masoud zaker

Puccinia graminis f. sp. tritici is the causal agent of wheat stem rust disease. This fungus is heteroecious with complete life cycle that its intermediate host plant is barberry (Berberis spp.) In some areas that urediniospores cannot survive in winter conditions, basidiospores produced from teliospores in feat barberry which result in the survival of the fungus and its transmission to the next season. In this research, samples of barberry leaves showing symptoms of rust disease were collected from North Khorasan, Mazandaran, Golestan, Semnan, Fars, Lorestan and South Khorasan provinces. Host plant species and infecting fungal species were determined based on their morphological characteristics. In addition, the relationship of these fungal species to stem rust of wheat was investigated by inoculating them on two susceptible wheat cultivars Moroco and Local Red. A total of five hybrids and species of barbery as Berberis vulgaris, B. integerrima × vulgaris, B. integerrima × cartingia, B. orthobotrys and B. integerrima were identified as the host. According to morphological characteristics, three fungal species were identified as: Puccinia magelhaenica, P. brachypodii s.lat. And Aecidium berberidis, where none of these species are known as wheat stem rust disease agent. Inoculation of aecidiospores obtained from Barberry species on the susceptible wheat cultivars showed that only two samples produced stem rust symptoms indicating most barberry shrubs in Iran are the host for rust species that are not pathogenic on wheat and may not have significant impact on epidemic of stem rust in the region.

During the last several decades the efficacy of plant extracts and essential oils in controlling plant diseases specially those of leaf spots and fruit rots have raised the interest of many researchers worldwide. Several findings have approved the antifungal potential of plant products containing Thymol and Carvacrol compounds against a wide range of plant fungal diseases including grape gray rot. Botrytis cinerea, the causal agent of grape gray rot has a wide host range and can cause severe loss in the field and during storage. In this study the antifungal efficacy of five essential oils, ie: Wild marjoram, Savory, Fennel, Wormwood and Rosemary were evaluated at three concentrations 200, 400 and 600 ppm on mycelia growth, spore germination and germ tube elongation of B. cinerea under laboratory conditions. Results indicate that Wild marjoram, Savory and Fennel at 200, 400 and 600 ppm could completely (100%) inhibit the mycelia growth as well as spore germination of this fungus respectively, while Wormwood and Rosemary had either very little or no effect on this fungus . Results also approve that Wild marjoram and Savory essential oils which contain Thymol and Carvacrol compounds, specially the first one containing both the compounds showed the highest antifungal activity against B. cinerea.

Fire blight of pome fruits caused by Erwinia amylovora is one of the most devastating disease especially on pear and quince in Semnan province. A total of eighty strains were isolated from different localities and hosts including apple, pear, quince and rose during 2006-2007. Fifty strains were studied for their phenotypic characteristics, genotypic variability, pathogenicity and also resistance to streptomycin and cupper oxychloride. On the basis of physiological, biochemical and morphological features, tested strains were identified as E. amylovora. They were Gram negative, formed levan, facultative anaerobic and induced hypersensitivity reaction in tobacco leaves. They did not produce fluorescent pigment on King`s B medium. On the basis of Phenotypic features, host rang and geographical distribution, eight representatives were selected for evaluating the genetic diversity among them, by rep-PCR using ERIC and BOX primers. All strains were identical to ATCC 49946 strain. On the basis of these experiments no resistance to antibiotics and copper oxychloride was found among the E. amylovora strains causing fire blight of pome fruit trees in Semnan province, therefore chemical bactericides can be safely used in an integrated management program of the disease in Semnan province orchards and this similarity may help to follow a similar method in selecting resistant varieties and forecasting of the disease management.

