جستجوی مقالات مرتبط با کلیدواژه « phytophthora » در نشریات گروه « کشاورزی »

 Effect of Aliado fungicide (Masio, Spain) with active ingredient of Mancoezbe 40%, chlorothalonil 20% and simoxanil 5% as a 65% WP formulation for control of citrus gummosis disease in laboratory, greenhouse and orchard conditions was compared with common fungicides (copper oxychloride and Bordeaux mixture in ratios of 100 and 50 g/l respectively). The growth of Phytophthora parasitica and P. citrophthora was controlled in the culture media containing the recommended doses of 15, 20, 25, 30 and 35 g/l. Results of greenhouse experiment with one-year-old sweet orange seedlings of Siavaraze (a local variety) indicated that Aliado is effective on prevention of the wound development at the doses of 25 and 35 g/l for P. parasitica and 20 and 35 g/l for P. citrophthora. The best result was obtained with painting of 15 grams per liter of the fungicide twice a year (spring and autumn) in the field assessment.

 In this study, P. parasitica and P. citrophthora were isolated from the infected soil. The fungi were stored after purification and cultivation in the test tube for the next steps. To evaluate the effect of Aliado in laboratory conditions, different doses of the fungicide containing 0, 15, 20, 25, 30 and 35 grams per liter were added to the CMA medium and distributed in petri dishes. Then, 5 mm discs were prepared from the 7-day-old pragmatic margin of the fungus-like and placed in the center of Petri dishes. After maintaining them at 24 °C for 4 days, the radial growth of mycelium was measured. In order to investigate the effect of the fungicide in greenhouse condition, seeds of Siavaraze local sweet orange as a sensitive variety was prepared and treated with 0.5 percent sodium hypochlorite solution and cultivated in a soil composition disinfected with water vapor in a controlled greenhouse of Citrus and subtropical Fruit Research center. Evaluation of the effect of fungicides was carried out after seedlings reached about 20 centimeters. For staining treatments, 24 one year old seedlings of Siavaraze were used. First, at 15 cm above the surface of the soil, a part of the bark was removed from the trunk and discs of the same size from the fungi-like colonies were placed instead. In the control plants, the culture medium without mycelium was placed on the surface of the wood. To evaluate the treated seedlings, about 40 days after application of the fungicides, the size of the new wound was calculated. To study the effect of Aliado in orchard condition, 24 trees of 12 years old with Bakraee and Lime rootstocks infected with trunk gummosis in Kerman (Jiroft) and Fars (Jahrom) provinces were used in a randomized complete block design with 8 treatments in 3 replications. The wound of the trunk marked and bark of the infected area was gently scratched and painted by a brush with the same treatments and doses of the laboratory test. Six months after application, the size of the new wound was recorded. The analysis of variance and the mean comparison were performed based on MSTATC statistical program and the Tukey's test.

 Laboratory studies showed that Aliado fungicide completely prevented the growth of fungi-like in the recomended doses of the company. Under greenhouse conditions, painting of Aliado with 25 and 35 grams per liter for P. parasitica and 20 and 35 grams per liter for P. citrophthora have been effective in stopping the development of stem wounds. This research was also conducted in field conditions in the orchards with gummosis symptoms in Kerman and Fars provinces. In the orchard condition, two times application of all treatments containing Aliado fungicide (even a dose of at least 15 g/l) was effective. The results of the experiment are in agreement with those of the world's researchers, which have reported the use of fungicide as an effective method for controlling phytophthora fungus-like of gummosis. Therefore, in citrus cultivation areas of the country, especially the southern provinces, where the climatic conditions are favorable for the activity of the fungi-like, treatment of the crowns of citrus trees with Aliado in the spring and the autumn with the minimum proposed dose of the fungicide is recommended. Observations showed that all treatments of Aliado are effective by drying the gum in controlling disease progression through disinfection. In some treatments, the emergence of gum in the new places was observed with a little distance from the previous wounds. It can be because the effect of fungicide has decreased after a few months. In climatic conditions of the southern regions of the country the fungi-like are active throughout the year. So the use of fungicide in spring and autumn is recommended. The use of Aliet fungicide in two doses of 160 and 200 g in 100 liters of water had a protective effect less than one year.

