Citricultura. El cuajado del fruto. Polinización y partenocarpia. Las giberelinas

El objeto de aprendizaje describe la relación entre el cuajado, bien sea sexual o asexual, y las giberelinas.Mesejo Conejos, C. (2012). Citricultura. El cuajado del fruto. Polinización y partenocarpia. Las giberelinas. http://hdl.handle.net/10251/1689

The flower to fruit transition in Citrus is partially sustained by autonomous carbohydrate synthesis in the ovary

[EN] Why evergreen fruit tree species accumulate starch in the ovary during flower bud differentiation in spring, as deciduous species do during flower bud dormancy, is not fully understood. This is because in evergreen species carbon supply is assured by leaves during flower development. We suggest the existence of an autonomous mechanism in the flowers which counteracts the competition for photoassimilates with new leaves, until they become source organs. Our hypothesis is that starch accumulated during Citrus ovary ontogeny originates from 1) its own photosynthetic capacity and 2) the mobilization of reserves. Through defoliation experiments, we found that ovaries accumulate starch during flower ontogeny using a dual mechanism: 1) the autotrophic route of source organs activating Rubisco (RbcS) genes expression, and 2) the heterotrophic route of sink organs that hydrolyze sucrose in the cytosol. Defoliation 40 days before anthesis did not significantly reduce ovary growth, flower abscission or starch concentration up to 20 days after anthesis (i.e. 60 days later). Control flowers activated the energy depletion signaling system (i.e. SnRK1) and RbcS gene expression around athesis. Defoliation accelerated and boosted both activities, increasing SPS gene expression (sucrose synthesis), and SUS1, SUS3 and cwINV (sucrose hydrolysis) to maintain a glucose threshold which satisfied its need to avoid abscission.Mesejo Conejos, C.; Martinez Fuentes, A.; Reig Valor, C.; Agustí Fonfría, M. (2019). The flower to fruit transition in Citrus is partially sustained by autonomous carbohydrate synthesis in the ovary. Plant Science. 285:224-229. https://doi.org/10.1016/j.plantsci.2019.05.014S22422928

Warm temperature during floral bud transition turns off EjTFL1 gene expression and promotes flowering in Loquat (Eriobotrya japonica Lindl)

[EN] The Rosaceae family includes several deciduous woody species whose flower development extends over two consecutive growing seasons with a winter dormant period in between. Loquat (Eriobotrya japonica Lindl.) belongs to this family, but it is an evergreen species whose flower bud initiation and flowering occur within the same growing year. Vegetative growth dominates from spring to late summer when terminal buds bloom as panicles. Thus, its floral buds do not undergo winter dormancy until flowering, but a summer heat period of dormancy is required for floral bud differentiation, and that is why we used loquat to study the mechanism by which this summer rest period contributes to floral differentiation of Rosaceae species. As for the deciduous species, the bud transition to the generative stage is initiated by the floral integrator genes. There is evidence that combinations of environmental signals and internal cues (plant hormones) control the expression of TFL1, but the mechanism by which this gene regulates its expression in loquat needs to be clarified for a better understanding of its floral initiation and seasonal growth cycles. Under high temperatures (>25 & DEG;C) after floral bud inductive period, EjTFL1 expression decreases during meristem transition to the reproductive stage, and the promoters of flowering (EjAP1 and EjLFY) increase, indicating that the floral bud differentiation is affected by high temperatures. Monitoring the apical meristem of loquat in June-August of two consecutive years under ambient and thermal controlled conditions showed that under lower temperatures (<25 & DEG;C) during the same period, shoot apex did not stop growing and a higher EjTFL1 expression was recorded, preventing the bud to flower. Likewise, temperature directly affects ABA content in the meristem paralleling EjTFL1 expression, suggesting signaling cascades could converge to refine the expression of EjTFL1 under specific conditions (T<25 & DEG;C) during the floral transition stage.García-Lorca, A.; Reig Valor, C.; Martinez Fuentes, A.; Agustí Fonfría, M.; Mesejo Conejos, C. (2023). Warm temperature during floral bud transition turns off EjTFL1 gene expression and promotes flowering in Loquat (Eriobotrya japonica Lindl). Plant Science. 335. https://doi.org/10.1016/j.plantsci.2023.11181033

