Effect of epiphytes on the extent of necrotic injuries of resistant and susceptible poplar clones infected with Dothichiza populea.

Poplar cuttings of a resistant clone, Populus 'Grandis', and susceptible clones, Populus nigra 'Italica' and Populus 'Robusta', were infected with the pathogenic fungus Dothichiza populea alone, or with the pathogen and one of five strains of epiphytes antagonistic towards it (in vitro), isolated from poplar bark. The extent of injury was examined for 28 days after infection by determining the length of necrotic patches and their area as expressed in per cent of the total area of a cutting or the area of necrotic injuries caused by the pathogen alone. All the poplar cuttings of both the resistant and susceptible clones became diseased when infected with the pathogen alone.

Epiphytic microflora of poplar clones susceptible and resistant to infection by Dothichiza populea.

One-year-old poplar shoots (nodes, internodes and lenticels) of clones susceptible to infection by the pathogenic fungus Dothichiza populea, viz. Populus nigra Italica and P. Robusta, resistant ones, viz.

The development of fungi as affected by pH and type of soil, in relation to the occurrence of bacteria and soil fungistatic activity.

A study was made on the effect of liming (Ca(OH)2) on the numbers of colony-forming units (CFU) and the biomass of fungi in loamy sand (ls) and a loose sandy soil (lss) during 90 days under laboratory conditions. Liming inhibited the growth of fungi more strongly in the lighter soil. Raising the pH of lss from its native 4.

CO2 release as an index of biological activity of cultivated soils.

In 15 soils from the region of Wielkopolska, estimations of CO2 release and bacterial biomass size were made. It follows from the present studies that CO2 release from the soil can be an index of its metabolic activity. It is necessary to take into consideration also the dynamics of that process in each type of soil and to determine the degree and time of its response to variation of ecological conditions.