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"Safor" Mandarin: A New Citrus Mid-late Triploid Hybrid
Get PDFWorld mandarin production rose from 18.3 million tons to 27.9 million tons between the years 2000 and 2007 (FAO, Food and Agriculture Organization, 2009). In Spain, 87% of mandarin production in the last 5 years has been destined to the fresh fruit market (Intercitrus, Interprofessional Citrícola Española, 2008), which demands high-quality, seedless fruits throughout the marketing season. Therefore, the production of seedless varieties is very important.
Triploid plants are generally considered an evolutionary dead end, because they generally give rise to aneuploid gametes with very low fertility (Otto and Whitton, 2000). Predominantly trivalent and a high number of bivalent and univalent associations are formed during meiosis of citrus triploid hybrids (Frost and Soost, 1968). Moreover, abortion of the megasporogenesis in the period between the embryo-sac first divisions and the fecundated egg cell is common (Fatta Del Bosco et al., 1992). For this reason, citrus triploid hybrids are generally sterile, although they can occasionally produce fruits with very few seeds and induce seed formation in fruits of other cultivars.
Citrus triploid hybrids can be obtained by means of 2x × 2x hybridizations through the production of unreduced gametes by the female parent (Esen and Soost, 1971). The frequency of unreduced gamete formation depends on the genotype (Esen and Soost, 1971; Luro et al., 2004). Triploid embryos are preferentially found in seeds between one-third and one-sixth smaller than normal seeds and these small seeds generally do not germinate under conventional greenhouse conditions. Embryo rescue from these small seeds is required to reach high germination rates (Navarro et al., 2002). Luro et al. (2004) proposed that Second Division Restitution is the mechanism controlling unreduced gamete formation in clementines, whereas in sweet orange, Chen et al. (2008) proposed First Division Restitution to be the mechanism involved. In these two genetic mechanisms, only one part of the maternal heterozygosity is transmitted to the triploid hybrid and the rate of maternal heterozygosity varies among the loci in relation with the rate of single crossing over between the centromere and a given locus (Ollitrault et al., 2008).
Ploidy level determination by histological methods is too laborious for large-scale analyses. However, ploidy level can be accurately determined relatively rapidly in large populations by flow cytometry (Ollitrault and Michaux-Ferriere, 1992). Embryo rescue and flow cytometry are two indispensable techniques for extensive triploid citrus breeding programs. These techniques allow the efficient recovery of plants from embryos contained in small seeds and enable the ploidy level of regenerated plantlets to be determined quickly and easily with just a small piece of leaf while the plants are still in the test tube (Navarro et al., 2002).
In Spain, there are numerous problems associated with the production season of mandarin cultivars, which include satsumas [Citrus unshiu (Mak.) Marc.], clementines (C. clementina Hort. ex Tan.), and mandarin hybrids. Satsumas and clementines are traditionally harvested from the beginning of September until mid-February. Satsumas produce seedless fruits because they have sterile pollen and ovules. Clementines, the most widely grown mandarins in Spain, are self-incompatible and also produce seedless fruits if grown in isolation. However, their pollen and ovules are viable, and consequently they are able to pollinate and be pollinated by other sexually compatible cultivars. As a result of the demand for late-season mandarins by international markets, several mid- and late-maturing mandarin hybrids were introduced in Spanish citriculture. These hybrids are self-incompatible, but their pollen and ovules are viable and cross-pollinate with clementines, producing fruits with seeds in both groups of cultivars, which causes substantial economic losses.
With a view to solving this problematic situation, a triploid breeding program was started in Spain in 1996. The main objective was to produce new mid- and late-maturing triploid cultivars through sexual hybridization, embryo rescue, and ploidy analysis by flow cytometry (Navarro et al., 2002). Recently we released the late-maturing triploid variety Garbí [(C. clementina × C. tangerina) × (C. reticulata × C. sinensis)] (Aleza et al., 2010), which reaches optimum maturation during the second half of March. This variety of mandarin is replacing ‘Fortune’ mandarin (C. clementina × C. tangerina), which reached a peak production of 300,000 tons but is currently being replaced rapidly as a result of its high susceptibility to Alternaria alternata. Another problem is the low fruit quality of ‘Hernandina’ clementine, our latest maturing clementine, when grafted on ‘Carrizo’ citrange (Citrus sinensis × Poncirus trifoliata), which is by far the most predominant rootstock. Fruit peel deteriorates quickly after mid-January, and in practice, no clementine fruits are available by February.
