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The Genome of Cardinium cBtQ1 Provides Insights into Genome Reduction, Symbiont Motility, and Its Settlement in Bemisia tabaci
Get PDFMany insects harbor inherited bacterial endosymbionts. Although some of them are not strictly essential and are considered facultative, they can be a key to host survival under specific environmental conditions, such as parasitoid attacks, climate changes, or insecticide pressures. The whitefly Bemisia tabaci is at the top of the list of organisms inflicting agricultural damage and outbreaks, and changes in its distribution may be associated to global warming. In this work, we have sequenced and analyzed the genome of Cardinium cBtQ1, a facultative bacterial endosymbiont of B. tabaci and propose that it belongs to a new taxonomic family, which also includes Candidatus Amoebophilus asiaticus and Cardinium cEper1, endosymbionts of amoeba and wasps, respectively. Reconstruction of their last common ancestors’ gene contents revealed an initial massive gene loss from the free-living ancestor. This was followed in Cardinium by smaller losses, associated with settlement in arthropods. Some of these losses, affecting cofactor and amino acid biosynthetic encoding genes, took place in Cardinium cBtQ1 after its divergence from the Cardinium cEper1 lineage and were related to its settlement in the whitefly and its endosymbionts. Furthermore, the Cardinium cBtQ1 genome displays a large proportion of transposable elements, which have recently inactivated genes and produced chromosomal rearrangements. The genome also contains a chromosomal duplication and a multicopy plasmid, which harbors several genes putatively associated with gliding motility, as well as two other genes encoding proteins with potential insecticidal activity. As gene amplification is very rare in endosymbionts, an important function of these genes cannot be ruled out
Resistance Inducers Modulate Pseudomonas syringae pv. Tomato Strain DC3000 Response in Tomato Plants
Get PDFThe efficacy of hexanoic acid (Hx) as an inducer of resistance in tomato plants against Pseudomonas syringae pv. tomato DC3000 was previously demonstrated, and the plant response was characterized. Because little is known about the reaction of the pathogen to this effect, the goal of the present work was to determine whether the changes in the plant defence system affect the pathogen behaviour. This work provides the first demonstration of the response of the pathogen to the changes observed in plants after Hx application in terms of not only the population size but also the transcriptional levels of genes involved in quorum sensing establishment and pathogenesis. Therefore, it is possible that Hx treatment attenuates the virulence and survival of bacteria by preventing or diminishing the appearance of symptoms and controlling the growth of the bacteria in the mesophyll. It is interesting to note that the gene transcriptional changes in the bacteria from the treated plants occur at the same time as the changes in the plants. Hx is able to alter bacteria pathogenesis and survival only when it is applied as a resistance inducer because the changes that it promotes in plants affect the bacteria
Virus-Viroid Interactions: Citrus Tristeza Virus Enhances the Accumulation of Citrus Dwarfing Viroid in Mexican Lime via Virus-Encoded Silencing Suppressors
No full textAn assay to identify interactions between Citrus dwarfing viroid (CDVd) and Citrus tristeza virus (CTV) showed that viroid titer was enhanced by the coinfecting CTV in Mexican lime but not in etrog citron. Since CTV encodes three RNA silencing suppressors (RSSs), p23, p20 and p25, an assay using transgenic Mexican limes expressing each RSS revealed that p23 and, to a lesser extent, p25 recapitulated the effect observed with coinfections of CTV and CDVd
Sequencing of diverse mandarin, pummelo and orange genomes reveals complex history of admixture during citrus domestication
