ReDivia - Repositorio Digital de l'Instit Valencià d'Investigacions Agràries
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Acta Horticulturae
No full textPersimmon trees (Diospyros kaki) belongs to the so-called group of minor fruit tree species. The main persimmon cultivar grown in Spain is ‘Rojo Brillante’, which produces an astringent fruit. This implies the need of deastringency post-harvest treatments prior commercialization. Persimmon growing in Spain is concentrated in an area of water scarcity, but there is no information about tree water needs or responses to deficit irrigation. With this in mind, an experiment was started with the objective to determine tree water needs and yield responses to water restrictions applied during different stages of fruit growth. Moreover the effect of the deficit irrigation period on the level of astringency at harvest and after a deastringency treatment with elevated CO2 were determined. Four irrigation treatments where applied including watering at 100% the estimated tree evapotranspiration during the entire season, and other three treatments where irrigation inputs were severely reduced but only during certain periods (spring, summer or fall). Water deficit, particularly if applied during spring or summer, reduced yield, mainly due to reduced fruit weight. However, water restrictions, particularly when applied late in the season lead to lower fruit firmness than the control. Therefore, this treatment accelerated fruit ripening. None of the deficit irrigation treatments affected the astringency level of the fruit at harvest or after the deastringency treatment
Nitrogen remobilization response to current supply in young citrus trees
No full textInternal nitrogen (N) storage and remobilization processes support seasonal growth (flowering/fructification and subsequent leaf development) in particular in early spring, when soil temperatures are unfavourable for adequate N uptake. Storage nitrogen mobilization in young citrus trees was studied under two contrasting N supplies; high N (HN) and low N dose (LN) in the critical period of flowering and fruit set. N-15 labelling technique was used to distinguish N derived from internal remobilization from that taken up by the roots. Regardless N supply, the greatest N remobilization took place from the beginning of the vegetative activity until flowering. Low N availability significantly increased (+14%) N retranslocation at the end of June drop agreeing with the hypothesis that reserve mobilization depends on soil N availability during flowering and fruit set. At the end of fruit drop, N remobilization contributed up to 70% and 61% of total N of young organs for LN and HN, respectively. Remobilized N was mainly recovered in abscised organs of both HN and LN trees and to a lesser extent in new flush leaves; however a greater percentage partitioned to abscised organs of LN as a consequence of the greater remobilization rate and the increased fruit abscission. Old leaves of LN remobilized significantly higher N, while woody organs and root system did not show differences between HN and LN supplied trees. The results presented in this paper demonstrate that the amount of N remobilized by young citrus plants depends on external N availability. Thus, low N application rates in early stages (flowering and fruit set) lead to higher translocation of N stored during the previous cycle to developing new organs
Actas Portuguesas de Horticultura
Get PDFLa producción de estátice en el sur de la Comunidad
Valenciana es de gran relevancia en la floricultura. Se trata de una especie halotolerante en la que, hoy por hoy, para el manejo de su fertirrigación se utilizan aguas de baja salinidad en la que se incorporan elevados contenidos de nutrientes. Tanto el hecho de que se consigan elevados rendimientos de calidad como el coste menor que suponen los fertilizantes respecto a los del resto de los insumos de cultivo, explican que esta práctica se haya establecido. Se sabe, sin embargo, que el estátice es una planta poco exigente en nutrientes minerales, por lo que son de suponer elevadas pérdidas de los mismos por lixiviación, que no son permisibles desde una perspectiva de sostenibilidad. Minimizar los aportes minerales sin que se produzcan mermas ni en el rendimiento ni en la calidad de la cosecha es un claro objetivo a perseguir. El periodo de recolección se inicia a final de octubre y es continuo hasta final de mayo con variaciones estacionales
de las tasas de producción. Este trabajo se plantea para conocer los efectos de la reducción en un 50% de los aportes minerales sobre el rendimiento y la calidad de la cosecha a lo largo del ciclo de cultivo.
Para ello, en un mismo invernadero y a lo largo de todo un ciclo de cultivo, se ha llevado el seguimiento y comparación de la producción de tallos florales de dos poblaciones de Limonium sinuatum cv. Duel
Violet, con la misma fecha de plantación. Para cada uno de los tratamientos, se han determinado semanalmente tanto la cantidad (número de tallos florales, pesos fresco y seco) como la calidad
(longitud de los tallos, de las panículas, relaciones peso seco vs peso fresco) de los tallos florales cosechados. Paralelamente, se han obtenido relaciones de la biomasa producida con respecto a la radiación interceptada y la integral térmica. No se muestran diferencias cualitativas entre ambos tratamientos en casi todo el periodo de cultivo. Cuantitativamente, desde noviembre hasta marzo
las respuestas de los tratamientos son similares, dependiendo el rendimiento tanto de la radiación interceptada como de la integral térmica, sin embargo, en primavera, con temperaturas medias elevadas y fotoperiodos más largos que revierten en mayores tasas de producción, la menor aportación mineral resulta en un ligero descenso del rendimiento en unidades totales al final del cultivo, que la planta compensa aumentando el peso de los tallos florales, y la calidad de los mismos
Shock absorbing surfaces for collecting fruit during the mechanical harvesting of citrus
