Reaction of chlorine nitrate with hydrogen chloride and water at antarctic stratospheric temperatures

Laboratory studies of heterogeneous reactions important for ozone depletion over Antarctica are reported. The reaction of chlorine nitrate (ClONO(2)) with H(2)0 and hydrogen chloride (HCl) on surfaces that simulate polar stratospheric clouds [ice and nitric acid (HNO(3))-ice and sulfuric acid] are studied at temperatures relevant to the Antarctic stratosphere. The reaction of ClONO(2) on ice and certain mixtures of HNO(3) and ice proceeded readily. The sticking coefficient of ClONO(2) on ice of 0.009 +/- 0.002 was observed. A reaction produced gas-phase hypochlorous acid (HOCl) and condensed-phase HNO(3); HOC1 underwent a secondary reaction on ice producing dichlorine monoxide (Cl(2)O). In addition to the reaction with H(2)0, ClONO(2) reacted with HCl on ice to form gas-phase chlorine (Cl(2)) and condensed-phase HNO(3.) Essentially all of the HCl in the bulk of the ice can react with ClONO(2) on the ice surface. The gaseous products of the above reactions, HOCl, Cl(2)0, and Cl(2), could readily photolyze in the Antarctic spring to produce active chlorine for ozone depletion. Furthermore, the formation of condensed-phase HNO(3) could serve as a sink for odd nitrogen species that would otherwise scavenge the active chlorine.     

Radiation carcinogenesis at low doses

An analysis of experimental findings indicates that the induction of a manmmary neoplasm in the Sprague-Dawley rat is dependent on the action of radiation on more than one cell. Although a linear relation between incidence and x-ray dose might be consistent with available data, such a relation would be fortuitous and linear extrapolation to lower doses is unjustified.     

Der Einfluß von Fichtennadelwachs auf Nadelzersetzung und Erlenkeimung

The influence of spruce needle wax on the degradation of the needles and the germination of alder seeds 1- and 3-year old needles of Picea abies, each untreated or with the wax layer removed, were burried in a field. Dry-weight of needles without wax decreased faster during an exposition period of 1 to 5 months. Because the wax proved to be a highly selective substrate for microbial colonisation, it retarded the needle degradation. Wax on 1-year old needles slowed degradation down during 2 months, wax on 3-year old needles during 5 months. Degradation time varied for different wax components. The site of wax decomposition was determined by analysing the lipids eluted from different soil layers (depth 0–30 cm) in a natural spruce forest. Lipids forming the wax decreased in depth 1–5 cm and were missing in depth 7–14 cm. Microorganisms isolated from 3 soil layers (depth 1–7 cm) were able to use fatty acids and fatty alcohols out of the wax as a carbon source. But only microorganisms from depth 7–14 cm degraded all wax components. Wax of 1-year old needles delayed seed germination (Alnus glutinosa) for 6 days. Wax of 3-year old needles delayed and inhibited germination for at least 12 days. Pure stearic acid did not influence germination. The different effects show the importance of the chemical wax composition rather than of the water repellent property.     

Nitrogen transfer from green manure to organic cherry tomato in a greenhouse intercropping system

Abstract

This work aimed to evaluate the nitrogen transfer, the yield and the nutrient contents of organic cherry tomatoes intercropped with legumes in two successive years. The randomized block experimental design was used with eight treatments and five replicates, as follows: two controls with single cherry tomato crop (with and without corn straw cover); cherry tomato intercropped with jack bean (Canavalia ensiformis DC); white lupine (Lupinus albus L.); sunn hemp (Crotalaria juncea L.); velvet bean-dwarf [(Mucuna deeringiana (Bort) Merrill)]; mung bean (Vigna radiata (L.) Wilczek), and cowpea (Vigna unguiculata (L.) Walp). The number of total fruits, the weight of total fruit and an average weight of the total fruit in the first year was 25%, 33% and 13% higher than the second-year, respectively. The lower N-content of cherry tomato leaves in the treatment with mung bean can be reflected of lower %N transfer of cherry tomato leaves in the same treatment compared to treatment with cowpea bean. The N-content and %N transfer of cherry tomato leaves was 50 and 42% higher in year 1 than in year 2, successively. Nevertheless, in general, the legumes used in this study contributed equally in the N transfer to the cherry tomato plants. The P, K, Mg, Ca, Cu, Mn, Fe and Zn content in the leaf and shoot were no difference between the treatments. However, the Mg, Ca, Cu, Fe, Mn and Zn content of the leaf were higher in year 2 than year 1.     

