ReDivia - Repositorio Digital de l'Instit Valencià d'Investigacions Agràries
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Genetic transformation of sweet orange with the coat protein gene of Citrus psorosis virus and evaluation of resistance against the virus
No full textCitrus psorosis is a serious viral disease affecting citrus trees in many countries. Its causal agent is Citrus psorosis virus (CPsV), the type member of genus Ophiovirus. CPsV infects most important citrus varieties, including oranges, mandarins and grapefruits, as well as hybrids and citrus relatives used as rootstocks. Certification programs have not been sufficient to control the disease and no sources of natural resistance have been found. Pathogen-derived resistance (PDR) can provide an efficient alternative to control viral diseases in their hosts. For this purpose, we have produced 21 independent lines of sweet orange expressing the coat protein gene of CPsV and five of them were challenged with the homologous CPV 4 isolate. Two different viral loads were evaluated to challenge the transgenic plants, but so far, no resistance or tolerance has been found in any line after 1 year of observations. In contrast, after inoculation all lines showed characteristic symptoms of psorosis in the greenhouse. The transgenic lines expressed low and variable amounts of the cp gene and no correlation was found between copy number and transgene expression. One line contained three copies of the cp gene, expressed low amounts of the mRNA and no coat protein. The ORF was cytosine methylated suggesting a PTGS mechanism, although the transformant failed to protect against the viral load used. Possible causes for the failed protection against the CPsV are discussed
IS53: an insertion element for molecular typing of Pseudomonas savastanoi pv. savastanoi
No full textA worldwide collection of Pseudomonas savastanoi pv. savastanoi strains from olive knots was examined for the distribution, variation in position and copy numbers of the IS53 insertion element. Southern hybridization analysis of plasmid DNA from six olive strains using IS53 and repA probes revealed that this insertion element was present in the chromosomal replicon and not in a plasmid, as had been originally described in an oleander strain. Southern hybridization analysis also revealed that IS53 was present in multiple copies in all analyzed strains. Copy numbers of IS53 elements ranged from 4 up to 10. Although all strains displayed a remarkably high degree of restriction fragment length polymorphism, we demonstrated that transposition of this element is extremely rare in bacteria grown in vitro for up to 390 generations. The genetic diversity of 62 olive strains based on 47 different IS53 RFLP fingerprints and UPGMA analysis enabled all strains to be clustered into eight groups with 60% similarity. IS53 typing can be considered a suitable marker for epidemiological and ecological studies, given its widespread distribution on P. savastanoi pv. savastanoi olive populations, its high stability and the high degree of polymorphism generated
ACTA HORTICULTURAE
No full textThe optimization of water and mineral supply in closed soilless culture relies on the knowledge of crop needs at each given climatic condition. Moreover, establishing the relationship between plant mineral uptake and transport with plant nitrogen, soluble sugar and starch contents and distribution, informs on the plant capacity for generating and mobilizing resources for growth and development. A rose crop (Rosa x hybrida cv. Grand Gala) was grown for all-year-round production in a closed hydroponic system in a greenhouse. Plants were pruned down to two nodes in order to study their development throughout the growing cycle of the flower stem. Daily N, P, K, Ca and Mg uptake rates were measured throughout the cycle and biomass partitioning, total non-structural carbohydrate (TNC) contents and N content were determined at three stages of the development of the flower stem. The stages were: TO just after pruning, VB when the flower bud becomes visible and HT at harvest. Warmer air and root temperatures in summer than in winter are the main environmental differences, whilst daily maximum PAR averages were always above the optimum for rose photosynthesis requirements. Dry biomass per plant and daily plant water uptake rate expressed either with respect to plant leaf area or to plant dry biomass, were larger in summer than in winter. Contrary to water uptake rates, mineral uptake rates, and also the concentration levels of nitrogen and starch resources, were lower in summer than in winter. The high level of competition for assimilates between roots and shoots together with the high root zone temperature could have limited the root mineral uptake capability during summer. Results will prove useful to improve crop management, particularly with respect to adjusting root uptake capacity to the actual mineral demand of the rose plant
Efficacy of some acaricides on 'Tetranychus urticae' (Acari: Prostigmata) and their side-effects on selected natural enemies occurring in citrus orchards
No full textThree groups of natural enemies are fundamental in citrus Integrated Pest Management strategies in the Mediterranean. These are the coccinellids, the hymenopterans and the phytoseiids. The spider mite, Tetranychus urticae, is an important pest of citrus whose biological control has not yet been fully achieved. Therefore, acaricides are usually applied against this pest when problems appear. In this study, the efficacy of six different acaricides on this mite and their side-effects on three selected natural enemies (the coccinellid Cryptolaemus montrouzieri, the phytoseiid Neoseiulus californicus and the braconid Aphidius colemani) have been measured. Our results indicate that highly effective products harmless to A. colemani exist (mineral oil, tebufenpyrad, clofentezin and fenazaquin). However, almost all tested products resulted slightly harmful for both C. montrouzieri and N. californicus, and fenazaquin was even moderately harmful for this phytoseiid
Wall teichoic acids are dispensable for anchoring the PNAG exopolysaccharide to the Staphylococcus aureus cell surface
