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La diversidad genética del arroz cultivado en climas templados
Get PDFEl arroz se domesticó hace más de 6.500 años en una región de clima tropical
situada en el sureste asiático. Desde allí, el cultivo se extendió al resto del mundo
diversificándose, mediante mutaciones espontáneas o hibridaciones, con la aparición de
alelos en genes clave que aportaban cualidades que favorecían la adaptación a las nuevas
regiones alcanzadas y que han facilitado el desarrollo de plantas adaptadas a los nuevos
ambientes. El estudio de la diversidad genética y los cambios fenotípicos asociados, permite
realizar asociaciones que son útiles para entender los procesos biológicos de la planta y
también permite aprovechar de manera eficiente los recursos genéticos en los programas de
mejora. En el laboratorio, llevamos en marcha estudios sobre la diversidad del arroz
adaptado a clima templado. Entre los objetivos está la variabilidad en los genes reguladores
de la floración. El arroz se considera como una especie de día corto. Sin embargo, en
Europa, el cultivo se realiza en verano, cuando los días son largos. Hemos analizado los
alelos de los genes reguladores de la floración presentes en una colección de variedades
adaptadas a clima templado y hemos podido determinar diferencias respecto a las variedades
de clima tropical que permiten que florezcan en días largos.
También estamos obteniendo el perfil genético de una colección amplia de variedades
modernas y antiguas, adaptadas al clima templado. Para ello hemos obtenido y analizado la
secuencia del genoma de variedades representativas. A partir de los datos de las secuencias
estamos diseñando un microchip de DNA con 3000 polimorfismos que permitan distinguir, a
nivel molecular, las variedades que son cultivadas en nuestro entorno, así como el desarrollo
de marcadores moleculares, útiles en los programas de mejora de variedades
Energy reserves of parasitoids depend on honeydew from non-hosts
No full textAdult parasitoids depend on sugar-rich foods such as nectar and honeydew to meet their energy requirements and control insect pests. However, it is poorly known whether parasitoids can detect and feed on honeydew in agroecosystems, where it is the primary carbohydrate source, because this sugar source is less apparent in comparison to nectar and sometimes contains repellent compounds for parasitoids.
High-performance liquid chromatography (HPLC) analyses were carried out to test whether Aphytis melinus DeBach (Hymenoptera: Aphelinidae), a parasitoid whose host does not produce honeydew, feeds on honeydew from non-hosts. In addition, the correlation between the parasitoid's sugar reserves and honeydew abundance was determined. To do this, both the levels of honeydew producers and the sugar levels of individual collected parasitoids were assessed during different seasons. The overall sugar content was treated as an indicator of energy reserves and the erlose–melezitose ratio as an indicator of honeydew feeding.
The data show that A. melinus fed commonly on honeydew from non-host hemipterans. More than 50% of the female parasitoids collected in spring and summer had recently fed on honeydew and most of them showed a high sugar content.
However, in autumn, when the number of honeydew producers was three times lower than in spring and summer, less than 20% of A. melinus were found to have fed on honeydew, with the average total sugar content being reduced by a factor of three.
This study demonstrates that A. melinus commonly feeds on honeydew in the field, even though its host does not produce honeydew. The results also suggest that the exploitation of honeydew by A. melinus is a function of the density and species of honeydew producers
In vivo fertilising ability of frozen-thawed boar sperm treated with cholesterol-loaded cyclodextrins prior to cryopreservation
No full textThe use of frozen-thawed (FT) sperm for the artificial insemination of pigs is rare. Treating boar sperm with cholesterol-loaded cyclodextrins (CLC) prior to cryopreservation enhances the penetration of immature oocytes in vitro, and this phenomenon has been positively correlated with in vivo fertilisation ability in pigs. The objective of this study was to compare the in vivo fertilising ability of boar sperm treated with 0 (control) or 1 mg CLC/120 x 106 sperm (CLC) prior to freezing. The fertilising ability of the FT sperm was compared in hormonally treated (equine/human chorionic gonadotropin hormones; eCG/hCG) weaned sows inseminated once (cervical insemination) at the following fixed-times after hCG administration: 37 h (experiment 1) or 30 h (experiment 2). In experiment 1, both treatments exhibited similar fertility rates of 67.7 and 55.9% for the control and CLC, respectively (P>0.05); however, the CLC group had a smaller litter size (11.3 +/- 0.9) than the control group (13.6 +/- 0.8) (P0.05) for both treatments. These results indicate that the timing of insemination developed for the FT control sperm may not be suitable for CLC-treated sperm and that CLC-treated sperm may benefit from a shorter time interval between the hCG treatment and insemination. Moreover, acceptable results can be obtained with FT boar sperm with a single artificial insemination performed 30 h after hCG treatment, which is the time interval recommended for fresh sperm. (C) 2013 Elsevier B.V. All rights reserved
Biology, ecology and management of the south american tomato pinworm, tuta absoluta
