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Large changes in anatomy and physiology between diploid Rangpur lime (Citrus limonia) and its autotetraploid are not associated with large changes in leaf gene expression
No full textVery little is known about the molecular origin of the large phenotypic differentiation between genotypes arising from somatic chromosome set doubling and their diploid parents. In this study, the anatomy and physiology of diploid (2x) and autotetraploid (4x) Rangpur lime (Citrus limonia Osbeck) seedlings has been characterized. Growth of 2x was more vigorous than 4x although leaves, stems, and roots of 4x plants were thicker and contained larger cells than 2x that may have a large impact on cell-to-cell water exchanges. Leaf water content was higher in 4x than in 2x. Leaf transcriptome expression using a citrus microarray containing 21 081 genes revealed that the number of genes differentially expressed in both genotypes was less than 1% and the maximum rate of gene expression change within a 2-fold range. Six up-regulated genes in 4x were targeted to validate microarray results by real-time reverse transcription-PCR. Five of these genes were apparently involved in the response to water deficit, suggesting that, in control conditions, the genome expression of citrus autotetraploids may act in a similar way to diploids under water-deficit stress condition. The sixth up-regulated gene which codes for a histone may also play an important role in regulating the transcription of growth processes. These results show that the large phenotypic differentiation in 4x Rangpur lime compared with 2x is not associated with large changes in genome expression. This suggests that, in 4x Rangpur lime, subtle changes in gene expression may be at the origin of the phenotypic differentiation of 4x citrus when compared with 2x
The role of horizontal gene transfer in Staphylococcus aureus host adaptation
Get PDFStaphylococcus aureus is an important
human pathogen that also causes economically
important infections of livestock.
In a recent paper, we employed a
population genomic approach to investigate
the molecular basis of ruminant host
adaptation by S. aureus. The data suggest
that the common pathogenic clone
associated with small ruminants originated
in humans but has since adapted
to its adopted host through a combination
of allelic diversification, gene loss
and acquisition of mobile genetic elements.
In particular, a new subfamily
of staphylococcal pathogenicity islands
(SaPI) was identified encoding a novel
von Willebrand factor-binding protein
(vWBP) with ruminant-specific coagulase
activity. The wide distribution of
vWBP-encoding SaPIs among ruminant
strains implies an important role in hostadaptation.
In the current article we
summarize the findings of the paper and
comment on the implications of the study
for our understanding of the molecular
basis of bacterial host adaptatio
Effects of citrus rootstocks on growth, yield and fruit quality of Navelate orange
No full textThe aim was to study the performance of Navelate sweet orange on five rootstocks: Carrizo citrange [Citrus sinensis (L.) Osb. x Poncirus trifoliata (L.) Raf.]; Cleopatra mandarin (C. reshni Hort. ex Tan.); C. volkameriana Ten. & Pasq. and two new hybrids C-13 (C. depressa Hay. x P trifoliata) developed at the University of California Citrus Research Center and 020326 [Troyer citrange (C. sinensis x P trifoliata) x Cleopatra mandarin] developed at the Instituto Valenciano de Investigaciones Agrarias in Valencia, Spain. The investigation was conducted in Almeria, Spain. The soil was sandy, with pH>8 and electric conductivity in the saturation extract below 4.5 mmhos cm(-1). The design was a complete-block with randomised single-tree plots and eight replications. Tree spacing was 4.5 m x 4 m. Yield was recorded during the first nine harvests, fruit quality was determined for the 50(th), 6(th) and 9(th) harvests and tree size was evaluated 11 years after planting. Trees on C. volkameriana rootstock produced the highest yield and largest fruits. Trees on the C-13 hybrid selection were the most yield-efficient on a canopy volume basis, and had fruit with the highest soluble solid content, but there were few differences between rootstocks for the latter parameter. Cleopatra mandarin and 020326 induced the lowest individual fruit weight and diameter
Influence of Gamma Irradiation on Seedless Citrus Production: Pollen Germination and Fruit Quality
Get PDFSeedlessness is a desirable characteristic in citrus fruits sold for fresh consumption. Gamma irradiation is widely used to obtain seedless citrus fruits. Here, different clones of the self-incompatible parthenocarpic ‘Moncada’ mandarin, obtained by gamma irradiation, were studied to assess seedlessness, pollen germination, fruit characteristics and qua- lity attributes. Findings indicate that irradiation altered aspects other than seedlessness, such as pollen germination, and some of the clones presented different weight, size, acidity and maturity index. Fruit quality and nutritional bio- components were affected differently; some clones presented no changes compared to the control ‘Moncada’ man-darin, while other clones showed significant differences. In general, all clones examined presented low seed numbers and re- duced pollen viability. Some of these clones, which ripen late in the season and whose fruit quality is maintained or improved, are in the process of registration
