جستجوی مقالات مرتبط با کلیدواژه « گندم » در نشریات گروه « گیاهپزشکی »

So far, several bacterial diseases, including wheat stripe spots caused by Xanthomonas translucens and mild bacterial mosaics caused byClavibacter tessellarius , have been reported in Poaceae family plants. In recent years, reports have been published on the presence of Clavibacter zhangzhiyongii bacteria in barley plants in some countries, such as Australia and China. This research was conducted to track and identify the mentioned bacteria using biochemical and molecular methods and determining its host range. For this purpose, in the years 2021 and 2022, wheat, barley, and weeds with symptoms of brown spots, mild mosaic, decay, and yellowing of leaves were sampled in the provinces of Golestan, Bushehr, Qazvin, Zanjan, and Fars. Bacterial isolation was performed according to standard bacteriological methods. Phenotypic and biochemical tests identified isolates and housekeeping genes atpD, gyrB, ppK, and recA. Pathogenicity tests were performed by spraying and stem injection. Based on biochemical and molecular tests, 15 isolates of the genus Clavibacter were identified, and among the studied isolates, three isolates were identified as C. zhangzhiyongii.

One of the damaging agents for wheat is the cereal cyst nematode (Heterodera avenae). Plant Growth Promoting Bacteria (PGPR) are a group of bacteria that have beneficial properties for plant growth, including iron chelation, siderophore production, phosphate dissolution, nitrogen fixation, as well as the production of protease and chitinase enzymes. These bacteria can also be used as biological control agents. In this study, wheat roots showing suspicious symptoms of cereal cyst nematode were collected from the Dezful county in Khuzestan province during 2022-2023.  After initial investigations, nematode identification and purification was done. According to the morphometric and morphological characteristics of the larvae and cysts, especially its cone top, H. avenae was diagnosed. the effect of seven native growth-stimulating bacterial strains on egg hatching rate and mortality of cereal cyst nematode larvae in the Petri dish was investigated in the laboratory. The effect of four selected bacterial strains with sulfur treatment and Nematex EC nematicide was investigated in the greenhouse against grain cyst nematode. The results showed that in laboratory conditions, the bacterial strains were able to reduce the egg hatching rate by 62% on average. Bacillus pumilus bacteria caused the greatest decrease in egg hatching by 73%. The percentage of mortality of larvae in the laboratory test was also shown to be 63% on average, and the treatment of B. pumilus bacteria showed the highest percentage of mortality with 70%. The results of the greenhouse investigations showed that the treatments involving sulfur-healthy plants, sulfur-nematode, and the B. pumilus and P. fluorescens bacteria were most effective in promoting healthy plant growth and controlling nematode infestation. These treatments resulted in significant improvements in plant height, as well as fresh and dry plant and root weights. Additionally, the greatest reduction in the number of cysts was observed in the B. pumilus treatment, with an average of 49 ± 1 cysts. When examining the number of eggs within the cysts, the most substantial decrease was observed in the Nematex EC and B. pumilus bacteria treatments, with 67 ± 1 and 111 ± 2 eggs, respectively. Furthermore, in the assessment of the number of live larvae in the pot, the greatest decrease in the number of larvae was observed in the Nematex treatment, with 87 ± 1..

Tan spot disease caused by Pyrenophora tritici-repentis is a destructive disease in wheat production areas around the world. The disease has a high prevalence and distribution in the Golestan, Mazandaran, and northern regions of Ardabil province. Due to the lack of suitable resistant varieties in Iran, the damage caused by the disease is high. In this study, the evaluation of 50 wheat lines resistance belonging to the 9HLBSN treasury of the International Maize and Wheat Research Center (CIMMYT) was investigated using race1 of the pathogen. By inducing the fungal isolates to produce abundant conidia, the infection was established in the wheat seedlings through inoculation of the suspension of fungal conidia. The results of this study demonstrated that lines number 1, 17, 18, 22, 25, 29, 33, 34, 35, 36, 37, 38, 44, 45, and 47 had a susceptible reaction, and other lines which included 70% of investigated lines, were resistant. In addition, the mean disease index in different lines was calculated and compared. In terms of the mean disease index on the evaluated lines, 13 groups were obtained, which had 8, 8, 8, 4, 3, 5, 12, 23, 24, 28, 28, 26, and 22 members, respectively. Considering the susceptibility of most of the country's commercial cultivars to this disease, the resistant lines obtained in this study are good sources of resistance to be used in the breeding programs of wheat.

