weekly carried out during April to the middle of September 2016 in alfalfa fields (1-year-old, 3-years-old and 4-year-old) of Eyvan city (Ilam province), the west of Iran. The specimens were collected using shaking alfalfa plants in a white tray and transferred them to vials containing 75% ethanol. After transferring to the laboratory, all thrips specimens were mounted onto slides, and identified at the species level. The dominant thrips species were determined and biodiversity of thrips species in different alfalfa cuttings was calculated by biodiversity indices i.e. Shannon-Wiener, Simpson, Margalef and Evenness Shannon.

In the present study, 10 thrips species belonging to six genera and four different families were collected and identified from alfalfa fields. Among the collected species, the highest and the lowest frequency was obtained for Thrips tabaci (59.12%) and Tenothrips frici (0.24%), respectively. According to the calculations, the Shannon-Wiener, Simpson, Margalef and Evenness Shannon indices in 1-year-old alfalfa field were 2.71 ± 0.04, 0.92 ± 0.04, 3.49 ± 0.02 and 0.89 ± 0.01, in 3-year-old alfalfa field were 2.26 ± 0.09, 0.88 ± 0.009, 2.58 ± 0.18 and 0.91 ± 0.006, and in 4-year-old alfalfa field were 2.09 ± 0.14, 0.85 ± 0.01, 2.31 ± 0.29 and 0.92 ± 0.01, respectively. The results showed that the Shannon-Weiner, Simpson and Margalef indices of thrips species in 1-year-old alfalfa field were significantly higher than the 3 and 4-year-old alfalfa, however, the Evenness Shannon in 4-years-old alfalfa field was more than 1-year-old and 3-years-old alfalfa fields, this difference was not significant.

In this study, Shannon-Wiener index values varied between at least 2.09 in a 4-year-old alfalfa and a maximum of 2.71 in a 1-year-old alfalfa fields. The range of Shannon-Weiner index variables from 0 –5 and typically from 1.5 - 3.5. Lower values of this range indicates the presence of tension in the environment and instability, and more than it showed an increasing the biodiversity of the area. These values are good in comparison to the range of Shannon-Weiner index variables, which are generally between 1.5 and 3 in their sources. As the age of the plant raises, the amount of food decreases, so, insects less likely tend to establish on the host plants, and their variety will be reduced. Thrips tabaci is one of the most important pests with more than 300 host plants in the world. Considering that in the present study T. tabaci is a dominant species in the alfalfa fields, its infestation level should be managed correctly with respect to control method.

The most threatening factor in cotton production worldwide is Lepidoptera pests. The pest management using chemicals imposes huge costs and environmental side effects. Introduction of genetic engineering as a modern technology has opened a new insight for investigators to control the pests through transgenic pest resistant varieties. Cotton was the first transgenic crop which received cry genes, and introduced to farmers after numerous field trials. The field trials on evaluation of transgenic lines are a complex process in three levels comprising mini, mid and large scale trials, but the first step in this process is evaluation of transgene in the field condition along with considering other important crop properties. There are several Lepidoptera pests causing damage to cotton in nearly all cotton producing areas worldwide. However, bollworm (Helicoverpa armigera Hübner) and spiny cotton bollworms (Earias vittella Fabricius and Earias insulana Boisduval) are the most the most important pests in Iran. Also, there are many biotypes among different geographical populations. This fact implies that the transgenic lines should be tested in different locations within a country. A number of research works has been conducted to produce transgenic cotton via both modern biotechnology and traditional backcrosses in Iran. As a result, some different transgenic lines harbouring cry genes were produced. Primary evaluation of these transgenic lines was resulted to a few lines exhibited the most resistance characters against the pests. More precise evaluation of the lines for pest resistance traits and yield was done in this study.

Three transgenic lines harbouring cryIAc gene comprising A, B and CRI lines along with a non-transgenic variety as negative control (Varamin) were used in the experiment. The experiment was conducted in a Lepidoptera pest affected farm at Minab, Hormozgan from June to July of 2015. A complete randomized block design with eight replications was adopted as the statistical model. Each plot consisted of eight lines with 8 meters length in which the distance between lines were 80 cm. All agricultural operations including irrigation, fertilizer and weeding were carried out according to local recommendations. During growing season, some properties related to the pest resistance including number of bolls per plant, percentage of contaminated bolls, percentage of contaminated locule, and percentage of boll injuries were recorded, and damage index was then calculated. The varieties yield was recorded as well. All traits were recorded on two separate dates i.e. June and July, 2015. The data were analyzed using SAS software according to the adopted statistical model.

