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Comparison of Xanthomonas arboricola pv. juglandis isolates from walnut trees grown in Romania and Hungary
65-69.Views:262Among 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 of 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.
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Epidemiological survey of Xanthomonas arboricola pv. juglandis and Gnomonia leptostyla on natural population of walnut (Juglans regia) in eastern Transylvania
7-9.Views:2077In Romania, walnut Juglans regia L. is an important fruit crop, although most of the fruit production comes from non-grafted walnut trees, which are natural hybrids. Breeding programs have been launched during last 30 years to develop new cultivars with uniform fruit quality. In addition, foreign cultivars have been introduced and tested to establish a valuable walnut genepool. To improve the present assortment of generative rootstocks in walnut and to examine the infestation level, a long term survey was carried out in Eastern Transylvania. The main physical characteristics of fruits and its variation to the infestation level were considered. The cumulative distribution of Xanthomonas arboricola pv. juglandis and Gnomonia leptostyla were relatively low and the maximum value was around 15%. The highest infestation of husk with X. arboricola pv. juglandis was observed for roundish forms and differences were statistically significant comparing with other phenotypes. Infestation with G. leptostyla was similar for roundish, elliptic and thwarting egg-shaped phenotypes, while the husk infestation for egg-shaped phenotypes was not observed. The walnut population studied in our experiment can be considered as a genetically valuable population. More than 20% of them have upper class quality fruits with at least or more than 50% of nutmeat. Do to the large scale climate variation in Eastern Transylvania and the high humidity favourable for pathogen infestations, these population can be considered resistant and well adapted to abiotic and biotic factors.
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The effects of foliar nutrition containing various macro and microelements on the growth and development of young grafted walnut (Juglans regia L.) plants
33-37.Views:153The Stopgril liquido (S), a foliar fertilizer containing nitrogen, calcium and magnesium was used to improve the spring and the summer growth of grafted walnut plants in the second year of cultivation in the nursery. To accomplish early termination of vegetative growth and good lignification, the composed mineral fertilizer Hascon M 10 AD (H) containing phosphorous, potassium and microelements B, Mn and Mo was applied on the same plants. Four treatments (S, H, SH, C) were applied three times in a growing season. Their effects on the height and the basal diameter of the plants in the nursery depended on the starting height of the plants and the time of application. During the first growth period in the orchard, the number of developed buds on the plant, the circumference of the plants and their height were influenced by the treatment in the previous year in the nursery. According to the results obtained through the investigation, three applications of Stopgril + Hascon in the nursery per year can be recommended in order to obtain high enough and well lignified two-year-old grafted walnut plants.