Root signalling and modulation of stomatal closure in flooded citrus seedlings
No full textIn this work, we studied the sequence of responses induced by flooding in citrus plants, with the aim of identifying the signals that lead to stomatal closure. One-year-old seedlings of Carrizo citrange, grown in sand under greenhouse conditions, were waterlogged for 35 d and compared with normally watered well-drained plants. Significant decreases in stomatal conductance and transpiration were detected between flooded and control seedlings from a week after the beginning of the experiment. However ABA concentration in leaves only started to increase after three weeks of flooding, suggesting that stomata closed in the absence of a rise in foliar ABA. Therefore, stomatal closure in waterlogged seedlings does not appear to be induced by ABA, at least during the early stages of flood-stress. The low levels of ABA detected in roots and xylem sap from flooded seedlings indicated that it is very unlikely that the ABA increase in the leaves of these plants is due to ABA translocation from roots to shoots. We propose that ABA is produced in old leaves and transported to younger leaves. Flooding had no effect on water potential or the relative water content of leaves. Soil flooding reduced root hydraulic conductance in citrus seedlings. This effect was already evident after a week of waterlogging, and at the end of the experiment, flood-stressed seedlings reached values of root hydraulic conductance below 12% of that of control plants. This reduction was related to down-regulation of the expression of PIP aquaporins. In addition, whole plant transpiration was reduced by 56% after 35 d under flooding conditions. Flood-stress also decreased the pH of sap extracted from citrus roots. Evidence is presented suggesting that acidosis induced by anoxic stress in roots causes gating of aquaporins, thereby decreasing hydraulic conductance. Additionally, stomata] closure finely balances-out low pH-mediated losses of root hydraulic conductance therefore maintaining stable leaf hydration. (C) 2011 Elsevier Masson SAS. All rights reserved
Effect of number of oocytes and embryos on in vitro oocyte maturation, fertilization and embryo development in bovine
Get PDFThe aim of this study was to identify the in vitro development stage at which the culture of a single or low number (n = 5 or 10) of oocytes/embryos could impair development in comparison with culture in group (n = 50). In the Experiment 1, it was confirmed that single in vitro embryo production yielded lower cleavage and blastocyst rates than in group (49.4 vs. 83.0%; 0% vs. 37.8%, respectively; p < 0.05). In Experiment 2 and 3, it was observed no effect on embryo development of culturing single or low number of oocytes during maturation and fertilization, respectively. In Experiment 4, it was observed a detrimental effect on blastocyst rate when cultured single or low number of embryos during post-fertilization in vitro culture (2.9; 10.2-10.8; 33.2% in single, low number of embryos (5-10), and control-grouped, respectively; p < 0.05). In Experiment 5, it was observed that the last part of the culture period (day 3 onwards) seemed to be more affected by the low number of embryos placed in culture. In conclusion, post-fertilization culture, especially on days 3 to 7 after fertilization, seems to be the most important stage for embryo development on single and/or low number (5-10) of embryos culture
Larval morphology of Metaphycus flavus and its role in host attachment and larval cannibalism
No full textMetaphycus flavus (Howard) (Hymenoptera: Encyrtidae) is a facultatively gregarious endoparasitoid of soft scales (Hemiptera: Coccidae). When it develops in superparasitised hosts, the larvae often attack and consume brood mates six or more days post oviposition. Under our laboratory conditions (25 +/- 1 degrees C and 14 hours of light followed by 18 +/- 1 degrees C and ten hours of darkness in 50-70% R. H.), M. flavus eggs hatched three days after oviposition. Measurements of the mandibles and tentorium indicate there are four larval instars, and M. flavus reaches the fourth instar by day six post oviposition, and pupates on day eight. Thus, cannibalism among M. flavus larvae occurs during the fourth instar. During this instar, M. flavus larvae separate from their attachment to the scale cuticle, to which they were tethered by a respiratory structure during the previous three larval instars. Once detached, they are free to move within the scale, which increases the probability of larval encounters and aggressive behaviours. Moreover, the mandibles of the fourth instar are better adapted for fighting than are those of the first three larval instars, since they are larger and more sclerotized. The cranium and mouthparts of M. flavus have four different types of sensory organs, some of which are almost certainly olfactory, an unexpected function for a larva that presumably is surrounded by an aqueous medium where gustatory sensilla would seem to be more appropriate. The cranium also bears two pairs of what appear to be secretory pores