Some species of Phytophthora genuse cause crown and root rot, and damping off of tomato seedlings. Fruits that contact with soil containing pathogen are affected by a type of decay called buckeye rot of tomato. In this research Pathogens were isolated from soil, tomato root and crown in North Khorasan province and identified as Phytophthora capsici and P.nicotianae . Pathogenicity of both species were demonstrated on tomato seedlings.The production Zoospores was investigated under different light and temperature conditions. The results showed that there was a significant differences between species in reaction to temperature condition. Temperature also had significant effect on the release of zoospore in both species. The highest release of zoospores occured in one of the P.capsici isolates at 20°C under dark conditions.In the case of P.nicotianae at 25°C and light conditions the highest zoospore were released. The largest wound length occurred in isolate Pc2 of P.capsici . It reached to 50 mm at 25°C and dark condition after 5 days. In the case of P.nicotianae the highest pathogenicity of zoospores occured at 27°C under light condition.

Plant diseases play a critical and limiting role in crop production and their control by using pesticides cause serious problems regarding food safety and environmental health and increase the need for other sustainable disease management techniques. Some of plant pathogens may infect the aerial parts of plants, but spent part of their life cycle in the soil and maintained their survival. In such cases, part of the life cycle of the plant pathogen in soil may be very important, even if that microorganism does not infect the roots. Mono culturing and cultivation of crops belonging to the same family increase the potential of disease incidence. Using and applying the suitable and correct cultural practices that limit damage of root diseases is necessary for sustainable management of soil-borne pathogens. Cultural operations, including the use of cover green crops, crop rotation, organic composts, certified seeds and propagative materials, amended organic material to soil, proper tillage systems, soil solarization, resistant cultivars, mycorrhizal fungi, all are reported and confirmed as management options for long time saving soil quality and good sustainable management of soil borne diseases.

Plants are usually attacked by several pathogens. Different defense pathways in plants have evolved in reaction to pathogens. Plant defense responses have been shown to be regulated by various plant hormones. Brassinosteroids are plant-specific steroid hormones that play important roles in regulating growth and developmental processes. In addition to acting as a regulator of plant growth, they also play a role in defense responses to pathogens. Many researches have been done on their role in plant resistance to fungi, bacteria and viruses, which are described in this article. Further understanding of the role of these hormones in plant defense responses can be useful in inducing resistance or producing plants resistant to pathogens.

Pepper (Capsicum sp.) with numerous variations having abundant utilizations such as ornamental, food and pharmaceutical aspects. In this research, the genetic diversity of 37 resistant and susceptible ornamental and edible pepper genotypes to damping-off disease, caused by Phytophthora capsici, was analyzed by 47 morphological attributes and 20 ISSR primers. Results of ISSR assay indicated that 19 primers out of 20 primers produced scorable polymorphic bands. Totally, 188 bands were produced, which 185 bands were polymorphic. The polymorphism mean percent (P%) in ISSR markers was 98.5% and on average, 9.9 bands were produced using each primer. Polymorphism percent varied from 78% to 100%. Average of polymorphism information content (PIC) was 0.449. Based on the results of ISSR analysis, the genotypes were divided into five main groups. Morphological attributes also divided the genotypes into five distinct groups. Correlation between molecular and morphological similarity coefficients was non-significant. The screening results of resistance to damping-off disease demonstrated that five genotypes including 11BlockyP-YToran, 19OrnP-PBI, 23CherryP-Orsh, 32OrnP-China and 37ChilP-Paleo, which have the lowest mortality at seedling and maturity stages, were belong to ornamental and long peppers groups. The correlation coefficient of genetic diversity and resistant of the related genotypes to damping-off, Phytophthora capsici clustered the five resistant genotypes except 37ChilP-Paleo in one morphological group and all five genotypes were placed in four different molecular groups.

In order to investigate the oomyceteous flora associated with ornamental trees of Shiraz County (Iran), during 2017–18, rhizosphere soil and plant debris of ornamented trees from various parks and green spaces of Shiraz County (including 11 districts) were sampled. Based on morphological, morphometrical and physiological analyses, three Phytophthora species, namely, Ph. cactorum*, Ph. capsici, and Ph. nicotianae*, five Phytopythium species including Pp. litorale, Pp. oedochilum*, Pp. ostracodes, Pp. palingenes†*,and Pp. vexans,and 11 Pythium species including Py. aphanidermatum*, Py. catenulatum*, Py. echinulatum, Py. hydnosporum*, Py. irregulare*, Py. kashmirense, Py. megalacanthum†, Py. middletonii, Py. nunn, Py. oligandrum,and Py. sylvaticum† were identified. Taxa with asteric were predominant and species with dagger sign were new to Iran mycobiota.

Black cumin, an annual flowering plant in the family Ranunculaceae, is a medicinal herb with many pharmacological properties. Crown and root rot disease of this plant has been reported in most countries worldwide. This study was conducted to investigate the occurrence of this disease and identifying the causal agent in southwest of Iran.

