pythium

Delaramifar M,  Pirnia M,  Keykhasaber M, Sarani SA,  Khajeh H (2023) Reaction of eight luffa genotypes to damping-off disease. Plant Pathology Science 12(2):76-85. 

Damping-off caused by Pythium aphanidermatum is one of the major diseases of luffa. Identifying and planting of resistant varieties is an environmentally friendly solution for integrated disease management. This study was conducted to determine the reaction of eight native and non-native luffa genotypes to the disease.

The pathogen (Pythium aphanidermatum IRAN597C) was obtained from the collection of fungi of the Iranian Institute of Plant Protection Researches. It was inoculated into seedlings of eight luffa genotypes. After the appearance of yellowing symptoms and seedling death, the disease index (DI) and the area under the disease progression curve (AUDPC) were calculated for each genotype. Koch's postulates were carried out to prove pathogenicity and the pathogen was isolated from diseased seedlings. Then, for molecular confirmation of the pathogen, ITS-rDNA sequencing was used.

The sequencing of the ITS-rDNA region of the pathogen showed a phylogenetic affinity of 99% with other isolates of P. aphanidermatum. According to the DI, the northern large and the long luffa genotypes were grouped as sensitive genotypes, and other genotypes including northern black seed, northern white seed, toori, Afghani, grooved and Brazilian were grouped as resistant genotypes. Based on the AUDPC, the northern black seed, and northern white seed genotypes showed the lowest level, toori, grooved, Afghani and Brazilian genotypes showed the medium level, and northern large and long luffa genotypes showed the highest AUDPC level.

Considering the low values of the DI and AUDPC in the northern black seed and northern white seed genotypes, planting these two genotypes is suggested for management of the disease in luffa.

Turf grass is the most important grown plant in urban green space, which functions such as temperature adjustment, increase in relative humidity, air softness and dust absorption. Fungal and fungal-like diseases are the most common lawn diseases in Iran, affecting this plant at all stages of growth, causing its decline. Pythium, Fusarium, Microdochium, Rhizoctonia, Bipolaris, Pyricularia and Colletotrichum species are known as damping-off, root and crown rot, leaf spot and anthracnose pathogens of lawns in Iran. The symptoms of these diseases, the morphological characteristics of pathogens and the methods for their management are described.

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.

Using resistant cultivars is the best way to reduce damages caused by sugar beet root rot and rhizomania. In order to develop resistant cultivar to these diseases, sugar beet genotypes were evaluated under artificial inoculation to rhizoctonia and one of the pollinators was selected as the most resistant population to rhizoctonia (SB19) in 2003. Self-fertile lines and hybrids were derived from non-inoculated roots of this population in 2004 and 2005, respectively. Selected hybrids were compared in terms of yield in different regions for two years and also pollinator lines were evaluated in terms of resistance under micro plot conditions in Hamedan. Results showed that sugar yield of a hybrid that its pollinator was selected as Ekbatan cultivar’s pollinator was 10.2 t.ha-1 and decease index of its pollinator was 2.16. Average sugar yield of Ekbatan in infested and non- infested regions with rhizoctonia was 9.1 and 7.0 t.ha-1, respectively. According to the results of yield and resistance to rhizoctonia evaluation, 10 superior lines were selected. In order to obtain resistant hybrid to rhizoctonia as well as tolerant torhizomania, 18 hybrids were developed by crossing those 10 superior lines with some male sterile lines that were resistant to rhizomania. Yield comparison of the hybrids was performed in three different regions that were naturally infested with rhizoctonia and rhizomania during 2010 and 2011. Two-years averages of sugar yield for (7112*SB36)*S1-24 hybrid that was released as Ekbatan in those regions were 8.7, 8.9 and 9.3 ton.ha-1, respectively. In general, results indicated that yield and resistance of Ekbatan cultivar was similar to the foreign resistant cultivar. The time needed to reach 90% seed germination by Ekbatan was 80 hours that is faster than that for Flores and Jolgeh cultivars. This indicates the higher germination rate of this cultivar.

Aspergillus species are saprophytic fungi which can live on plant debris in the soil and water and also on some plant products, stored fruits and grains. They can be identified by studying the features of colonies, conidiophores, vesicles, phialids and conidia, on selective culture media. The biocontrol potential of some isolates of A. flavus, A. fumigatus, A. niger, A. piperis, A. repens, A. tamarii, A. terrus and A. tubingensis, against some plant diseases such as cocoa black pod, root galls and Fusarium root rot of tomato, Alternaria leaf spot, Fusarium dry rot, potato pink and soft rot of tubers has been proven. They also can act as plant growth promoter and aflatoxin reducer agent in seeds and nuts. Key morphological characteristics of these eight species of Aspergillus is described in this paper. Most of these species are reported from Iran, thus identification and application of their efficient isolates can be suggested in plant diseases management as well as the plant growth enhancement programs.