Loquat Fruit Lacks a Ripening-Associated Autocatalytic Rise in Ethylene Production

[EN] Loquat is considered as a non-climacteric fruit; however, there is an evidence of a climacteric-like maturation. Therefore, it seems its ripening behavior has yet to be satisfactory classified. Because autocatalytic regulation of ethylene production during fruit ripening is one of the primary features defining climacteric-like fruit maturation, we examined its ability of autocatalysis during ripening by applying the ethylene-releasing compound ethephon to the on-tree-fruit or ethylene to detached fruit of 'Algerie' loquat and measuring its ethylene and CO2 production. We also analyzed indoleacetic acid (IAA), gibberellin, cytokinin, and abscisic acid (ABA) contents as plant hormones involved in fruit ripening. The fruit response to ethephon (500 mg l(-1)) applied at color change was immediate producing increasing amounts of ethylene during the 4 h following the treatment, but 24 h after treatment onward values were similar to those produced by untreated fruit. Similar results were obtained when applying ethylene to detached fruit (10 mu l l(-1)). Accordingly, applying ethephon (200 mg l(-1)) did not advance harvest; neither the color nor the percentage of fruit harvested at the first picking date differed significantly from the untreated fruit. Flesh firmness, total soluble solid concentration, and acidity of juice were not significantly altered either. IAA concentration reached the maximum value when fruit stopped growing, declining sharply at fruit color change; active gibberellins and cytokinins declined continuously during the fruit growth period, and ABA content sharply increased during ripening, peaking after fruit color break. Results indicate that 'Algerie' loquat lacks a ripening-associated autocatalytic rise in ethylene production, and suggest that a decline in gibberellin, cytokinin, and IAA concentrations might be needed to allow its ripening process to proceed.Reig Valor, C.; Martínez Fuentes, A.; Mesejo Conejos, C.; Rodrigo, M.; Zacarias Garcia, L.; Agustí Fonfría, M. (2016). Loquat Fruit Lacks a Ripening-Associated Autocatalytic Rise in Ethylene Production. Journal of Plant Growth Regulation. 35(1):232-244. doi:10.1007/s00344-015-9528-3S232244351Agustí M, Guardiola JL, Almela V (1981) The regulation of fruit cropping in mandarins through the use of growth regulators. Proc Int Soc Citric 1:216–220Amorós A, Zapata P, Pretel MT, Botella MA, Serrano M (2003) Physicochemical and physiological changes during fruit development and ripening of five loquat (Eriobotrya japonica Lindl.) cultivars. 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Tree water status influences fruit splitting in Citrus

[EN] Fruit splitting or cracking is a major physiological disorder in fruit trees markedly influenced by environmental conditions, but conclusive data still are required to provide a definite explanation and preventive measures. Changes in climatic conditions critically influence fruit splitting incidence. We studied plant-soil-ambient water relations in splitting-prone citrus grown under 4 contrasting environmental conditions (climate type and soil), in Spain and Uruguay, over a six years period. Automatic trunk and fruit diameter measurements (trunk and fruit growth rate and maximum daily trunk shrinkage), which are a tree water status indicator, together with factors modifying the tree and fruit water relationship (temperature, ET, rainfall, soil texture, soil moisture, rootstock and xylem anatomy) were studied and correlated with splitting. A close fruit splitting and soil texture relationship was found, inversely correlated with clay and silt percentages, and positively with those for sand. Under 85%-sand soil conditions, slight changes in soil moisture due to fluctuations in temperature, ET, or rainfall changed trunk and fruit growth rate patterns during few hours and induced splitting. Splitting incidence was higher in trees with larger xylem vessels in the fruit peduncle due to rootstock ('Carrizo' and 'C-35' citrange being higher than 'FA-5', 'Cleopatra' and Poncirus trifoliata). Finally, reducing the frequency of irrigation by half increased midday canopy temperatures (similar to 5 degrees C) and splitting (+15%). We conclude that irregularities in the tree water status, due to interactions among soil moisture, rootstock and climatic conditions, leads to a number of substantial changes in fruit growth rate increasing the incidence of fruit splitting. (C) 2016 Elsevier B.V. All rights reserved.Mesejo Conejos, C.; Reig Valor, C.; Martinez Fuentes, A.; Gambetta, G.; Gravina Telechea, A.; Agustí Fonfría, M. (2016). Tree water status influences fruit splitting in Citrus. Scientia Horticulturae. 209:96-104. doi:10.1016/j.scienta.2016.06.009S9610420