Analysis of variance showed that all recorded traits in the experiment were significant for cultivars effect, except for boll injuries percentage. Primarily, the current results demonstrate that all cultivars were exposed to the pest equally. Other traits including number of bolls per plant, percentage of contaminated bolls, percentage of contaminated locule, damage index and yield differed significantly between the cultivars. The mean comparison for number of boll per plant showed that transgenic A and B (transgenic) lines produced and kept the most boll number, and CRI transgenic line and Varamin cultivar ranked as the second. This trait is very important, because it not only acts as a yield component, but also involves in resisting against pests. The mean comparison for contaminated boll and contaminated locule traits showed that non-transgenic Varamin cultivar had the largest contamination amounts. In contrast, transgenic A and B lines exhibited the least contamination for both traits.
The most important trait expressing resistance is damage index. The lowest damage index was calculated for B line (0.69 and 0.46% in June and July, respectively) and A line (0.75 and 0.56% in June and July, respectively), and CRI line ranked as the second (2 and 5%). Meanwhile, the damage index of Varamin cultivar in this experiment was 3.8 and 11.5% in June and July, respectively. The damage index for A and B transgenic lines in the first and second recording show a downward pattern in contrast to CRI line and Varamin cultivar. Hence, Lepidoptera pests does not succeed in feeding on the A and B lines. Moreover, A and B lines exhibited the best yield (5041 and 4466 kg/ha, respectively), and the CRI line ranked as the second (3382 kg/ha). The Varamin cultivar yield was 3071 kg/ha which was the least record.

In general, two out of three transgenic lines comprising A and B lines had the best yield, the minimum contaminations and injuries by Lepidoptera pests. Varamin cultivar, as non-transgenic control line showed the least tolerance and yield and the CRI cultivar were ranked between the superior transgenic and non-transgenic lines. Both A and B transgenic lines have proper agronomic traits and the best resistance characters against Lepidotera pests. It can be concluded that these lines, as the first Iranian transgenic varieties, can be used for registration and commercialization.

Transient and persistence of weed seed banks impact on weed population dynamics. Therefore, any management tools with having a reducing role can affect weed population size. Reduction of weed seed rain using effective control tools can reduce weed density. The seed bank density is the main factor corresponding to seedling density. Decline of seed bank is critical to success in crop production, so that,   poor performance in weed control only for a season cause to rain weed seeds and to improve soil seed bank. Most of the commonly used herbicides recommended for controlling weeds in wheat fields are not efficiently able to control the wild barley (Hordeum spontaneum C. Koch). Hence, utilizing appropriate agronomic strategies to control this weed is critical. Evaluation the effect of wild barley spike cut-off in the previous wheat field, and the effects of chickpea planting date and chemical weed control in chickpea cultivation in rotation on wild barley weed population in chickpea cultivation are among the aims of this study.

The effect of wild barley spike cut-off in the previous wheat field, and sowing date and management strategies in chickpea on its population in chickpea for the following years was evaluated in Khorramabad, Lorestan, Iran during 2009-10 and 2010-11 growing seasons. The experiment was arranged in a factorial split plot in a completely randomized block design with three replications.  The wild barley spike cut-off in wheat (at two levels: No cut-off and with cut-off) and chickpea planting date in the next season (at two levels: early planting and late planting) were assigned into the main plots. Chickpea weed management treatments (at five levels: pre emergence application of metribuzin at 0.7 kg per hectare, pre emergence application of imazethapyr 0.7 litter per hectare, post emergence application of Clethodim 1 liter per hectare, weed free treatment, and weedy infest)was assigned into the sub plots.

