Applied Entomology and Phytopathology
Year:2004 | Volume:71 | Issue:2|Papers Count:11

Tobacco plants (Nicotiana tabacum cv. Samsun) were transfonned by coat protein gene of potato virus Y necrotic strain (PVyN-CP) using pBINI9 binary vector and agroinoculation method. The primers designed so that the inserted PVY-CP transgene had not any start codon and so, it was unable to be translated into coat protein Jroduct.. Resistance of 31 transgenic Nicotiana tabacum cv. Samsun lines containing PVYN coat protein transgene (PVyN_CP), were evaluated against the mechanical challenge inoculation of 3 prevalent Iranian PVY strains. On the basis of biological and serological properties, 3 Iranian PVY isolates include PVYn-H, PVYn-Mz (necrotic strain of PVY) and PVYo-Ar (an Ordinary strain). Symptom evaluation and ELISA tests showed that after challenge inoculation of 31 transgenic lines with PVYn-H, PVYn-Mz and PVYo-Ar isolates, 5,4 and 0 lines showed resistant phenotype, 9, 10 and 2 lines showed moderate symptoms of the disease and 17, 17 and 29 lines showed susceptible phenotype, respectively. Using TAS-ELISA and Westemblot analysis, the protein product of PVYN -CP transgene could not be detected in any of 31 transgenic lines. It seems that an RNA mediated resistance is responsible for resistance in the PVY-CP transgenic tobacco plants. In Nicotiana species, natural resistance sources to PVY infection are poor and development of engineered resistance sources against PVY infections would be usefu

Using demographic toxicology, an experiment was carried out to evaluate efficiency of buprofezin, pyriproxyfen (Insect growth regulators) and fenpropathrin (a pytethroid) on greenhouse whitefly T. vaporariorum. The experiment was carried out at 26±1oC, 60±5 %RH and photoperiod of 16:8 (L: D). Leaf cages were put on bean leaves which were already immersed in the sublethal doses of the above mentioned insecticides and a male and a virgin female were released inside the cage. Thereafter, various parameters such as adult longevity, daily fecundity rate and percentage of egg hatching were recorded. Fenpropathrin reduced adult longevity (5.3 days) compared to the control (9.7 days), while buprofezin (8.1 days) and pyriproxyfen (9.4 days) didnt have any significant difference compared with the control. Number of eggs laid per female in fenpropathrin (24.6) treatment were significantly less than the control (53.4), but the other two insecticides didnt show any significant differences with the control. mean egg hatch percentage during lifetime in buprofezin (38%) and pyriproxyfen (24%) showed significant reduction compared with control (96%). Fenpropathrin didnt have any effects on the egg hatching. The effect of buprofezin and pyriproxyfen on the egg hatching caused heigh reduction in number of fertile egg per day, gross fertility rate and gross hatch rate compared with the control. Although fenpropathrin was effective on adult mortality and oviposition rate, however, due to ultimate effects of buprofezin and pyriproxyfen on reproductive parameter, they cause sever reduction in population growth rate in following generation and could be recommended in IPM program.

Wild oat (Avena ludoviciana Durieu.) is one of the important weeds in winter wheat. Seeds produced by this plant are viable in soil for a long time and germinate gradually. Physiological basis of wild oat seed dormancy was investigated. Results showed that complete germination of dormant seeds was obtained when the covering structures (glumels, peri-carp, endosperm, aleurone layer) were removed. This shows that embryo may not be the main factor in dormancy and that it is non dormant. There are two factors that affect seed dormancy. The first is the presence of glumels that prevent seed germination mechanically and the second one is the aleurone layer in caryopsis. It causes dormancy by decreasing water potential in embryo. Using electrophoretic separation (SDS-PAGE), the protein composition of non dormant and dormant seeds were recognized. There were eight special polypeptide bands in dormant seeds, four of them had molecular weights of more than 66000 Da , and molecular weights of others were, 38695, 53380, 46505 and 20334 Da. However, in non dormant seeds 2 special polypeptide bands with molecular weights of 32197 and 25587 Da were observed. This may mean the presence of gene influence in seed dormancy and germination.