Black cumin farms were visited in Kohgiluyeh and Boyer-Ahmad province and southwest of Iran. Plants with crown and root rot were sampled. Pieces of infected root and crown were washed with tap water, dry blotted and plated on CMA-PARP. In total, 17 isolates of two different fungus-like species were isolated from rotted root and crown. Species identification was done based on morphological characteristics and temperature requirement. Pathogenicity test of the isolates were done on 3-week-old seedlings of Baft cultivar under greenhouse condition.

Eleven isolates were identified as Pythium aphanidermatum and six isolates as Phytophthora drechsleri. Both of these fungus-like species were pathogenic on the tested black cumin variety.

Crown and root rot disease is present in the farms of black cumin in the southwest of Iran. The causal agents of this disease were identified as Pythium aphanidermatum and Phytophthora drechsleri. The black cumin cultivar Baft is susceptible to these pathogens.

Iranian Pistachio is one of the most important horticultural product in export market. Crown and root rot caused by Phytophthora species is the most serious disease of plant, which annually destroys a considerable number of mature and young trees. This disease has been reported from all provinces of Iran. The pathogen is soil-borne and is distributed by sporangia or the released zoospores and infects the healthy trees. In the most Pistachio orchards, the key factors of disease development are the sensitivity of pistachio crown to Phytophthora and the flooding method of irrigation. The symptoms of the disease are include blight in early spring, drying of the green leaves during the growing season, gum exudation from the crown of tree  and the root rot. Gummosis can be successfully controlled by integrated disease management including orchard constructing in non-infected areas, using resistant or tolerant cultivars, using healthy rootstocks, improving the irrigation methods and avoiding the direct contact of water with tree crown, isolating the contaminated parts of the orchard from the healthy parts, using suitable fungicide, and biological control based on Trichoderma and Bacillus species.

During recent years, citrus trees decline has becoming one of the most important factors of limiting the area of citrus orchards in the south of Iran including Fars province. Different biotic and abiotic agents were attributed to citrus decline worldwide, but it appears that some abiotic stresses including soil drought, and soil or water salinity, as well as some infectious diseases including gummosis, dieback, citrus nematode and witch’s broom are more important in Fars province. This is an attempt to gather information of the potential agents of complex diseases known as “citrus trees decline”, as well as, discussion on management strategies of citrus decline in Fars province.

Almond (Prunus amygdalus L.) is a deciduous tree in the Rosaceae family and is grown mostly for its edible seed. It is one of the most popular nuts on a worldwide basis and widely grown in Iran in Isfahan and Chaharmahal and Bakhtiari provinces. Root and crown rot causal agents which are caused by several pathogens were studied. According to morphological characteristics, 53 isolates were identified as Phytopythium litorale (13 isolates), Phytophthora cactorum (19 isolates), and P. crytogea (21 isolates). Out of 53 isolates, 25 isolates were selected for molecular studies. Specific primer pairs of BPhycacL87FRG (F)/BPhycacR87RRG and Cryp1(F)/Cryp2 were used to confirm morphological identification of species. The reaction of crown and root of 8-month-old almondcultivars Sangi, Rabee, Shahrood12 and GF677 to virulent isolates of P. cactorum, P. cryptogea,and Pp. litorale was evaluated under greenhouse conditions. Comparison of pathogenicity means revealed that there are significant differences among P. cactorum, P. cryptogea,and Pp. litorale isolates.The results alsoshowedthat Pp. litorale was more aggressive than P. cactorum. On all tested almond cultivars, disease severity percentage showed that Sangi is the most susceptible cultivar and GF677 showed the least susceptibility. In this study, phylogenetic relationships of some Phytophthora and Phytopythium species based on sequencing of the rDNA-ITS region is provided. This is the first report of isolation and pathogenicity of Phytopythium litorale from almond orchards in Iran.