Wild barley spike cut-off in previous wheat reduced 71% of the density and biomass of this weed in chickpea cultivation in the following years. This suggests the importance of recent year's wild barley seeding rain in the completion of the soil seed bank for the next season. Early planting of chickpea compared to late planting decreased the wild barley density by 75%. It was mainly related to the ineffectiveness of planting operations in full control of the large wild barley plants in the late planting treatment. Early planting of chickpea under wild barley weed spike cut-off in previous wheat crop condition, was completely free of wild barley. Accordingly, the prevention of wild barley seed rain and the completion of the soil seed bank in the previous year, along with the timely planting of chickpea led to full control of this weed. Triple interaction effects of experiment factors on wild barley biomass in chickpea was statistically significant. This suggests the difference of wild barley biomass response to weed management treatments in different planting date of chickpea in spike cut-off and without spike cut-off of wild barley in the previous wheat crop. In addition to manual weeding treatments in different conditions, all weed management practices, even uncontrolled weedy check, in early chickpea planting under spike cut-off of wild barley conditions in wheat cultivation in the previous year, did not emerged any wild barley seedling. This indicates the high efficiency of spike cut-off of wild barley in the previous year and the prevention of seeding and the timely planting of chickpeas in the management of this weed.

Thus, it seems that the major part of the growing population of this weed is dependent on previous year seed rain. In the other words, the wild barley population dynamics is largely dependent on the temporary transient seed bank instead of a persistent seed bank. This suggests the possibility of managing problematic wild barley and reducing its population below the economic damage threshold through prevention of seed rain and soil seed bank management.

The presence of weeds seriously reduces potato yield by particularly where crop competition is reduced because of poor growing conditions or disease or in cultivars where development rate is slow. Weeds can also have a serious effect on harvesting the crop, entangling equipment and slowing operations. They can also encourage some pests and diseases such as slugs, free living nematodes, wireworm and Rhizoctonia. The potato crop, once the haulm meets in the rows, is usually effective in reducing late weed emergence through shading. However, weeds emerging before row closure can grow above the crop canopy. Noxious weeds such as field bindweed and knotgrass can grow through the crop, and tall weeds, such as fat-hen, sow thistles, and grasses, can grow above the crop, shading and competing strongly for resources. Weed control needs to start whilst the weeds are accessible to treatment, that is, pre-emergence of the crop to before the crop shades emerged weeds. The treatment needs to be able to maintain weed control for up to 6-8 weeks after crop emergence to allow the crop canopy to close and shade further weed emergence. In less vigorous and less competitive varieties, canopy closure may take longer, or remain incomplete. In conventional farming systems, treatments are based on herbicide treatment. This may be before weeds and crop emergence with a residual soil-acting herbicide which gives a number of weeks of control, depending on dose, soil type and weather conditions. Some residual herbicides have some foliar as well as root activity and can be used as the weeds and crop emerge. Mixtures with a contact herbicide are often used at this timing. This timing, slightly later than purely pre-emergence of the crop, allows the residual effect of soil-acting herbicides to persist for longer into the season. This is particularly useful for slow growing varieties or in slow growing conditions. The objective of this study was to evaluate the effect of integrated weed management, using chemical and mechanical methods, on weed density and biomass of potato C.V. Agria. 

To evaluate the effect of cultivator and herbicide application on yield and weed community of potato, an experiment was conducted using factorial arrangement based on randomized complete block design with four replications at the Research Field of Ferdowsi University of Mashhad in 2015. Factors included cultivator at two levels (no and once cultivator) and herbicide application at six levels (pre-planting application of pendimethalin+broadcast application of metribuzine as post-emergence, pre-planting application of pendimethalin+band application of metribuzine as post-emergence, pre-planting application of pendimethalin alone, broadcast application of metribuzine as post-emergence alone, band application of metribuzine post-emergence  alone, and no herbicide treatment). In addition to these treatments, a weed free treatment as a control considered in each block. Weed flora, total weed density and total weed biomass recorded at 15, 30, 45 and 90 days after treatment using a 0.35×0.75 m-2 quadrates. At the harvest time, tuber yield and potato biomass recorded in 2 m2 area. Data analysis; including ANOVA and mean differences at the 5 %significant level was done using SAS 9.1 and figures created using Excel 2007.

The results showed that cultivator just had significant effect on total weed density and had no significant effect on total weed biomass and potato yield. Application of pendimethalin+metribuzine using broadcast or band application method reduced total weeds density and total weed biomass and increased tuber yield, and biomass of potato. The lowest weed biomass (250.2 and 212.2 g.m-2) and highest tuber yield observed in application pendimethalin+metribuzine broadcast and band application  method, 41.158 and 36.168 ton.ha-1 ,respectively and highest weed biomass (900.1 and 933.9 g.m-2) and lowest tuber's yield observed in no herbicides and pendimethalin alone, 16.482 and 18.752 ton.ha-1 , respectively.