Simulation modelling of yield losses caused by wheat stem rust

Stem rust, or black rust, of wheat, caused by Puccinia graminis f. sp. tritici, has recently re-emerged in several parts of the world, with epidemics occurring in eastern Africa, as well as northern and southern Europe. Damage mechanisms from disease dynamically affect the physiology of the crop as it grows and develops, and as the epidemic progresses, leading to yield losses in the stem rust-diseased wheat stand. Process-based agrophysiological models that include disease-induced damage mechanisms can help to better understand the physiological processes leading to yield losses, and to inform strategic decisions such as breeding strategies. Such models have not been developed for wheat stem rust so far. Two damage mechanisms for stem rust, light stealing and assimilate diversion, were incorporated in the agrophysiological simulation model WHEATPEST. The model, tested from experimental field data retrieved from the literature, provides a satisfactory representation of the system, although consistently underestimates relative yield losses by about 6.9%, resulting in relative yield losses between 17% and 56%. Analyses highlight the importance of the diversion of assimilates toward the pathogen in the magnitude of yield loss. Considering only the reduction of green leaf area would underestimate damage from stem rust by at least threefold. The analysis also shows the importance of the dynamic interplay between disease and crop growth, especially the dynamics of leaf area, on yield loss. Directions to consider additional damage mechanisms are proposed, and perspectives for future research, especially in relation to plant breeding strategies under climate change, are offered.     

Ecology-based analysis of a recent association between Spartium junceum and 16SrV phytoplasma

An outbreak of Spartium witches’ broom (SpaWB) in Sicily prompted us to identify and characterize associated phytoplasmas. Over 80 samples of Spanish broom (Spartium junceum) and around 270 individuals of the potential vector Livilla spectabilis were collected and analysed. Single and mixed infections of 16SrV and ‘Candidatus Phytoplasma spartii’ were detected in Spanish broom samples and for the first time in L. spectabilis. The 16SrV isolates were further characterized by multilocus sequence typing (MLST) to determine their phylogenetic relationship with flavescence dorée phytoplasma (FDp) and to evaluate the risk of host-jumping to grapevine. Phylogenetic analysis of most of the analysed genes using the MLST approach grouped S. junceum 16SrV-C isolates with FDp isolates infecting grapevine and Scaphoideus titanus. Notably, phylogenetic analysis of the vmpA gene clustered the S. junceum isolates with FDp genotypes transmitted by S. titanus. This study extends the knowledge of SpaWB epidemiology, focusing on the possible risk of a 16SrV host jump from Spanish broom to grapevine. Spanish broom was identified as a reservoir and potential inoculum source of phytoplasmas that cause severe disease in cultivated crops. Furthermore, the L. spectabilis psyllid may be involved in the epidemiology of this 16SrV-C phytoplasma, although in the absence of in vivo transmission trials. The study further confirms the strong ability of phytoplasmas to adapt to new hosts and vectors, thus leading to potential phytosanitary emergencies.     

Population structure of Phytophthora infestans collected on potato and tomato in Italy

Late blight caused by the oomycete Phytophthora infestans is a disease of potato and tomato of worldwide relevance and is widespread throughout Europe and the Mediterranean region. While pathogen populations in northern Europe have been sampled and characterized for many years, the genetic structure of populations from southern Europe, including Italy, has been less studied. Between 2018 and 2019, we collected 91 samples of P. infestans from potato and tomato crops in Italy, Algeria, and Tunisia on FTA cards and genotyped them using 12-plex microsatellites. These samples were compared to genotypes of P. infestans previously collected within the framework of the EuroBlight network and from published sources. Four clonal lineages were identified: 13_A2 (Blue 13), 2_A1, 23_A1, and 36_A2. Two other isolates collected could not be matched to any currently known clonal lineage. The 13_A2 and 36_A2 lineages were found exclusively in southern Italy and Algeria, while 2_A1 was only found in Algeria. This is the first report of the 36_A2 lineage in Italy. Two isolates from Solanum nigrum were 13_A2, suggesting this weed host could be a reservoir of inoculum. The 23_A1 lineage was found widely on infected tomato crops in Italy and is the same as the lineage US-23 that is widespread in North America. Differences in genotypes across the country suggests that there may be different sources of introduction into Italy, possibly via infected seed tubers from other countries in Europe, tubers for consumption from North Africa, or tomatoes.     

Fusarium genetic traceability: Role for mycotoxin control in small grain cereals agro-food chains

Risks associated with mycotoxin contamination of cereals, that are included in the ten major staple foods and greatly contribute to the dietary energy intake, are of worldwide relevance. In small grain cereals, mycotoxins are produced by fungi such as Aspergillus, Penicillium, Alternaria and Fusarium that colonize the plant in the field and can grow during the post-harvest period, producing several classes of mycotoxins. The identification of mycotoxigenic fungal species and strains is essential for developing effective strategies for control. For this purpose, genetic traceability has proved to be a valuable tool that can be applied along the whole production chain, starting in the field for early diagnosis of FHB (Fusarium Head Blight) disease to the final processing steps, such as malting or pasta making. In this paper, DNA-based analytical tools that are currently available for the identification and quantification of mycotoxigenic fungal species and strains are reviewed, with particular emphasis on Fusarium, and their possible applications in mycotoxin control in small grain cereal chains are discussed.     

Introduction of exotic fish species and decline of native species in the lower Po basin,north‐eastern Italy

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