The best cherry rootstock for Iranian nurseries and orchards is Prunus mahaleb (L.) Mill. Mahaleb is tolerant to lime-induced iron chlorosis and zinc deficiency. It is a good rootstock on light, calcareous soils and arid climates in Iran but sensitive to Phytophthora. Iran represents a significant source of germplasm of different fruit species, especially for those from the genus Prunus. Collection and research on P.mahaleb was initiated at the Horticultural Department of Khorasan Razavi Agriculture and Natural Resources Research and Education Center in 1997 for mahaleb cherry rootstock. Some researchers have reported pathogenicity of Phytophthora species (Banihashemi and Sartipi, 2004; Wilcox and Mircetich, 1985; Exadaktylou and Thomidis, 2005; Tomidis et al., 2008). This study was conducted to evaluate the susceptibility of 30 selected dwarf Mahaleb genotypes to P.nicotianae, P.citricola, P.cactorum and P. citrophthora under greenhouse and orchard conditions.
Material and In this study, the response of 30 selected dwarf Mahaleb genotypes (188, 171, 165, 162, 161, 155, 139, 136, 131, 120, 106, 104, 101, 100, 90, 194, 195, 199, 200, 224, 228, 247 , 249, 265, 266, 267, 268, 270, 272, 277) to disease caused by four species of the fungus Phytophthora root and crown rot were investigated under greenhouse and orchard conditions. Greenhouse experiments were performed based on Ribeiro and Baumer, 1977 and modified it by Feichtenberger et al., 1984. For evaluation the index disease was performed based on the method of Broadbent and Gollnow 1992. Orchard terials was laid out in the Toragh research station in Mashhad. Evaluation of genotypes and contamination based on Tomidis, 2001 was performed by measuring the area of necrosis.
In evaluating the reaction of young seedling dwarf mahaleb genotypes to four Phytophthora species under greenhouse conditions, results showed that four species of Phytophthora pathogens on all mahaleb genotypes but P.citricola, P.cactorum showed disease severity than P.citricola, P. nicotianae. In response assessment test seedlings in the greenhouse genotypes Mahaleb highest rate of infection to P.cactorum in genotype 277 and the lowest index of disease severity showed in genotypes 100, 188, 199, 200, 224 and 266, respectively. The highest and lowest number of leaves was counted on 199, 272 and 277 respectively. The least and highest shoot dry weight were related to 277 and 100 genotype respectively. The maximum and minimum disease severity to P.citrophthora revealed in 265 and 265, 100, 188, 194, 199 genotypes, respectively. The highest and lowest number of leaves was counted on 188 and 249 respectively. The least and highest shoot dry weight were related to 249 and 100genotype respectively. The least and highest root dry weight was measured on 265 and 100 genotype, respectively. In response assessment test seedlings in the greenhouse genotypes Mahaleb highest rate of infection to P.citricola in genotype 265 and the lowest index of disease severity showed in genotypes 100, 162, 171, 188, 199, 200,224, respectively. The highest and lowest number of leaves were counted on 100and 277, 272 respectively. The least and highest shoot dry weight were related to 272 and 100 genotype respectively. The least and highest root dry weight were related to 277 and 100 genotype respectively. The highest rate of infection to P.nicotianae in 120 genotype and the lowest index of disease severity were related to the genotype of 188 and 199. The highest number of leaves in genotype No.100 and the lowest number of leaves were belonging to genotypes 272 and 277, respectively. The least and highest shoot dry weight were related to 247 and 100 genotype respectively. The least and highest root dry weight were related to 265 and 100 genotype respectively. The results of the assessment of the two year old seedlings mahaleb genotypes under orchard conditions showed that four Phytophthora species had different degrees of disease symptoms. Phytophthora species in their ability to create the symptoms are different. The lowest level of necrosis is created by P.cactorum. The highest and lowest levels of necrosis of P.cactorum were measured in 267 and 162 genotypes, respectively. In P. citrophthora, the highest and lowest levels of necrosis were measured in 277 and 188 genotypes, respectively. The highest and lowest levels of necrosis of P. nicotianae were measured in 272 and 188 genotypes, respectively.
ConclusionThe results of the assessment Mahaleb genotypes to four species of Phytophthora in the orchard showed that the lowest level of tissue necrosis in genotypes of 106, 139, 162, 188, 195, 224, 266 and 270, respectively. Finally our results revealed that P.citricola, P.cactorum were pathogenic Phytophthora species and three mahaleb genotypes (266, 224 and 188) had highest potential resistance to P. nicotianae, P.citricola, P.cactorum and the P.citrophthora respectively.

Brown rot disease of citrus fruits caused by Phytophthora citrophthora and Phytophthora parasitica is one of the most threats to citrus plantation in northern Iran. In evaluation of different methods to control of citrus brown rot, an experiment was achieved in Northern Iran based on Randomized Complete Block Design (RCBD) in factorial test with five replications. In reciprocal effects study of fungicides (metalaxyl, cupper oxychloride and burdux mixture) and skirt pruning, a significant difference was observed among the treatments. The results showed that the best treatment was obtained from the application of cupper oxychloride skirt pruning in August. In reciprocal effects study pruning and fungicides application time, no significant differences were observed among treatments, however maximum and minimum percent of decay were depended on "no pruning spraying in September and pruning spraying in May" respectively. There were also differences among spraying time and fungicides application, as maximum and minimum percent of decay were related to application of metalaxyl and cupper oxychloride in September.