Take-all is one of the most important wheat diseases worldwide. The present study assessed the effect of nitrogen and phosphorus fertilizers, and endophytic fungus Microdochium bolleyi on controlling this disease in wheat ‘Pishgam’ cultivar for the first time. A greenhouse experiment was conducted based on a completely randomized design (CRD) with the treatments of control, nitrogen+phosphorus fertilizers (100 and 200 mg kg-1 urea, and 50 and 100 mg kg-1 triple superphosphate) alone and their combination with pathogen Gaeumannomyces graminis and endophytic fungus M. bolleyi. Then, root dry and shoot fresh weights, plant height, and leaf chlorophyll content, as well as the percentage of root contamination were measured. Based on the results, root dry and shoot fresh weight, plant height, and leaf chlorophyll content were significantly maximized following the treatments containing urea and triple superphosphate at various levels, and endophytic fungus (p<0.05). In terms of pathogenesis control, about 46% decrease was observed in take-all disease for the treatment receiving urea+triple superphosphate alone. The disease was respectively controlled by around 58 and 75% after applying endophytic fungus M. bolleyi alone and in combination with the highest amount of urea+triple superphosphate, respectively.

Pseudomonas fluorescens bacteria are the most important rhizosphere bacteria that have a positive effect on vegetative and biochemical traits of the plant. In this study, genetic diversity of 22 Pseudomonas fluorescens strains and their effect on defense enzymes and growth factors of wheat plant were performed in three stages of greenhouse, molecular and biochemical evaluation. In molecular evaluation, 12 RAPD primers were used to evaluate the genetic diversity of strains. Biochemical evaluation was performed in 4 stages of 0, 3, 6 and 9 days after inoculation on wheat to measure the defense enzymes peroxidase and phenylalanine ammonialyase. VUPF5 strain on wheat increased shoot and biological weight. RAPD-PCR separated strains with similar geographic location and similar host. Greenhouse, molecular, and biochemical groupings identified almost the top strains. Strains 680, 738, 50, 354, 49, 58 and VUPF5, which had a positive effect on molecular evaluation in one group, were shared with the superior group of enzymes. T26-2 and F-68 in OP-I15 and OP-H8 primers amplified 1300 bp and 1200 bp bands, respectively witch these bands can evaluated after be further studies as candidate bands in the expression of these enzymes in wheat.

Bacterial mosaic of wheat is caused by the gram positive bacterium Clavibacter tessellarius. The symptoms of the disease are uniformly distributed small chlorotic spots with mosaic pattern on the entire leaf surface resemble those symptoms of nutrient deficiencies and some viral diseases, and it may be difficult to determine. Due to the seed-borne nature of the disease, use of healthy and certified pathogen free seeds is the most important strategy for managing this disease. The wheat bacterial mosaic has been reported in wheat fields in several provinces of Iran and it seems to be widespread in different wheat growing areas. In order to better understand the disease, its various aspects including the symptoms, pathogen biology and its host ranges, and management of the disease are reviewed in this article.

