Evaluation of in vitro antifungal activity of potassium bicarbonate on Rhizoctonia solani AG 4 HG-I, Sclerotinia sclerotiorum and Trichoderma sp.

The effect of increased concentrations of potassium bicarbonate (KHCO3) as a possible alternative to synthetic fungicides for controlling Rhizoctonia solani AG 4 HG-I and Sclerotinia sclerotiorum was evaluated in vitro, in this study. In addition, the effect of potassium bicarbonate on Trichoderma sp., a natural antagonist on R. solani AG 4 HG-I and S. sclerotiorum was determined. Potassium bicarbonate substantially inhibited (P<0.05) the growth of the three fungal strains. Mycelial growth of R. solani AG 4 HG-I significantly decreased as the concentration of bicarbonate increased, especially at concentrations greater than 200 mM. Similarly, mycelial growth of both S. sclerotiorum and Trichoderma sp. dramatically reduced in increasing concentrations of KHCO3. Mycelial growth of either fungi was completely inhibited when exposed to 100 mM bicarbonate. In addition, KHCO3 concentrations higher than 10 mM caused significant (P<0.05) reduction of the sclerotium formation of S. sclerotiorum. Also, sclerotium germination and de novo sclerotium formation were significantly inhibited as the concentrations of KHCO3 increased. As a result, it was concluded that potassium bicarbonate was an alternative chemical agent for  controlling R. solani AG 4 HG-I and S. sclerotiorum. Also, KHCO3 was found to have negative effects on Trichoderma sp.Key words: Antifungal effect, KHCO3, soil borne pathogens, sclerotium germination

Mass size distribution and source identification of particulate matter metal components at four urban sites and a background site of Istanbul

In this study, the size distribution characteristics and metal contents of particulate matter (PM) have been determined. In this scope, PM sampling has been done at five stations in Istanbul. PM filter samples were collected for eight different sizes using the Anderson cascade impactor. PM filters were decomposed and analyzed for 20 metals. The highest median concentration for Fe, Ca, K, and Mg, known as soil metals, were observed as follows: Fe and Ca were observed at Goztepe station (1.20 and 8.28 mu g/m(3)), K was observed at Kilyos station (0.33 mu g/m(3)), and Mg was observed at Avcilar station (0.37 mu g/m(3)). The highest median concentrations for Zn, Cu, Pb, Ni, Cr, V, As, Se, Co, and Cd, known as anthropogenic metals, were observed at Avcilar, Goztepe, and Besiktas stations. Although the lowest metal concentrations was determined at Kilyos stations that was selected as the urban background. The enrichment factors (EFs) of most metals in the fine PM is higher than those in the coarse mode. According to the factor analyses, the most important emission source was observed to be industrial facilities at Avcilar; traffic at Besiktas; traffic and domestic heating at Goztepe; and domestic heating, sea salt aerosols, and ship traffic (in the Bosphorus Channel of Istanbul) at Rasathane