ReDivia - Repositorio Digital de l'Instit Valencià d'Investigacions Agràries
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Maximum-likelihood method identifies meiotic restitution mechanism from heterozygosity transmission of centromeric loci: application in citrus
Get PDFPolyploidisation is a key source of diversification and speciation in plants. Most researchers consider sexual polyploidisation leading to unreduced gamete as its main origin. Unreduced gametes are useful in several crop breeding schemes. Their formation mechanism, i.e., First-Division Restitution (FDR) or Second-Division Restitution (SDR), greatly impacts the gametic and population structures and, therefore, the breeding efficiency. Previous methods to identify the underlying mechanism required the analysis of a large set of markers over large progeny. This work develops a new maximum-likelihood method to identify the unreduced gamete formation mechanism both at the population and individual levels using independent centromeric markers. Knowledge of marker-centromere distances greatly improves the statistical power of the comparison between the SDR and FDR hypotheses. Simulating data demonstrated the importance of selecting markers very close to the centromere to obtain significant conclusions at individual level. This new method was used to identify the meiotic restitution mechanism in nineteen mandarin genotypes used as female parents in triploid citrus breeding. SDR was identified for 85.3% of 543 triploid hybrids and FDR for 0.6%. No significant conclusions were obtained for 14.1% of the hybrids. At population level SDR was the predominant mechanisms for the 19 parental mandarins
Genome-wide changes in histone H3 lysine 27 trimethylation associated with bud dormancy release in peach
No full textBud dormancy is an evolutionary adaptation of perennial plants to the seasonal fluctuation of temperatures in temperate climates, affected by intrinsic and environmental signals. Recent investigations point to a relevant role of epigenetic mechanisms in the regulation of bud dormancy. We have performed a chromatin immunoprecipitation sequencing (ChIP-seq) analysis of histone H3 lysine-27 trimethylation (H3K27me3), a chromatin mark associated with stable gene silencing, in dormant (D) and dormancy-released (ND) buds of peach (Prunus persica). H3K27me3 regions were more abundant in gene-rich euchromatic zones of chromosomes and associated with gene bodies. The dormancy regulators DORMANCY-ASSOCIATED MADS-box (DAM) 1, DAM4, DAM5 and DAM6 were found significantly enriched in H3K27me3 in ND samples, in close agreement with their dormancy-specific expression. The DAM locus was modified at specific short regions, allowing the uneven regulation of distinct DAM genes. Additional regulatory factors related to meristem activity and flowering genes from Arabidopsis thaliana were differentially H3K27 trimethylated, which suggests that meristem reactivation and flower development could be also epigenetically regulated in reproductive buds of peach. A (GA)n motif and CACTA-type transposon-related sequences were found over-represented in H3K27me3 regions
Effect of active modified atmosphere and cold storage on the postharvest quality of cherry tomatoes
No full textThe effects of active modified atmosphere packaging (MAP) on the postharvest quality of cherry tomatoes stored at cold temperature (5 degrees C) and in bi-oriented polypropylene/low density polyethylene BOPP/LDPE bags were investigated. The atmosphere composition used in the packaging was 5% O-2 + 5% CO2 (MAP), and synthetic air (control). The variables measured were weight loss, firmness, sugar, organic acids, color, lycopene, respiration rate, and ethylene biosynthesis over 25 days. The results showed that active MAP could extend the shelf life of cherry tomatoes to 25 days and the gas concentration could influence the postharvest quality of cherry tomatoes. MAP treatment decreased the respiration rate and ethylene production rate while reducing weight loss, lycopene biosynthesis, and the formation of red color. Through the use of MAP it was possible to maintain firmness and delay changes in sugar and organic acid contents. The combination of active MAP and low temperature treatments was effective with regard to delaying maturity during the storage period, and preserving the quality of cherry tomatoes. (C) 2015 Elsevier B.V. All rights reserved
The hydrothermal carbonization (HTC) plant as a decentral for wet biomass