Fluorescent pseudomonads control plant pathogens by producing siderophore and inhibitory metabolites, and increase plant growth by producing plant hormones, some enzymes and mineral elements solubilization. In this study, 10 isolates of fluorescent pseudomonads from wheat rhizosphere cv. Zagros and Chamran (Dezful) and cv. Kohdasht and Zagros (Parsabad) in early April 2016 and early June 2017 were isolated by cultivation and purification on King B medium and also based on the production of green and yellow fluorescence pigment under UV light at 365 nm. These isolates were evaluated in terms of some metabolic characteristics such as inorganic phosphate solubilization, production of IAA, siderophore, ACC deaminase, hydrogen cyanide and protease, as well as control of wheat common root and crown rot disease caused by B. sorokiniana and increase in length and biomass of wheat shoots and roots in a randomized complete design (RCD) with three replications for each treatment.The UTP105 isolate showed the highest inhibition rate of pathogen growth with 62.5% and 70% in dualculture and production of volatile metabolites tests, respectively. In the greenhouse, the severity of disease was estimated at 85.3%, and UTP104 and UTP105 isolates showed the highest rate of disease reduction with 64.5% and 62.3%, respectively. Also, UTP105 and UTP104 were the most effective in increasing the wheat root and shoot growth parameters, respectively. These isolates are efficient for use in agriculture due to having favorable metabolic characteristics, disease control and plant growth enhancement..

Spraying is one of the most important agricultural operations in protection stage. It should be prevented from immoderate application of these pesticides/herbicides, while weeds, pathogens and insects are controlled in this stage. Apparently, establishing an appropriate time for spraying operation, estimating the number of required and approved days for this operation as well as weather observations are quiet necessary to achieve this target. In this study, four limiting factors including rain, wind speed, temperature and relative humidity were considered for spraying operation and the approved ranges were determined accordingly. To data analysis, each month is divided into six Five-day sections. According to weather observations related to 24 years (1994–2018), the numbers of working days were determined within the appointed ranges, considering the limiting factors. T test is then employed to determine probable average ranges. Based on the results, among the limiting factors, temperature was the most effective factor to determine the number of working days for spraying operation. According to this, totally 11.9 days were appropriate for this operation in a crop season. In this regard, the total number of days for chemical control of thin-leaf and broad-leaf weeds, aphids, grasshoppers, bugs and Hadena basilinea were 17.9, 19.4, 21.2, 11.9 and 16.9 days in a crop season, respectively.

Bacterial leaf streak of the cereal is one of the most important diseases of wheat and barley which was reported from Iran in 1989. The severity of this disease has increased since 2016 in some of the irrigated wheat fields of Iran. Using the resistant cultivars is the best way to manage this disease. In the past, the response of some elite lines and cultivars to this disease was studied and determined. As a result, it's critical to investigate how new promising lines respond to this illness. Under this context, the reaction of a variety of elite wheat lines and cultivars to this disease was examined in greenhouse settings in a recent research. In this study, the reaction of a number of wheat lines to this disease was evaluated in field conditions in three regions with different climates.

Seventy-one advanced lines received from the Seed and Plant Improvement Institute, were planted in the experimental farms of research stations in three provinces, including Hamadan, Lorestan, and Jiroft.  Each line was planted in two one-meter rows in a randomized complete block design in three repetitions. They were then sprayed with bacterial suspension (regional isolates) at a concentration of 108 cfu / ml by spraying at three times (during tillering, after stem elongation and at the beginning of heading/flowering). The percentage of leaf surface infection was recorded and evaluated fifteen days after the last inoculation. Data were analyzed using SAS software, and the means were compared using Duncan test at a 1% probability level.

The response of various lines to this bacterium was different in three regions. But, in general, the studied lines due to the reaction to this disease were evaluated susceptible (such as S-92-19, ICSBWEYT-17-3, N-91-17, ICSBWEYT-17-2, ICSBWEYT-17-9 and ICSBWEYT-17-7), Semi-sensitive (such as ICSBWEYT-17-11, ICSBWEYT-17-10, ICSBWEYT-17-16, ICSBWEYT-17-1 and ICSBWEYT-17-24) and tolerant (such as: C-91-4, N-91 -8, N-92-9 and CD-94-9).