Ethylene biosynthesis and perception during ripening of loquat fruit (Eriobotrya japonica Lindl.)

[EN] In order to gain insights into the controversial ripening behavior of loquat fruits, in the present study we have analyzed the expression of three genes related to ethylene biosynthesis (ACS1, ACO1 and ACO2), two ethylene receptors (ERS1a and ERS1b), one signal transduction component (CTR1) and one transcription factor (EIL1) in peel and pulp of loquat fruit during natural ripening and also in fruits treated with ethylene (10 mu LL-1) and 1-MCP (10 mu LL-1), an ethylene action inhibitor. In fruits attached to or detached from the tree, a slight increase in ethylene production was detected at the yellow stage, but the respiration rate declined progressively during ripening. Accumulation of transcripts of ethylene biosynthetic genes did not correlate with changes in ethylene production, since the maximum accumulation of ACS1 and ACO1 mRNA was detected in fully coloured fruits. Expression of ethylene receptor and signaling genes followed a different pattern in peel and pulp tissues. After fruit detachment and incubation at 20 degrees C for up to 6 days, ACS1 mRNA slightly increased, ACO1 experienced a substantial increment and ACO2 declined. In the peel, these changes were advanced by exogenous ethylene and partially inhibited by 1-MCP. In the pulp, 1-MCP repressed most of the changes in the expression of biosynthetic genes, while ethylene had almost no effects. Expression of ethylene perception and signaling genes was barely affected by ethylene or 1-MCP. Collectively, a differential transcriptional regulation of ethylene biosynthetic genes operates in peel and pulp, and support the notion of non-climacteric ripening in loquat fruits. Ethylene action, however, appears to be required to sustain or maintain the expression of specific genes. (C) 2016 Published by Elsevier GmbH.Enriqueta Alos was recipient of a post-doctoral contract JAE-DocCSIC (Fondo Social Europeo). The financial support of the researchgrants FP7-PEOPLE-2011-CIG-2011-303652 (Marie Curie Actions, European Union), AGL-2009-11558 and AGL-2012-34573 (Ministerio Economia y Competitividad, Spain), GV/2012/036 (Generalitat Valenciana, Spain) and PROMETEOII 2014/27 (Generalitat Valenciana) is gratefully acknowledged.Alós, E.; Martinez Fuentes, A.; Reig Valor, C.; Mesejo Conejos, C.; Rodrigo, M.; Agustí Fonfría, M.; Zacarias, L. (2017). Ethylene biosynthesis and perception during ripening of loquat fruit (Eriobotrya japonica Lindl.). Journal of Plant Physiology. 210:64-71. https://doi.org/10.1016/j.jplph.2016.12.008S647121

Involvement of ethylene in color changes and carotenoid biosynthesis in loquat fruit (Eriobotrya japonica Lindl. cv. Algerie)