Get PDFThe hydrothermal carbonization (HTC) is a very suitable process to transform wet biomass feedstocks into a peat-like material without drying the biomass input. Therefore, the energetic balance is more favorable than for alternative processes converting biomass as a whole. Further synergies can be achieved when the plant is employed as central hub for a regional biorefinery. Hence, a HTC pilot plant is operated with garden prunings and monitored during two years. It is shown that the elemental composition of HTC carbon is relatively constant. A carbon content of higher than 60% (based on dry, ash-free matter) is achieved. Fixed carbon content and volatile matter show low variation being the volatile content quite high with 61% on average. Dried in a post-process treatment which is less energy-demanding than drying of the raw biomass and pressed into pellets or briquettes the HTC carbon can be used as solid biofuel fulfilling the European standard (EN 14961-6). With a regional thermal valorization of the biofuel the ashes can be returned as phosphorous source to the crop land from which the biomass was harvested. Part of the process water, which involves a high amount of potassium, can be used for crop irrigation. In this way, valuable plant nutrients are recovered for soil remediation. Hence, closing the nutrient cycles a HTC plant can be considered as a sustainable local biorefinery producing a solid biofuel. Thereby, solar energy is exploited which was fixed before by photosynthesis together with the carbon dioxide which is liberated in the combustion of the solid biofuel. Optionally, the process water might serve as an alternative source of energy as it is demonstrated that its carbon content can be exploited for biogas production
Acta Horticulturae
No full textVery active programs to produce new mandarin varieties are being carried out in several countries using different approaches and technologies (diploid and triploid breeding, irradiation, somatic hybridization, genetic transformation, etc.). The objective of this workshop was to discuss about the most important breeding methods, the main limitations of the different approaches and methodologies, which is the challenge of new mandarin varieties in the next future and also their relationship with the legislation related to essentially derived varieties that in some cases may preclude the protection of breeder’s rights of new varieties
Carbon utilization by fruit limits shoot growth in alternate-bearing citrus trees
No full textFruit load in alternate-bearing citrus trees is reported to alter shoot number and growth during spring, summer, and autumn flushes, and the source-sink balance, which affects the storage and mobilization of reserve nutrients. The aim of this work was to assess the extent of shoot growth inhibition resulting from the presence of fruits in ` Moncada' mandarin trees loaded with fruit (ON) or with very light fruit load (OFF), and to identify the role of carbohydrates and nitrogenous compounds in the competition between fruits and shoots. Growth of reproductive and vegetative organs was measured on a monthly basis. C-13-and N-15-labeled compounds were supplied to trace the allocation of reserve nutrients and subsequent translocation from source to sink. At the end of the year, OFF trees produced more abundant flushes (2.4-and 4.9-fold higher in number and biomass, respectively) than ON trees. Fruits from ON trees accumulated higher C amounts at the expense of developing flushes, whereas OFF trees exhibited the opposite pattern. An inverse relationship was identified between the amount of C utilized by fruits and vegetative flush growth. C-13-labeling revealed an important role for mature leaves of fruit-bearing branches in supporting shoot/fruit growth, and the elevated sink strength of growing fruits on shoots. N availability for vegetative shoots was not affected by the presence or absence of fruits, which accumulated important amounts of N-15. In conclusion, our results show that shoot growth is resource-limited as a consequence of fruit development, and vegetative-growth inhibition is caused by photoassimilate limitation. The competence for N is not a decisive factor in limiting vegetative growth under the experimental conditions of this study. (C) 2014 Elsevier GmbH. All rights reserved
Comparative expression of candidate genes involved in sodium transport and compartmentation in citrus
No full textPlants possess a number of mechanisms to cope with sodium (Na+) under salt stress conditions that include minimizing Ne influx, maximizing efflux back to the growth medium or to apoplastic spaces via Na+/H+. antiporters in the plasma membrane, intracellular compartrnentation of Na+ into the vacuole, as well as recirculation of Na+ out of the shoot via the phloem. Na+ transport in plants constitutes a complex system, in which different Na+ transporters are closely related and their functions are matched tightly. The fact that in citrus under salt stress does chloride appear to be the more toxic ion has led to little attention being paid to Na+ uptake and transport mechanisms in citrus. The aim of this study was to provide insight