In order to investigate the Oomyceteous species of the rice paddy fields of Fars province (Iran), during 2013–15, infected roots and crowns together with soil around seedlings and irrigation water were sampled. Based on the morphological, morphometric and physiological studies along with phylogenetic analyses of internal transcribed spacer sequences based on neighbor joining method, twoPhytophthora species from Clades 6 and 8, including P. inundata, andP. pseudocryptogea and three Phytopythium species from a distinct clade, including Phpy. litorale, Phpy. ostracodes, and Phpy. sterile were identified. Phytopythium litorale, and Phpy. sterile were distinguished through morphological studies along with phylogenetic analysis.Phytopythium sterile was also new to the Oomyceteous mycobiota of Iran. All species were reported for the first time in the world from rice rhizosphere.

Phytopythium is a cosmopolitan genus found in different regions of the world from various substrates. This genus is a newly described taxon that was once a member of the genus Pythium sensu lato. Phytopythium is an intermediate genus between Pythium and Phytophthora with 34 formally described species. Recently, some studies focused on the phylogeny of this genus in Iran. Although not many studies concentrated on isolating species assigned to this genus from Iran, some comprehensive studies showed that Phytopythium is an important genus with vast distribution in this part of the world. Accurate identification and classification of Phytopythium species are quite challenging. Morphological identification of Phytopythium is troublesome due to the lack of identification keys, overlapping of some morphological features, the presence of species complexes, pleomorphism, and the absence of certain structures in some species. Besides, most species cannot be separated using only one or two loci for the phylogenetic analyses. In addition, some studies in Iran do not include molecular investigations to support their morphological identification or make it possible to reidentify the reported species. Having no accurate and current checklist of the country’s species also adds to the problem. This review focuses on the current systematics of Phytopythium species in Iran, discussing the challenges in the morphological and molecular identification of the species in the country. It also proposes some approaches to address the problem of characterizing the species in the genus Phytopythium.

Pink rot and pythium leak or watery rot of potato mainly caused by P. erythroseptica and P. ultimum are two important diseases occurring in several countries. Although other species of Phytophthora may also be the causal agent pf pink rot of potato tubers. These two diseases were recently observed in some potato growing areas of Semnan province. These are more prevelant in fields with heavy soils and poor drainage. Their secondary development takes place in stores with poor storage facilities. During 2002-2003 in a survey for identification of Pythiaceous species, the causal agents of pink rot and Pythium leak of potato tubers in Semnan province of northern Iran, Phytophthora megasperma and Pythium ultimum were found to be new records from potato tubers for Iran. In this survey 40 potato fields and related stores were inspected for detection of both diseases. Using BNPRA selective medium without hymixazole, 49 isolates belonging to PYTHIACEAE were isolated from disease speciments of some fields and stores. Results showed that 34.70% were Pythium (all having the characteristics of P. ultimum) and 65.30% were Phytophthora (majority belonging to P.cryptogea and remaining being P.erythroseptica and P.megasperma). Majority of Pythium isolates were seprated from stored potato tubers while Phytophthora isolates were mainly found on diseased tubers collected at harvesting time. Review of literature indicates that the two species P.megasperma and P.ultimum have not yet been reported from diseased potato tubers in Iran and seem to be new causal agents of pink rot and potato leak for Iran.

Sugar beet roots and attached soil are usually transferred to sugar factories for processing, then the roots are washed by pressurized water. Muddy water as waste flows in canal and is used to irrigate fields. The possibility of occurrence and fluctuations of the pathogenic organisms in waste were studied in 2005. The samples were collected from waste water once a week. Isolation of pathogens was done by a) citrus leaf baiting method and on PARPH selective medium, and common culture media such as PDA, CMA, MA, NA and WA, b) irrigation of sugar beet seedlings with waste water, c) bioassay with healthy sugar beet roots and d) cysts of nematode extracted from waste by sieves. Different pathogens were isolated from waste such as Fusarium oxysporum, Fusarium sp., Rhizopus stolonifer, Penicillium spp., Aspergillus spp., Pythium aphanidermatum Pythium sp., Phytophthora cryptogea, Ph.drechsleri, Mucor sp. Rhizoctonia solani,Geotrichum sp., Erwinia carotovora and cysts of Heterodera schachtii. Pathogencity tests were done for each pathogen. At early periods of processing, recovered populations of PYTHIACEAE and Erwinia carotovora were high, and in the last weeks of processing period population of Penicillium spp., Aspergillus spp., Mucor sp. and Geotrichum sp. were in high levels. Populations of Alternaria alternata، Rhizoctonia solani and Fusarium spp. were stable and cysts of Heterodera schachtii were variable during processing period. These pathogens were also isolated from fields of sugar beet irrigated with waste water.