[EN] In loquat (Eriobotrya japonica Lindl cv. Algerie) fruit, despite the non-climacteric ripening behaviour, evidence suggest that ethylene may participate in the regulation of several ripening- and postharvest-related processes. Color changes and carotenoid profile were analyzed in fruit at three developmental stages (breaker, yellow and colored fruits). At early stages, the fruit peel contained phytoene, phytofluene and other typical chloroplastic carotenoids that decreased during ripening, to accumulate ß-carotene, violaxanthin and ß-cryptoxanthin in mature fruits. In the pulp, carotenoid concentration increased during ripening to become predominant phytoene, followed by ß-carotene and ß-cryptoxanthin. Expression of the carotenoid biosynthetic genes (PSY, PDS, ZDS, CYCB and BCH) was downregulated in the peel during maturation, but increased in the pulp with the exception of BCH. The involvement of ethylene in the regulation of pigmentation was further evaluated by treating fruits at the three ripening stages with ethylene or its action inhibitor 1-MCP. At breaker fruit, ethylene accelerated and 1-MCP delayed fruit coloration, but the effect was progressively lost as fruit matured. Ethylene and 1-MCP produced different changes in carotenoids content and gene expression in peel and pulp. Application of ethylene enhanced ß-carotene content in both tissues whereas ß-cryptoxanthin was only stimulated in the pulp. 1-MCP suppressed these changes in carotenoid composition in the pulp but had little effect in the peel. A differential transcriptional level the pulp was more responsive to downregulated gene expression than the peel. Collectively, results indicate that: 1) ethylene is involved in the regulation of pigmentation and carotenoid biosynthesis in loquat fruits, 2) a differential regulation of carotenoid biosynthesis and response to ethylene appear to operate in the peel and the pulp, and 3) ß-carotene hydroxylase (BCH) is a key step in the regulation of carotenoid content and composition in both tissues of loquat fruit.Dr. E. Alos was recipient a post-doctoral contract JAE-Doc-CSIC (Fondo Social Europeo). The financial support of the research grants FP7-PEOPLE-2011-CIG-2011-303652 (Marie Curie Actions, European Union), AGL-2015-70218 (Ministerio Economia y Competitividad, Spain), GV/2012/036 (GeneralitatValenciana, Spain) and PROMETEO-II 2014/27 (Generalitat Valenciana) are gratefully acknowledged. MJR and LZ are members of Eurocaroten (COST_Action CA15136) and CaRed (Spanish Carotenoid Network, BIO2015-71703-REDT and BIO2017-90877-REDT).Alós, E.; Martinez Fuentes, A.; Reig Valor, C.; Mesejo Conejos, C.; Zacarias, L.; Agustí Fonfría, M.; Rodrigo-Esteve, MJ. (2019). Involvement of ethylene in color changes and carotenoid biosynthesis in loquat fruit (Eriobotrya japonica Lindl. cv. Algerie). Postharvest Biology and Technology. 149:129-138. https://doi.org/10.1016/j.postharvbio.2018.11.022S12913814

