ReDivia - Repositorio Digital de l'Instit Valencià d'Investigacions Agràries
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Ants impact the energy reserves of natural enemies through the shared honeydew exploitation
Get PDF1. Ants, as well as many species of parasitoids and predators, rely on sugar-rich foods such as honeydew to fulfill their energetic needs. Thus, ants and natural enemies may interact through the shared honeydew exploitation. 2. Ant-exclusion experiments were performed in a citrus orchard to test the hypothesis that ants may impact the energy reserves of predators and parasitoids through the competition for honeydew. Through the use of high-performance liquid chromatography (HPLC) the level of ant activity with the energy reserves and feeding history of individual specimens collected in the field during representative days of spring, summer, and autumn were related. 3. Out of 145 Aphytis chrysomphali Mercet parasitoids captured in the field, 65% were classified as sugar-fed and 24.7% as honeydew-fed. In summer, when ant activity peaked, there was a significant negative correlation between the level of ant activity and the total sugar content and honeydew feeding incidence by A. chrysomphali. Out of 47 individuals of the predator Chrysoperla carnea sensu lato (Stephens), captured in the field, 55.3% were classified as sugar-fed. We found a significant negative effect of the level of ant activity on the sugar-feeding incidence by C. carnea in spring. 4. The present study provides evidence that ants can interfere with the energy reserves of natural enemies. This interaction may be widespread in various ecosystems with important consequences for the arthropod community composition and with practical implications for biological control given that absence of sugar feeding is detrimental for the fitness of many species of predators and parasitoids
A Phylogenetic Analysis of 34 Chloroplast Genomes Elucidates the Relationships between Wild and Domestic Species within the Genus Citrus
Get PDFCitrus genus includes some of the most important cultivated fruit trees worldwide. Despite being extensively studied because of its commercial relevance, the origin of cultivated citrus species and the history of its domestication still remain an open question. Here, we present a phylogenetic analysis of the chloroplast genomes of 34 citrus genotypes which constitutes the most comprehensive and detailed study to date on the evolution and variability of the genus Citrus. A statistical model was used to estimate divergence times between the major citrus groups. Additionally, a complete map of the variability across the genome of different citrus species was produced, including single nucleotide variants, heteroplasmic positions, indels (insertions and deletions), and large structural variants. The distribution of all these variants provided further independent support to the phylogeny obtained. An unexpected finding was the high level of heteroplasmy found in several of the analyzed genomes. The use of the complete chloroplast DNA not only paves the way for a better understanding of the phylogenetic relationships within the Citrus genus but also provides original insights into other elusive evolutionary processes, such as chloroplast inheritance, heteroplasmy, and gene selection
A new method for assessment of bunch compactness using automated image analysis
No full textAbstract
Background and Aims:
Bunch compactness is a key feature determining grape and wine composition because tight bunches show a less homogeneous ripening, and are prone to greater fungal disease incidence. The Organisation Internationale de la Vigne et du Vin descriptor, the most recent method for the assessment of bunch compactness, requires visual inspection and trained evaluators, and provides subjective and qualitative values. The aim of this work was to develop a methodology based on image analysis to determine bunch compactness in a non‐invasive, objective and quantitative way.
Methods and Results:
Ninety bunches of nine different red cultivars of Vitis vinifera L. were photographed with a colour camera, and their bunch compactness was determined by visual inspection. A predictive partial least squares (PLS) model was developed in order to estimate bunch compactness from the morphological features extracted by automated image analysis, after the supervised segmentation of the images. The PLS model showed a capability of 85.3% for predicting correctly the rating of bunch compactness. The most discriminant variables of the model were highly correlated with the tightness of the berries in the bunch (proportion of visibility of berries, rachis and holes) and with the shape of the bunch (roundness, compactness shape factor and aspect ratio).
Conclusions:
The non‐invasive, image analysis methodology presented here enables the quantitative assessment of bunch compactness, thereby providing precise objective information for this key parameter.