In this article, we describe a new triploid hybrid named ‘Safor’ mandarin [(C. clementina × C. tangerina) × (C. unshiu × C. nobilis)] characterized by its high quality, seedless fruits, and mid-late ripening season
Field efficacy of imidacloprid and Steinernema carpocapsae in a chitosan formulation against the red palm weevil Rhynchophorus ferrugineus (Coleoptera: Curculionidae) in Phoenix canariensis
Get PDFBACKGROUND: The invasive red palm weevil, Rhynchophorus ferrugineus (Olivier), has become the major pest of palms in the Mediterranean Basin. Chemical control against this species is difficult because of its cryptic habits and is mainly based on the repeated application of large quantities of synthetic insecticides. The aim of this work has been to evaluate in the field the efficacy of imidacloprid (Confidor (R) 240 OD) and Steinernema carpocapsae Weiser with chitosan (Biorend R (R) Palmeras) as soil and stipe treatments respectively, alone or in combination, against this pest. RESULTS: All treatments significantly reduced the mean number of immature stages of R. ferrugineus per palm. However, there were no significant differences among the different treatments considered. Efficacies ranged from 83.8 to 99.7% for the mean number of immature stages found in the palms and resulted in a significant increase in palm survival compared with the untreated control (75.0-90.0% versus 16.5% respectively). CONCLUSION: Both imidacloprid and S. carpocapsae in a chitosan formulation proved highly effective against R. ferrugineus in the field, and their efficacies did not significantly change when used in combination. (C) 2009 Society of Chemical Industr
Evaluation of the Efficacy of an Insecticidal Paint Based on Chlorpyrifos and Pyriproxyfen in a Microencapsulated Formulation Against Rhynchophorus ferrugineus (Coleoptera: Curculionidae)
No full textThe weevil Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) is an important pest of palms. It has recently colonized the Mediterranean Basin where it is a serious problem on ornamental Phoenix canariensis (hort. ex Chabaud) palms. The efficacy of an insecticidal paint based on chlorpyrifos and pyriproxyfen in a microencapsulated formulation (Inesfly IGR FITO, Industrias Quimicas Inesba S.L., Paiporta, Spain) against this weevil has been studied. Laboratory results proved that pyriproxyfen has no effect against R. ferrugineus when applied in this microencapsulated formulation. Semifield trials dismissed Inesfly IGR FITO as a curative insecticide but showed the potential of this product in the preventative control of R. ferrugineus in palms. One single application could prevent infestation for up to 6 mo with a mean efficacy of 83.3%
Diagnosis and Detection of the Main Bacterial Pathogens of Stone Fruit and Almond
No full textDiagnosis and detection are key aspects related to plant health status. A critical review of the available diagnostic methods utilised for Agrobacterium rhizogenes and A. tumefaciens, Pseudomonas amygdali, P syringae pv. mors-prunorum, P syringae pv. persicae, P. syringae pv. syringae and Xanthomonas arboricola pv. pruni, the main pathogens of the stone fruit trees, is presented. As there is a general lack of updated standardized protocols for the detection of most of these bacteria, the most appropriate media for their isolation are reported along with serological reagents, PCR and real-time PCR protocols with comments on their accuracy for the analysis of these pathogens in plant samples. There are many selective media for isolation, especially for Agrobacterium spp., but fewer for Pseudomonas spp. and X. arboricola pv. pruni. Serological techniques are not: very useful for these pathogens due to the current lack of specific antibodies commercially available. As to molecular methods, it is surprising to find so many PCR protocols for Agrobacterium species, very few and unspecific for the Pseudomonas species pathogenic to stone fruit trees, and several recent PCR protocols for X. arboricola pv. pruni. The new advances in genomics and proteomics will provide information for selecting new targets to develop specific and sensitive techniques for the diagnosis and detection of these bacterial pathogens in plant material
Automatic detection of skin defects in citrus fruits using a multivariate image analysis approach
Get PDFOne of the main problems in the post-harvest processing of citrus is the detection of visual defects in order to classify the fruit depending on their appearance. Species and cultivars of citrus present a high rate of unpredictability in texture and colour that makes it difficult to develop a general, unsupervised method able of perform this task. In this paper we study the use of a general approach that was originally developed for the detection of defects in random colour textures. It is based on a Multivariate Image Analysis strategy and uses Principal Component Analysis to extract a reference eigenspace from a matrix built by unfolding colour and spatial data from samples of defect-free peel. Test images are also unfolded and projected onto the reference eigenspace and the result is a score matrix which is used to compute defective maps based on the T(2) statistic. In addition, a multiresolution scheme is introduced in the original method to speed up the process. Unlike the techniques commonly used for the detection of defects in fruits, this is an unsupervised method that only needs a few samples to be trained. It is also a simple approach that is suitable for real-time compliance. Experimental work was performed on 120 samples of oranges and mandarins from four different cultivars: Clemenules, Marisol. Fortune, and Valencia. The success ratio for the detection of individual defects was 91.5%, while the classification ratio of damaged/sound samples was 94.2%. These results show that the studied method can be suitable for the task of citrus inspection. (C) 2010 Elsevier B.V. All rights reserved
Sensitivity to high salinity in tetraploid citrus seedlings increases with water availability and correlates with expression of candidate genes
No full textWe investigated tolerance to high salinity in well-irrigated diploid and tetraploid citrus. Comparisons were made between two diploids (2x) of trifoliate orange (Poncirus trifoliata (L.) Raf.) and willow leaf mandarin (Citrus deliciosa Ten), their respective doubled diploids (4x) and the allotetraploid (FLHORAG1) obtained from the protoplast fusion of trifoliate orange and Willow leaf mandarin. Salinity stress was applied by progressively increasing the concentration of NaCl from 50 mM to 400 mM for 8 weeks. Two-year-old plants were watered daily. Maximum quantum yield of PSII, and leaf and root chloride and sodium content were monitored. We previously reported that under moderate saline stress, citrus 4x genotypes were more tolerant that the 2x, but under these experimental conditions, 4x seedlings were certainly more sensitive to salt stress than 2x, as they accumulated more toxic ions and were more affected than 2x. Chloride accumulation in 4x leaves was greater and the maximum quantum yield of PSII was more reduced in 4x than in 2x. The expression of several candidate genes involved in signal transduction, sodium and chloride transport, osmotic adjustment, regulation of the stomata opening and detoxification processes were also investigated by quantitative real-time reverse transcription-PCR. A high correlation was observed between phenotype of sensitivity to stress and gene expression changes
Genetic analysis of physiological components of salt tolerance conferred by Solanum rootstocks. What is the rootstock doing for the scion?