Genetic inhibition of flowering differs between juvenile and adult Citrus trees

[EN] Background and Aims In woody species, the juvenile period maintains the axillary meristems in a vegetative stage, unable to flower, for several years. However, in adult trees, some 1-year-old meristems flower whereas others remain vegetative to ensure a polycarpic growth habit. Both types of trees, therefore, have non-flowering meristems, and we hypothesize that the molecular mechanism regulating flower inhibition in juvenile trees is different from that in adult trees. Methods In adult Citrus trees, the main endogenous factor inhibiting flower induction is the growing fruit. Thus, we studied the expression of the main flowering time, identity and patterning genes of trees with heavy fruit load (not-flowering adult trees) compared to that of 6-month-old trees (not-flowering juvenile trees). Adult trees without fruits (flowering trees) were used as a control. Second, we studied the expression of the same genes in the meristems of 6-month, and 1-, 3-, 5-and 7-year-old juvenile trees compared to 10-year-old flowering trees. Key Results The axillary meristems of juvenile trees are unable to transcribe flowering time and patterning genes during the period of induction, although they are able to transcribe the FLOWERING LOCUS T citrus orthologue (CiFT2) in leaves. By contrast, meristems of not-flowering adult trees are able to transcribe the flowering network genes but fail to achieve the transcription threshold required to flower, due to CiFT2 repression by the fruit. Juvenile meristems progressively achieve gene expression, with age-dependent differences from 6 months to 7 years, FD-like and CsLFY being the last genes to be expressed. Conclusions During the juvenile period the mechanism inhibiting flowering is determined in the immature bud, so that it progressively acquires flowering ability at the gene expression level of the flowering time programme, whereas in the adult tree it is determined in the leaf, where repression of CiFT2 gene expression occurs.We thank Cristina Ferrandiz (IBMCP-UPV, Spain) and Fernando Andres (UMR AGAP, France) for useful comments on the manuscript. We thank D. Westall for her help in editing the manuscript. This work was supported by a grant from the Ministerio de Economia y Competitividad, Spain (RTA2013-0024-C02-02)Muñoz Fambuena, N.; Nicolas-Almansa, M.; Martinez Fuentes, A.; Reig Valor, C.; Iglesias, DJ.; Primo-Millo, E.; Mesejo Conejos, C.... (2019). Genetic inhibition of flowering differs between juvenile and adult Citrus trees. Annals of Botany. 123(3):483-490. https://doi.org/10.1093/aob/mcy179S4834901233Abe, M. (2005). FD, a bZIP Protein Mediating Signals from the Floral Pathway Integrator FT at the Shoot Apex. Science, 309(5737), 1052-1056. doi:10.1126/science.1115983Albani, M. C., & Coupland, G. (2010). Comparative Analysis of Flowering in Annual and Perennial Plants. Plant Development, 323-348. doi:10.1016/s0070-2153(10)91011-9Andrés, F., & Coupland, G. (2012). The genetic basis of flowering responses to seasonal cues. Nature Reviews Genetics, 13(9), 627-639. doi:10.1038/nrg3291Balanzà, V., Martínez-Fernández, I., Sato, S., Yanofsky, M. F., Kaufmann, K., Angenent, G. C., … Ferrándiz, C. (2018). Genetic control of meristem arrest and life span in Arabidopsis by a FRUITFULL-APETALA2 