Significance of the Study:
A quantitative, objective and accurate system based on image analysis was developed as an alternative to current visual methods for the estimation of bunch compactness. This novel method could be applied to the classification of table grapes and/or at the receival point of wineries for sorting and assessment of wine grapes before vinification
Genetic variation and evolutionary forces shaping Cucumber vein yellowing virus populations: risk of emergence of virulent isolates in Europe
No full textThe genetic variation and evolutionary mechanisms shaping Cucumber vein yellowing virus (CVYV) populations were investigated by analysis of nucleotide sequences coding for P1b, P1b/P3 and coat proteins (CP) from isolates collected in different countries. The complete genome sequence of isolate ISM from Israel was also determined and compared to those of isolates Jor from Jordan and ALM32 from Spain. This isolate had overall nucleotide identities of 94·23 and 94·96% with ALM32 and Jor, respectively. Nucleotide variation among isolates was not homogeneously distributed, with the 5′ half of the genome being more variable than the 3′ half. A Bayesian phylogenetic tree of the CP showed that CVYV isolates clustered into two main clades: isolates from the Middle East region (Lebanon, Israel and Jordan) clustered in both clades whereas the isolate from Tunisia clustered in clade I and the European isolates clustered as a homogeneous phylogroup in Clade II. A similar topology was observed for P1b but with incongruences with respect to the CP, suggesting genetic exchange among virus isolates, which were confirmed with recombination algorithms. The low genetic diversity within the European phylogroup with respect to the other isolates, neutralist tests and genetic differentiation analyses suggest that the Middle East region is the cradle of CVYV and that a unique virus introduction event occurred in Europe, where the virus spread rapidly. Taken together, these findings indicate a risk of emergence of virulent CVYV isolates in Europe either through migration from the Middle East or by genetic changes of the European isolate
A severe symptom phenotype in pepper cultivars carrying the Tsw resistance gene is caused by a mixed infection between resistance-breaking and nonresistance-breaking isolates of Tomato spotted wilt virus
Get PDFPepper (Capsicum annuum) plants with the Tsw resistance gene showing unusually severe symptoms consisting of local lesions, chlorosis, stunting and systemic necrosis on the apical leaves were found in a commercial field in north eastern Spain in 2009. The presence of Tomato spotted wilt virus (TSWV) was confirmed in all diseased plants. After mechanical inoculation of Nicotiana glutinosa with infected field samples, biological clones of the virus were isolated from individual local lesions. These biological clones produced two different types of symptoms after inoculation on Tsw resistant pepper plants: (I) typical symptoms caused by resistance-breaking (RB) isolates characterized by chlorosis and stunting, and (II) severe symptoms as observed in the field plants. Similar symptoms in pepper plants carrying the Tsw resistance gene were reproduced under controlled conditions, after simultaneous inoculation of RB and non-resistance-breaking (NRB) isolates. The NRB isolate was detected in a low proportion in the apical uninoculated leaves, whereas NRB isolates could not infect resistant pepper when inoculated alone. Co-infection by NRB and RB isolates induced disease synergism with systemic necrosis on the apical leaves. To our knowledge, this is the first case in which a synergic interaction between isolates of the same virus has been described, which has the ability to overcome a natural genetic resistance. This finding could have epidemiological implications for the management of TSWV
Acta Horticulturae
No full textVolatile organic compounds, most of them being terpenes, are signals emitted by plants for communication with the environment. Orange fruit accumulates mainly terpenes in mature peel oil glands with D-limonene accounting for approximately 97% of terpene content. We have generated transgenic orange plants carrying a D-limonene synthase gene in antisense (AS) configuration. Transgenic expression caused a dramatic decrease in the accumulation of D-limonene in fruit peels, being about 80-100 times lower in AS samples than in empty vector (EV) transgenic ones. This affected the interaction of fruits with their biotic environment because they resulted in resistance to different specialized pathogens. When antisense fruits were challenged with the fungus Penicillium digitatum, they showed marked resistance against this pathogen. A gene expression analysis of these fruits linked the decrease of D-limonene to upregulation of genes involved in the innate immunity response. High D-limonene content in mature orange peels may be a signal for attractiveness of microorganisms which might be likely involved in facilitating the access to the pulp of seed dispersal frugivores
