Phenological and physiological evaluation of first and second cropping periods of sorghum and maize crops

Environmental conditions influence phenology and physiological processes of plants. It is common for maize and sorghum to be sown at two different periods: the first cropping (spring/summer) and the second cropping (autumn/winter). The phenological cycle of these crops varies greatly according to the planting season, and it is necessary to characterize the growth and development to facilitate the selection of the species best adapted to the environment. The aim of this study was to characterize phenological phases and physiological parameters in sorghum and maize plants as a function of environmental conditions from the first cropping and second cropping periods. Two parallel experiments were conducted with both crops. The phenological characterization was based on growth analyses (plant height, leaf area and photoassimilate partitioning) and gas exchange evaluations (net assimilation rate, stomatal conductance, transpiration and water-use efficiency). It was found that the vegetative stage (VS) for sorghum and maize plants was 7 and 21 days, respectively, longer when cultivated during the second cropping. In the first cropping, the plants were taller than in the second cropping, regardless of the crop. The stomatal conductance of sorghum plants fluctuated in the second cropping during the development period, while maize plants showed decreasing linear behaviour. Water-use efficiency in sorghum plants was higher during the second cropping compared with the first cropping. In maize plants, in the second cropping, the water-use efficiency showed a slight variation in relation to the first cropping. It was concluded that the environmental conditions as degree-days, temperature, photoperiod and pluvial precipitation influence the phenology and physiology of both crops during the first and the second cropping periods, specifically cycle duration, plant height, leaf area, net assimilation rate, stomatal conductance and water-use efficiency, indicating that both crops respond differentially to environmental changes during the growing season.     

Toxoplasmosis in Pallas' cats (Otocolobus felis manul) at the Denver Zoological Gardens.

In May 1996 the Denver Zoological Gardens obtained two male and two female Pallas' cats (Otocolobus felis manul) that were wild-caught in the Ukraine. These animals were part of a group of 16 wild-caught adults (eight male and eight female) imported to the United States and Canada between 1995 and 1996. The Denver Zoological Gardens cats were quarantined at the zoo hospital for approximately I mo. During the quarantine period they were immobilized for physical examination, and sera were obtained from them to evaluate for exposure to Toxoplasma gondii. All cats were positive for T. gondii antibodies by latex agglutination (titers from 1:512 to 1:1,024). After being paired for breeding, one pair produced two litters, and another pair produced four litters, a total of 17 kittens between 1997 and 2001. Four kittens and two young adults died from a disseminated granulomatous and necrotizing inflammation consistent with toxoplasmosis. Toxoplasma gondii infection was confirmed in all six deceased cats by polymerase chain reaction performed on formalin-fixed tissues. An additional five kittens disappeared and were not available for necropsy. The fatality rate from toxoplasmosis was 35.3% (6/17) for cats that were available for necropsy and could have been as high as 64.7% (11/17) if it were assumed that the disappeared kittens were also affected. The Pallas' kitten survival rate at the Denver Zoological Gardens was 35.3%. This article describes the clinical and pathologic features of toxoplasmosis in a group of Pallas' cats at the Denver Zoological Gardens.     

Modeling multi-scale spatial ecological processes under the discrete event systems paradigm

A multi-scale spatial ecological model of a wet sclerophyllous forest subject to recurrent fires is presented. The model is specified in a Discrete Event Systems framework (DEVS) (Zeigler, 1990) interfaced with a Geographic Information System (GIS), and includes the ability to simulate landscape dynamics at several levels of resolution simultaneously. This is achieved by encoding a modular hierarchical representation of the forest landscape components into a set of nested, interconnected, and spatially referenced dynamic models. The results of the landscape dynamics simulations are displayed as sequences of maps through time, illustrating the potential of this modeling methodology for dealing with complex hierarchical structures that operate at several spatial and temporal resolutions.Research work supported by Junta Nacional de Investigaçäo Científica e Tecnológica, Portugal, and the Advanced Resource Technology Program, University of Arizona, USA.     