The grouping of the lines' susceptibility to this disease in six specific groups has high overall coordination and fit with each other, in three areas. However, the infection severity of wheat lines with this disease significantly varied in different regions. Therefore, the severity of wheat line infection in Boroujerd was higher than in the other two areas. On the other hand, some lines in various regions had different reactions to the disease. For example, MS-92-18 line had relatively good tolerance in Boroujerd region, but not in Hamadan and Jiroft regions. Climatic and geographical conditions can affect the behavior of wheat genotypes to the disease and change their response in different climates. Many other researchers have proved this. The results of this study showed that although most of the studied wheat lines are susceptible to this disease, but there are also lines among them, that have good relative resistance which can be used as resistance sources in wheat breeding programs.

Fungal species Fusarium pseudograminearum, F. culmorum and Bipolaris sorokiniana are the most economically important pathogens causing crown and root rot of cereals. The use of resistant cultivars can be the most efficient measure to reduce the effect of this disease. As an alternative strategy, screening of resistant wheat genotypes has been emphasized in the recent studies. This research was conducted to evaluate level of resistance of 66 genotypes of bread wheat and durum wheat to B. sorokiniana, F. pseudograminearum and F. culmorum isolates in greenhouse condition. These experiments were conducted based on completely randomized design with seven replications in greenhouse condition. The results showed that, 11 genotypes including C-87-11, C-87-18, BACANORA /3/MASON/JGR//PECOS, 05899G01-2, F06580G2-1, F06659G6-1, McCormick/Trego, VA01W-205/TX99D4628, GA951079-3-5/Neuse, Owl,85224*-3H-*o-HOH/7/T.SPH/2*H567.71//4/CMH79.959/6/Gaspard and AWD99*5725/FL9547 were moderately resistant to diseases caused by B. sorokiniana isolates and its combination with F. pseudograminearum and F. culmorum. Among these genotypes, three genotypes C-87-11, GA951079-3-5 / Neuse and 05899G01-2 were resistant to the combination of all diseases caused by these three fungal species. These genotypes have potential to be incorporated into wheat breeding programs. Cluster analysis of reaction of wheat genotypes to all diseases caused by these three fungal species, as well as to different combination of them were able to separate susceptibe and relatively resistant genotypes from each other. In both dendrograms, genotypes that were relatively resistant to disease caused byB. sorokiniana and its combination with other diseases caused by fungal species were grouped into cluster 3.

In order to be used in studies related to the production of a kit for detection of the causal agent of bacterial leaf streak of cereals, in contaminated wheat and barley seeds, a hybridoma cell line (named L-B7) secreting monoclonal antibody to Xanthomonas translucens pv. translucens by fusing SP2/0 myeloma cells with splenocytes from immunized BALB/c mice with one strain of this bacteria (UPB684 isolated from barley in Iran), were produced. The monoclonal antibody produced, reacted positively with X. c. pv. undulosa (15 strains) and pv. translucens (15 strains). Strains from other pathovars (X. c. pv. graminis and pv. poae) gave a negative reaction. Antibody potency was assessed by testing in ELISA. Whole cells were used both as immunogen and as antigen in ELISA tests. This antibody could be used to differentiate Xanthomonas translucens pathovars, causing bacterial leaf streak of cereals, from other pathovars, as well as in the process of producing a detection kit.

The internal factors of seeds and the conditions outside the seeds can affect the germination and emergence of seeds. In some cases, environmental conditions are suitable for seed to germinate, while the seeds do no seed dormancy which is regarded to be one of the factors in seed survival. Seeds are exposed to different conditions of temperature fluctuations, moisture fluctuations, activity of microorganisms, etc. by being located at different depths of the soil. For instance, seeds that are located in the surface layers of the soil are more exposed to soil moisture fluctuations, which may also affect their dormancy. The results of various experiments have shown that in addition to the depth of burial of seeds, their burial time also affects their germination. Due to the fact that no experiments have been performed on the germination of myagrum weed seeds in this field, this study was conducted to investigate the effect of time and burial depth on breaking seed dormancy and percentage of germination of myagrum.

