Efficient preconditioning for sequences of parametric complex symmetric linear systems

Solution of sequences of complex symmetric linear systems of the form Ajxj = bj, j = 0,..., s, Aj = A + αjEj, A Hermitian, E0, ..., E a complex diagonal matrices and α0, ..., αa scalar complex parameters arise in a variety of challenging problems. This is the case of time dependent PDEs; lattice gauge computations in quantum chromodynamics; the Helmholtz equation; shift-and-invert and Jacobi-Davidson algorithms for large-scale eigenvalue calculations; problems in control theory and many others. If A is symmetric and has real entries then Aj is complex symmetric. The case A Hermitian positive semideflnite, Re(αj) ≥ 0 and such that the diagonal entries of E j, j = 0,..., s have nonnegative real part is considered here. Some strategies based on the update of incomplete factorizations of the matrix A and A-1 are introduced and analyzed. The numerical solution of sequences of algebraic linear systems from the discretization of the real and complex Helmholtz equation and of the diffusion equation in a rectangle illustrate the performance of the proposed approaches

Isolation of diverse phytoplasmas from symptomatic grapevine samples

Phytoplasmas from different ribosomal groups were isolated from grapevine samples in which “flavescence dorée” or “bois noir” phytoplasmas had been identified. The results indicate that the developed medium is not phytoplasma specific and supports the growth of phytoplasmas which cannot be detected by other molecular methods and are very likely present in a very low titre in the endobiome of the plants. The applied method discriminates the presence of bacterial contamination already in the liquid phase, and the colony purification technique allows excluding the contamination

Assessment of susceptibility to European stone fruit yellows phytoplasma of new plum variety and five rootstock/plum variety combinations

Two separate experiments were carried out to assess the plum susceptibility to infection by European stone fruit yellows phytoplasmas during a five years period. Commercial varieties/cultivars and new selections grafted on Myrabolan 29C were evaluated in at least two plots of four plants each. Visual inspection and PCR/RFLP identification of phytoplasmas detected an increasing phytoplasma presence in both symptomatic and asymptomatic plants. Eight Japanese plum selections showed ESFY symptoms or pathogen presence in the 50% of the plants and nine selections showed ESFY infection in 20% of the plants. Only nine selections showed absence of both symptoms and pathogen. Although the European selections/cultivars were not symptomatic, plants belonging to six of these cultivars were positive for phytoplasma infection. The evaluation of cultivar/rootstock combinations indicate phytoplasma presence from the first year after plantation on. Two of the rootstocks seem to induce a delay in symptoms appearance and cultivar T.C. Sun resulted to be the most susceptible to the disease independently from the rootstock employed. Keywords: Japanese plum, European plum, European stone fruit yellows phytoplasmas, resistance, disease

Flavescence doree in France and Italy - Occurrence of closely related phytoplasma isolates and their near relationships to Palatinate grapevine yellows and an alder yellows phytoplasma

Grapevine yellows (GY) are diseases of Vitis vinifera caused by phytoplasmas. On the basis of DNA analysis, it is possible to distinguish different groups and subgroups among grapevine phytoplasmas. Flavescence doree (FD), the most serious problem in European vineyards, is caused by a phytoplasma which belongs to the elm yellows group (EY or 16SrV), Differences between 7 phytoplasma isolates in this group, found until now in French, Italian and German grapevines, and 4 phytoplasmas in the same group, isolated mainly from elm and alder in Europe and America, were investigated. These 11 EY-group isolates plus 3 non-EY phytoplasmas, were compared by PCR-RFLP analyses of two different DNA fragments using 8 restriction enzymes. Two French and two Italian grapevine isolates, classified as FD, appeared to be closely related and were also closer to an Italian alder phytoplasma. One French and one Italian FD isolate always showed the same restriction pattern. On the opposite, the three German grapevine isolates related to alder phytoplasmas in Germany appeared to be closer to the two elm phytoplasmas from America and Europe.

A new species of planthopper in the genus Agoo Bahder & Bartlett (Hemiptera: Fulgoroidea: Derbidae) from coconut palm (Cocos nucifera L.) in Jamaica

A new species of the genus Agoo Bahder & Bartlett, Agoo beani sp. n. was found associated with coconut (Cocos nucifera L., Arecaceae) in Jamaica. This species was discovered as part of a survey of the Caribbean basin to document planthopper diversity on palms. Cytochrome c oxidase subunit I (COI) and 18S sequence data strongly support placement of the new species in Agoo. The morphological features of Omolicna cocoana Rodriguez-Leon & Hidalgo-Gato from Cuba are reviewed and this species transferred into the genus Agoo

