جستجوی مقالات مرتبط با کلیدواژه "response" در نشریات گروه "زراعت"

To evaluate the effects of dose and application time of oxadiargyl, as a postemergence herbicide, on weed biomass and tuber yield of potato, a factorial experiment based on randomized complete block design with 3 replications was conducted at Alaroog Research Station at the University of Mohaghegh-Ardabili in 2013. Treatments consisted of oxadiargyl dosages (0, 0.05, 0.1, 0.2, 0.4, 0.6 and 0.8 lit a.i /ha), and its time of applications at different potato growth stages (potato emergence, stolon initiation and potato tuber bulking), weed free treatment was considered as control. Statistical analysis showed that 0.8 lit a.i/ha of oxadiargyl reduced biomass of weed by 66.16 percent. Oxadiargyl application at emergence time resulted in highest percent reduction of weed biomass. Results, also, showed that application 0.8 lit a.i/ha of oxadiargyl, after weed free condition, increased number of seed tuber and total tuber yield by 82.16 and 51.59 percent respectively, but it reduced number of non seed tuber by 43.17 percent. Application of oxadiargyl at emergence time, as compared with the other application times, resulted in highest increase in the number of seed tuber and total tuber yield, but it did not affected number of non seed tubers. Interaction effect of dose by time of oxadiargyl application revealed that using 0.8 lit a.i/ha dose at potato emergence time increased number of edible tubers by 100%. It may be conducted that application of this dose at potato emergence time was highly efficient in controlling weeds and increasing potato tuber yield.

Experiment was conducted in 2011 to evaluate the efficacy of reduced herbicide rates in combination with false seedbed for selective weed control in common bean. The experiment was carried out with a completely randomized factorial design. Factors were herbicide dose (post-emergence application of imazethapyr at the rates of 0، 25، 50، 75، and 100 g a. i. ha-1) and seedbed preparation (false seedbed and conventional seedbed). A hand weeding control was also included as check. In the absence of herbicide، there were significant differences in grass and total weeds biomass between two seedbeds (p< 0. 01)، however، biomass of broadleaved weeds was not significantly different in two seedbeds (P=0. 053). The false seedbed decreased grass and total weed biomass by 28 and 21%، respectively، as compared with conventional seedbed. Imazethapyr application greatly affected grass and broadleaf weed growth and biomass production. The rate of 50 g a. i. ha-1of imazethapyr was as effective as the 100 g a. i. ha-1 rate to maintain consistent weed control in the false seedbed، while، the rate of 75 g a. i. ha-1 was required to maintain effective weed control in conventional seedbed. Season-long weed competition resulted in 68 and 73% yield loss in common bean in the false and conventional seedbed، respectively. However، imazethapyr application decreased yield loss down to 4. 7 and 2. 9% in false and conventional seedbed، respectively. The study suggests that acceptable weed control in common bean of the weed species observed in the present study could be achieved using imazethapyr at the rate of 56 g a. i. ha-1 in combination with false seedbed، which can save the yield by 90%.

Septoria tritici blotch (STB) caused by Mycosphaerella graminicola is one of the most important diseases theating wheat crop worldwide. Use of resistant cultivars is the most effective and economically way to control the disease. To evaluate and identify sources of resistance to STB among wheat genotypes at seedling stage، infected leaf samples were collected from different ares of Khuzestan province during 2010-2011 cropping season. After purification and preparation of several isolates of the pathogen، four most virulent isolates were selected and inoculated on primary leaves of seedlings of 219 wheat cultivars and advance lines together with four check cultivars selected from breeding materials of Seed and Plant Improvement Institute، Karaj، Iran. Resistance of genotypes were evaluated based on reaction types of seedlings on day 21 after inoculation، pecentage of necrotic areas and pycnidial coverage. Based on the results، eight cultivars Arina، Riband، M3، Arya، Shotordandan، Karkheh، Soison and Chamran were resistant to all four isolates. Line Sep-49 was resistant to two isolates 90014 and 90018 but susceptible to isolates 91001 and 91002. Lines Sep-58 and Sep-59 were also susceptible to isolate 91002 but resistant to other three isolates. The remaining genotypes were susceptible to all four isolates.