Get PDFCultivated citrus are selections from, or hybrids of, wild progenitor species whose identities and contributions to citrus domestication remain controversial. Here we sequence and compare citrus genomes—a high-quality reference haploid clementine genome and mandarin, pummelo, sweet-orange and sour-orange genomes—and show that cultivated types derive from two progenitor species. Although cultivated pummelos represent selections from one progenitor species, Citrus maxima, cultivated mandarins are introgressions of C. maxima into the ancestral mandarin species Citrus reticulata. The most widely cultivated citrus, sweet orange, is the offspring of previously admixed individuals, but sour orange is an F1 hybrid of pure C. maxima and C. reticulata parents, thus implying that wild mandarins were part of the early breeding germplasm. A Chinese wild 'mandarin' diverges substantially from C. reticulata, thus suggesting the possibility of other unrecognized wild citrus species. Understanding citrus phylogeny through genome analysis clarifies taxonomic relationships and facilitates sequence-directed genetic improvement
Development of methods for cryopreservation of rooster sperm from the endangered breed "Gallina Valenciana de Chulilla" using low glycerol concentrations
No full textGlycerol (11%; v:v) is the cryoprotectant most often used for the cryopreservation of rooster sperm. However, chicken breeds differ in the resistance of their sperm to the cryopreservation process and endangered or local breeds usually present low fertilizing ability when conventional sperm cryopreservation protocol S are used. The objective of this study was to optimize the protocol for the cryopreservation of the sperm from the endangered breed "Gallina Valenciana de Chulilla". For this purpose, 10 pools of semen from 43 roosters of this breed were cryopreserved using 8%, 7%, 6%, or 4% glycerol, and the sperm quality was determined immediately after thawing and in the insemination doses. Lohmann Brown Classic laying hens (n = 40) were used for the insemination trials. The sperm quality after cryopreservation progressively decreased as the glycerol concentration was reduced (P < 0.01); samples frozen using 4% glycerol exhibited the lowest quality (38% total motile sperm and 49% live sperm), and samples frozen using 8% glycerol exhibited the highest quality (67% total motile sperm and 66% live sperm). These differences were also observed after the glycerol was removed (P < 0.01). However, the sperm fertilizing ability was similar for all the treatments (23%-30% fertilized eggs), and increased as the glycerol concentration decreased. In conclusion, semen from roosters frozen using 4% glycerol exhibited lower sperm quality but similar fertilizing ability compared with samples processed using higher glycerol concentrations. These results may provide useful information for developing cryopreservation protocols for other breeds. (C) 2014 Elsevier Inc. All rights reserved
Displacement of Aphytis chrysomphali by Aphytis melinus, parasitoids of the California red scale, in the Iberian Peninsula
Get PDFParasitoids are the main natural enemies of the California red scale, Aonidiella aurantii (Maskell) and on occasion can regulate their populations. To increase their effectiveness, inoculative or augmentative releases of parasitoids are promoted. Previous to the implementation of any release strategy an important and necessary step is to acquire knowledge on the parasitoid fauna associated with this key phytophagous pest. Parasitoids were surveyed and quantified in Spanish citrus orchards between 2005 and 2009. Aphytis melinus DeBach (87.1%) resulted as the dominant species, followed by Aphytis chrysomphali (Mercet) (15.9%), Encarsia perniciosi (Tower) (2.4%) and Aphycus hederaceus (Westwood) (0.004%). Overall, higher levels of parasitism were recorded in fruit than in twigs. Scales in fruit were parasitized at similar levels by the different parasitoid species whereas E. perniciosi was more active in twigs. Data eventually reveal the recent displacement of A. chrysomphali by A. melinus. The implications of these results on the biological control of A. aurantii are discussed and this information will be useful in the decision of IPM strategies for this pest
Performance of Navel orange trees grafted onto two new dwarfing rootstocks (Forner-Alcaide 517 and Forner-Alcaide 418)
