1,888 research outputs found
Pathogenicity of the root-knot nematode Meloidogyne javanica on potato
Host–parasite relationships and pathogenicity of
Meloidogyne javanica
on potatoes (newly recorded from Malta) were
studied under glasshouse and natural conditions. Potato cvs Cara and Spunta showed a typical susceptible reaction to
M. javanica
under natural and artificial infections, respectively. In potato tubers,
M. javanica
induced feeding sites that
consisted of three to four hypertrophied giant cells per adult female. Infection of feeder roots by the nematode resulted
in mature large galls which usually contained at least one mature female and egg mass. In both tubers and roots, feeding
sites were characterized by giant cells containing granular cytoplasm and many hypertrophied nuclei. Cytoplasm in giant
cells was aggregated alongside the thickened cell walls. Stelar tissues within galls appeared disorganized. The relationship
between initial nematode population density (
P
) [0–64 eggs + second-stage juveniles (J2s) per cm
3
soil] and growth of
cv. Spunta potato seedlings was tested under glasshouse conditions. A Seinhorst model [
y = m
+ (1
−
m
)
z
(
P
−
T
)
] was fitted
to fresh shoot weight and shoot height data of nematode-inoculated and control plants. Tolerance limits (
T
) for fresh
shoot weight and shoot height of cv. Spunta plants infected with
M. javanica
were 0·50 and 0·64 eggs + J2s per cm
3
soil,
respectively. The
m
parameter in that model (i.e. the minimum possible
y
-values) for fresh shoot weight and shoot height
were 0·60 and 0·20, respectively, at
P
= 64 eggs + J2s per cm
3
soil. Root galling was proportional to the initial nematode
population density. Maximum nematode reproduction rate was 51·2 at a moderate initial population density (
P
= 4
eggs + J2s per cm
3
soil).peer-reviewe
Structure, dynamics and bifurcations of discrete solitons in trapped ion crystals
We study discrete solitons (kinks) accessible in state-of-the-art trapped ion
experiments, considering zigzag crystals and quasi-3D configurations, both
theoretically and experimentally. We first extend the theoretical understanding
of different phenomena predicted and recently experimentally observed in the
structure and dynamics of these topological excitations. Employing tools from
topological degree theory, we analyze bifurcations of crystal configurations in
dependence on the trapping parameters, and investigate the formation of kink
configurations and the transformations of kinks between different structures.
This allows us to accurately define and calculate the effective potential
experienced by solitons within the Wigner crystal, and study how this
(so-called Peierls-Nabarro) potential gets modified to a nonperiodic globally
trapping potential in certain parameter regimes. The kinks' rest mass (energy)
and spectrum of modes are computed and the dynamics of linear and nonlinear
kink oscillations are analyzed. We also present novel, experimentally observed,
configurations of kinks incorporating a large-mass defect realized by an
embedded molecular ion, and of pairs of interacting kinks stable for long
times, offering the perspective for exploring and exploiting complex collective
nonlinear excitations, controllable on the quantum level.Comment: 25 pages, 10 figures, v2 corrects Fig. 2 and adds some text and
reference
Controlling the potential landscape and normal modes of ion Coulomb crystals by a standing wave optical potential
Light-induced control of ions within small Coulomb crystals is investigated.
By intense intracavity optical standing wave fields, subwavelength localization
of individual ions is achieved for one-, two-, and three-dimensional crystals.
Based on these findings, we illustrate numerically how the application of such
optical potentials can be used to tailor the normal mode spectra and patterns
of multi-dimensional Coulomb crystals. The results represent, among others,
important steps towards controlling the crystalline structure of Coulomb
crystals, investigating heat transfer processes at the quantum limit and
quantum simulations of many-body systems.Comment: 6+12 pages. arXiv admin note: substantial text overlap with
arXiv:1703.0508
Quantum coherence of discrete kink solitons in ion traps
We propose to realize quantized discrete kinks with cold trapped ions. We
show that long-lived solitonlike configurations are manifested as deformations
of the zigzag structure in the linear Paul trap, and are topologically
protected in a circular trap with an odd number of ions. We study the
quantum-mechanical time evolution of a high-frequency, gap separated internal
mode of a static kink and find long coherence times when the system is cooled
to the Doppler limit. The spectral properties of the internal modes make them
ideally suited for manipulation using current technology. This suggests that
ion traps can be used to test quantum-mechanical effects with solitons and
explore ideas for the utilization of the solitonic internal-modes as carriers
of quantum information.Comment: 5 pages, 4 figures ; minor correction
A survey of potential insect vectors of the plant pathogenic bacterium Xylella fastidiosa in three regions of Spain
The emergence of a rapid-spreading olive disease associated with Xylella fastidiosa in southern Italy represents a high risk to susceptible crops in other countries of the Mediterranean basin, if insect vectors occur in the region. The goal of this study was to identify xylem-feeding Auchenorrhyncha that could potentially act as vectors of X. fastidiosa in three regions of Spain (AndalucÃa, Murcia and Madrid). Samplings with sweep net and stem tap were carried out in October/2004 on grapevines and adjacent crops (olives, nectarine, citrus, Prunus spp.), ornamental trees and herbaceous weeds. Yellow sticky cards were placed in ten vineyards located across 100 km in AndalucÃa and in three vineyards distant 10-15 km apart in Murcia. Specimens of frequently-trapped species were tested by nested- or multiplex-PCR for the presence of X. fastidiosa. The Typhlocybinae leafhopper, Austroasca (Jacobiasca) lybica (Hemiptera: Cicadellidae) was the most abundant species in vineyards and citrus orchards. Planthoppers (Hemiptera: Fulgoroidea) and psyllids (Hemiptera: Psylloidea) were prevalent on olives. Cicadellinae leafhoppers (known as sharpshooters), which are major vectors of X. fastidiosa in the Americas, were not found in the samples. The only potential vectors were spittlebugs (Hemiptera: Cercopoidea) collected on Populus sp., herbaceous and on conifer trees (Pinus halepense); the spittlebug Neophileanus sp. was common on conifer trees adjacent to a vineyard in Jumilla. None of the insect samples tested positive for X. fastidiosa by PCR assays. However, spittlebugs already associated with susceptible crops in Spain may allow fast spread of X. fastidiosa in case this pathogen is introduced.We also acknowledge financial support from the
CNPq-CSIC bilateral grant no. 2004BR0004 and EU
grant ICA4-CT-2001-10005.Peer Reviewe
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