pathway. Nature Communications, 9(1). doi:10.1038/s41467-018-03067-5Bäurle, I., & Dean, C. (2006). The Timing of Developmental Transitions in Plants. Cell, 125(4), 655-664. doi:10.1016/j.cell.2006.05.005Betancourt, M., Sistachs, V., Martínez-Fuentes, A., Mesejo, C., Reig, C., & Agustí, M. (2014). Influence of harvest date on fruit yield and return bloom in ‘Marsh’ grapefruit trees (Citrus paradisiMacf.) grown under a tropical climate. The Journal of Horticultural Science and Biotechnology, 89(4), 435-440. doi:10.1080/14620316.2014.11513103Blázquez, M. A., Ferrándiz, C., Madueño, F., & Parcy, F. (2006). How Floral Meristems are Built. Plant Molecular Biology, 60(6), 855-870. doi:10.1007/s11103-006-0013-zBlümel, M., Dally, N., & Jung, C. (2015). Flowering time regulation in crops — what did we learn from Arabidopsis? Current Opinion in Biotechnology, 32, 121-129. doi:10.1016/j.copbio.2014.11.023Castillo, M.-C., Forment, J., Gadea, J., Carrasco, J. L., Juarez, J., Navarro, L., & Ancillo, G. (2013). Identification of transcription factors potentially involved in the juvenile to adult phase transition in Citrus. Annals of Botany, 112(7), 1371-1381. doi:10.1093/aob/mct211Chica, E. J., & Albrigo, L. G. (2013). Expression of Flower Promoting Genes in Sweet Orange during Floral Inductive Water Deficits. Journal of the American Society for Horticultural Science, 138(2), 88-94. doi:10.21273/jashs.138.2.88Endo, T., Shimada, T., Fujii, H., Kobayashi, Y., Araki, T., & Omura, M. (2005). Ectopic Expression of an FT Homolog from Citrus Confers an Early Flowering Phenotype on Trifoliate Orange (Poncirus trifoliata L. Raf.). Transgenic Research, 14(5), 703-712. doi:10.1007/s11248-005-6632-3Haberman, A., Ackerman, M., Crane, O., Kelner, J.-J., Costes, E., & Samach, A. (2016). Different flowering response to various fruit loads in apple cultivars correlates with degree of transcript reaccumulation of a TFL1-encoding gene. The Plant Journal, 87(2), 161-173. doi:10.1111/tpj.13190Hanano, S., & Goto, K. (2011). Arabidopsis TERMINAL FLOWER1 Is Involved in the Regulation of Flowering Time and Inflorescence Development through Transcriptional Repression. 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Fruit regulates seasonal expression of flowering genes in alternate-bearing ‘Moncada’ mandarin. Annals of Botany, 108(3), 511-519. doi:10.1093/aob/mcr164Muñoz-Fambuena, N., Mesejo, C., González-Mas, M. C., Primo-Millo, E., Agustí, M., & Iglesias, D. J. (2012). Fruit load modulates flowering-related gene expression in buds of alternate-bearing ‘Moncada’ mandarin. Annals of Botany, 110(6), 1109-1118. doi:10.1093/aob/mcs190Nishikawa, F., Endo, T., Shimada, T., Fujii, H., Shimizu, T., Omura, M., & Ikoma, Y. (2007). Increased CiFT abundance in the stem correlates with floral induction by low temperature in Satsuma mandarin (Citrus unshiu Marc.). Journal of Experimental Botany, 58(14), 3915-3927. doi:10.1093/jxb/erm246Peña, L., Martín-Trillo, M., Juárez, J., Pina, J. A., Navarro, L., & Martínez-Zapater, J. M. (2001). Constitutive expression of Arabidopsis LEAFY or APETALA1 genes in citrus reduces their generation time. Nature Biotechnology, 19(3), 263-267. doi:10.1038/85719Pillitteri, L. 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Bud sprouting and floral induction and expression of FT in loquat [Eriobotrya japonica (Thunb.) Lindl.]

