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Different concentrations of medicagenic acid and five glycosides of this acid isolated from alfalfa (Medicago sativa) were added to agar medium (com meal agar, CMA) inoculated with cultures of Gaeumannomyces graminis var. tritici (Ggt). After 7 days of incubation at 25°C colony radius was measured and % of inhibition calculated in relation to the control medium (CMA enriched with the solvent of the tested compounds). Within the tested concentrations, only 3-O-β -D -glucopiranoside medicagenate (monoglucoside) significantly reduced the growth of Ggt on CMA medium. This compound at 0.05 mM concentration completely inhibited the development of the fungus and the effect was shown to be fungi-toxic.
Acta Agrobotanica
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2002
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tom 55
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nr 1
359-365
The work was done in years 1998/1999 - 2000/2001 on plantations and field plot experiments. Aim of the work was evaluation of take-all occurrence on winter wheat in milk-wax growth stage in dependence on forecrop (oilseed rape, wheat or barley) as well as seed treatment with Latitude 125 FS when wheat was planted on fields after wheat or barley. Percentage of infected plants when seeds were not treated with Latitude 125 FS varied from 82-100 on fields after wheat or barley, and 54-69 on fields after oilseed rape. In treatments with wheat grown after wheat or barley the percentage of infected plants amounted 20-100 when seeds were not treated with Latitude 125 FS and 13-86 when seeds were treated with Latitude 125 FS. Mean degree of infection was low when percentage of infected plants was low and high when percentage of infected plants was high.
Gaeumannomyces graminis is an etiologic agent of take-all, economically important disease of cereals worldwide. A polymerase chain reaction with variety-specific primers was successfully used for detection of G. graminis var. tritici in plant tissue. Obtained results showed that this diagnostic method is a very sensitive and useful tool for detection of the pathogen even before disease symptoms arise. DNA polymorphism revealed by RAPD-PCR with three arbitrary primers was suitable for assessing genetic variation among Ggt isolates originating from wheat and rye.
Pseudomonas fluorescens strains III107 and II21 and Bacillus mycoides strains JC192 and K184, stimulating growth of winter wheat, were chosen for the studies. The bacterial strains inhibited on agar nutrient medium the growth of Gaeumannomyces graminis var. tritici (Ggt) - the pathogenic fungus causing take-all on wheat. Both strains of pseudomonads synthesized relatively high amounts of Fe³⁺ chelators. The strains of bacilli were characterized by the very fast spreading on agar media. Furthermore, strain II21 was highly cyanogenic, and strain JC192 highly chitinolytic. Bacterization of winter wheat seeds (especially with strains III107 and JC192) significantly reduced the percentage of the plants infested with the pathogen in the 28 day glasshouse pot experiment. In the plot experiment, the winter wheat seeds were inoculated with a mixture of strains III107, II21 and JC192. Due to the bacterization the yield of wheat grain and straw was higher in comparison to the series with Ggt alone by 122% and 75%, respectively, but it amounted only to 45% and 43% of the control series not contaminated with Ggt. The decrease of percentage of wheat ears with weight less than 500 mg from 61% in Ggt-series to 25% in Ggt-bacterized-series, and especially the decrease of percentage of wheat ears with weight less than 200 mg from 43% to 14% additionally indicate the partial protection of the winter wheat against Ggt by the rhizobacteria. In the experimental series not contaminated with Ggt the percentage of these wheat ears fractions did not exceed 3% and 0.5%, respectively.
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