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Shaping the biology of citrus: I. Genomic determinants of evolution
Get PDFWe performed genomic analyses on wild species of the genus Citrus to identify major determinants of evolution. The most notable effect occurred on the pathogen-defense genes, as observed in many other plant genera. The gene space was also characterized by changes in gene families intimately related to relevant biochemical properties of citrus fruit, such as pectin modifying enzymes, HDR (4-hydroxy-3-methylbut-2-enyl diphosphate reductase) genes, and O-methyltransferases. Citrus fruits are highly abundant on pectins and secondary metabolites such as terpenoids and flavonoids, the targets of these families. Other gene types under positive selection, expanded through tandem duplications and retained as triplets from whole genome duplications, codified for purple acid phosphatases and MATE-efflux proteins. Although speciation has not been especially rapid in the genus, analyses of selective pressure at the codon level revealed that the extant species evolved from the ancestral citrus radiation show signatures of pervasive adaptive evolution and is therefore potentially responsible for the vast phenotypic differences observed among current species. by changes in gene families intimately related to relevant biochemical properties of citrus fruit, such as pectin modifying enzymes, HDR (4-hydroxy-3-methylbut-2- enyl diphosphate reductase) genes, and O-methyltransferases. Citrus fruits are highly abundant on pectins and secondary metabolites such as terpenoids and flavonoids, the targets of these families. Other gene types under positive selection, expanded through tandem duplications and retained as triplets from whole genome duplications, codified for purple acid phosphatases and MATE-efflux proteins. Although speciation has not been especially rapid in the genus, analyses of selective pressure at the codon level revealed that the extant species evolved from the ancestral citrus radiation show signatures of pervasive adaptive evolution and is therefore potentially responsible for the vast phenotypic differences observed among current species
Insights of Phenolic Pathway in Fruits: Transcriptional and Metabolic Profiling in Apricot (Prunus armeniaca)
Get PDFThere is an increasing interest in polyphenols, plant secondary metabolites, in terms of fruit quality and diet, mainly due to their antioxidant effect. However, the identification of key gene enzymes and their roles in the phenylpropanoid pathway in temperate fruits species remains uncertain. Apricot (Prunus armeniaca) is a Mediterranean fruit with high diversity and fruit quality properties, being an excellent source of polyphenol compounds. For a better understanding of the phenolic pathway in these fruits, we selected a set of accessions with genetic-based differences in phenolic compounds accumulation. HPLC analysis of the main phenolic compounds and transcriptional analysis of the genes involved in key steps of the polyphenol network were carried out. Phenylalanine ammonia-lyase (PAL), dihydroflavonol-4-reductase (DFR) and flavonol synthase (FLS) were the key enzymes selected. Orthologous of the genes involved in transcription of these enzymes were identified in apricot: ParPAL1, ParPAL2, ParDFR, ParFLS1 and ParFLS2. Transcriptional data of the genes involved in those critical points and their relationships with the polyphenol compounds were analyzed. Higher expression of ParDFR and ParPAL2 has been associated with red-blushed accessions. Differences in expression between paralogues could be related to the presence of a BOXCOREDCPAL cis-acting element related to the genes involved in anthocyanin synthesis ParFLS2, ParDFR and ParPAL2
Neonicotinoids from coated seeds toxic for honeydew-feeding biological control agents
Get PDFSeed coating (‘seed treatment’) is the leading delivery method of neonicotinoid insecticides in major crops such as soybean, wheat, cotton and maize. However, this prophylactic use of neonicotinoids is widely discussed from the standpoint of environmental costs. Growing soybean plants from neonicotinoid-coated seeds in field, we demonstrate that soybean aphids (Aphis glycines) survived the treatment, and excreted honeydew containing neonicotinoids. Biochemical analyses demonstrated that honeydew excreted by the soybean aphid contained substantial concentrations of neonicotinoids even one month after sowing of the crop. Consuming this honeydew reduced the longevity of two biological control agents of the soybean aphid, the predatory midge Aphidoletes aphidimyza and the parasitic wasp Aphelinus certus. These results have important environmental and economic
implications because honeydew is the main carbohydrate source for many beneficial insects in agricultural landscapes
Role of Na+ transporters HKT1;1 and HKT1;2 in tomato salt tolerance. I. Function loss of cheesmaniae alleles in roots and aerial parts