No full textThe aim of the present work was to study the performance of two new dwarfing citrus rootstocks (FornerAlcaide 517 and Forner-Alcaide 418) in comparison with Carrizo citrange. To carry out these experiments, rootstocks were budded with Navelina Navel orange scions. In young plants, rootstocks' size-controlling capacity was associated to their hydraulic conductance. In the case of Forner-Alcaide 418, lower hydraulic conductance was related to a smaller lumen area of root xylem vessels with respect to the other rootstocks. Also, hydraulic resistance of bud union segments of the stem was found to decrease with increasing vigour of plants grafted onto the different rootstocks. Furthermore, the graft union may provide resistance to sucrose transport in dwarfing rootstocks, as indicated by the reduced translocation of 13C-labelled photoassimilates from leaves to roots and reduced soluble sugar and starch concentrations under the graft union. This may result in a deficient carbohydrate supply to roots in dwarfing rootstocks, thereby stunting their growth. Accordingly, small root size and low hydraulic conductivity may cause water deficit in leaves during periods of high evaporative demand, inducing stomata! closure. This leads to a decrease in photosynthetic assimilation rate, which may affect plant growth negatively. These effects occur to a different extent in scions on both dwarfing rootstocks, appearing to be the cause of their reduced growth. Moreover, plants on both dwarfing rootstocks showed decreased translocation of 13 C-photoassimilates to roots, possibly contributing to higher availability of these compounds in the scion, and resulting in increased 13C transport towards the fruits. This effect could explain the higher yield efficiencies found in dwarfing rootstocks. A ten-year long field experiment, with trees grafted onto the three rootstocks, showed that FornerAlcaide 517 and Forner-Alcaide 418 induced lower canopy volumes and higher yield efficiencies than Carrizo citrange. In addition, our results show both dwarfing rootstocks produce good fruit quality, are suitable for high density plantings and can be cultured in alkaline soils. (C) 2014 Elsevier B.V. All rights reserved
Molecular characterization of divergent grapevine Pinot gris virus isolates and their detection in Slovak and Czech grapevines
No full textAnalysis of complete genome sequences of three Slovak isolates of grapevine Pinot gris virus (GPGV) showed their low heterogeneity (reaching 1.7 %) and a close relationship to the Italian NC_015782 isolate (4.2-4.5 % divergence). Comparison of Slovak and Italian isolates revealed an unusual accumulation of 21 indel mutations in ORF1, resulting in a localized high divergence in the encoded amino acid sequences. An elevated divergence in the 5' extremity of the GPGV genomes is suggestive of a recombination between Slovak isolates and grapevine berry inner necrosis virus. RT-PCR allowed the frequent detection of closely related GPGV isolates in grapevines from Slovakia and the Czech Republic
Acta Horticulturae
No full textPersimmon (Diospyros kaki) culture is gaining importance as a temperate fruit crop in the Mediterranean area. The main persimmon cultivar grown in Spain is 'Rojo Brillante', which produces an astringent fruit. This implies the need of a deastringency post-harvest treatment prior commercialization. Persimmon culture in Spain is concentrated in an area of water scarcity, but there is no information about tree water needs nor responses to deficit irrigation. With this in mind, an experiment was conducted over three consecutive seasons in order to determine yield responses to water restrictions applied during different stages of fruit growth. Moreover, the effects of timing of deficit irrigation on fruit quality at harvest and on the effectiveness of a postharvest deastringency treatment were evaluated. Four irrigation treatments were applied including watering at 100% of the estimated tree evapotranspiration (ETc) during the entire season, and other three treatments where irrigation inputs were reduced at 50% ETc only during certain periods (spring, summer or fall). In all three seasons, water deficit, when applied during spring, reduced June fruit drop. This effect could be either positive or negative depending on the tree crop level and the grower´s final fruit size target. However, water restrictions regardless of the period when they were applied, significantly affected (up to 22% reduction) fruit weight at harvest suggesting high sensitivity of Kaki trees to water stress. Fruit ripening was accelerated when water restriction were applied during fall; this is reflected in a higher external color and lower firmness of the fruit at harvest maintaining high quality. None of the deficit irrigation treatments affected the effectiveness of deastringency treatment with high CO2 concentration. It is concluded that, despite Diospyros kaki being a crop sensitive to water stress, deficit irrigation can still be used as a measure for increasing tree crop level and accelerating fruit ripening