No full textThis chapter focuses on the South American tomato pinworm Tuta absoluta (I) origin, spread and current distribution; (II) basic but critical information regarding bioecology; (III) rearing techniques; (IV) known host plants; (V) sampling and monitoring techniques; and (VI) control methods available from both South America and newly infested areas, as well as their potential use for integrated pest management. Some hints are provided on present and future management strategies
An S-Locus Independent Pollen Factor Confers Self-Compatibility in 'Katy' Apricot
Get PDFLoss of pollen-S function in Prunus self-compatible cultivars has been mostly associated with deletions or insertions in the Shaplotype-specific F-box (SFB) genes. However, self-compatible pollen-part mutants defective for non-S-locus factors have also been found, for instance, in the apricot (Prunus armeniaca) cv. ‘Canino’. In the present study, we report the genetic and molecular analysis of another self-compatible apricot cv. termed ‘Katy’. S-genotype of ‘Katy’ was determined as S1S2 and SRNase PCR-typing of selfing and outcrossing populations from ‘Katy’ showed that pollen gametes bearing either the S1- or the S2-haplotype were able to overcome self-incompatibility (SI) barriers. Sequence analyses showed no SNP or indel affecting the SFB1 and SFB2 alleles from ‘Katy’ and, moreover, no evidence of pollen-S duplication was found. As a whole, the
obtained results are compatible with the hypothesis that the loss-of-function of a S-locus unlinked factor gametophytically expressed in pollen (M’-locus) leads to SI breakdown in ‘Katy’. A mapping strategy based on segregation distortion loci mapped the M’-locus within an interval of 9.4 cM at the distal end of chr.3 corresponding to ,1.29 Mb in the peach (Prunus
persica) genome. Interestingly, pollen-part mutations (PPMs) causing self-compatibility (SC) in the apricot cvs. ‘Canino’ and ‘Katy’ are located within an overlapping region of ,273 Kb in chr.3. No evidence is yet available to discern if they affect the same gene or not, but molecular markers seem to indicate that both cultivars are genetically unrelated suggesting that every PPM may have arisen independently. Further research will be necessary to reveal the precise nature of ‘Katy’ PPM, but fine-mapping already enables SC marker-assisted selection and paves the way for future positional cloning of the underlying gene
Emergence and Phylodynamics of Citrus tristeza virus in Sicily, Italy
Get PDFCitrus tristeza virus (CTV) outbreaks were detected in Sicily island, Italy for the first time in 2002. To gain insight into the evolutionary forces driving the emergence and phylogeography of these CTV populations, we determined and analyzed the nucleotide sequences of the p20 gene from 108 CTV isolates collected from 2002 to 2009. Bayesian phylogenetic analysis revealed that mild and severe CTV isolates belonging to five different clades (lineages) were introduced in Sicily in 2002. Phylogeographic analysis showed that four lineages co-circulated in the main citrus growing area located in Eastern Sicily. However, only one lineage (composed of mild isolates) spread to distant areas of Sicily and was detected after 2007. No correlation was found between genetic variation and citrus host, indicating that citrus cultivars did not exert differential selective pressures on the virus. The genetic variation of CTV was not structured according to geographical location or sampling time, likely due to the multiple introduction events and a complex migration pattern with intense co- and recirculation of different lineages in the same area. The phylogenetic structure, statistical tests of neutrality and comparison of synonymous and nonsynonymous substitution rates suggest that weak negative selection and genetic drift following a rapid expansion may be the main causes of the CTV variability observed today in Sicily. Nonetheless, three adjacent amino acids at the p20 N-terminal region were found to be under positive selection, likely resulting from adaptation events
A nuclear phylogenetic analysis: SNPs, indels and SSRs deliver new insights into the relationships in the 'true citrus fruit trees' group (Citrinae, Rutaceae) and the origin of cultivated species
No full textBackground and Aims:
Despite differences in morphology, the genera representing ‘true citrus fruit trees’ are sexually compatible, and their phylogenetic relationships remain unclear. Most of the important commercial ‘species’ of Citrus are believed to be of interspecific origin. By studying polymorphisms of 27 nuclear genes, the average molecular differentiation between species was estimated and some phylogenetic relationships between ‘true citrus fruit trees’ were clarified.
Methods:
Sanger sequencing of PCR-amplified fragments from 18 genes involved in metabolite biosynthesis pathways and nine putative genes for salt tolerance was performed for 45 genotypes of Citrus and relatives of Citrus to mine single nucleotide polymorphisms (SNPs) and indel polymorphisms. Fifty nuclear simple sequence repeats (SSRs) were also analysed.
Key Results:
A total of 16 238 kb of DNA was sequenced for each genotype, and 1097 single nucleotide polymorphisms (SNPs) and 50 indels were identified. These polymorphisms were more valuable than SSRs for inter-taxon differentiation. Nuclear phylogenetic analysis revealed that Citrus reticulata and Fortunella form a cluster that is differentiated from the clade that includes three other basic taxa of cultivated citrus (C. maxima, C. medica and C. micrantha). These results confirm the taxonomic subdivision between the subgenera Metacitrus and Archicitrus. A few genes displayed positive selection patterns within or between species, but most of them displayed neutral patterns. The phylogenetic inheritance patterns of the analysed genes were inferred for commercial Citrus spp.