Effect of feeding diets containing barley, wheat and corn distillers dried grains with solubles on carcass traits and meat quality in growing rabbits
Get PDFThe effect of dietary inclusion of distillers dried grains with solubles (DDGS) on carcass and meat quality of longissimus muscle was studied in 100 growing rabbits from 28 to 59 days old. Diets with no DDGS (C), barley (Db20), wheat (Dw20) and corn (Dc20) DDGS at 20% and corn (Dc40) DDGS at 40% were formulated. No effects on most of the carcass traits, texture and water holding capacity were found. Barley and corn DDGS led to a higher dissectible fat percentage. Meat redness was higher with Dw20 and pH was higher with Dw20 and Db20 than with Dc20. Protein and saturated fatty acids concentration declined as corn DOGS level increased. Dc40 led to the lowest saturated/unsaturated fatty add ratio, atherogenic index and thrombogenic index. In conclusion, dietary inclusion of these DDGS at 20% did not affect most of the carcass and meat quality traits in rabbits
Hydroxypropyl methylcellulose-beeswax edible coatings formulated with antifungal food additives to reduce alternaria black spot and maintain postharvest quality of cold-stored cherry tomatoes
Get PDFEdible composite coatings based on hydroxypropyl methylcellulose (HPMC), beeswax (BW), and food preservatives with antifungal properties were formulated and evaluated on cherry tomatoes during cold storage. Selected food preservatives included: sodium methyl paraben (SMP), sodium ethyl paraben (SEP) and sodium benzoate (SB). Cherry tomatoes artificially inoculated with Alternaria alternata were coated and stored up to 21 d at 5 degrees C followed by 4 d of shelf-life at 20 degrees C. All antifungal coatings reduced the incidence and severity of alternaria black spot on inoculated cherry tomatoes, being the SB-based coating the most effective. Analytical and sensory fruit quality was evaluated on intact and cold-stored tomatoes. In contrast to coatings containing SMP or SEP, the SB-based coating was effective to reduce weight loss and respiration rate and maintain the firmness of coated cherry tomatoes. Peel color, ethanol and acetaldehyde content of the juice, sensory flavor, off-flavors, and fruit appearance were not adversely affected by the application of the antifungal coatings. In conclusion, HPMC-BW coatings containing the food additive SB at 2% showed potential for industrial application, including the production and commercialization of organic cherry tomatoes. (C) 2015 Elsevier B.V. All rights reserved
Acta Horticulturae
No full textThe endoparasitoid Diachasmimorpha longicaudata (Ahsmed) (Hymenptera: Braconidae) is one of the larval parasitoids used in biological control of Tephritid fruit flies. Ceratitis capitata (Diptera: Tephritidae) is an economically important fruit fly of special importance in Spain, and mainly in the Valencia Community by the economic importance of the citrus sector. Nowadays the control of C. capitata in Valencia is based on the integration of area-wide Sterile Insect Technique (SIT) program with pest monitoring, mass trapping and chemical applications. The biological control of C. capitata is under study, for this reason in 2009 the larval parasitoid D. longicaudata was imported from Mexico. A release study is presented here to determine its contribution to medfly control. Different densities of D. longicaudata adults were released once each season in a citrus plot to determine its dispersion on the plot and the parasitism rate exerted in infested sentinel apples. The results showed that the parasitoid D. longicaudata is able to disperse and parasitize C. capitata larvae in Mediterranean climatic conditions
La poda del caqui
Get PDFTal y como se indica en otros capítulos de este libro, en el cultivo del caqui se aplican diferentes técnicas y labores culturales (marcos de plantación,
riegos, abonados, tratamientos fitosanitarios, podas y sistemas de conducción) todas ellas enfocadas a lograr tres objetivos básicos: – Cantidad. Se pretende obtener el máximo de frutos por árbol. La cantidad está directamente relacionada con el número de árboles por unidad de superficie y con la producción. Cuando las plantaciones están formadas por árboles adultos en plena producción ésta se puede clasificar en: • Baja: de 18.000 a 25.000 kg/ha
• Media: de 25.000 a 50.000 kg/ha
• Alta: más de 50.000 kg/ha – Calibre. Los frutos deben tener un tamaño comercial. Si la producción es alta, pero está formada por frutos de pequeño calibre, la rentabilidad disminuye. – Calidad. Los frutos tienen que tener la forma, tamaño y color de sus características varietales. Así mismo deben cumplir una serie de requisitos sobre los que existe una normativa. Los frutos de caqui están sujetos a una serie
de alteraciones fisiológicas (malformación de frutos) y físicas, sobre todo en la epidermis del fruto (tales como planchado por golpes de sol, rozaduras y
manchas) que hacen que pierdan su valor comercial