The Eucalyptus (Eucalyptus Camaldulensis) extract contains eucalyptol as active ingredient and has disinfectant and antifungal properties. Its fast degradation and very less toxicity for mammals has caused attention toward its use as a safe pesticide. Its efficacy in controlling the mycelial growth and spore germination of Alternaria alternata the causal agent of Alternaria leaf spot of potato under laboratory condition has been approved. During 2011, the efficacy of 5, 10 and 15% of its EC formulation in controlling Alternaria leaf spot disease of potato was conducted in a completely randomized design with five treatments and four replications under green house condition. Fungicide mancozeb 0.2% was used for better comparison. Results indicated that all three eucalyptus concentrations with 24.80, 16.28 and 9.29% disease incidence respectively showed significant differences at 1% level of probability in controlling the disease compared to control. Eucalyptus formulation (15%) and mancozeb were kept in same statistical group. By increasing the percentage of eucalyptus formulation its phytptoxicity was increased. Percentage of phytotoxicity in 5, 10 and 15% of eucalyptus formulations were 4.02, 10.65 and 21.34% respectively. Further studies are needed for omitting its phytotoxicity, so that it might be used as a safe bio-fungicide in controlling Alternaria leaf spot of potato.

Application of Trichoderma species is a harmless method in controlling soil borne plant diseases thus reducing hazardous pesticide use and environmental pollution. Some Trichoderma isolates performing proper inhibitory effect against Fusarium oxysporum f. sp. tuberosi under laboratory and green house conditions were screened against wilt disease of potato caused by this pathogen under field condition in Shahrood Agricultural Research Center, Iran, during 2009-2010. Results of two years field studies indicated that T. virens (T7) followed by T. asperellum (T2) were superior to others in reducing the disease in comparison to infested control. In comparison to Fusarium infested plots, yield was higher in all plots treated with Trichoderma, but highest yields were obtained from plots in which T. virens (T7) and T. asperellum (T2) were involved respectively. It might be stated that isolates of T. virens and T. asperellum are among the effective biocontrol agents against Fusarium wilt disease of potato and can be used as formulated biofungicides in reducing this disease.

Biological efficacy of Trichoderma species may differ due to variations in ecosystems. This study was conducted to assess the biocontrol efficacy of some native Trichoderma isolates against Fusarium oxysporum، an important causal agent of potato wilt disease under lab. and green house conditions in Shahrood Agricultural Research Center، Shahrood، Iran during 2006-2007. Fourteen isolates were collected among which eight showed promising ability in inhibiting the growth of the pathogen through dual culture and production of volatile and non-volatile inhibitors but T. asperellum (T2) and T. atroviride (T3) were almost more efficient than other isolates in inhibiting the mycelial growth of the pathogen in comparison to control (P ≤ 0. 01). Eight isolates were evaluated against the disease under green house condition. Potted plants treated with Trichoderma isolates + F. oxysporum showed lower disease incidence in comparison to Fusarium infested control (P ≤ 0. 05). Best disease control was observed in potted plants treated with F. oxysporum + T. asperellum (T2) showing 2. 5 % disease incidence in comparison to Fusarium infested control، in which disease incidence was 73 %.

Application of botanical and biological methods in plant disease controls are unique techniques in reducing environmental pollutions. Trichoderma species are effective agents in biocontrol strategies and identifying their useful isolates for further studies seems to be helpful. The purpose of this study was to assess the in-vitro biocontrol efficacy of some native Trichoderma isolates against Pythium aphanidermatum an important causal agent of sugar beet root rot disease in North Iran. Evaluations were conducted in Shahrood Agricultural Research Center, North Iran during 2007. Collected Isolates of Trichoderma belonging to four species (T. harzianum,. longibrachatum, T. erinaceum and T. koningii), among which T. erinaceum is a new fungus for Irans'' mycoflora. Results of lab tests including dual culture technique, assessment of volatile and non-volatile effects on pathogen'' colony growth indicated the effectiveness of all ten isolates against P. aphanidermatum. In dual culture T. harzianum-2733 and T. longibrachatum-2734 were best in reducing the colony growth of P. aphanidermatum by 57% compared to control. Volatile antibiotic compounds of T. longibrachiatum-2737 and non-volatile antibiotic compounds of T. harzianum-2739 were best among Trichoderma isolates and controlled the colony growth of the pathogen by 66 and 87% respectively.