It was concluded that one cultivator alone not only could not help to weed control program, but also excite weed emergence. Then repeating the cultivator operation or application of pre-planting or post-emergence herbicide is necessary to achieve a good weed control in potato. In addition, integration band application of post emergence metribuzine and cultivation between rows reduced significantly herbicide application in potato.

The herbicide application has caused some environmental problems. Therefore, optimal application of herbicides was followed in recent years. For this purpose, it is essential to minimize the exo-drift and/or endo-drift of spray droplets. The amount of exo-drift and/or endo-drift is directly related to the size of spray droplets. By decreasing the size of spray droplets, the exo-drift increases and the endo-drift decreases (34). This intricate issue is a stimulus to develop the types of nozzles in different sizes (color) producing different sizes of spray droplets at different spraying pressures. Such a development in the production of nozzles has caused difficulty and confusion in selecting a suitable type of nozzle (2). On the other hand, the agriculture sector is faced with water crisis in recent years. Considering that water is the most important carrier of herbicides, selecting a suitable spray volume is thus necessary. According to previous studies (26), the efficacy of different herbicides can influence spray volume negatively (30), neutrally (29), or positively (12). So far, the effect of spray volume on the efficacy of cycloxydim against any weed has not been investigated. Also, since the types of triplet flat fan nozzles have been recently developed, no investigation has been done on their performance compared to the types of single and twin flat fan nozzles. The current study aimed to fill this knowledge gap.   

The seeds of wild barely (Hordeum spontaneum Koch.) were treated to germinate. Then, 8 seedlings were planted within each 3-L pot and grown in the Research Greenhouse of Bu-Ali Sina University, Hamedan, Iran. At the four-leaf stage, they were treated with 0, 6.25, 12.5, 25, 50, and 100 g cycloxydim ha-1 using 3 nozzle types (i.e. Standard, Anti-Drift, and Air Induction), at 3 orifice numbers (i.e. single, twin, and Triplet) and 3 nozzle sizes (i.e. 11002, 11003, and 11004). The treatments were sprayed at a pressure of 300 kPa when the wind speed was less than 0.4 m s-1. The volume of spray created by 11002, 11003, and 11004 nozzle sizes was 160, 240 and 320 L ha-1, respectively. Three weeks after spraying, the dry weight of plants was determined. The date were fitted using a four-parameter log-logistic model to estimate the dose required to achieve 50% wild barley control (ED50).
 

The ED50 was significantly affected by the type, size, and orifice number of nozzle. In all types of nozzles (Standard, anti-Drift and Air Induction) and sizes (11002, 11003 and 11004), an increase in orifice number significantly reduced the values of ED50 for cycloxydim against wild barely, indicating increased efficiency of herbicide. This can be explained by two reasons. Firstly, with an increase in orifice number in each type of nozzles, the size of spray droplets decreases. Previous studies have proven that there is a negative relationship between the amount of spray droplets deposited on the target surface and the size of spray droplets. Therefore, by decreasing the size of spray droplets, they can be deposited more on the target surface, resulting in an improvement in the foliage-herbicides efficiency. Secondly, increasing the orifice number of nozzle can lead to the penetration of spray droplets into the canopy. Among the nozzles of 11002 in any orifice number, the performance of nozzles was ranked as Standard > Anti-Drift > Air Induction. However, among the nozzles of 11003 or 11004 in any orifice number, the performance of nozzles was as Standard = Anti-Drift > Air Induction. Among all types of nozzles in any orifice number, increasing spray volume from 160 to 240 L ha-1 reduced the ED50. However, only in the types of nozzles of Air Induction in any orifice number, increasing spray volume from 240 to 320 L ha-1 reduced the ED50. 

It can be recommended that the most suitable nozzle for the application of cycloxydim against wild barely at a wind speed of less than 0.4 m s-1 with the aim of optimizing simultaneously both the dose of herbicide and the consumption of water is "Triplet Standard Flat Fan Nozzle 11003 " (spray volume= 240 L ha1).