[EN] EjFT1 and EjFT2 genes were isolated and sequenced from leaves of loquat. EjFT1 is involved in bud sprouting and leaf development, and EjFT2 in floral bud induction. Loquat [Eriobotrya japonica (Thunb.) Lindl.] is an evergreen species belonging to the family Rosaceae, such as apple and pear, whose reproductive development, in contrast with these species, is a continuous process that is not interrupted by winter dormancy. Thus, the study of the mechanism of flowering in loquat has the potential to uncover the environmental and genetic networks that trigger flowering more accurately, contributing for a better understanding of the Rosaceae floral process. As a first step toward understanding the molecular mechanisms controlling flowering, extensive defoliation and defruiting assays, together with molecular studies of the key FLOWERING LOCUS T (FT) gene, were carried out. FT exhibited two peaks of expression in leaves, the first one in early to mid-May, the second one in mid-June. Two FT genes, EjFT1 and EjFT2, were isolated and sequenced and studied their expression. Expression of EjFT1 and EjFT2 peaks in mid-May, at bud sprouting. EjFT2 expression peaks again in mid-June, coinciding with the floral bud inductive period. Thus, when all leaves of the tree were continuously removed from early to late May vegetative apex differentiated into panicle, but when defoliation was performed from early to late June apex did not differentiate. On the other hand, fruit removal advanced EjFT1 expression in old leaves and the sooner the fruit detached, the sooner the bud sprouted. Accordingly, results strongly suggest that EjFT1 might be related to bud sprouting and leaf development, while EjFT2 might be involved in floral bud induction. An integrative model for FT functions in loquat is discussed.This work was supported by Grants BIO2011-26302 (Spanish Ministry of Science and Innovation) for M. A. Perez-Amador, and RTA2013-00024-C02-02 (Instituto Nacional de Investigaciones y Tecnologia Agraria y Alimentaria-Ministerio de Economia y Competitividad) for C. Reig. The authors thank Dr. P. M. Hernandez-Delgado and Dr. V. Galan (Insituto Canario de Iinvestigaciones Agrarias, Tenerife, Spain) for their collaboration and Debra Westall (Universidad Politecnica de Valencia) for revising the manuscript.Reig Valor, C.; Gil-Muñoz, F.; Vera-Sirera, F.; Garcia-Lorca, A.; Martínez Fuentes, A.; Mesejo Conejos, C.; Perez Amador, MA.... (2017). Bud sprouting and floral induction and expression of FT in loquat [Eriobotrya japonica (Thunb.) Lindl.]. Planta. 246(5):915-925. https://doi.org/10.1007/s00425-017-2740-6S9159252465Agustí M, Reig C (2006) Fisiología. In: Agustí M, Reig C, Undurraga P (eds) El cultivo del níspero japonés. Gráficas Alcoy, Alcoy, pp 97–129Batten DJ, McConchie CA (1995) Floral induction in growing buds of lychee (Litchi chinensis) and mango (Mangifera indica). Aust J Plant Physiol 22:783–791Bernier G, Kinet J-M, Sachs RM (1981) The flowering process at the shoot apex: macromorphological events. In: Bernier G, Kinet J-M, Sachs RM (eds) The physiology of flowering, vol II. Transition to reproductive growth. CRC Press, Boca Raton, pp 21–34Bustin SA (2002) Quantification of mRNA using real-time reverse transcription PCR (RT-PCR): trends and problems. J Mol Endocrinol 29:23–39Carmona MJ, Calomje M, Martínez-Zapater JM (2007) The FT/TFL1 gene family in grapevine. Plant Mol Biol 63:637–650Chen Y, Jiang P, Thammannagowda S, Liang H, Wild GD (2013) Characterization of peach TFL1 and comparison with FT/TFL1 gene families of the Rosaceae. J Am Soc Hortic Sci 138:12–17Doyle JJ, Doyle JL (1987) A rapid isolation procedure for small quantities of fresh leaf tissue. Phytochem Bull 19:11–15Endo T, Shimada T, Fujii H, Kobayashi Y, Araki T, Omura M (2005) Ectopic expression of an FT homolog from Citrus confers an early flowering phenotype on trifoliate orange (Poncirus trifoliata L. Raf.). Transgenic Res 14:703–712Esumi T, Tao R, Yanemori K (2005) Isolation of LEAFY and TERMINAL FLOWER 1 homologues from six fruit tree species in the subfamily Maloideae of the Rosaceae. Sex Plant Reprod 17:277–287Esumi T, Hagihara C, Kitamura Y, Yamane H, Tao R (2009) Identification of an FT ortholog in Japanese apricot (Prunus mume Sieb. et Zucc.). J Hortic Sci Biotechnol 84:149–154Evans RC, Campbell CS (2002) The origin of the apple subfamily (Maloideae; Rosaceae) is clarified by DNA sequence data from duplicated GBSSI genes. Am J Bot 89:1478–1484Fatta del Bosco G (1961) Indagini sull’epoca di differenziazione delle gemme nel nespolo del giappone. Riv Ortoflorofruttic Ital XLV 2:104–118Gisbert AD, Martínez-Calvo J, Llácer G, Badenes ML, Romero C (2009) Development of two loquat [Eriobotrya japonica (Thunb.) Lindl.] linkage maps based on AFLPs and SSR markers from different Rosaceae species. Mol Breed 23:523–538Hanke M-V, Flachowsky H, Peil A, Hättasch C (2007) No flower no fruit—genetic potential to trigger flowering in fruit trees. Genes Genomes Genom 1:1–20Hättasch C, Flachowsky H, Kaptrska D, Hank M-V (2008) Isolation of flowering genes and seasonal changes in their transcript levels related to flower induction and initiation in apple (Malus domestica). Tree Physiol 28:1459–1466Hiraoka K, Yamaguchi A, Abe M, Araki T (2013) The florigen genes FT and TSF modulate lateral shoot outgrowth in Arabidopsis thaliana. 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Hydrated Lime Soil Coverage: Effect On Soil Temperature Reduction And Early Mandarin Colour Break