Get PDFWe analyzed the physiological impact of function loss on cheesmaniae alleles at the HKT1;1 and HKT1;2 loci in the roots and aerial parts of tomato plants in order to determine the relative contributions of each locus in the different tissues to plant Na+/K+ homeostasis and subsequently to tomato salt tolerance. We generated different reciprocal rootstock/scion combinations with non-silenced, single RNAi-silenced lines for ScHKT1;1 and ScHKT1;2, as well as a silenced line at both loci from a near isogenic line (NIL14), homozygous for the Solanum cheesmaniae haplotype containing both HKT1 loci and subjected to salinity under natural greenhouse conditions. Our results show that salt treatment reduced vegetative growth and altered the Na+/K+ ratio in leaves and flowers; negatively affecting fruit production, particularly in graft combinations containing single silenced ScHKT1;2- and double silenced ScHKT1;1/ScHKT1;2 lines when used as scion. We concluded that the removal of Na+ from the xylem by ScHKT1;2 in the aerial part of the plant can have an even greater impact than that on Na+ homeostasis at the root level under saline conditions. Also, ScHKT1;1 function loss in rootstock greatly reduced the Na+/K+ ratio in leaf and flower tissues, minimized yield loss under salinity. Our results suggest that, in addition to xylem Na+ unloading, ScHKT1;2 could also be involved in Na+ uploading into the phloem, thus promoting Na+ recirculation from aerial parts to the roots. This recirculation of Na+ to the roots through the phloem could be further favoured by ScHKT1;1 silencing at these roots
Parthenocarpy and Self-Incompatibility in Mandarins
Get PDFCitrus reproductive biology is complex. One of its characteristic features is parthenocarpy that enables seedless fruit production. Citrus parthenocarpy and self-incompatibility knowledge is only partial and sometimes discrepant. Increasing such knowledge is relevant for better managing cultivated varieties and improving the selection of parents in breeding strategies to recover seedless varieties such as mandarins. This work develops an efficient protocol to characterize selfincompatibility and different parthenocarpy types based on emasculation, hand self-pollination, and hand cross-pollination. It analyzes fruit setting and seed production coupled with histological pollen performance observations. We analyzed the reproductive behavior of nine mandarin varieties with relevant characteristics as parents for seedless mandarin breeding. ‘Clemenules’ clementine and ‘Moncada’ mandarins were strictly self-incompatible with facultative and vegetative parthenocarpy; ‘Imperial’ mandarin and ‘Ellendale’ tangor displayed no strict self-incompatibility associated with facultative and vegetative parthenocarpy; ‘Fortune’ mandarin was self-incompatible with facultative and stimulative parthenocarpy; ‘Campeona’ and ‘Salteñita’ mandarins were self-compatible with vegetative parthenocarpy; ‘Serafines’ satsuma was associated with male sterility together with facultative and vegetative parthenocarpy; and ‘Monreal’ clementine was self-compatible and nonparthenocarpic. Our protocol can be applied for screening of mandarin germplasm and to characterize new parents. Reproductive behavior knowledge is important for optimizing seedless mandarin breeding programs based on diploidy, triploidy, or induced mutagenesis
Genetic Analysis of Root-to-Shoot Signaling and Rootstock-Mediated Tolerance to Water Deficit in Tomato
Get PDFDeveloping drought-tolerant crops is an important strategy to mitigate climate change impacts. Modulating root system function provides opportunities to improve crop yield under biotic and abiotic stresses. With this aim, a commercial hybrid tomato variety was grafted on a genotyped population of 123 recombinant inbred lines (RILs) derived from Solanum pimpinellifolium, and compared with self- and non-grafted controls, under contrasting watering treatments (100% vs. 70% of crop evapotranspiration). Drought tolerance was genetically analyzed for vegetative and flowering traits, and root xylem sap phytohormone and nutrient composition. Under water deficit, around 25% of RILs conferred larger total shoot dry weight than controls. Reproductive and vegetative traits under water deficit were highly and positively correlated to the shoot water content. This association was genetically supported by linkage of quantitative trait loci (QTL) controlling these traits within four genomic regions. From a total of 83 significant QTLs, most were irrigation-regime specific. The gene contents of 8 out of 12 genomic regions containing 46 QTLs were found significantly enriched at certain GO terms and some candidate genes from diverse gene families were identified. Thus, grafting commercial varieties onto selected rootstocks derived from S. pimpinellifolium provides a viable strategy to enhance drought tolerance in tomato
Correction to: The olfactive responses of Tetranychus urticae natural enemies in citrus depend on plant genotype, prey presence, and their diet specialization
No full textIn the original publication of the article, the authors have inadvertently presented Figs.1-4 that were prepared from an incorrect data-set and were therefore inaccurate. The corrected figures and related statistical results are published herein. In addition, data supporting the corrected figures are provided as new supplementary online material (Supplementary Table 2 and Supplementary Figs. 3-6).
