نشریه بوم شناسی علف های هرز
سال دوم شماره 1 (بهار 1390)

In order to study genetic diversity of Canarygrass (Phalaris minor Retz.), RAPD Technique was applied to 8 seed samples taken from eight different parts of Iran. Thirty four random Ten-mer primers were tested by using Polymerase Chain Reaction (PCR) in genetic distances. 27 Primers showed polemorphism in all samples. Out of total 710, 430 fragments of reproduced DNA (60.56 %) fragments showed polymorphism. To estimate the genetic distances, the mentioned primers were used. Cluster analysis was carried out based on presence (1) and absence (0) of the band. Jaccard similarity coefficients were calculated using UPGMA method. Based on Jaccard and simple comparative Coefficiency in cluster analysis, the samples were divided in 6 groups in similarity level of 75%. The results taken from comparing and analyzing data of RAPD and similar matrix presents genetic diversity among the samples. Minimum genetic similarity 41%) was observed between Torbat_e Jam (Ph8) and Bojnord (Ph1) as well as Moghan (Ph 5) and Varamin (Ph 3) (42%) samples. While maximum value (71 %) was observed between Gorgan (Ph6) and Amol (Ph4) samples. The Results revealed lack of adaptability between studied genetic and geographic diversity.

The present study was conducted to investigate the effect of tomato (Lycopersicum esculentum) transplanting date on broomrape (Orobanche spp) density in Golmakan, Khorasan-Razavi Province during 2010 growing season. The experiment was laid out in a completely randomized block design with four replications. The treatments included five transplanting dates of tomato: 31, 41, 51, 60 and 69 days after 21st March. The results showed significant differences in density and dry matter of broomrape among treatments. The latest transplanting date presented less density and dry matter of broomrape compared to the 2nd transplanting date. The first and the forth transplanting dates showed less density and dry matter of broomrape than the second and the third transplanting dates, significantly. Early and late transplanting dates were the best treatments with the maximum tomato yield and less infection by broomrape. It may show high correlation between broomrape infection and seasonal temperature.

In order to investigate the species and functional diversity and the structure of weed communities in apple orchards in Fariman, 48 orchards were studied in 2010. At first, all orchards based on the amount of used input (gathered by questioner were divided to 3 groups: high input, medium input and low input. Then weed population samples were collected. After sampling, weed density, frequency percentage and evenness coefficient were determined based on genus and species separation. The results showed that weed community in different orchards are composed of 54 species in 17 plant families. Among the community, 45 species were dicotyledonous and 9 species were monocotyledons. Also, 48 species were C3 plants and others were C4 species. They were 40 annuals and 14 perennials. Asteraceae, Fabaceae and Chenopodiaceae families had the most diversity among dicotyledonous and Poaceae, with the most diversity, was among monocotyledons. Shannon- Weiner index varied between 11.35 and 2.73; high-input orchards had the most species diversity in Shannon index. The investigation of elative frequency amounts in different orchard groups indicated that weed species density was affected by different weed management systems.

Wild barley (Hordeum spontaneum) is one of the most troublesome weed species in wheat (Triticum aestivum) in Iran. In order to compare the efficacy of sulfosulfuron, sulfosulfuron+metsulfuron-methyl as the two sulfonylurea herbicides on wild barley control in relation with growth stages of wild barley, an experiment was conducted. It was based on RCBD with 3 replications in Marvdasht, Fars Province in 2010. The treatments included sulfosulfuron trade form as Apyrus® (30 g/ha-1+surfactant) and sulfosulfuron+metsulfuron-methyl trade form as Total® (45 g/ha-1+1250 ml surfactant) in 2-4 leaf, second node and 2-4 leaf+second node of wild barley and control (untreated). The results showed that Total® herbicide had better efficacy to control wild barley in comparison with Apyrus® so that by using Total in the second node and 2-4 leaf+second node density decreased to 0 (score 1). The application of herbicide Apyrus® in the second node and 2-4 leaf +second node stage of wild barley were low in quantity of wild barley efficient density and dry weight (score 5), respectively. Total® efficacy was high in 2-4 leaf stage compared to Apyrus® with decreasing 90.78% and 95.55% density and dry weight of wild barley, respectively.

In order to distinguish the weed competitive cultivars of rice in reducing the use of Butachlor dosage, an experiment was conducted in a completely randomized block design (RCBD) with three replications in factorial arrangement of treatments. The experiment was done in research field of Islamic Azad University of Chaloos in 2009. The treatments included rice cultivars (Hashemi, Fajr and Shiroodi) and Butachlor herbicide doses (0, 1.5, 2, 2.5, 3, 3.5 L.ha-1). The results showed that lack of herbicide use caused the highest weed density and dry weight of Barnyard Grass. Also, the least yield (seed and biologic yield) and yield component (total number of tiller, percentage of fertilized tiller, number of spike in an square meter, number of spikelet in a spike, and percentage of full spikelet in a spike) was obtained in the presence of all cultivars. Weed density and dry weight of Barnyard Grass decreased and yield and yield component increased. An increase in Butachlor from 2.5 to 3.5 liter per hectare did not affect on weed density, dry weight of Barnyard Grass and yield and yield components significantly. In Shiroodi cultivar, the least weed density and biomass was obtained; it was recognized as the competitive cultivar in the presence of weed. Also in the presence of competitive cultivar of Shiroodi, the greatest (seed and biologic yield) and yield component (total number of tiller, percentage of fertilized tiller, number of spike in an square meter, number of spikelet in a spike, and percentage of full spikelet in a spike) was obtained in comparison with other cultivars.

To investigate the possibility of tank-mix application of two herbicides – Nicosulfuron and Bromoxynil + MCPA – to control narrow and broad leave weeds in corn fields, an experiment was carried out in Karaj. The experiment was conducted in a completely randomized block design and factorial format with twofactor combination and in four replications. The first factor was Bromoxynil + MCPA at 0, 1.0, 1. and 2.0 liters per hectare and the second factor was Nicosulfuron dosage at four levels of 0, 0.5, 1.0 and 1.5 liters per hectare. In additionally to experimental treatments, an evidence treatment with complete hand weed was added. Then the efficiency of the treatments on weed of the field and corn yield was studied. The results showed that the best combination of tank-mix of the above mentioned herbicides considering weed control efficiency, the percent of corn yield augmentation and the minimal environmental risk was 0.5 to 1.0 liters per hectare of Bromoxynil + MCPA and 1.5 liter per hectare of Nicosulfuron.

Chemical herbicides, despite their known toxicity, are widely used in developing counties. Evaluating the patterns of farmers’ use of the herbicides would help highly in recognition and their change of behavior. In this study, the attitudes associated with chemical herbicides use and exposure was evaluated among farmers in Markazi district of Karaj. Out of 1598 farmers of Markazi district, 130 farmers completed Cochran questionnaire; they were studied through accidental sampling. Cronbach’s alpha coefficient was used to identify the validity of the questionnaire that was higher than 0.7. It was favorable for this study. The validity of the questionnaire was confirmed by experts’ panel. The results indicated that the attitude and the education have positive, direct and significant effects among farmers in using chemical herbicides. Based on the results, variables such as age, education, land area, distance of land to habitats, and job experience through effects on herbicide use cause a change in behavior about chemical herbicides use among farmers.