Biomedical subjects

M Okhovat

Publications and source records attributed to M Okhovat.

5 recordsLinked to original sources

PubMed2005

Biological control of Tiarosporella phaseolina the causal agent of charcoal rot of soybean.

Charcoal rot caused by Tiarosporella phaseolina (Tassi) Van der Aa is an important disease of soybean in Gorgan province of Iran. Experiments were carried out with 95 bactenal isolates that were collected from the rhizosphere of soybean plant. Among these bacteria only 50 isolates showed antagonistic effect on Tiarosporella phaseolina using dual culture test. Six highly effective bacteria were selected for subsequent studies. Based on biochemical physiological and morphological tests, isolates Pf-12 and Pf-63 were identified as Pseudomonas fluorescens, isolates B-13, B-42,B-126 and B-84 as Bacillus subtilis. The isolates of P. fluorescens produced antibiotics as well as volatile metabolites that inhibited mycelial growth of fungus. Bacillus subtilis isolates inhibited the fungal growth through volatile and non-volatile metabolites production. Only P. fluorescens isolates produced hydrogen cyanide. In greenhouse studies, the isolates B-13 and B-126 reduced 59% and 66% the intensity of charcoal rot of soybean respectively. The combinations of isolates B-13 and B-126 were also effective on reducing the intensity of disease.

Antibiosis↗

PubMed2004

Effect of tea dust residues to control root-knot nematode of tomato.

In this research, control of tomato root- knot nematode (Meloidogyne incognita) was conducted using tea dust residues at different rates. First, the species and race of nematode were identified by employing diagnostic keys. Then, with 5 replications in complete randomized design. Tea dust residues were used at 9 treatments (0, 5, 10, 15, 20, 25, 30, 35 and 40 g/kg of soil). Statistical analysis on mean treatments rates showed that treatment with 25 g/kg soil economically was effective in growth rates and reduction in gall index.

Animals↗

PubMed2003

Study on interaction between root-knot nematode Meloidogyne javanica and wilt fungus Verticillium dahliae on olive seedlings in greenhouse.

Verticillium dahliae has been reported as a limiting factor in cotton, olive, potato and tomato fields from several countries in the world. Root-knot nematodes Meloidogyne javanica causes considerable damage to olive groves in olive growing areas. Since the presence of these two pathogens in olive trees and seedlings were confirmed in Golestan Province, this study was proposed to find the mode of their action and interaction with olive seedlings in greenhouse. The non-defoliant strain of the fungus (SS-4) was isolated from olive groves showing symptom in Golestan Province. M. javanica was also recovered from the infested olive seedlings. After species identification, it was reared on tomato seedlings var. Rutgers. The larvae were used as a source of inoculum. Conidia and microsclerotia of V. dahliae were used as a source of inoculum for pathogenesis in this study. Stem cuttings of olive cultivar Zard were transplanted in different sets of pots containing 720 ml. of sterilized loamy soil and sandy soil. Experiment was conducted in Completely Randomized Design with 6 treatments and 8 replicates including control, nematode alone, fungus alone, nematode and fungus simultaneously, nematode and fungus concomitantly, fungus two weeks prior to nematode, nematode and fungus concomitantly, nematode two weeks prior to fungus. Pots were inoculated with 1500 larvae of nematodes and 7200 microsclerotia of V. dahliae. Experiment was terminated after 9 months and following parameters were determined i.e. fresh weight of roots, number of galls and females, per root system and discoloration of leaf and root tissues. Presence of nematode prior to fungus caused reduction in colonization of fungus in the roots and the stems and vis presence of fungus prior to nematode caused reduction in number of galls produced by nematode. Sever symptom on aerial parts of plant was observed when both pathogens were inoculated simultaneously. However fresh weight of roots was reduced in all treatments. Galling and population density in root system were higher in pots filled with sandy soil than in loamy soil, but fungal colonization in roots and stems was much more in seedlings grown in loamy soil and diseases symptoms in aerial parts of plants were much severe in plants grown in loamy soil than in pots with sandy soil.

Agriculture↗

PubMed2002

Interaction between root lesion nematode Pratylenchus vulnus and two species of Fusarium on growth and development of maple seedlings.

Producing healthy seedlings and distributing them to far areas, is one of the most important factor for developing forests. Because of easy planting, rapid growth and good wood quality, Acer velutinum is the most useful species, among the softwood and hardwood trees. Growth and development of the nurseries were effected by different pests and diseases, the nematodes are one of these agents. They are not actively surveyed in the forest nurseries in Iran. On a survey of maple seedling in the forest nurseries Pratylenchus vulnus, Fusarium solani and F. oxysporum were identified. The interaction between these two fungi and nematode were studied in randomized complete block design with four replications and six treatments. For mass production and multiplication of the nematodes, they were sterilized with Streptomycin Sulfate, they were reared on carrot disc culture. The nematodes were then added to each pot. The results showed a highly significant difference (p = 0.01) between different treatments. In the treatment with nematodes alone growth of seedlings was minimum and population density of nematodes in soil and root tissue was maximum. In this treatments 75% of seedlings were died and seedling average height were 2.25 cm. In the treatments with nematode and fungi together the population of nematodes were decreased and the growth of seedlings were increased, in comparison with nematode alone. F. oxysporum showed more antagonistic effect on nematodes than F. solani. In the nematode + F. oxysporum treatment, 25% of seedlings were died and seedling average height was 12.75 cm. In the nematode + F. solani treatment, 50% of seedlings were died and the seedling average height was 5.5 cm. This is the first report of pathogenecity of Pratylenchus vulnus and its interaction whit fungi on maple seedlings in Iran.

Acer↗

PubMed2002

Barley leaf stripe disease.

Leaf stripe is one of the most important diseases of barley in Iran especially in Gorgan, Mazandran and near Tehran (Varamin). Most obvious symptoms of the disease are described. Long pale or yellow stripes become darker as the fungus sporulates on the leaf surface. Infected plants usually are stunted and produce sterile spikes, rarely a few seeds are produced. Infected spikes and late-forming tillers may produce fertile spikes. The fungus is seed brone and survives in the outer layers of infected seed. To study the seed-borne disease, we have used the different methods (ISTA). Coleoptiles of seedlings are infected by the fungus under cool, moist conditions, a soil temperature below 15 degrees C is necessary for seed infection. The fungus penetrates through coleoptiles and grows systemically within the plant, produces toxin and kills cells and discolors leaf tissue between veins, thus causing striped lesions. When conditions are wet or humid, spores are produced on the surface of leaves at above the time spikes of healthy plant. Morphological characteristics of the vegetative and reproductive structures of the fungus show that it is Drechslera graminea (Rabenh) Shoemaker.

Cotyledon↗