The studies were carried out both in in vitro and in vivo conditions. The field experiment was conducted during the years 2005-2007 at the Experimental Station in Mydlniki, owned by the Department of Plant Protection at the University of Agriculture in Krakow. The aim of these studies was to determine the effect of tuber dressing and plant spraying with Polyversum (B.A.S. Pythium oligandrum) and Biochikol 020 PC (B.A.S. chitosan) bio-preparations on the top leaves and tubers of ‘Ibis’ potatoes infested by Phytophthora infestans. The chemical preparation Vitavax 2000 FS (B.A.S. karboxin and thiuram) was used. The in vitro evaluation of Polyversum and Biochikol 020 PC bio-preparations on the P. infestans mycelium linear growth was investigated. The above-mentioned preparations were applied at three different concentrations. The experiment was carried out using the Kowalik and Krechniak method (1961). Based on the results it was found that the preparations under examination significantly inhibited top leaf and tuber infestation by Phytophthora infestans. Moreover, according to the results obtained from in vitro tests, a significant effect from the Vitavax 2000 FS and Polyversum preparations and from the highest concentration (2%) of Biochikol 020 PC preparation on the percentage inhibition of P. infestans mycelium linear growth was observed (in comparison to the control).
Symptoms of discoloration and necrosis of the leaves/needles and shoots of plants are an increasingly common phenomenon in nurseries. They necessitate the withdrawal of the affected plants from sale, which has significant economic consequences. In 2010-2011, observations were conducted of the health of shrubs in nurseries of the Małopolska province. Disease symptoms were mostly found in juniper (Juniperus horizontalis 'Wiltonii'), rose (ground-cover rose 'Star Profusion'), yew (Taxus × media 'Hillii') and highbush blueberry (Vaccinium corymbosum 'Patriot'). These species were selected for further study. The affected shrubs represented more than 46% of the population of a given species. Fragments of the diseased organs: the leaves or needles, the base of the shoots, and the roots, were collected from the borderline between healthy and diseased tissue, and used to isolate and identify the microorganisms colonizing the diseased parts. The affected organs were found to be inhabited to the largest extent by the fungus Alternaria alternata (Fr.) Keissl., which accounted for 19.7 to 47.5% of the isolates from the tested species of shrubs. There were also large populations of fungi of the genera: Botrytis (up to 9.82%), Cladosporium (up to 5.66%), Colletotrichum (up to 5.13%), Fusarium (up to 18.38%), Mortierella (up to 7.26%), Pestalotia (up to 5.36%), Rhizoctonia (up to 5.36%), Sclerotinia (up to 6.99%), and Trichoderma (up to 17.09%). The fungus A. alternata, being by far the dominant pathogen, was tested for its pathogenicity for the shoots of the chosen species of shrubs. The test was conducted for 14 days in a chamber with parameters so programmed that they reflected the natural conditions at the height of the growing season. The fungus A. alternata exhibited pathogenicity for all of the tested species of shrubs. Necrosis developed on all the inoculated fragments of shoots. The surface area of necrotic lesions was larger on the shoots of juniper and blueberry.
The aim of the study was to establish whether the redroot pigweed (Amaranthus retroflexus L.), which is a common weed in potato crops can be a source of Alternaria alternata, the causal agent of Alternaria leaf blight, and to determine the genetic diversity of isolates of this pathogen infecting the weed and the potato cultivar tested. With the A. alternata isolates selected for genetic testing, homosporous cultures were obtained, from which DNA (deoxyribonucleic acid) was subsequently isolated. The genetic diversity of A. alternata isolates was determined by the RAPD-PCR (random amplification of polymorphic-polymerase chain reaction) method. Based on the results obtained, it was found that the dominant fungi present on the diseased leaves of both potato and pigweed plants were: Alternaria alternata, A. solani, Cladosporium cladosporioides, C. herbarum, Epicoccum purpurascens and Fusarium sambucinum. Presence of A. alternata as a dominant fungus on redroot pigweed suggests that if weed infestation is extensive, the pathogen is very likely to spread and its population to increase.
Buxus sempervirens (L.) is an evergreen shrub often used in urban plantings intended for forming the trimmed hedges, as well as for creating geometrical shapes. Its decorative qualities are often diminished by the effects of pathogens colonizing the roots, shoots and leaves. The study was conducted in three consecutive growing seasons. The experimental material originated from a nursery located in southern Poland. The subjects under study were diseased leaves, stems and roots of the boxwood variety ‘Suffruticosa’. Samples consisting of 720 diseased fragments of the shrub were taken for mycological examination. Mycological isolations were performed according to the standard methods used in phytopathology. A total of 1059 colonies of fungi and fungus-like organisms were isolated from the diseased boxwood plants. The fungus Alternaria alternata dominated among all the isolates. The pathogens frequently isolated from the leaves included Macrophoma candollei, Volutella buxi and Fusarium buxicola. Those frequently isolated from the shoots included: Pestalotiopsis sydowiana, Volutella buxi and Fusarium avenaceum. The root system, in turn, was colonized in large numbers by: Fusarium oxysporum, F. avenaceum, Rhizoctonia solani, Botrytis cinerea and Phytophthora cinnamomi. Results of the three-year study show a comprehensive participation of phytopathogens in the disease process affecting the boxwood variety ‘Suffruticosa’.
The results received from field experiments indicate that, during all years of study these preparations significantly reduced tubers infestation by Streptomyces spp. The Polyversum bio-preparation, which was applied to tuber dressing and sprayed on plants four times during vegetation period, showed the best protective effect against Streptomyces spp.
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