Diverse phytoplasmas associated with maize bushy stunt disease in Peru

Corn plants showing symptoms of midribs chlorosis, and leaf reddening, short internodes, ear pro- liferation, and plant growth reduction were collected in Peru from fields in nine localities in the provinces of Huancayo, Chupaca, and Jauja in the Junín region, and tested to verify phytoplasma presence and identity. Primers amplifying the phytoplasma ribosomal 16S and ribosomal protein genes were used. The phytoplas- ma presence was detected in symptomatic samples from all the surveyed areas. The sequencing of the obtained amplicons indicated the presence of ‘Candidatus Phy- toplasma asteris’ and ‘Ca. P. pruni’-related strains. A BLASTn search of sequenced genes showed that the two ‘Candidatus Phytoplasma’ strains identified in corn shares 100% and 99.82% identity with the ‘Ca. P. asteris’ strains from maize and 99.92% and 99.55% with ‘Ca. P. pruni’-related strains, respectively. The RFLP analyses allowed to enclose these phytoplasma strains in the 16SrI-B and 16SrIII-J subgroups; howev- er, the two phytoplasmas were, in some cases, present in mixed infection. The 16SrIII-J phytoplasma is for the first time reported associated with the maize bushy stunt disease and this represent a relevant information for the disease epidemiology towards its appropriate manage- ment in the affected area

Update and new epidemiological aspects about grapevine yellows in Chile

none9siTo date, phytoplasmas belonging to six ribosomal subgroups have been detected to infect grapevines in Chile in 36 percent of the sampled plants. A new survey on the presence of grapevine yellows was carried out from 2016 to 2020, and 330 grapevine plants from the most important wine regions of the country were sampled and analyzed by nested PCR/RFLP analyses. Phytoplasmas enclosed in subgroups 16SrIII-J and 16SrVII-A were identified with infection rates of 17% and 2%, respectively. The vineyards in which the phytoplasma-infected plants were detected were further inspected to identify alternative host plants and insects of potential epidemiological relevance. Five previously unreported plant species resulted positive for 16SrIII-J phytoplasma (Rosa spp., Brassica rapa, Erodium spp., Malva spp. and Rubus ulmifolius) and five insect species were fully or partially identified (Amplicephalus ornatus, A. pallidus, A. curtulus, Bergallia sp., Exitianus obscurinervis) as potential vectors of 16SrIII-J phytoplasmas. The 16SrVII-A phytoplasmas were not detected in non-grape plant species nor in insects. This work establishes updated guidelines for the study, management, and prevention of grapevine yellows in Chile, and in other grapevine growing regions of South America.openQuiroga N., C. Gamboa, D. Soto, A.M. Pino, A. Zamorano, J. Campodonico, A. Alma, A. Bertaccini, N. FioreQuiroga N., C. Gamboa, D. Soto, A.M. Pino, A. Zamorano, J. Campodonico, A. Alma, A. Bertaccini, N. Fior

Refinement of the NISECI ecological index reference conditions for Italian freshwater fish communities in the eastern Emilia-Romagna region

Following the Water Framework Directive 2000/60/CE (WFD), each member state of the European Union must monitor compliance of its rivers with ecological quality standards through biological quality indicators. The New Italian Index of the Ecological State of Fish Communities (NISECI) was developed in 2017 for the assessment of fish communities, as directed by the WFD in Italian freshwater habitats. According to the WFD, the general reference conditions (GRCs) of NISECI must be refined on a regional scale through new calculation of its metrics and sub-metrics. In the present study we used environmental and ichthyological data from 457 fish samplings distributed among 299 sampling sites within 84 different water bodies collected from 1995 to 2012 to develop: 1) new lists of expected species for six homogeneous zones identified in the Reno basin (Italy) and in the eastern regional basins of the Emilia-Romagna region; and 2) the threshold values for their species-specific abundance. Results were set as refined reference conditions (RRCs) for two of the metrics used in the application of the NISECI index in the study area (i.e. X1, relating to indigenous species and X2,b, for the abundance of expected species). The RRCs were tested by applying NISECI to 24 monitoring sites of the regional surface water monitoring network (i.e., ARPAE) and comparing the results with the application of NISECI using the GRCs. Furthermore, the analytical power of the refined NISECI was evaluated by relating the findings to three expertbased blind assessments of fish community ecological status. The results confirmed an increase in refined NISECI values and its higher consistency with expert-based assessment, supporting the validity of the presented method for RRC development and its potential for application in other regions

Molecular modeling of a tandem two pore domain potassium channel reveals a putative binding Site for general anesthetics

[Image: see text] Anesthetics are thought to mediate a portion of their activity via binding to and modulation of potassium channels. In particular, tandem pore potassium channels (K2P) are transmembrane ion channels whose current is modulated by the presence of general anesthetics and whose genetic absence has been shown to confer a level of anesthetic resistance. While the exact molecular structure of all K2P forms remains unknown, significant progress has been made toward understanding their structure and interactions with anesthetics via the methods of molecular modeling, coupled with the recently released higher resolution structures of homologous potassium channels to act as templates. Such models reveal the convergence of amino acid regions that are known to modulate anesthetic activity onto a common three- dimensional cavity that forms a putative anesthetic binding site. The model successfully predicts additional important residues that are also involved in the putative binding site as validated by the results of suggested experimental mutations. Such a model can now be used to further predict other amino acid residues that may be intimately involved in the target-based structure–activity relationships that are necessary for anesthetic binding