During 2009 and 2010 growing seasons, different irrigated fields were surveyed in Gorgan region. Infected plants with symptoms such as damping off, crown and root rot, and foliar blight were collected. Samples were washed in running tap water and cultured on CMA+PARPH. Isolates were identified on the basis of morphological and some physiological characteristics.50 isolates belonging to four species were identified. The species were: Phytophthora citrophthora from persimmon fruits (Diospyros kaki); Phytophthora cryptogea from kiwi trees (Actinidia chinensis) with root and crown rot sympotoms, crown and root of potato (Solanum tuberosum) and gerbera (Gerbera jamesonii), Phytophthora nicotoanae from tomato (Lycopersicum esculentum) root and stem, Phytophthora palmivora from root and crown of olive (Olea europae) seedlings and Phytophthora inundata from root and stem of broad bean (Vicia faba). All of Phytophthora isolates were found pathogen on their host at greenhouse conditions. Based on our knowledge isolation of P. cryptogea group II from kiwi and potato and Phytophthora palmivora from olive trees were new for Iran, also P. inundata from broad bean was new for Iran and the world.

The reaction of nineteen different cultivars of Cucurbita spp. including Cucurbita pepo, Cucurbita maxima and Lagenaria siceraria to Phytophthora capsici, Phytophthora melonis and Phytophthora drechsleri was studied under greenhouse conditions. Plants were grown in steam sterilized soil. One-month-old plants were inoculated with vermiculate hempseed extract inocula of Phytophthora and were flooded for 24 hours. The activity of the pathogens was monitored during the experiment by using citrus leaf discs. Seedling mortality was monitored two months after inoculation. None of the species were infected with P. drechsleri or P. melonis. Cucurbita maxima cultivars Hamedan and ACE South Korea, C. pepo cultivar Shabestar and Lagenaria siceraria were not infected with P. capcisi. The possibility of using these cultivars as root stocks for grafting against Phytophthora species is discussed.

The dissemination of Phytophthora spp. in the surface irrigation water was studied during 1993-94 in Marvdasht area and certain other parts of Fars province. Monthly the water samples were taken along 100Km of the Kor river 22Km up stream from the Doroudzan Dam to about 80Km down stream to Mardvdasht where Sivand and Kor rivers joined. The other sampling locations includede the Maeen river adjecent to the Dam, and the Sivand river from Dashte-Morghab to Mardasht. Few samples were also obtained from Shapour and Dalaky rivers and also from Yasouj and the Sisakht regions in Khkilueh and Boir Ahmad. The water temperature, pH and EC were measured and samples were assayed on the same day of the collection. The water sample was filtered through the two layers of the cheese cloth and about 1L was placed in a plastic container (30 × 20 Cm) 2-3C deep and 100 fresh citrus leaf disks (6mm dia) were also added and incubated at the room temprature. After 48hr, disks were collected, washed, blotted dry and plated on Phytophthora were collected, washed, blotted dry and plated on Phytophthora selective medium (PARPH). At least 50 disks were used in the 5 plates for each sample. The five to 8 boiled hemp seeds were placed on each growing colony and transferred to the distilled water, after 12hr for sporangium production. The Phytophthora species were idenified by their morphological characteristic and temperature requirement. Phytophthora spp. were present in the most rivers except the Shapour and Dalaky. The predominant species were non-popilate high temperature (above 35C) species mainly P. cryptogea and P. drechsleri. In some cases P. capcisi and the other unidentified species were also detected. Phytophthora spp. were present throughout the year but the lowest population was detected during winter months. The fluctuation of the phytophthora population and the other water microorganisms in the Kor river after shiraz petrochemical complex during the growing season was very high, but sometimes reduced to zero (perhaps due to the water pollution). No Phytophthora colonies were detected in the dam lake or in the most cases in the cement canals.

Using biocontrol agents is one of the methods to reduce mortality of Phytophthora root rot in pistachio orchards. In the present study, the effect of arbuscular mycorrhizal fungi (AM) (mixture of three species), Trichoderma harzianum (Th) and their combination (AM+Th) were evaluated on Phytophthora root rot caused by Phytophthora drechsleri (Pd) in pistachio seedlings cv. Momtaz. Arbuscular mycorrhizal fungi, Th and their combination were inoculated at the time of sowing pistachio seeds, but the pathogen was inoculated two months later. The results showed that AM, Th and AM+Th treatments and their interaction with Pd significantly increased growth, nutritional and biochemical characteristics of seedlings compared to the control and Pd treatment. The highest increase was observed in AM+Th and AM+Th+Pd treatments. At the end of the experiment, the mortality of pistachio seedlings was significantly reduced from 92% in Pd treatment and reached to 67, 67 and 50% in AM+Pd, Th+Pd and AM+Th+Pd treatments, respectively. It is concluded that inoculation of AM, Th and especially their combination improved the growth, nutritional and biochemical characteristics which can lead to biological control of Phytophthora root rot of pistachio seedlings.