No full textBiofilm formation in Staphylococcus aureus is usually associated with the production of the poly-N-acetylglucosamine (PNAG) exopolysaccharide, synthesized by proteins encoded by the icaADBC operon. PNAG is a linear beta-(1-6)-linked N-acetylglucosaminoglycan that has to be partially deacetylated and consequently positively charged in order to be associated with bacterial cell surfaces. Here, we investigated whether attachment of PNAG to bacterial surfaces is mediated by ionic interactions with the negative charge of wall teichoic acids (WTAs), which represent the most abundant polyanions of the Gram-positive bacterial envelope. We generated WTA-deficient mutants by in-frame deletion of the tagO gene in two genetically unrelated S. aureus strains. The Delta tagO mutants were more sensitive to high temperatures, showed a higher degree of cell aggregation, had reduced initial adherence to abiotic surfaces and had a reduced capacity to form biofilms under both steady-state and flow conditions. However, the levels as well as the strength of the PNAG interaction with the bacterial cell surface were similar between AtagO mutants and their corresponding wild-type strains. Furthermore, double Delta tagO Delta icaADBC mutants displayed a similar aggregative phenotype to that of single Delta tagO mutants, indicating that PNAG is not responsible for the aggregative behaviour observed in Delta tagO mutants. Overall, the absence of WTAs in S. aureus had little effect on PNAG production or anchoring to the cell surface, but did affect the biofilm-forming capacity, cell aggregative behaviour and the temperature sensitivity/stability of S. aureus
Plum pox virus silencing of C5 transgenic plums is stable under challenge inoculation with heterologous viruses
No full textTransgenic C5 cv. Honey Sweet is a clone of Prunus domestica L. transformed with the Plum pox virus coat protein gene (PPV-CP). This transgenic plum displays post-transcriptional gene silencing (PTGS) which makes it highly resistant to PPV infection. To test the effect of heterologous viruses on the efficacy and stability of PTGS against PPV, transgenic C5 trees were graft-inoculated with different combinations of Prunus necrotic ringspot virus (PNRSV), Apple chlorotic leaf spot virus (ACLSV), Prune dwarf virus (PDV) and PPV-D strain. The potential for suppression of the silencing mechanism mediated by these viruses was evaluated. Challenge experiments were performed under greenhouse, nursery and field conditions in Romania and Spain, comprising two different environments, continental and Mediterranean, respectively. Virus infections were evaluated by visual monitoring of symptom and by serological and molecular assays. The engineered resistance to PPV in C5 transgenic plums was stable and was not suppressed by the presence of the challenging heterologous viruses over a three-year experimental period across all trials
Lecture Notes in Computer Science
No full textThe detection of rotten citrus in packing lines is carried out manually under ultraviolet illumination, which is dangerous for workers. Light emitted by the rotten region of the fruit due to the ultraviolet-induced fluorescence is used by the operator to detect the damages. This procedure is required because the low contrast between the damaged and sound skin under visible illumination difficult their detection. We study a set of techniques aimed to detect rottenness in citrus using visible and near infrared lighting trough an hyperspectral imaging system. Methods for selecting a proper set of wavelengths are investigated such as correlation analysis, mutual information, stepwise or genetic algorithms. The image segmentation relies on the combination of band selection techniques and pixel classification methods such as classification and regression trees and linear discriminant analysis
An evaluation of the basis and consequences of a stay-green mutation in the navel negra citrus mutant using transcriptomic and proteomic profiling and metabolite analysis
Get PDFA Citrus sinensis spontaneous mutant, navel negra ( nan), produces fruit with an abnormal brown- colored flavedo during ripening. Analysis of pigment composition in the wild- type and nan flavedo suggested that typical ripening- related chlorophyll ( Chl) degradation, but not carotenoid biosynthesis, was impaired in the mutant, identifying nan as a type C stay- green mutant. nan exhibited normal expression of Chl biosynthetic and catabolic genes and chlorophyllase activity but no accumulation of dephytylated Chl compounds during ripening, suggesting that the mutation is not related to a lesion in any of the principal enzymatic steps in Chl catabolism. Transcript profiling using a citrus microarray indicated that a citrus ortholog of a number of SGR ( for STAY- GREEN) genes was expressed at substantially lower levels in nan, both prior to and during ripening. However, the pattern of catabolite accumulation and SGR sequence analysis suggested that the nan mutation is distinct from those in previously described stay- green mutants and is associated with an upstream regulatory step, rather than directly influencing a specific component of Chl catabolism. Transcriptomic and comparative proteomic profiling further indicated that the nan mutation resulted in the suppressed expression of numerous photosynthesis- related genes and in the induction of genes that are associated with oxidative stress. These data, along with metabolite analyses, suggest that nan fruit employ a number of molecular mechanisms to compensate for the elevated Chl levels and associated photooxidative stress
El trampeo masivo de Ceratitis capitata y su incidencia sobre la fauna de depredadores y parasitoides en una parcela de cítricos ecológicos
Get PDFLa generalización del trampeo masivo, con cebos y feromonas, como uno de
los métodos alternativos al uso intensivo de insecticidas químicos en el control de la
mosca de la fruta Ceratitis capitata (Wiedemann, 1824) ha suscitado el interés por la
realización de estudios sobre la incidencia que este tipo de control puede estar
teniendo sobre la fauna auxiliar natural presente en los ecosistemas citrícolas
valencianos. De hecho, se ha podido constatar la presencia de parasitoides y
depredadores de insectos, que son plagas importantes en cítricos, en las trampas con
atrayentes ensayadas en estudios anteriores (BOLINCHES et al., 2006) y en el
presente trabajo.
Debido a que la Administración valenciana, en los insectarios del Servicio de Sanidad Vegetal y Protección Fitosanitaria, y también algunas empresas privadas
están llevando a cabo la cría en cautividad de parasitoides y depredadores para su
utilización en control biológico de diversas plagas agrícolas, se ha creído conveniente,
además, enfocar el estudio de la incidencia del trampeo masivo de la mosca de la fruta
sobre uno de los depredadores más utilizados en la cría y suelta contra plagas de
cítricos como es el coleóptero coccinélido Cryptolaemus montrouzieri Mulsant, 1853