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Tétel Szabadon hozzáférhető Carbohydrate utilization of Erwinia amylovora in vitro(2004-05-10) Hevesi, M.; Farkas, A.; Kása, A.; Orosz-Kovács, Zs.Nectar is a multi-component aqueous solution that promotes bacterial multiplication. The concentration of nectar in plant flowers is not stable since it is under the influence of environmental conditions, especially free moisture and relative humidity. Experiments were conducted with "artificial nectar" and directed along two lines: (1) determination of the optimal concentrations of carbohydrates for the growth of E. amylovora development (2) consumption of different carbohydrates besides basic sugars. Solutions of "artificial nectar" were prepared in different compositions by changing the dominance of basic sugars (fructose — glucose —sucrose) in proportions of 2:1:1, 1:2:1, 1:1:2 and between concentrations of 10-0.6% (diluted with Basal minimum broth) in order to determine optimal conditions for the development of E. amylovora. At a basic sugar concentration of 10% bacterial multiplication started and continued until I log degree (from 10 6 to 10 7 cfu/ml). At concentrations of 5% and 2,5 % cells developed with nearly the same kinetics (from 10 6 to 8x10 7 cfu/ml and from 10 6 to 9x10 7 cfu/ml, respectively). Multiplication was more pronounced and nearly the same at concentrations of 1.2 % and 0.6 % (from10 6 to 2x10 8 cfu/ml). At a basic sugar concentration 30% total sugars bacterial multiplication did not occur, while at 20 % it was negligible, not measurable photometrically. At minimal concentrations of F, G, S (between 1-0.1 %) bacterial cells were still able to multiply, producing organic acids from sugars. Our study showed that E. amylovora requires only a small amount of sugars (0.1%) for multiplication (acid production) while high concentrations inhibit multiplication. There was a negative correlation between sugar content and cell density. The optimal range of sugar concentration was at about 1%. Effect of "less frequent carbohydrates" to E. amylovora multiplication was also determined using the API 50 CH strip. We could provide information on utilization of 39 carbohydrates by the bacterium at different categories as follows: Not utilized-, Slowly and weakly utilized-, Slowly and completely utilized-, Quickly and completely utilized carbohydrates. We suppose that carbohydrates that belong to the latter two groups could play an important role as nectar components in promoting E. amylovora multiplication in the blossoms of pome fruit trees.Tétel Szabadon hozzáférhető Flavonoids, chalcones and phenyl-propanoids in apple and pear flowers(2004-05-10) Horváth, Gy.; Farkas, A.; Szabó, Gy. L.The presence of phloretin-glycosides in the hypanthium and pistil of apple and pear flowers can be verified. Thin layer chromatography is a reliable method for detecting phloretin, gained by acidic hydrolysis. The dominance of phloretin was equally characteristic for flowers in apple (`Sampion', 'Freedom') and pear (Tem - re Bosc', 'Conference') cultivars treated with various bioregulators (Biomit, Bion 50WG, Regalis), no significant difference could be found visually as compared to control samples. Chlorogenic acid and caffeic acid was detected in all apple and pear samples, rutin was present only in pear, and hyperoside was found only in a few apple samples.Tétel Szabadon hozzáférhető Floral biological investigations of apple cultivars in relation to fire blight(2004-05-10) Orosz-Kovács, Zs.; Farkas, A.; Bubán, T.; Bukovics, P.; Nagy Tóth, E.; Déri, H.Floral activity was studied in two apple cultivars: an Erwinia-tolerant (Treedorn') and a sensitive one (`Sampion'). Since more types of protogyny occur in apples, the period of stigma activity is different. Papillae of the exposed stigma in flowers of 'Freedom' function longer (usually more than a week) than in the delayed homogamous `Sampion'. Despite of this, cv. 'Freedom' is tolerant to Erwinia amylovora (Burr.) Winslow et al., suggesting no relationship between the floral biological type (including the exposure and longevity of stigma) and the infection by E. amylovora. According to SEM micrographs, nectary stomata in `Freedom' are already open in the flower bud, where nectar secretion starts and continues until the senescence of the stigma. However, the long period of nectar secretion does not create optimal conditions for bacterial growth, since nectar production is scant in the flowers of 'Freedom'. The surface of the nectary, its nectar-retaining capacity, and the amount and concentration of nectar may influence the susceptibility of apple cultivars. It is manifested well by the smooth nectary surface with nectary stomata rising slightly above the epidermis in flowers of cv. 'Freedom', contrasting the wrinkled, striate nectary surface with slightly sunken stomata in the flowers of 'Sampion'.Tétel Szabadon hozzáférhető Floral biological studies on pear cultivars in relation to fire blight susceptibility(2004-05-10) Farkas, A.; Orosz-Kovács, Zs.; Bubán, T.Floral biological characteristics that may influence cultivar susceptibility to fire blight were studied in 10 pear cultivars in two Hungarian orchards from 1999 to 2003. The receptaculo-ovarial, automorphic nectary is usually bigger in tolerant cultivars than in susceptible ones. Nectary stomata are meso- or xeromorphic. Susceptible cultivars tend to have more xeromorphic stomata, where guard cells are located 1-3 cell rows below the epidermis. The size of nectar chambers is usually smaller in susceptible cultivars. Floral nectar, consisting mainly of glucose and fructose, is more abundant and less concentrated if the cultivar is susceptible to fire blight. The amount of chlorogenic acid was higher in the flowers of tolerant cultivars than in susceptible ones.