Get PDFDamage to fresh citrus caused by impact of fruits onto collecting surfaces has restricted the adoption of mechanical harvesting. Two different experiments were carried out: investigating free-falling citrus and investigating the shock absorbing capacity of various surfaces. In free-falling experiment damage to mandarin, orange and lemon was studied. Three collecting surfaces were studied: a concrete floor, an elevated canvas provided with a frame and wheels, and a concrete floor covered with a shock absorbing canvases. Three dropping heights were used. In the shock absorbing experiment, an electronic sphere and a triaxial accelerometer were used to measure the shock capacity of seven receiving surfaces: earth, earth covered with a shock absorbing canvas, earth covered with weeds, earth covered with a mulch and an elevated canvas provided with a frame and wheels. The elevated canvases had a higher shock absorbing capacity compared to the other surfaces (260 m s(-2) maximum acceleration compared with 1753 m s(-2) to 2772 m s(-2)). Weeds, mulch and the shock absorbing canvases showed significantly higher shock absorbing capacity than the bare earth. Also, the shock absorbing canvas covering the concrete floor reduce impact and fruit damage (1866 m s(-2) maximum acceleration compared to 2477 m s(-2)). Citrus damage susceptibility during harvest depended on variety. Weeds, mulch and shock absorbing canvases were shown to reduce impact when they cover earth during the mechanical harvesting of citrus. Elevated canvases could be used as collection systems for the mechanical harvesting of fresh citrus
First Report of Bacterial Canker of Kiwifruit Caused by Pseudomonas syringae pv. actinidiae in Spain
No full textEffect of ground-cover management on spider mites and their phytoseiid natural enemies in clementine mandarin orchards (II): Top-down regulation mechanisms
No full textTetranychus urticae Koch (Acari: Tetranychidae) is a key pest of citrus that can also feed on most plant species occurring in the ground cover associated with this crop. To determine the effect of the management of the ground cover on the biological control of this mite, we have studied the dynamics of both tetranychid and phytoseiid mites in four commercial clementine mandarin orchards under three different ground cover management strategies: (1) bare soil, (2) resident wild cover and (3) a sown cover of Festuca arundinacea Schreb. (Poaceae). Our results provide evidence that the management of ground cover can affect both Tetranychid and Phytoseiid mite populations. We hypothesize that both natural enemies (top-down mechanisms) and plant resources (bottom-up mechanisms, discussed in a previous paper) play important regulatory roles. T. urticae specialist phytoseiid mites were consistently found in the F. arundinacea cover and this may explain the better regulation of Tetranychid mite populations on trees grown in association with this cover crop. In contrast, the more regular provision of alternative food (pollen) in the wild cover relative to the F. arundinacea cover, could explain the higher abundance of generalist pollen feeder phytoseiids in the former. As a result, more efficient T. urticae-specialized phytoseiids could suffer increased competition from generalist pollen feeders in the wild cover. This fact, in combination with periods of prey scarcity, could result in their disappearance from the agroecosystem, resulting in an inadequate control of Tetranychid mites in trees grown in association with a wild cover
Pantoea applied genomics to understand and improve biocontrol activity against fire blight
No full textPantoea agglomerans and P. vagans (ex. Erwinia herbicola) are common epiphytes of pome fruit flowers and three strains (E325, P10c, C9-1) have been commercially developed as effective biocontrol products for managing
fire blight (Erwinia amylovora
Erwinia piriflorinigrans sp. nov., a novel pathogen that causes necrosis of pear blossoms
No full textEight Erwinia strains, isolated from necrotic pear blossoms in Valencia, Spain, were compared with reference strains of Erwinia amylovora and Erwinia pyrifoliae, both of which are pathogenic to species of pear tree, and to other species of the family Enterobacteriaceae using a polyphasic approach. Phenotypic analyses clustered the novel isolates into one phenon, distinct from other species of the genus Erwinia, showing that the novel isolates constituted a homogeneous phenotypic group. Rep-PCR profiles, PCR products obtained with different pairs of primers and plasmid contents determined by restriction analysis showed differences between the novel strains and reference strains of E. amylovora and E. pyrifoliae. Phylogenetic analysis of 16S rRNA, gpd and recA gene sequences showed that the eight novel strains could not be assigned to any recognized species. On the basis of DNA-DNA hybridization studies, the novel isolates constituted a single group with relatedness values of 87-100% to the designated type strain of the group, CFBP 5888(T). Depending on the method used, strain CFBP 5888(T) showed DNA DNA relatedness values of between 22.7 and 50% to strains of the closely related species E. amylovora and E. tasmaniensis. The DNA G+C contents of two of the novel strains, CFBP 5888(T) and CFBP 5883, were 51.1 and 50.5 mol%, respectively. On the basis of these and previous results, the novel isolates represent a novel species of the genus Erwinia, for which the name Erwinia piriflorinigrans sp. nov. is proposed. The type strain is CFBP 5888(T) (=CECT 7348(T))
Estimation of Leaf Wetness Duration Requirements of Foliar Fungal Pathogens with Uncertain Data-An Application to Mycosphaerella nawae
No full textWetness of the host surface is a critical environmental factor for the development of foliar fungal diseases, but it is difficult to estimate the wetness durations required by pathogens for infection when only few experimental data are available. In this paper, we propose a method to estimate wetness duration requirements of foliar fungal pathogens when precise experimental data are not available. The proposed method is based on approximate Bayesian computation. It only requires lower and upper bounds of wetness duration requirements for one or fewer temperatures. We describe the method, show how to apply it to an infection model, and then present a case study on Mycosphaerella nowae, the causal agent of circular leaf spot of persimmon. In this example, the parameters of a simple infection model were estimated using experimental data found in the literature for the pathogen, and the model was applied to assess the risk in a Spanish area recently affected by the disease. The results showed that the probability of successful infection was higher than 0.5 for 32% of the on-site wetness durations recorded in the affected area. Results obtained with simulated data showed that our method was able to improve the estimation of wetness duration requirement. Given the flexibility of the proposed method, we expect it to become adopted for assessing the risk of introduction of exotic fungal plant pathogens