Zagros Mountains in the west of Iran and some areas in the north of Iran are covered by oak trees. Four important diseases of Iranian oak trees are charcoal rot, chestnut blight, sudden death and powdery mildew. The symptoms of these diseases and the characteristics of pathogens as well as their prevalence are described in this article. Some strategies for protecting the oak trees from these diseases are also proposed here.

Iran is one of the biggest sweet cherry producers in the world. Turkey, the U.S.A and Iran are among the major producers of cherry in the world. Mahaleb(Prunus mahaleb L.) is used as a principal rootstocks for sweet and sour cherries in Iran. Mahaleb is a good rootstock on light, calcareous soils and arid climates in Iran. Since pathogenic species, P.citricola, P.cryptogea, P.dreschleri, P.cactorum, P. syringae, P.cinnammomi, P.megasperma, P.cambivora on mahaleb been reported by different researchers (Sajadinejad et al., 2011) According to the pathogenesis of four species of P. nicotianae, P.citricola, P.cactorum and P.citrophthora on stone fruit trees in Iran and other countries, based on the hypothesis that the relative resistance to Phytophthora species in selected dwarf Mahaleb genotypes adapted to environmental conditions exist and can be introduced as resistant rootstocks to crown rot disease, this study was conducted to evaluate the susceptibility of 30 selected dwarf Mahaleb genotypes to P.nicotianae, P.citricola, P.cactorum and P. citrophthora. Sofar, the selection of resistant or tolerant to Phytophthora cherry rootstock, studies have not been done. Therefore, it is appropriate to introduce the cherry trees for planting in various parts of the country, the need to evaluate several species of Phytophthora resistance or tolerance to the grades mentioned above. Considering the history of the pathogenesis off our species of P. nicotianae, P.citricola, P.cactorum and P.citrophthora the stone fruits this study aimed to evaluate the reaction of 30 cultivars of dwarf Mahaleb to P.nicotianae, P.citricola, P.cactorum, P.citrophthora was carried out.
In this study, the reaction of 30 dwarf Mahaleb genotypes were investigated to disease caused by four species of the fungus Phytophthora root and crown rot. Excised twig, annual and perennial shoots to measuring resistance using laboratory methods. Excised twig, excised annual and perennial shoots assessment based on Jeffers et al., (1981) and Matheron and Mircetich(1985) respectively.
In evaluating the reaction of excised twig, excised annual and perennial shoots dwarf mahaleb genotypes to four species of Phytophthora, rot and discoloration symptoms were observed, All control shoots of Mahaleb genotypes were evaluated in this trial did not show any symptoms of discoloration and Phytophthora rot but shoots treated with four species of Phytophthora showed that different degrees of light brown to dark discoloration and decay. The results of the analysis of variance showed that the genotypes of disease progression on the tissues of all three types of excised shoots inoculated with four species of Phytophthora were difference statistically significant. Also, the results of comparing the length average of progression of symptoms (necrosis) on this experiment were as follows which are outlined below.
P.cactorum
On the test assessment the reaction of excised twig, excised annual and perennial shoots dwarf mahaleb genotypes, least amount of sensitivity to species belongs to genotype199 with an average contamination of 12.44%, 162 with an average contamination of 1.42% and 162 with an average contamination 0.01 %, respectively.
P.citrophthora
On the test assessment the reaction of excised twig, excised annual and perennial shoots dwarf mahaleb genotypes, least amount of sensitivity to species belongs to genotype 265 with an average contamination of 15.67%, 155 and 162 with an average contamination of 0.01% and 262, 228, 224 and 188 with an average contamination 0.01 %, respectively.
P.citricola
On the test assessment the reaction of excised twig, excised annual and perennial shoots dwarf mahaleb genotypes, least amount of sensitivity to species belong to genotype 124 with an average contamination of 11.80%, 100 with an average contamination of 0.60% and 266 with an average contamination 3.13 %, respectively.
P.nicotianea
On the test assessment the reaction of excised twig, excised annual and perennial shoots dwarf mahaleb genotypes, least amount of sensitivity to species belong to genotype 120 with an average contamination of 16.15%, 100 and 95 with an average contamination of 0.01% and 188 with an average contamination 0.87%, respectively.
There were significant differences between the genotypes of disease progression in the tissues of all three types of excised shoots inoculated with four Phytophthora species.
The results showed that, some mahaleb genotypes (100, 124, 155, 162, 188, 195, 199, 224, 266 and 265) have potential resistance to species P.nicotianae, P.citricola, P.cactorum and P.citrophthora, that can be considered in breeding programs.