This study aimed to investigate the effect of burial time and burial depth on breaking seed dormancy and germination of myagrum seeds in factorial experiment based on a randomized complete block design with 4 replications in the research farm of Razi University of Kermanshah in 2014-2015. Experimental factors include burial time (270, 360 and 420 days), burial depth (0, 5, 10, 20 and 40 cm), temperature (25 ° C, 5/10 and 10/20 °C variable temperature) and light (light and dark). In June 2014, myagrum seeds were collected from plants that had become mature and were in the full mature stage stored in plastic nylon at 25 °C until the seeds were tested. At the beginning of the experiment, the seeds were packed in lace bags that had small pores from which the seeds could not exit and then placed at different depths of the farm soil. 340 seeds were placed in each lace bag. The lace bags were such that the seeds were exposed to the moisture, temperature and chemical regimes of the soil. To make it easier to exit the lace bags from the soil, a thread was attached to each bag that was placed on the soil surface. After each level of burial time in the soil (270, 360 and 420 days), lace bags were exited from different depths. Firstly, the number of germinated seeds in each lace bag was counted and the germination percentage was calculated. Germinated seeds were then removed from the bags and the residual of seeds was transferred to the Agriculture Laboratory of the Agricultural and Natural Resources Campus of Razi University. The results of Mondani et al. (16) study showed that myagrum seeds have physiological dormancy and mechanical dormancy due to hard outer shell. Therefore, seeds do not germinate included damaged seeds and seeds had physiological dormancy and mechanical dormancy. Extracted seeds (not germinated seeds) from different depths in each burial time were disinfected in sodium hypochlorite solution (2%) for ten minutes. Then, to ensure the viability of the seeds, a number of seeds of any depth were randomly selected and tested using tetrazolium solution (0.1%). The appearance of red color indicated the existence of respiration and viability of the seeds (13). To remove the mechanical dormancy caused by the hard outer shell in the seeds, the outer shell of the seeds was removed and then the seeds were placed in sterile petri dish with a diameter of 7 cm containing Whatman No. 1 filter paper and 5 ml of distilled water (30 seeds were placed in per petri dish) and to prevent water evaporation, the petri dishes were closed with parafilm. The petri dishes were then exposed to different temperatures (25 °C, 5/10 and 10/20 °C variable temperature) inside the germinator and in light and dark conditions. To exert the effect of darkness, petri dishes were wrapped in an aluminum foil. After 14 days, the number of germinated seeds in each petri dish was counted. Germination criterion was visible root exit. Finally, data analysis was performed by SAS (version 9.4) software and mean comparisons were performed based on Duncan at 5% probability.

The results showed the germination percentage of myagrum weed seeds in light and dark were not significantly difference, and also seed burial time, temperature, burial depth and burial time * temperature interaction had a significant effect (p ≤ 0.01) on the germination percentage. The highest germination percentage was observed after 420 days of burial at a variable temperature of 10/20 °C. Also, at the soil surface and with the increasing seed burial depth (more than 5 cm) the survival and seed germination percentage decreased compared to soil depth of 5 cm because seeds need special moisture and temperature conditions for germination. According to the results, these conditions existed at a depth of 5 cm in the soil, so it can be concluded that deep plowing and going -deep seeds may help to manage this weed.

Considering that the highest germination percentage was observed in the temperature regime of 10/20 °C, it can be assumed that this weed can be problematic in summer and autumn crops because this temperature range synchronizes in late winter and early spring. On the other hand, it is possible to control this weed in wheat fields. In fact, in wheat fields, herbicides such as 2,4-D and MCPA are used to control broad-leaf weeds in late March and early April, when the temperature is about 10/20 ° C and the time of germination and emergence of myagrum is used. However, if this weed appears in chickpea fields, it is difficult to control because there is no specific herbicide in chickpea fields to control broadleaf weeds, including myagrum. Also, as the depth of burial increased, the germination percentage of the seeds decreased, so deep plowing and deepening of the seeds may help to manage this weed.