Get PDFGrafting desirable crop varieties on stress-tolerant rootstocks provides an opportunity to increase crop salt tolerance. Here, a commercial hybrid tomato variety was grafted on two populations of recombinant inbred lines developed from a salt-sensitive genotype of Solanum lycopersicum var. cerasiforme, as female parent, and two salt-tolerant lines, as male parents, from S. pimpinellifolium, the P population, and S. cheesmaniae, the C population, to identify an easy screening method for identifying rootstocks conferring salt tolerance in terms of fruit yield. Potential physiological components of salt tolerance were assessed in the scion: leaf biomass, [Na(+)], nutrition, water relations and xylem ABA concentration. A significant correlation between scion fruit yield and scion leaf fresh weight, water potential or the ABA concentration was found in the C population under salinity, but the only detected QTL did not support this relationship. The rootstocks of the P population clearly affected seven traits related to the sodium, phosphorous and copper concentrations and water content of the scion leaf, showing heritability estimates around 0.4 or higher. According to heritability estimates in the P population, up to five QTLs were detected per trait. QTLs contributing over 15% to the total variance were found for P and Cu concentrations and water content of the scion leaf, and the proportion of fresh root weight. Correlation and QTL analysis suggests that rootstock-mediated improvement of fruit yield in the P population under salinity is mainly explained by the rootstock's ability to minimise perturbations in scion water status
Adaptation of Staphylococcus aureus to ruminant and equine hosts involves SaPI-carried variants of von Willebrand factor-binding protein
No full textStaphylococci adapt specifically to various animal hosts by genetically determined mechanisms that are not well understood. One such adaptation involves the ability to coagulate host plasma, by which strains isolated from ruminants or horses can be differentiated from closely related human strains. Here, we report first that this differential coagulation activity is due to animal-specific alleles of the von Willebrand factor-binding protein (vWbp) gene, vwb, and second that these vwb alleles are carried by highly mobile pathogenicity islands, SaPIs. Although all Staphylococcus aureus possess chromosomal vwb as well as coagulase (coa) genes, neither confers species-specific coagulation activity; however, the SaPI-coded vWbps possess a unique N-terminal region specific for the activation of ruminant and equine prothrombin. vWbp-encoding SaPIs are widely distributed among S. aureus strains infecting ruminant or equine hosts, and we have identified and characterized four of these, SaPIbov4, SaPIbov5, SaPIeq1 and SaPIov2, which encode vWbpSbo4, vWbpSbo5, vWbpSeq1 and vWbpSov2 respectively. Moreover, the SaPI-carried vwb genes are regulated differently from the chromosomal vwb genes of the same strains. We suggest that the SaPI-encoded vWbps may represent an important host adaptation mechanism for S. aureus pathogenicity, and therefore that acquisition of vWbp-encoding SaPIs may be determinative for animal specificity
Comparative genome-wide segregation analysis and map construction using a reciprocal cross design to facilitate citrus germplasm utilization
Get PDFCitrus genetic resources are rich but underutilized in breeding because their complex reproductive biology and the scarceness of inheritance studies on agronomic traits. Here, we investigated the genomic distribution of segregation distortion regions, the inheritance of organelle DNA and colinearity between scion citrus linkage maps by using a reciprocal cross design. The parents were Fortune, a hybrid mandarin from C. clementina, and Chandler, a hybrid pummelo from C. grandis that largely differ in fruit size, taste and colour. The inheritance of organelle DNA was studied in 201 hybrids by using four organelle DNA markers, and the linkage maps were based on 174 of those hybrids. Around ten percent of the seedlings derived from the pummelo as female parent showed the same organelle markers as those of the mandarin, indicating a possible exception to their expected maternal inheritance in citrus. Most segregation distortion affects just the allele frequencies, generally representing differences in pollen fertilization success, as a likely consequence of the presence of gametal factors affecting the functionality of gametes and pollen-pistil interactions. The large extension of colinearity found when comparing the C. grandis and C. clementina linkage maps to those previously reported for rootstock species (C. aurantium and P. trifoliata), will be helpful to infer the position of orthologous genes and QTLs in citrus species and for a more useful genetic characterization of citrus germplasm collections