Conclusions:
Numerous molecular polymorphisms (SNPs and indels), which are potentially useful for the analysis of interspecific genetic structures, have been identified. The nuclear phylogenetic network for Citrus and its sexually compatible relatives was consistent with the geographical origins of these genera. The positive selection observed for a few genes will help further works to analyse the molecular basis of the variability of the associated traits. This study presents new insights into the origin of C. sinensis
Hyperspectral LCTF-based system for classification of decay in mandarins caused by Penicillium digitatum and Penicillium italicum using the most relevant bands and non-linear classifiers
No full textGreen mold (Penicillium digitatum) and blue mold (Penicillium italicum) are important sources of postharvest decay affecting the commercialization of mandarins. These fungi infections produce enormous economic losses in mandarin production if early detection is not carried out. Nowadays, this detection is performed manually in dark chambers, where the fruit is illuminated by ultraviolet light to produce fluorescence, which is potentially dangerous for humans. This paper documents a new methodology based on hyperspectral imaging and advanced machine-learning techniques (artificial neural networks and classification and regression trees) for the segmentation and classification of images of citrus free of damage and affected by green mold and blue mold. Feature selection methods are used in order to reduce the dimensionality of the hyperspectral images and determine the 10 most relevant. Neural Networks were used to segment the hyperspectral images. Result's achieved using classifiers based on decision trees show an accuracy of around 93% in the problem of decay classification
Complex Mixtures of Viroids Identified in the Two Main Citrus Growing Areas of Iran
No full textThe citrus industry in Iran is based on graft propagation of local and imported cultivars on a limited number of rootstocks such as sour orange, Mexican lime and Bakraee, a local natural hybrid. Infection of the available cultivars with graft-transmissible agents, viroids in particular, may have deleterious effects on the productivity of citrus and, more importantly, limits the choice of rootstocks. Rootstocks other than sour orange and Mexican lime will be needed as a consequence of the introduction and spread of Citrus tristeza virus (CTV) in the country. In the present study, two cv. Sanguinello sweet orange and two cv. Duncan grapefruit trees were selected on the basis of the bark scaling symptoms observed on the trifoliate orange and Troyer citrange rootstocks. Analysis by sPAGE and Northern blot hybridization of nucleic acid preparations of Etrog citrons graft-inoculated with these sources revealed the presence of several viroids: Citrus exocortis viroid (CEVd) and Hop stunt viroid (HSVd), the causal agents of exocortis and cachexia, respectively, as well as Citrus bent leaf viroid (CBLVd), Citrus dwarfing viroid (CDVd) and Citrus bark cracking viroid (CBCVd). These viroids were sequenced and compared with the corresponding reference sequences. To extend these results, samples from different citrus cultivars were collected in the two main citrus growing regions and analyzed for viroids. Of the 49 samples tested, 22 were viroid-positive, witnessing the occurrence of cultivars infected with CEVd, HSVd, CBLVd, CDVd, or CBCVd as mixed infections in the surveyed regions. One sample was also co-infected with the newly described Citrus viroid V (CVd-V)
Carry-over effects of deficit irrigation applied over seven seasons in a developing Japanese plum orchard
No full textDeficit irrigation is a strategy that in the short term often allows increasing water use efficiency with minimal impacts on tree performance. However, the long-term and carry-over effects of this practice have not been sufficiently investigated. Here, we report a research that was conducted over eight years in a young Japanese plum orchard planted with cv. Black-Gold in Valencia, Spain. Different deficit irrigation and crop load regimes were applied in the first seven seasons. In the last experimental season, however, all trees were well irrigated in order to explore the possible carry-over effects of the water restrictions applied previously. The results obtained indicate that under the experimental conditions of the current research (low irrigation water salinity, and Mediterranean climate with some intense rainfall events during fall and spring), deficit irrigation applied for seven consecutive seasons did not lead to accumulation of salts in the soil, a concern when deficit irrigation is applied in the long-term. Nonetheless, water restrictions impaired the fruit bearing capacity quantified as the number of fruit per unit branch length before thinning application. This effect was partly explained by a decrease in the concentration of starch reserves in the root system in one of the deficit irrigated treatments. A decrease in the fruit bearing capacity itself did not impair yield as the cultivar employed in this study required intense thinning that offset the initial differences in the number of fruit per branch length. However, deficit irrigation led to smaller trees (31% in tree shaded area in the most stressed treatment against 47% in control trees). This effect was the ultimate cause of the 29% yield reduction observed in the eighth season, when the previous deficit irrigated trees were fully watered. It is then concluded that deficit irrigation strategies in developing orchards should be used with caution. Only slight restrictions can be imposed in order to avoid the long-term carry-over effects of deficit irrigation on tree performance. (C) 2013 Elsevier B.V. All rights reserved