In the summer of 2022, sansevieria plants with symptoms of root and crown rots were detected in greenhouses of Isfahan province, Iran. Symptomatic tissues of the root were cultured on CMA-PARPH. Recovered oomycete isolates were purified by single-zoospore technique on WA. The baiting method using citrus leaf disc was also used to isolate Phytophthora spp. isolates from the soil around roots. Four isolates were obtained directly from infected root tissues and two isolates from soil. Fungal isolates were identified based on morphological characteristics and molecular data of β-tubulin (βtub) and translation elongation factor 1-alpha gene (tef1-α) genes. According to the morphological and phylogenetic analysis, all isolates were recognized as Phytophthora occultans. Koch's postulates were completed and confirmed that Phytophthora occultans isolates were responsible for sansevieria root and crown rots. To our knowledge, this is the first report that Phytophthora occultans associated with root rot of sansevieria in Iran and probably in the world.

One of the major field constraints to seed production in safflower has proven to be soil born pathogens, Phytophthora drechsleri and Pythium ultimum. In order to evaluate the efficiency of a field-laboratory selection method to improve resistance of safflower against soil born pathogens, Ph. drechsleri and P. ultimum, a two-year investigation was conducted. The results showed that selection is an efficient method for increasing resistance to seed and seedling death caused by Phytophthora and Pythium in safflower. Selection could have improved germination percent, days to 50% germination, percent of undamaged seedlings and index of disease percent when genotypes were faced with both pathogens. Regarding kind of damages, Pythium caused more seed rot and Phytophthora induced more seedling death. It could be concluded that selection for resistance to Pythium, could also increase resistance to Phytophthora. Safflower was, however, more susceptible to Phytophthora than Pythium. Also, genes for resistance to seed rot are different than those controlling resistance to seedling death, so preemergence damping off should be considered a completely independent trait from post-emergence damping off in safflower. It was concluded that used fieldlaboratory selection method could well improve resistance of safflower to pathogens Phytophthora and Pythium and hence seed yield.

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.

Tree decline induced by pathogenic soil fungi is one the most important problems in the orchards of stone fruit trees in Iran. Phytophthora spp. are the most principal fungi that particularly prevent the root and crown growth of stone fruit trees. This study aimed to assess the relative resistance of five new stone fruit trees rootstocks Penta، Cadaman، Tetra، Mr. S2/5 and GF677، to Phytophthora cactorum and P. drechsleri. The experiment was conduced in laboratory by active and dormant cutting shoot method and also the pot soils artificially inoculated with the fungus. The inoculum grown on vermiculite containing cannabis extract was placed next to the crown and root and the necrosis length was measured four months after inoculation. Results showed that trees exhibited different sensitivity to two Phytophthora species. P. drechsleri was less virulent than P. cactorum. The results of the laboratory and glasshouse assessments showed that Cadaman and GF677 rootstocks had the maximum necrosis length، while Penta and Tetra indicated the minimum value. Hence، Penta and Tetra rootstocks seem to have high relative resistance to crown rot.

Phytophthora root and crown rot caused by various species Phytophthora are the major threat to agricultural crops in Iran. Phytophthora melonis and P. capsici are reported on cucurbits in Iran but major species in cucurbits considered to be P.melonis and the importance of P.capsici in cucurbits has not been much investigated. In the present study the reactions of different cucurbits were compared to both species under greenhouse conditions. Two months old of 36 cucurbit species and cultivars were inoculated with vermiculite hempseed extract inoculums. The production of zoospore in drained water and reactions of cultivars were monitored during two months after inoculation. The results showed that cantaloupe and long melon were more susceptible to P. melonis and reacted differently to P.capsici. Pumpkin was resistant to both species but squash and water melon were more susceptible to P.capsici than P. melonis.

Interspecific hybridization is an important evolutionary process contributing to adaptation and speciation. During the last decade, advances in the molecular taxonomy techniques have led to increasing the number of descriptors interspecific hybrids in the genus Phytophthora. In Phytophthora hybrids, inheriting and recombining genes from both parents may result in increased aggressiveness and broader host range compared with either parent. Some Phytophthora natural hybrids have also been reported in Iran to date. Consequently, identification, pathogenicity and host range tests of these hybrids as well as preventing the formation of new hybrids before experiencing large economic losses are recommended for management of plant diseases caused by this fungal-like organisms.