Influence of rootstock and cultivar on bioactive compounds in citrus peels
No full textBACKGROUND: Citrus fruits have a beneficial effect on human health because of their nutritional and antioxidant properties, and their consumption is associated with a decrease in the incidence of cardiovascular disease and reduced risk of certain cancers. Seven cultivars of mandarin and orange species from the Mediterranean area, grafted onto different rootstocks (Cleopatra mandarin and Troyer citrange), have been analysed. The influence of the rootstock on the content of bioactive compounds is discussed. RESULTS: In all citrus cultivars and rootstocks studied, hesperidin and narirutin flavonoids were the main flavanone glycosides identified, beta-cryptoxanthin and violaxanthin the most abundant carotenoids, limonene was the most abundant essential oil, calcium and potassium were the dominant macronutrients and, among the micronutrients, iron and boron represented the highest proportions. CONCLUSION: We have been found clear differences in the content of bioactive compounds for the different groups, in agreement with the Citrus classification. Although both mandarin and orange varieties showed similar tendencies concerning the majority of bioactive constituents, the proportion of the individual nutrients ranged among different cultivars and our results indicated differences between rootstocks although it would be necessary to carry out more analyses, and with the new rootstocks obtained from different breeding programmes, to elucidate conclusive values. (C) 2011 Society of Chemical Industr
Evaluation of the use of sulfur dioxide to reduce postharvest losses on dark and green figs
No full textPostharvest diseases limit the storage period and market life of fresh figs (Ficus carica L.). The objective of this work was to determine the effect of sulfur dioxide (SO(2)) applied by fumigation and/or by dual release SO(2) generating pads on postharvest decay and quality retention of 'Black Mission' and 'Brown Turkey' (dark skin), and 'Kadota' and 'Sierra' (green skin) figs. A protocol for the computer-controlled application of gaseous SO(2) has been developed which allows the application of very low specific concentration x time products of SO(2) and simultaneous monitoring of the application progress. In vitro tests with important fungal, yeast and bacterial postharvest pathogens plated on Petri dishes and exposed to a SO(2) concentration x time product (C x t) of 100 (mu L/L) h at different temperatures showed fewer survived at 20 degrees C than at 0 degrees C. Therefore, fumigations were carried out at 20 degrees C in the rest of the experiments. The evaluation of different SO(2) concentration x time products showed that a product of 25 (mu L/L) h provided the best compromise between decay control and fruit injury. The performance of SO(2) fumigations on warm or cold fruit, its combination with SO(2) generating pads, and the use of repeated fumigations during cold storage were also evaluated. All the SO(2) treatments tested reduced the percentage of decay, extending the market life of fresh figs. However, in some cases, the use of SO(2) generating pads increased the incidence of skin bleaching. Fumigation of warm fruit at 25 (mu L/L) h of SO(2) reduced populations of Alternaria and Rhizopus spp. growing on the fig surface. The treatment was more effective against Rhizopus spp. than against Alternaria spp. Contamination of fruit by Botrytis spp. and Penicillium spp. was also reduced by SO(2). In conclusion, results showed that SO(2) can be a potential tool to control postharvest rots and therefore increase the market life of fresh figs. (C) 2010 Elsevier B.V. All rights reserved
Short communication. Susceptibility of Phoenix theophrasti (Palmae: Coryphoideae) to Rhynchophorus ferrugineus (Coleoptera: Curculionidae) and its control using Steinernema carpocapsae in a chitosan formulation
Get PDFThe invasive red palm weevil, Rhynchophorus ferrugineus Oliv. (Coleoptera: Curculionidae) is the most destructive pest of palms in the world. It has been reported on 19 palm species belonging to 15 different genera. The host status of the Cretan Date Palm, Phoenix theophrasti, remains unclear. Therefore, the present study was carried out to ascertain the host status of this protected palm species. Additionally, the efficacy of entomopathogenic nematodes in a chitosan formulation to control this pest in P theophrasti was assessed. Our results showed that healthy 4-yr-old P theophrasti palms were not infested by adult females after 9 days exposure in a population density of 3 adults per plant. However, infestation was successful when neonate larvae were artificially introduced in palms. Therefore, natural populations of P theophrasti could be at risk. Gummy secretion was observed in both naturally and forced infested palms indicating the existence of antibiosis in this species. Curative applications with the entomopathogenic nematode Steinernema carpocapsae in a chitosan formulation in early infested P theophrasti palms managed to reduce insect's activity and could help the palms to recover