Fumigation toxicity and repellency of essential oil of Artemisia aucheri Boiss (Asteraceae) was investigated on four species of stored products pests including: Callosobruchus maculates F.(Col.; Bruchidae), Tribolium castaneum Herbst (Col.; Tenebrionidae), Sitophilus oryzae L., Sitophilus granarius L. (Col.; Curculionidae) at 30 ±2 oC, 60 ± 5 r. h. under dark condition. After 48 h. of fumigation, mortality of adult insects was found to increase as the essential oil concentration increased. At the highest concentration of essential oil (0.926µ1/ cm3)mortality was recorded 84.41, 85.41, 84.70 and 83.04% for C. maculates, T. castaneum, S. oryzaeand S. granarius, respectively. During 3, 6 and for 9 h. after fumigation adult insects of C. maculates with 20.33, 35.70 and 47.96 % mortality were found more susceptible than other species. LCso values of essential oil were found to be 0.1074,0.1221,0.1277 and 0.1389µ1/cm3 for C. maculates, T. castaneum, S. oryzae and S. granarius, respectively.The essential oil significantly repelled insects and at 0.03 µ1/cm3 caused 41.99,51.45,47.31 and 46.31% repellency for C. maculates, T. castaneum, S. oryzae and S. granarius, respectively. Repellency of the essential oil for all tested species was found to increase as its concentration was increased.

Efficacy of flaming was compared to common methods of weed control in onion fields during the years of 1999 and 2000, in E.Azarbijan. The experiments were conducted in the framework of Radomised Complete Block Design with 10 treatments and 4 replications. -Thetreatments included ioxynl (as TotriI22.5%) + sethoxydim (as Nabu-S 12.5%)at 3+3 l/ha post emergence with and without one hand weeding; chlorthal dimethyl (as Dacthal 75%) at 12kg /ha preemergence with and without one hand weeding; paraquat (20%) at 3 l/ha, post emergence of weeds when onions were at 5cm stage, with and without hand weeding; flaming at the pace of 0.25 m/second, post emergence of weeds and when onions were 5cm high; weedy and weed free checks. Results showed that all treatments plus one hand weeding controlled weeds effectively and boosted yields. It is, therefore, concluded that flaming can replace herbicides in onion fields.

In order to evaluate soybean growth indicies in competition with some weed species, an experiment was conducted in Karaj during 1999-2000. The experimenta1design was --rnn

One of the most important pests of stored wheat and rice is a curculionid named rice weevil Sitophilus oryzae. Study on biology of this pest on 5 local rice cultivar in Mzandaran Province (Tarom, Neda, Nemat, Fajr and Khazar) was performed in 3 treatments. The experiment was carried out under28 ± 1oC and R.H. 75 ± 5% condition. Separated bottles were provided for each cultivars and 30 gr. of rice grains poured in each bottles. In each bottle 35 one day old males & females were released and duration of egg, larval, pupal and adult stages were determined. This study was performed in completely randomized design with three replications and means comparison was done using Dunncan multiple rarge test. The results showed that, there were no significant difference between embryonic growth on different rice cultivars. The longest larval stage period was on Fajr and Khazar cultivars, the longest pupal stage period was on Fajr and the shortest pupal stage period was on Neda, Nemat and Local Tarom cultivars. The longest period of insect staying inside nidus and complete life cycle were found on Fajr cultivar.

Phenotype and genotype of populations are affected by ecological factors and are main components of the process of speciation. Therefore, bioclimatological studies are used In taxonomy researches. On the basis of these studie sthe range of distribution of msects and also the factors which influence their distribution can be discussed. Thus their possible distribution to other places could be forecasted. The bioclimatological study of termite fauna of Iran has been carried out usmg De Martannes modified system of climatic classification. The climatic parameters used m this classification were obtained directly from data base bank of meteorology of irrigation Dept. (Collage of Agriculture, Tehran University) or obtained from equation which correlated these parameters to geographical coordmates (e.g. Long. Lat. and Elevation) for 82 site samples. So the main factors P (mean annual precipitation,), T (mean annual temperature )and m (mean of mm. temperatures m the coldest month of the years) and finally the Aridity Index (lA)were obtained for 82 sites. The plotting position of each region on modified De Martannes clirnogram were plotted and as a result the ecological niches of the 20 species of termites were well identified. The importance of ecological niches m taxonomy of termites, specially differentiation of near species was discussed.

The ß -exotoxin (also called thuingiensin and thermo stable toxin) is toxic to human and other animals. Because of vertebrate toxicity, most commercial preparation of B. thuringiensis is composed of subspecies or isolates that do not produce ß -exotoxin. As a condition for registration for pesticide use on food in USA, B. thuringiensis active ingredients must be tested to show the abscense of ß -exotoxin. In this study screening methods for the presence of ß-exotoxin in a product of B. thuringiensis subsp. aizawai (Bill) were based on laboratory bioassay against lepidopteran larvae and High Performance Liquid Chromatography (HPLC). The bioassay and HPLC assay results indicated that the ß -exotoxin was presence in the product of B. thuringiensis subsp. aizawai (Bill). Bioassay was showed to be more sensitive than High Performance Liquid Chromatography (HPLC). Bioassay can be used to detect and qualify B. thuringiensis ß -exotoxin and can be a useful tool for quality control.