into the links between the expression levels of candidate Na+ transporter genes (SOS1, NHX1, HKT1), as well as tonoplast proton pumps (V-ATPase, V-PPiase), and Na+ tolerance in two citrus rootstocks, Cleopatra mandarin and trifoliate orange, differing in their Na+ exclusion capacity under salt stress. According to the results of this preliminary study, we hypothesize that higher root Na+ concentration in trifoliate orange genotype, and thus lower allocation of this ion in the shoots, is the result of an enhanced retrieval of Na+ from xylem stream, and an impaired translocation to the shoot tissues, probably as a consequence of the overexpression of putative SOS1 (in roots) and HKT1 (both in roots and shoots). Moreover, the higher transcriptional levels of putative NHX1 found in roots and shoots of trifoliate orange plantlets compared to those of Cleopatra mandarin, together with the enhanced activity of the tonoplast proton pumps in the former, might reveal the preferential sequestration into vacuole of retrieved Na+ from xylem mainly in roots. (C) 2014 Published by Elsevier B.V
Phloem restriction of viroids in three citrus hosts is overcome by grafting with Etrog citron: potential involvement of a translocatable factor
No full textViroid systemic spread involves cell-to-cell movement from initially infected cells via plasmodesmata, long-distance movement within the phloem and again cell-to-cell movement to invade distal tissues including the mesophyll. Citrus exocortis viroid (CEVd), hop stunt viroid, citrus bent leaf viroid, citrus dwarfing viroid, citrus bark cracking viroid and citrus viroid V remained phloem restricted when singly infecting Citrus karna, Citrus aurantium and Poncirus trifoliata, but not Etrog citron, where they were additionally detected in mesophyll protoplasts. However, when CEVd-infected C. karna was side-grafted with Etrog citron with the resulting plants being composed of a C. karna stock and an Etrog citron branch the viroid was detected in mesophyll protoplasts of the former, thus indicating that the ability of Etrog citron to support viroid invasion of non-vascular tissues was transferred to the stock. Further results suggest that a translocatable factor from Etrog citron mediates this viroid trafficking
Acta Horticulturae
No full textCitrus tristeza virus (CTV) causes one of the most devastating diseases of citrus worldwide. It induces the death of sweet orange, mandarin, lime and grapefruit trees budded on sour orange which has caused its replacement by other CTV-tolerant rootstocks. The availability of a CTV-resistant rootstock with the sour orange attributes of productivity, fruit quality and tolerance to abiotic stresses would be a major benefit to the citrus industry worldwide. The objective of this work was to evaluate the response to CTV of 10 sour orange (Citrus aurantium) transgenic lines carrying CTV-derived sequences. They were obtained in the laboratories of IVIA, Spain and planted at INTA Experiment Station in Concordia, Argentina, where CTV is endemic and efficiently transmitted by the brown citrus aphid (Toxoptera citricida). Trees were obtained by budding rooted cuttings of transgenic sour orange lines with non-transgenic and virus-free Valencia late sweet orange (C. sinensis). Valencia trees budded on tolerant rootstocks as well as non-transgenic sour orange were planted as controls. Trees were planted in a complete randomized design with two trees per plot and 5 replications. Every six months imprints were taken to determine the progress of CTV infection in each tree. Four years after planting, almost 100% of the trees are CTV infected, showing stunting growth and yellowing of foliage
El cultivo del caqui
No full textEl caqui es un frutal caducifolio con un área de cultivo muy extensa, a pesar de estar considerado como un frutal subtropical. Su adaptación a diferentes tipos de climas es mayor que la de los cítricos, llegando a producir bien en las zonas templadas de clima mediterráneo, en toda el área de cultivo del melocotonero, hasta una latitud de unos 40º (Agustí, 2004). Al ser un frutal de hoja caduca necesita reposo invernal y tiene unas necesidades mínimas de horas frío (HF); así denominadas porque la temperatura es igual o inferior a 7,2º C. Las necesidades de horas frío de los cultivares o variedades no-astringentes es menor que las de los astringentes.
La gama completa es de unas 200-400 HF. Sin embargo, las variedades cultivadas en las comarcas de la ribera del Júcar (Valencia) se están mostrando poco exigentes, incluso por debajo de 200 HF no muestran ningún desarreglo fenológico. Un frío invernal insuficiente puede provocar el retraso en la caída de las hojas y una falta de uniformidad en la brotación en la primavera siguiente, que repercutirá en un deficiente cuajado de los frutos y una disminución de la cosecha