Twenty two scab-resistant apple cultivars, harvested in the 2007 and 2008 seasons, were analysed for phenolic compounds content and polyphenol oxidase (PPO) activity. Tyrosine content was determined in the raw juices of five selected cultivars. The results showed substantial differences in the composition between the investigated apple cultivars, particularly in the phenolic compounds contents. Their total polyphenol content ranged from 161.9 to 882.4 mg/kg f.w., with hydroxycinnamic acids as the main phenolic compounds. The level of PPO activity ranged from 5 to 240 U/g f.w. Almost half of the 22 cultivars show PPO activity below 50 U/g f.w. 'Angold', 'Selena' and 'Gold Milenium' showed the highest PPO activity; between 125-133 U/g f.w. 'Rebella', 'Sampion', 'Topaz', 'Rewena', 'Enterprise' and 'Gerlinde' showed the lowest PPO activity. Statistical analysis showed no correlation between PPO activity and total polyphenol content or hydroxycinnamic acids. No correlation can be confirmed between PPO activity and tyrosine content.
The experiment was conducted at Fruit Experimental Station Samotwór near Wroclaw in the years 1998–2003, The aim of the experiment was to estimate the influence of six rootstocks on the growth, cropping and fruit quality of some new scabresistant apple cultivars. Two of the cultivars were Polish –Waleria and Sawa, and four of them were Czech – ‘Rosana’, ‘Rubinola’, ‘Rajka’ and ‘Topaz’. In the spring of 1998 maiden trees on rootstocks M.9, P2, P60, P16, P22 and M.27 were planted at the spacing 3.5×1.2 m (2380 trees/ha). The results of six-year-long studies confirmed that ‘Rubinola’ and ‘Rajka’ were characterised by the strongest vigour (the lowest crop efficiency indices – CEI), while ‘Rosana’ grew very weakly (the highest CEI). Fruit quality in terms of presentation and taste was the best in the case of ‘Rubinola’. ‘Sawa’, ‘Rubinola’ and ‘Topaz’ had the biggest potential for commercial production. The rootstocks M.9 and P60 proved to be the most useful for the studied apple cultivars.
Antagonistic activity of 63 bacterial isolates, originating from soil and apple leaves, against Venturia inaequalis was studied in dual culture on PDA medium. Based on measurement of inhibition zones, 16 isolates appeared to be most active. Three of them /57M, 59M (Pseudomonas spp.) and 103M (Collimonas sp.), significantly protected apple trees against apple scab on Gala trees in the net-glasshouse. Of 6 ethanol plant extracts (sage leaf, rhizomes of Potentilla, oak and willow bark and the aboveground parts of St. John's-wort and tetterwort), the highest activity in inhibition of V. inaequalis conidia germination, even after 10- and 20-fold dilution in water, showed extract from rhizomes of Potentilla. Applied at two concentrations (5 and 10%) on Gala apple trees it totally protected leaves against apple scab.