 The stem rust of wheat (Puccinia graminis f.sp. tritici) is one of the most important diseases of wheat in Iran causing severe yield loss in some years in the case of favourable condition for disease epidemic. In the recent years, a new race of stem rust (Ug99) and its new variants have been emerged, which are virulent on most resistance genes, such as Sr31, Sr38, etc., and have potential to spread rapidly and cause severe yield loss. The Ug99 race was first reported in 2009 from Lorestan and Hamadan provinces of Iran.Materials and

Results of a recent study conducted during 2011-2013 in Iran showed virulence on Sr36, Sr38, SrMcN and SrTmp genes and since, these genes have been used widely in genotypes resistant to Ug 99, there is a possibility of breakdown of these genes in Iran. Therefore, genetic variability of pathogen should be continuously investigated and resistance sources should be developed based on this information. For achieving this aim, 56 stem rust differential cultivars/lines obtained from the Cereal Research Center, Manitoba State, in Canada were planted in Ardabil Province, northwestern Iran under natural field conditions. The seeds of each cultivar/line were planted in two rows with 1 m of length and were irrigated every 10 days to promote disease development. Disease severity and type of infection of each cultivar/line were recorded based on the standard protocol at late flowering stage.

In the first year, the disease was developed only in Ardabil region. The SrMcN gene was the most susceptible gene, however, there was no virulence on Sr5, Sr21, Sr9e, Sr7b, Sr11, Sr6, Sr36, Sr9b, Sr30, Sr9a, Sr9d, Sr24, Sr31, Sr38, Sr8b, Sr9h, Sr12, Sr16, Sr19, Sr20, Sr22, Sr26, Sr27, Sr28, Sr32, Sr37, Sr39, Sr40, Sr41, Sr42, Sr43, Sr44, Sr45, Sr47, Sr50 ,and Sr53 genes. Other genes were moderately susceptible to virulence. In the second year, the disease was also developed.  SrMcN, Sr9h, and Sr42 genes were the most susceptible genes. However, no virulence was observed on Sr24 and Sr47 genes. The genes of Sr31 and Sr36 were resistant and susceptible, respectively. It seems that Sr36 and Sr38 genes have no potential to be used in breeding for achieving resistance against stem rust disease in Iran. However, Sr24 and Sr47 genes, which were resistant in the study area, are recommended to be incorporated in breeding wheat for obtaining resistance against stem rust disease. In addition, Sr31, Sr26, Sr27, and Sr28 genes, which were relatively resistant in most areas, were found to have potential to be combined with Sr24 and Sr47 genes in wheat breeding programs.

The bacterial mosaic induced by Clavibacter tessellarius is one of the wheat seed-borne diseases that causes mosaic and chlorotic leaf spots on infected plants. The disease has previously been reported in a few regions within Iran. There is still no information on the disease's prevalence and distribution in the major wheat-growing areas of southern Iran. The disease may have gone unnoticed in part due to its mild symptoms and resemblance to those caused by viruses and certain non-infectious wheat diseases. This study aimed to determine the occurrence and distribution of wheat bacterial mosaic in wheat fields in southern Iran.

Between 2019 and 2020, surveys in wheat fields in four southern Iranian provinces, including Fars, Khuzestan, Kerman, and Bushehr were conducted, and 192 plant samples with symptoms resembling the bacterial mosaic were collected. Bacteria were isolated and purified using semi-selective media, and Gram-positive isolates were selected using Gram staining and KOH solubility tests. The isolates were identified using a polymerase chain reaction (PCR) with Clavibacter-specific primer pair CMR16F1/CMR16R1, as well as their phenotypic and pathogenicity characteristics. Additionally, a fragment of the gyrB gene from the representative isolates was amplified by PCR using primer pair 2F/4R. The PCR products were purified and directly sequenced. The obtained sequences were aligned, trimmed, and compared to those of related strains in the GenBank using the BLAST search method. A phylogenetic tree based on the gyrB sequences was constructed using the MEGAX software employing the neighbor-joining method.

