Dynamical emergence of Markovianity in local time scheme.

Recently we pointed out the so-called local time scheme as a novel approach to quantum foundations that solves the preferred pointer-basis problem. In this paper, we introduce and analyse in depth a rather non-standard dynamical map that is imposed by the scheme. On the one hand, the map does not allow for introducing a properly defined generator of the evolution nor does it represent a quantum channel. On the other hand, the map is linear, positive, trace preserving and unital as well as completely positive, but is not divisible and therefore non-Markovian. Nevertheless, we provide quantitative criteria for dynamical emergence of time-coarse-grained Markovianity, for exact dynamics of an open system, as well as for operationally defined approximation of a closed or open many-particle system. A closed system never reaches a steady state, whereas an open system may reach a unique steady state given by the Lüders-von Neumann formula; where the smaller the open system, the faster a steady state is attained. These generic findings extend the standard open quantum systems theory and substantially tackle certain cosmological issues.

Tissue Necrosis of Sour Cherry Fruits, An Unusual Disease Occurrence Caused by a Phoma sp. in Serbia.

Following frequent rains during May and June of 1999, a high incidence of an unknown disease on sour cherry (Prunus cerasus) fruits was observed in western Serbia (Sabac). Initially, small, water-soaked, dark green spots appeared on the fruit tissue similar to infections caused by Pseudomonas syringae or a Colletotrichum sp. (1,2). Later, spots enlarged, coalesced, and became necrotic and covered most of the fruit surface. The diseased tissue was slightly depressed and fruit shriveled and dried. Approximately 60 to 80% of the total yield was affected. Numerous hyaline, unicellular, and ellipsoidal conidia were observed with a microscope. Orange spore masses often occurred on the necrotic tissue following rain. Symptoms of the disease were not expressed during the dry spring of 2000, but were observed in rainy 2001. The most susceptible cultivar was Haiman's Rubin. Disease symptoms were absent on the domestic cultivar Oblacinska. Placing small necrotic fragments on potato dextrose agar (PDA) resulted in grayish fungal colonies that produced black, globose pycnidia with hyaline, unicellular, and ellipsoidal conidia under daylight conditions that were similar to those formed on necrotic sour cherry fruit in the orchard. At 25°C, colonies covered the entire 9-cm diameter surface of PDA after 5 to 6 days. No teleomorph was observed. Bacterial isolations on nutrient agar were unsuccessful. Unripe sour cherry fruits were punctured with a sterile needle and small colony fragments of the fungus were placed over the wound. Symptoms typical of those on fruit found in orchards were observed after 7 days of incubation at 25°C. No symptoms developed on control fruits punctured with a sterile needle. The fungus was reisolated from the inoculated fruits and shown to be identical to the original strains. On the basis of pathogenicity and morphological characteristics of the strains investigated, the fungus was determined to be a Phoma sp. (3), also known as sour cherry necrosis in other fruit-tree-growing regions. To our knowledge, this is the first report of the fungus on sour cherry fruit in Serbia. References: (1) J. Balaz and M. Arsenijevic. Proc.Int. Conf. Plant. Path. Bact. 7:515, 1990. (2) M. Ivanovic and D. Ivanovic. Zast. Bilja 201:211, 1992. (3) B. C. Sutton. Pages 379-391 in: Coelomycetes. CMI, Kew, Surrey, England, 1980.

First Report of a Wilt and Stem Rot of Muskmelon and Watermelon Transplants Incited by Pseudomonas cichorii in Serbia.

In 1989, a wilt and stem rot of muskmelon (Cucumis melo L.) was reported on seedlings grown under plastic in northern Serbia (1). In 1998, a similar disease of watermelon (Citrullus vulgaris L.) transplants occurred in central Serbia, resulting in losses estimated at 20% of plants grown in the nursery. Initial symptoms appeared as water-soaked lesions on the stem and lower surfaces of cotyledons and first true leaves. Necrosis started from leaf water-soaked areas and spread over the entire plant. Many stems softened and toppled. Wilting was also associated with the latter stages of the disease. Six representative strains isolated from water-soaked stem lesions on muskmelon in 1989 (three strains) and on watermelon in 1998 (three strains) were characterized. All strains were gram negative, strictly aerobic, motile, rod-shaped, and fluorescent on King's B medium, but negative for levan production, soft rot of potato, and arginine dihydrolase activity. Furthermore, strains were oxidase positive and induced a strong hypersensitive reaction in tobacco leaves. All of these reactions are characteristic of Pseudomonas cichorii (2). All six strains were confirmed to be P. cichorii based on analysis of cell-wall fatty acid profiles using the Microbial Identification System (MIDI, Newark, DE). Similarity indices ranged from 0.87 to 0.97. Pathogenicity of the P. cichorii strains was confirmed by prick inoculation of the hypocotyl of 2-week-old plants of domestic muskmelon cv. Sezam and watermelon cv. Rosa. Six plants of each cultivar were pricked with a dissecting needle dipped into a bacterial suspension (108 CFU/ml) prepared from each of the six strains and placed in a humidity chamber at 26°C for 48 h. Water-soaking occurred on all plants around the inoculation site after 24 h. The upper part of the plants lost turgor and wilted. Eventually, the hypocotyl and leaf veins became water-soaked, and the stem tissue softened, resulting in toppling of plants. The symptoms were identical to those described on muskmelon in 1989 and observed on watermelon in 1998. No symptoms developed on control plants. The bacterium was reisolated from the inoculated plants and shown to be identical to the original strains, confirming that P. cichorii was responsible for the disease of muskmelon and watermelon seedlings in 1989 and 1998, respectively. References: (1) M. Arsenijevic and V. Stojsin. Contemp. Agric. 9:487, 1989. (2) R. A. Lelliott et al. J. Appl. Bacteriol. 29:470, 1966.

First Report of Black Rot of Cauliflower and Kale Caused by Xanthomonas campestris pv. campestris in Yugoslavia.

In Yugoslavia, Xanthomonas campestris pv. campestris was isolated from forage kale in 1964 and cabbage in 1997 (1). Recently, the incidence and severity of black rot symptoms on cabbage, cauliflower, and kale have increased. Gram-negative, rod-shaped, motile bacteria were isolated from the diseased leaf and vascular tissues of cauliflower and kale plants collected from 1995 to 1998. The isolates formed yellow, convex, mucoid colonies on yeast dextrose chalk medium, metabolized glucose oxidatively, grew at 37°C, hydrolyzed gelatin and esculin, produced acids from d-arabinose, glucose, sucrose, and trehalose, and did not reduce nitrates. They were nonfluorescent, amylolytic and pectolytic, oxidase negative and catalase positive, and tolerant to 5% NaCl but not to 0.1% triphenyl tetrazolium chloride. Koch's postulates were completed by injecting bacterial suspensions (108 CFU/ml) into leaf petioles of cabbage, cauliflower, and kale seedlings (2- to 3-leaf stage). Dark green watersoaking of petioles and leaf veins followed by yellowing and collapse of inoculated plants was observed after 3 to 5 days. When compared with published information (2), the isolates were identified as X. campestris pv. campestris. This is the first occurrence of this bacterium in cauliflower and kale in Yugoslavia. References: (1) O. Jovanovic et al. Plant Prot. Belgrade 221:175, 1997. (2) N. W. Schaad. 1988. Laboratory Guide for Identification of Plant Pathogenic Bacteria. 2nd ed. The American Phytopathological Society, St. Paul, MN.