To study the resistance of wild musturd populations to acetolactate synthase inhibitors، 31 suspicious wheat fields to resistance (included of 14، 12 & 5 fields located in Golestan، Khoozestan & Keramanshah، respectively) were studied during 2012. Some important management information was analyzed in the first part of experiment. In the second part، the effect of three acetolactate synthase inhibitor herbicides (ALS) including of Tribenuron methyl (Granstar)، sulfosulfuron + metsulfuron-methyl (Total) and Iodosulfuron methyl sodium+Mesosulfuron Methyl+Mephen payer (Atlantis) on the growth of suspicious populations was examined on the base of complete randomized block design. To study dose-response reactions، different doses of mentioned herbicides were sprayed on resistant populations (G3، G4 & G5 of Gorgan، Kh1، Kh5 & Kh7 of Khoozestan and Ker1 of Kermanshah) and three sensitive populations (G9، Kh3 & Ker1 of mentioned province) in the third part of this experiment. According to the results of the first part، the only crop sequence of herbicides was not observed in more than 80% of the fields and wheat was cropped as in 39% of these fields. In addition، Khoozestan had the weakest crop rotation with 50% single cropping. The results of second part showed that 20% and 10% of populations were resistant to Tribenuron methyl and sulfosulfuron + metsulfuron-methyl respectively، but، high resistance to Iodosulfuron methyl sodium+Mesosulfuron Methyl+Mephen payer. Also، 10% of populations were resistant to Tribenuron methyl and sulfosulfuron+metsulfuron-methyl. According to the results of dose-response experiment، G3، G4، G5 (Golestan) and Kh7 (Khoozestan) populations had low، Ker2 (Kermanshah) had medium and two populations of Kh1 and Kh5 (Khoozestan) had high resistance to Tribenuron methyl. In addition، Kh5، Kh7 (Khoozestan) and G3 (Golestan) had low، medium and high resistance to sulfosulfuron+ metsulfuron-methyl، respectively.

In order to evaluate the effect of Rimsulfuron, EPTC (Eradican), oxadiargyl, metribuzin and Metribuzin herbicides for controling of Lambsquarter (Chenopodium album) and prostrate pigweed (Amaranthus retroflexus), an experiment was conducted at the Mohaghegh Ardabili University green house in 2008. A dose-response assay was conducted based on completely randomized design with four replications. The potato cultivar was Agria (common cultivar in Ardabil). Herbicides were used in six doses included reduced and overdoses rather than recommended doses. Common lambsquarter and prostrate pigweed were sprayed during the 2-4 leaves stage and potato was in 15-20 cm. Results showed that the most effective herbicides for weed control were Metribuzin, Oxadiargyl, Rimsulfuron and EPTC, respectively. Also the least herbicides damage for potato was in Rimsulfuron, EPTC, Oxadiargyl and Metribuzin, respectively.

In order to evaluate the resistance of wild oat bitypes to clodinafop-propargyle, pinoxaden and their mixture (traxos), collected from Fars and Khoozestan provinces, pot and Petri dish bioassay studies were conducted on 8 suspected to resistance wild oat biotypes as well as one susceptible biotype at Iranian Research Institute of Plant Protection during 2008-2009. In pot bioassay experiments which were conducted as RCBD with four replications, wild oat plants were sprayed during 2-4 leaves stage using 0.25-16 times the recommended dose. Based on herbicide recommended rates (0.8, 0.45 and 1.5 l/ha for clodinafop-propargyle, pinoxaden and traxos, respectively), the applied doses were 0, 16, 32, 64, 128, 256, 512 and 1024 g ai ha-1 for clodinafop-propargyle, 11.25, 22.5, 45, 90, 180, 360 and 720 g ai ha-1 for pinoxaden and 16.87, 33.75, 67.5, 135, 270,540 and 1080 g ai ha-1 for traxos. In Petri dish bioassay studies, after determination of discriminating dose for each herbicide (0.05, 0.03 and 0.01 mg ai/l for clodinafop-propargyle, pinoxaden and traxos respectively), dose response experiments using 0.25-16 times of the discriminating dose were conducted on germinated seeds. The results indicated that all biotypes was resistant to clodinafop propargyl and cross resistance to clodinafop-propargyle, pinoxaden and their mixture (traxos) in Khoozestan populations were confirmed. Greater than 37% of biotypes were controlled by pinoxaden or traxos herbicides and the resistance level of all biotypes to traxos was lower than other herbicides.