In total, 400 bacterial isolates were obtained. Based on positive PCR results with specific primers for the genus Clavibacter along with the pathogenicity test on wheat, and the phenotypic and biochemical characteristics, 61 isolates were identified as C. tessellarius. In ten representative isolates, a ~530 bp fragment of the gyrB gene was amplified by PCR. The gyrB gene partial sequences were edited and deposited in GenBank under the accession numbers MZ014474–MZ01483. A BLAST search confirmed that all ten isolates shared the highest nucleotide identity (98.8% to 99.5%) with their corresponding sequences in C. tessellarius strains in GenBank. In the phylogenetic tree, these isolates with C. tessellarius strains from GenBank were clustered in a clade distinct from Clavibacter species and subspecies of Clavibacter michiganensis.

C. tessellarius was isolated from 53 out of 192 wheat fields (27.60%), exhibiting bacterial mosaic symptoms. The Fars, Khuzestan, Kerman, and Bushehr provinces had disease incidences of 35.7% (30 infected farms out of 84 sampled farms), 30.55%, 22.7%, and 7.1%, respectively, indicating the relatively widespread occurrence of the disease in these provinces. To our knowledge, the wheat bacterial mosaic is reported for the first time in the provinces of Khuzestan, Kerman, and Bushehr, and its occurrence in other parts of the country would not be unexpected.

The rose-grain aphid, Metopolophium dirhodum is one of the most important species among wheat and barley aphids and its population trajectory in field is characterized by rapid boom. In the present study, three datasets from M. dirhodum population in a wheat field in Varamin (Tehran) from 1999 to 2001 and two datasets from a barley field in Aleshtar (Lorestan) in 2017 and 2018 were used for modeling the aphid population dynamics. We demonstrate that Normal and Hyperbolic Secant Squared models presented a much better description of M. dirhodum population dynamics in the whole season for all datasets from wheat and barley fields than the Exponential or Logistic Growth models. The Normal and Hyperbolic Secant Squared model analysis of data showed that the models were useful representations of the data, gave biologically reasonable descriptions of rose-grain aphid population dynamics, and were statistically powerful basis for the analysis of experimental data obtained in this research. The parameters of two mentioned models are the predicted peak size, Nmax, the predicted time of peak, tmax, and an approximate per capita birth rate, all of which are of interest in practical applications. Overall, the results of this study showed that the Normal and Hyperbolic Secant Squared regression models were shown to fit diverse abundance curves adequately and the parameters of the mechanical model can be estimated by the parameters of these models.

Take-all disease of wheat caused by Gaeumannomyces graminis var. tritici is one of the important diseases of wheat worldwide. In this study, application of two Trichoderma species on the control of this disease was evaluated under laboratory and greenhouse conditions. The causal agent of disease was isolated from suspected diseased plants in wheat fields of Khorrramabad district, identified according to scientific mycological literatures and its pathogenicity was proven in greenhouse. The mycelial inhibition potential of Trichoderma harzianum and T.viride in dual culture and volatile metabolite effects against the pathogen were tested in vitro. Then, single and combined greenhouse application of the two Trichoderma isolates and triadimenole fungicide for control of take-all disease were investigated using a completely randomized design with 16 treatments and four replications and disease severity and growth indices were recorded and analyzed statistically. In vitro experiments showed that both of the Trichoderma species disintegrated the hypha and inhibited the mycelia growth of G. graminis. Combined application of triadimenole fungicide with the two antagonists, triadimenole, and single application of T. harzianum and T. viride reduced take-all severity by 70.6, 58, 47.06 and 47.06 percent, respectively in greenhouse after 30 days of sowing. Trichoderma biocontrol agent and integration of chemical compounds with antagonists would provide promising strategy for management of wheat talke-all disease.