[EN] Citrus fruit colour is an important marketing feature. In view of the relative independence between internal and external maturity, in early mandarins fruit harvest takes place before reaching fruit full colouration. Since citrus fruit colour break is associated to natural temperature reduction, this work evaluated the efficiency of hydrated lime soil coverage on the advance of fruit colour break of Satsuma and Clementine. Experiments were carried out in Spain (Satsuma 'Iwasaki' and Clementina 'Clemenpons', grafted on citrange 'Carrizo') and in Uruguay (Satsuma 'Okitsu' and 'Clementina de Nules', grafted on P. trifoliata). Hydrated lime was applied between two and four months before harvest. Treatment diminished soil temperature between 0.5 °C and 3 °C in all situations. In Satsuma, treatment could not advance colour break, since soil temperature remained above 23 °C and 18 °C, thresholds below which root metabolism of citrange 'Carrizo' and P. trifoliata, respectively, is reduced. In Clementine, maturing two months later, the soil temperature remained below thresholds during at least one month before harvest, significantly advancing fruit colour break and increasing the percentage of fruit harvested early[ES] El color de los frutos cítricos es una característica importante para su comercialización. En la medida en que la maduración interna y externa presentan una regulación relativamente independiente, en las mandarinas precoces la cosecha de los frutos se realiza sin haber alcanzado la coloración adecuada para su comercialización. Considerando que el cambio de color de los frutos cítricos se asocia a la disminución de la temperatura, en este trabajo se evaluó la eficacia de la cobertura del suelo con cal en el adelanto del cambio de color de mandarinas Satsuma y Clementina. Los experimentos se realizaron en España (Satsuma 'Iwasaki' y Clementina 'Clemenpons', injertados sobre citrange 'Carrizo') y en Uruguay (Satsuma 'Okitsu' y 'Clementina de Nules', injertados sobre P. trifoliata). La cal se aplicó entre los dos y cuatro meses previos a la cosecha. El tratamiento disminuyó la temperatura del suelo entre 0,5 °C y 3 °C en todas las situaciones. En Satsuma el tratamiento no logró anticipar el cambio de color, ya que la temperatura del suelo permaneció por encima de 23 °C y 18 °C, umbrales por debajo de los cuales disminuye la actividad de las raíces de citrange 'Carrizo' y P. trifoliata. En Clementina, que madura dos meses más tarde, la temperatura del suelo permaneció por debajo de los umbrales durante por lo menos un mes antes de la cosecha, adelantando significativamente la coloración de los frutos y permitiendo incrementar el porcentaje cosechado en forma temprana.A las empresas Agrimarba S.A. (España), Frutícola Libertad S.A., El Repecho, S.A. y Antonio De Souza e hijos (Uruguay). Trabajo parcialmente financiado por el Programa ALßan, becas de alto nivel de la Unión Europea para América Latina (NI E03D15012UR) y la Comisión Sectorial de Investigación Científica (Universidad de la República, Uruguay).Gambetta Romaso, G.; Mesejo Conejos, C.; Gravina Telechea, A.; Agustí Fonfría, M.; Fasiolo, C.; Rey, F.; Reig Valor, C.... (2015). Cobertura del suelo con cal: efecto de la reducción de la temperatura y cambio de color de las mandarinas precoces. Agrociencia. 19(1):31-40. http://hdl.handle.net/10251/73903S314019