This study aims to identify factors important pathogenic fungi in the roots, crown and base irrigated wheat in Western Azerbaijan Province in 1393 was carried out. For this purpose, wheat fields in different regions of Urmia, Naghadeh, Mahabad, Miandoab, Piranshahr, Oshnavieh, Khoy, Salmas and Qarah Zia od Din visited and from fields with symptoms of growth retardation accompanied by discoloration and decay in root, crown and base samples were taken. Pieces of 1 cm in length from the root, crown, and base were grown on acidic PDA media. Separation and purification steps of fungi were performed on WA, PDA, CMA, SNA, PCA and NM culture media. Pathogenicity test on the wheat seedling of pioneer cultivar using wheat grains and placement of mushroom blocks in the vicinity of plant organs under greenhouse conditions was carried out. Based on morphological characteristics including color and colony growth, Shape and dimensions of conidia, and conidia producing cells identified using valid keys. In this study, samples were taken from 56 farms and 81 fungal isolates belonging to the genus Fusarium, Bipolaris, Rhizoctonia and Pythium were isolated and identified. In this study, species, F. culmorum, F. avenaceum, F. graminearum, F. acuminatum and B. sorokiniana as important factors in irrigated wheat fields to nominate dumped into decay. Most of the distribution range of the genus Fusarium respectively.

Pythium is a fungus-like genus with worldwide distribution that is found in most terrestrial and aquatic ecosystems. It is a species-rich genus contains important plant pathogenic species. Little is known on the systematics of Pythium in West Azarbaijan province (N.W. Iran). Thus, the aim of this study was to identify 200 isolates collected from different cultivated soils of West Azarbaijan province during 2012–13. Based on morphological and molecular (ITS and coxI sequences) data, 14 Pythium species from six clades, A, D, E, F, I and J, were identified. Of these, P. ornamentatum from clade D, P. nodosum from clade J and P. stipitatum from clade E are new records for Iran mycobiota. Molecular data failed to separate P. glomeratum, P. ornamentatum and P. viniferum from closely related species and they were identified based on morphological features. Detailed description is presented here for P. minus, P. ornamentatum, P. nodosum and P. stipitatum.

The aim of this research, identifying the fungi taxa associated with root and crown rot of walnut trees in Kermanshah. For this purpose, the soil around root of trees and root and crown samples of walnut trees showing disease were collected in different region in Kermanshah. The purified isolates were identified using morphological characters on the different culture media, asexual and sexual organ as well as growth rates at different temperatures. In this research, 13 isolates, belong to three species including Phytophthora cactorum, P. citricola and Pythium sp. were identified. Pythium sp. maybe is a new species, because characteristics of this species did not match completely with other recognized Pythium species. Pythium sp. (1) and Pythium sp. (2) isolated from diseased tissue and infected soil, respectively. Pathogenicity test of these species were performed on excised shoots and seedlings In vitro and In vivo, respectively. Results of In vitro indicated that the most disease extension was appeared by Phytophthora cactorum, but was placed in one statistical group with Pythium sp. (1). Phytophthora citricola and Pythium sp. (2) were placed in the following statistical group. Results of greenhouse experiment shown that, P. citricola and P. cactorum caused complete death of seedlings after 8 and 12 days, respectively. Pythium sp. (1, 2) after 14 days caused drying of stem and leaves and death of seedlings.

To study the role of Pythium species as the turf pathogenic agents, during theyears 2005 and 2006, diseased samples and soil samples from green spaces andsport fields were collected from different regions of Tehran province. Fromisolates identified, Pythium catenulatum Matthews has been reported fromturfgrasses in other countries, but our study is the first report of this species inIran. Pythium okanoganense Lipps has been isolated from soil in Iran but hasn’tbeen recorded from turfgrasses in Iran and other countries yet.

The importance of plant protection is increasing with the need of optimizing the quality of agricultural yields. This is essential to search for suitable and appropriate microorganisms for biological control and also study and practice on how to use the optimal conditions for the successful management of plant diseases. One of these microorganisms is the fungus-like, Pythium oligandrum that live saprophytic in the soil. This microorganism has antagonistic and hyper parasitic effects on some of soil borne pathogens. This is not virulent on the 12 species of plants, belonging to six families and only present on their root surface. It is used for control of the wide range of pathogens of the field crops and also can stimulate plant growth, result in increasing the yield.

Damping off is one of the prevalent diseases in forest nurseries, which makes sever damages to conifer seedlings every year. Damping off caused to changes in color and curvature of seedling into puteal and become to seedling mortality. This study was executed in order to identify the causes of damping off in conifer seedlings in the nurseries of Lakan in Guilan province. For this purpose, the infected seedlings were collected and transferred to the laboratory for further research. After isolation and purifying the morphologic characteristics, the macroscopic and microscopic characteristics of the pathogenic agents were studied. The detected isolated pathogens were: Rhizoctonia solani Kuhn, Pythium sp., Fusarium solani (Mart.) Sacc., F. oxysporum Schlecht, F. semitectum Berk. & Rav. and Fusarium sp. The all symptoms of pathogens distinguished were similar to the primary contaminated seedling. The obtained results showed that the abundant of Pythiium sp. was higher than the other patogens in Lakan nursery. We can mention that, this is the first report of the presence of Fusarium semitectum var. majus at the pine trees in the Guilan province in Iran.