Laboratory diagnosis and disease occurrence in the current African swine fever eradication program in Spain, 1989–1991

The purpose of this study was to determine the rate of decline and geographical distribution by municipality of clinical and subclinical African swine fever (ASF) in the affected areas of Spain. A second aim was to evaluate the performance of diagnostic tests in the Spanish ASF eradication program. Clinical outbreaks were confirmed using both the direct and indirect immunofluorescence test (and if both were negative, by the hemabsorption test). The serological status of swine was determined by an enzyme-linked immunosorbent assay (ELISA) and suspect serum samples were confirmed by the immunoblot assay.

The number of clinical outbreaks (herds) of ASF for 1989, 1990 and 1991 was 170, 347 and 207, respectively. The numbers of municipalities within each affected province experiencing acute outbreaks for the same time periods were 49, 69 and 48, respectively. Serologically diagnosed animals positive for ASF were 1.1% of animals tested in 1989, 0.5% in 1990 and 0.8% in 1991. The corresponding positive predictive values of the standard ELISA test used were 99.0, 97.9 and 98.8, respectively. Similarly, the number of municipalities within each affected province experiencing serologically positive subclinically infected animals was 269, 178 and 147 for each of the years 1989, 1990 and 1991, respectively.     

Check-list for scientific names of common parasitic fungi. Series 3b: Fungi on bulbs: Amaryllidaceae and Iridaceae

This list is a continuation of Series 3a (Neth. J. Pl. Path. 94 (1988), Supplement 1), an account of the nomenclature of common parasitic fungi on bulbs as used in official publications of the Netherlands Society of Plant Pathology and the Netherlands Ministry of Agriculture and Fisheries. The selected names include one new species,Curvularia gladioli Boerema & Hamers, one new pathogenic form,Fusarium oxysporum f.sp.croci Boerema & Hamers, and one new combination,Sclerotium narcissi (Sacc.) Boerema & Hamers.A contribution towards the costs of publication provided by the Landbouw Export Bureau Fund, Wageningen, is gratefully acknowledged.     

Sensitivity,specificity, and predictive values of reagent test strip estimations of blood urea nitrogen

Azostix-reagent-tests(R) strips (Ames, Miles, Inc., Diagnostic Division, Elkhart, IN) were used to measure blood urea nitrogen values in blood samples from 125 dogs and cats at the North Carolina State University, College of Veterinary Medicine. Results of the tests were compared with standard serum urea nitrogen results. Sensitivity, specificity, and negative predictive values were high (86.4, 90.3, and 96.5%, respectively). Positive predictive value was low, 65.5% of the dogs and cats with elevated blood urea nitrogen values were correctly classified as abnormal The test performs well when the prevalence of abnormal values is near 50%.     

Melanin biosynthesis in Pyricularia oryzae: Site of tricyclazole inhibition and pathogenicity of melanin-deficient mutants

Tricyclazole (5-methyl-1,2,4-triazolo[3,4-b]benzothiazole) inhibits melanin synthesis in Pyricularia oryzae at concentrations less than 0.01 μg/ml. The primary site of inhibition in the biosynthetic pathway occurs between scytalone and vermelone. Accumulation of several metabolites derived from melanin precursors along branch pathways is associated with inhibition of melanin biosynthesis. At low tricyclazole concentrations (0.01–1 μg/ml), predominant accumulation of 2-hydroxyjuglone and 3,4-dihydro-3,4,8-trihydroxy-1-(2H)-naphthalenone (3,4,8-DTN) occurs as a result of the primary block between 1,3,8-trihydroxynaphthalene and vermelone. As the concentration of tricyclazole is increased from 1 to 10 μg/ml, flaviolin accumulation is markedly enhanced, whereas that of 3,4,8-DTN and 3,4-dihydro-4,8-dihydroxy-1-(2H)-naphthalenone is depressed, indicating possible secondary sites of inhibition in the main and branch pathways. Five melanin-deficient mutants of P. oryzae that phenotypically resemble the tricyclazole-treated wild-type strain were nonpathogenic or rarely infected two rice varieties. Three of the mutants studied were genetically defective in the melanin biosynthetic pathway at the site blocked by tricyclazole in the wild type. The wild-type strain converted both scytalone and vermelone to melanin; whereas the three mutants and the tricyclazole-treated wild type converted only vermelone to melanin. The data suggest a relationship between melanin biosynthesis and pathogenicity in P. oryzae.