Nowadays, the global effort in modern agriculture is to reduce the use of harmful herbicides and introduce new methods of weed control, one of which is the use of allelopathic properties. Among allelopathic species, aromatic plants have the ability to transmit allelochemical constituents as essential oils through diffusion and thus affect their surrounding organisms. Since the use of essential oils and volatile compounds will not have residues on the crop, these allelopathic compounds can be very effective in preventing weed growth before and after crop cultivation. Studies have shown that some essential oils or their components effectively reduce plant growth. This study was aimed to identify novel allelopathic species and their inhibitory compounds.

Plant samples consisting of 112 different plant organs including root, rhizome, corm, stem, leaf, flower, fruit, fruit peel, aerial part, and plant exudate such as oleogum belonging to 97 aromatic species from 16 different plant families were collected from different areas of Iran. The essential oils were extracted by water distillation using Clevenger. The oils were then dehydrated in glass containers with anhydrous sodium sulfate and stored at 4 °C during the experiment. The study was conducted in two separate experiments on germination and seedling growth, and lettuce was used as the test plant. The effect of 112 essential oils at two concentrations of 1 and 3 μL was investigated. The factorial experiments were conducted in completely randomized design with four replicates. Allelopathic effects of volatile compounds were evaluated by cotton swab method. The traits related to germination including Germination percentage (G%), Mean Germination Time (MGT), percentage of seed Dormancy induction (D%), percentage of embryo death as Lethal effect (L%), and seedling growth traits consist of Hypocotyl (H), Radicle (R), and Vigor Index (VI) were studied. The components of the strongest allelopathic essential oils were analyzed by headspace gas chromatography and mass spectrometry.

The results showed significant inhibitory effects of essential oils even on 1 µl concentration on the studied traits. The essential oils of Pelargonium graveolens, Pimpinella anisum and Thymus daenensis had the greatest inhibitory effect on G% (100% inhibitory); and the essential oils of Amomum subulatum, Atremisia sieberi, Dracocephalum moldavica and Thymus transcaspicus had the highest effect on MGT (more than 224%). The essential oils of Ziziphora tenuior, Pimpinella anisum, and Pelargonium graveolens caused the highest seed dormancy (more than 22%). The essential oil of Pimpinella anisum and Thymus daenensis caused the highest percentage of embryo death (100% lethality). According to seedling growth, the essential oils of Pimpinella anisum, Origanum vulgare, Perovskia abrotanoides and Thymus daenensis resulted in the highest inhibition of hypocotyl (more than 92%). Thymus daenensis and Origanum vulgare essential oil exhibited the greatest effect on decreasing radicle growth (more than 97%). Overall, the essential oils of Anise, Oregano, Russian Sage and “Denaee” Thyme were the most inhibitors of seedling growth. Finally, with respect to germination and seedling growth percentages, 25 essential oils mainly from the Lamiaceae family (12 essential oils), and some other families e.g. Asteraceae (4 essential oils), Apiaceae (3 essential oils), Rutaceae and Geraniaceae (2 essential oil), Liliaceae and Zingiberaceae (1 essential oil) had the greatest inhibitory effect on the Vigor index. According to the results of the headspace gas chromatography, compounds such as borneol, eucalyptol, limonene, alpha and beta-pinene, carvacrol, and camphene were the dominant compounds in essential oils with severe inhibitory effects. Other studies have also reported phytotoxic, antibacterial, antifungal, and pesticidal effects of some of these compounds, scant literature is, however, available on the allelopathic effects of some other ones.

Our results showed that the essential oils of medicinal and aromatic species were highly toxic to lettuce. In addition to inhibition of germination percentage and seedling growth, traits such as seed dormancy induction, embryo death and delayed germination were also affected by essential oils. In allelopathic researches, such traits are often overlooked, while they can play an important role in growth inhibition and are valuable traits for weed control. Further research is needed to identify the compounds responsible for allelopathic activity in these plants essential oils and to understand the biological roles of these compounds in natural ecosystems. Such information could provide a broader perspective for researchers on the production of new bioactive chemicals from natural products. Identification of allelopathic plants and compounds, and their biological functions are important for the biological control of weeds in organic agriculture as well as species that can adversely affect forestry projects.