Among diseases that affect walnut, bacterial blight is considered the most important one in all walnut growing areas both from Hungary and Romania. For the determination of susceptibility/resistance of walnut cultivars in our posterior work planned, 61 bacterial isolates were collected from walnuts showing symptoms of blight, with the purpose o...f isolating Xanthomonas arboricola pv. juglandis (Xaj). The characteristic Xaj colonies, frequently present as saprophytes in the infected plant tissues, were separated from other bacteria according to their morphology, yellow colour, hydrolysis of starch, and oxidation of glucose. All isolates were tested for pathogenicity by hypersensitive reaction on tobacco leaves (Nicotiana tabacum L.), bean pods (Phaseolus vulgaris L) and unripe nuts (Juglans regia L.). Determination of taxonomy of the selected isolates denotes a possible subdivision (races, biotypes) of Xaj occurring in different geographical areas, API 20NE and API 50CH kits were used. Hungarian and Romanian strains showed a high degree of similarity of carbohydrate utilization but slightly differed from the type strain. All were Cu-sensitive.
The aim of our preliminary studies was to characterize the change in the activity of enzymes PPO and PDX, the concentration of total soluble phenolic compounds and soluble protein content of different tobacco cultivars measured in tobacco plants during cultivation. The results suggest that a shorter cultivation period (13-14 weeks) is ...more favourable for tobacco plants as protein source than for tobacco industrial use (16-17 weeks). We found some correlation between the concentration of total soluble phenolic compounds and PPO activity data. In the increasing and maximum period of total phenol content the PPO activity was high. But later because of decrease of substrate phenol content the activity of PPO also decreased. We found higher soluble protein concentrations in Virginia than in Burley varieties.