In order to select appropriate combined model to describe the relationship between herbicide dose–response and nitrogen fertilizer levels in predicting jimsonweed and redroot pigweed control a experiment was laid out in a factorial design based on complete randomized design (CRD) with three replicates in research greenhouses of Agriculture Campus of Tehran University, Karaj in 2009. The four levels of nitrogen (0, 90, 180 and 360 kg ha-1 urea fertilizer) and five levels of Nicosulfuron (0, 0.5, 1, 1.5 and 2 L.ha-1) were applied. Analysis of variance demonstrated the there were significant effects of fertilizer and herbicide treatment and interaction between herbicide and nitrogen on both of weed biomass.‌ The standard dose–response curve was considered for base model. Then efficiency of this model assesses to weed biomass determination at each nitrogen level that accuracy of this model confirms. For determination of relation each of parameters of base model with fertilizer levels, possible models were considered and appropriate models as sub-model were settled at base model, ultimately final combined model presented. The biomass of both weeds at no-herbicide treatment (Wo) showed a different behavior with increasing nitrogen. Trend of these changes at nitrogen levels was well described by the linear and quadratic models for redroot pigweed and jimsonweed, respectively. Increasing nitrogen didn’t change herbicide dose-response of jimsonweed, because steepness of the curve (β) and the effective dose required to reduce weed biomass by 50% (ED50) parameters of this weed not showed a clear behavior with increasing nitrogen. Therefore standard dose–response curve with constant β and ED50 parameters was best describing of jimsonweed biomass as affected by both the herbicide dose and nitrogen level. But standard dose–response curve of redroot pigweed was modified by replacing the parameter β and ED50 with the exponential and linear curves, respectively. The final presented models can be used to predict weed control by an herbicide as affected by both the herbicide dose and nitrogen level.

Responses of ten pomegranate cultivars Malas Torsh Saveh, Malas Shirin Saveh, Agha Mohammad Ali Shirin, Alk Torsh Saveh, Alk Shirin Saveh, Poost Sefid Shirin, Poost Sefid Torsh, Poost Siyah Shirin, Tabestani Torsh Saveh and Poost Sefid Bihasteh Shomal to population density of Tenuipalpus punicae were evaluated during 2001-2002 in Saveh region. A Randomized Complete block design in three replications was used for analysing the data collected from forthnightly sampling of mites onset from mid. May up to mid. November. Maximum number of mites on both sides of leaves was recorded 67.66 and 24.33 at the middle and end of August on Poost Sefid Shirin cultivar during two years of sampling, respectively. Maximum (13.47) and minimum (0.4) mites densities were recorded on Poost Sefid Shirin and Malas Torsh cultivars in the first year and rather similar densities in the second year determined them as susceptible and resistance cultivars to the mite density respectively, but in general no significant difference was observed among the cultivars with population density of mite. Analysis of data from eleven sampling intervals indicated only peak of mite population during September which can be related to the high temperature occurred during this period. Population of mite was highly affected by color and taste of pomegranate cultivars. Cultivar Poost Sefid and local cultivars with white color and sweet taste attracted higher populations of mite. Maximum mite-days (225 days) was also observed on Poost sefid Torsh cultivar. These findings indicate that white colored pomegranate cultivars accepting higher populations of mites and longer time of activity, seems to be more sensitive to the mite.