Bacterial leaf streak of cereal was first reported from wheat and barley in the early twentieth century. This disease was observed in wheat and barley fields of Kerman province in 1987 and then isolated and identified from infected wheat and barley in different provinces of Iran, as Xanthomonas translucens pv. undulosa and X. t. pv. translucens respectively. In recent years, this disease became epidemic in Iran. For this reason, it was necessary to re-examine once again the different characteristics of the causal agents of this disease in different regions of Iran to determine if there is any possible genetic modification in these bacteria.

The phenotypic and genetic diversity of 12 bacterial strains isolated from wheat and barley (four isolates from wheat, six isolates from barley, one isolate from Phalaris sp. and one isolate from Lolium sp.) originated from Kerman, Kermanshah, and Fars provinces was studied. These isolates (selected from 67 isolates) were compared with three ancient Iranian standard strains (obtained from Unité de Phytopathologie, UCL, Louvain-la-Neuve, Belgium). The strains' pathogenicity test was performed on wheat and barley seedlings by spraying and injection methods. Then, the biochemical and physiological characteristics and SDS-PAGE profiles of the whole cell proteins of isolates were examined. Finally, using rep-PCR by BOX A1R, ERIC 1R, and ERIC 2 primers, the genetic diversity of isolates was performed.

All strains were Gram, oxidase, and urease negative, and catalase positive. All strains produced xanthomonadin pigment. The strains could produce hydrogen sulfide from cystine and peptone. Negative results were obtained for arginine dihydrolase, urease, starch hydrolysis, nitrate reduction, acetoin and indole production, and methyl red reaction. All isolates produced acid from cellobiose, fructose, galactose, di-mannose, arabinose, xylose, trehalose, arabitol, but not from salicin, mannitol, melibiose, rhamnose, dulcitol, sorbitol, and mesoinositol. They utilized acetate, citrate, and lactate but not d-tartrate and inulin. Only barley isolates could utilize lactose and hydrolyze lecithin and starch. There are no discriminating bands among PAGE profiles of wheat, barley, and standard strains. Genomic fingerprinting of isolates was performed, and the data were analyzed using NTSYS V 2.2 software and the UPGMA cluster analysis method. All isolates of wheat, Phalaris sp., Lolium sp. and one isolate from barley along with UPB922 standard strain were formed one group consists of three subgroups. Isolates of this group could infect wheat and barley plants. The rest of barley isolates, which were pathogenic only on barley, separated from the first group at a similarity coefficient of 84% and formed the second group, including the standard strain UPB922. Furthermore, this group had three subgroups. This grouping was completely related to the host range from the isolates. Based on biochemical, physiological, pathogenicity (host range) characteristics of strains and their genetic diversity compared to the standard strains, the first group, and the second group isolates were identified as X. t. pv. undulosa and X. t. pv. translucens, respectively.

It was found that the isolates are divided into two separate groups based on their host range. One group could contaminate wheat and barley plants, and another group infected only barley plants. Biochemical and physiological tests did not show much difference among the strains, but some tests were able to distinguish two pathovars, such as lactose utilization, the activity of lecithinase and lipase enzymes (hydrolysis of Tween 80), the tolerance of NaCl in the culture medium and the amount of slimes, produced on the nutrient agar medium containing glucose or sucrose. Rep-PCR tests could show the differences and variations within each pathovar. The grouping formed based on these tests showed a high correlation with the strain host range of pathovars. Using both BOX and ERIC primers showed that the genetic diversity of isolates was strongly related to the pathovars type and their host range. Since previous studies showed the same diversity in Iranian isolates, so it seems that there has not been a genetic change in the causal agent of this disease in Iran. The disease widespread occurred in recent years could be mainly due to environmental conditions and wheat and barley cultivars response to this disease.