The ecological relevance of certain responses to particular treatments were still discussed when P-values neared 0.05 (Wasserstein et al. 2019). This was the case of the preferences of Tetranychus urticae for (a) conspecific infested plants, where Cleopatra mandarin was preferred to sour orange (P ≤ 0.058), and (b) when having to choose between clean and infested Cleopatra mandarin, where infested plants were mostly preferred (P = 0.058) (Fig. 1; Supplementary Fig. 3). Similarly, the preferences of Euseius stipulatus and Neoseiulus californicus for T. urticae body odors were associated with a P-value of 0.058 (Figs. 2 and 3; Supplementary Figs. 4, 5). Finally, when having to choose between the same plant genotype, either infested or not, a P = 0.058 was obtained for N. californicus and sour orange (Fig. 3; Supplementary Fig. 5) and for Phytoseiulus persimilis and both sour orange and Cleopatra mandarin (Fig. 4; Supplementary Fig. 6). As a consequence, the conclusions discussed in the paper remain valid
A Minor Role of Host Fruit on the Parasitic Performance of Aganaspis daci (Hymenoptera: Figitidae) on Medfly Larvae
Get PDFHost fruit is known to strongly affect the performance of both fruit pests and their potential natural enemies. This is particularly important in the control of tephritid fruit flies, whose larvae develop inside the fruit and thus create a set of foraging problems for parasitoids. In the present study, we assessed the response of female Aganaspis daci (Weld) (Hymenoptera: Figitidae), one of the most promising parasitoids for tephritid biocontrol in the Mediterranean Basin, to different potential host fruit species. We measured the olfactory response to medfly-infested and uninfested fruits, and several biological parameters of A. daci when different infested fruits were offered under both laboratory and greenhouse conditions. Our results showed that this parasitoid was significantly more attracted to apples and uninfested fruit. Moreover, parasitic activity was similar among the tested fruits under both conditions, showing very high values in the laboratory and a much poorer performance when conditions were variable. This suggests that A. daci may be a good candidate to be included in mass releases against the medfly regardless of the affected crop, but only when climate conditions are not expected to hinder its normal activity
Evidence that Xylella fastidiosa is the Causal Agent of Almond Leaf Scorch Disease in Alicante, Mainland Spain (Iberian Peninsula)
No full textIn 2017, Xylella fastidiosa, a quarantine plant-pathogenic bacterium in Europe, was detected in almond trees associated with leaf scorch symptoms in Alicante, a Mediterranean area in southeastern mainland Spain. The bacterium was detected by serological and molecular techniques, isolated in axenic culture from diseased almond trees, and identified as X. fastidiosa subsp. multiplex sequence type (ST) 6. Inoculation experiments on almond plants in greenhouse trials with a characterized strain of X. fastidiosa subsp. multiplex ST6 isolated in the outbreak area have proved that it was able to multiply and systemically colonize inoculated plants. Disease symptoms characteristic of leaf scorch like those observed in the field were observed in the inoculated almond trees after 1 year. Furthermore, the pathogen was reisolated and identified by molecular tests. With the fulfillment of Koch’s postulates, we have demonstrated that X. fastidiosa is the causal agent of the almond leaf scorch disease in the Alicante outbrea
Antifungal edible coatings for postharvest preservation of fresh fruit
Get PDFPostharvest losses of fresh fruit are mainly caused by weight loss, physiological disorders, and decay during storage and commercialization. Currently, postharvest treatments with conventional chemical fungicides and/or synthetic waxes are commonly used in combination with low-temperature storage to reduce such losses and minimize their economic impact. However, their continuous use by the industry for many years has arisen important health and environmental problems related to the production of chemical residues and the proliferation of resistant pathogenic fungal biotypes. Therefore, safe and eco-friendly alternatives should be commercially implemented as part of non-polluting integrated disease management (NPIDM) programs for preservation of fresh fruit. Among them, the development of edible coatings with antifungal activity is a technological challenge and a very active research field worldwide. The main advantage of these coatings is that they could provide a single solution for both physiological and pathological major postharvest issues. While some natural coatings such as chitosan or Aloe spp. gels show inherent antifungal activity, specific food-grade antifungal ingredients should be incorporated into composite matrixes of hydrocolloids (polysaccharides such as cellulose derivatives, alginates, pectins, gums, and peptides or proteins) and lipids to form synthetic edible coatings with antifungal properties. These ingredients include natural or low-toxicity compounds, such as inorganic or organic salts (e.g., carbonates, sorbates, benzoates, paraben salts) and essential oils or other plant extracts approved as food additives or generally recognized as safe (GRAS) compounds by competent authorities, and biological control agents such as antagonistic strains of some microorganisms