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Sugars as complementary alternative food for the establishment of Nesidiocoris tenuis in greenhouse tomato
No full textNesidiocoris tenuis (Reuter) (Hemiptera: Miridae) is an omnivorous generalist predator which is augmentatively released and conserved for control of whiteflies (Hemiptera: Aleyrodidae) and Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) in tomato crops. Eggs of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) are often provided as factitious prey to improve the establishment of N.tenuis after its release. We first tested different amounts of E.kuehniella eggs per plant to optimize N.tenuis establishment and then investigated whether the amount of eggs that optimized N.tenuis establishment might be reduced by adding sugars (hydrocapsules filled with 0.5m sucrose) under walk-in cage and commercial greenhouse conditions. These experiments demonstrated that the addition of sugar to the diet of N.tenuis could half the amount of E.kuehniella eggs required to establish N.tenuis. Under greenhouse conditions, the progeny of N.tenuis per plant did not differ significantly between E.kuehniella alone or the half amount of E.kuehniella plus hydrocapsules. These results demonstrated that the sugar could partially substitute for E.kuehniella eggs improve establishment of N.tenuis and suggest that natural sugars such as nectar and honeydew might also beneficial
Acta Horticulturae
No full textPsorosis disease of citrus is characterized by bark scaling in the stem and main branches of trees at least 10 years old. Graft-inoculation of sweet orange (Citrus sinensis (L.) Osb.) seedlings in the greenhouse with non-scaled bark pieces from an infected tree incites the psorosis A syndrome (PsA), including a shock reaction of the first flush and transient chlorotic flecking in young leaves of the following flushes, whereas inoculation with scaled bark pieces incites the psorosis B syndrome (PsB), that in addition to PsA symptoms includes gummy pustules in old leaves and branches. Psorosis disease is presumably caused by Citrus psorosis virus (CPsV), an ophiovirus with three negative-stranded genomic RNAs. While comparison of RNA1 or RNA3 fragments by single-strand conformation polymorphism (SSCP) analysis did not show any difference between plants affected by the PsA or the PsB syndromes, a fragment of RNA2 enabled discriminating both syndromes by their SSCP profile. A plant inoculated with scaled bark did not show PsB at 6 months post-inoculation (mpi) and its RNA2 gave a PsA-type SSCP profile. At 12 mpi this plant showed pustules in the trunk but not in the leaves. SSCP analysis of RNA2 showed only PsA-type variants in the leaves, whereas the pustuled trunk areas contained both PsA and PsB variants, the latter being predominant. These results suggest that psorosis-affected trees contain the two sequence variants and that the PsB variant is associated with pustules and tends to accumulate in the trunk bark
Strategies to avoid salinity and hydric stress of pepper grafted plants
Get PDFSweet pepper is one of the most important vegetable crops in arid and semiarid regions. Grafting has been proposed as an interesting strategy that improves the responses of crops under the salinity and hydric deficits occurring in these areas.
In a previous work, we selected Capsicum spp accessions with different degrees of salinity and hydric stress tolerance to be used as rootstocks (the highest to lowest): Capsicum chinense Jacq. ‘ECU-973’ (code 12), Capsicum baccatum L. var. pendulum ‘BOL-58’ (code 14) and Capsicum annuum L var. ‘Serrano’ (code 5). The behavior of commercial cultivar seedlings grafted onto these rootstocks was compared during 14 days under water stress (5% polyethylene glycol) and salinity (40 mM NaCl) in hydroponic culture.
Different physiological parameters were measured to test the hypothesis that tolerance might be related to the role of rootstock in altering the stress perception by the scion and to identify differences in pepper-grafted plants adaptation mechanisms in response to salt and osmotic stresses.
At a similar osmotic pressure of the solution, grafted plants onto the 12 and 14 rootstocks activated tolerance mechanisms based on ion specific responses under salinity, whereas osmotic adjustment based on proline accumulation was performed under water stress. The maintenance of the scion's homeostasis under salinity was achieved through the restriction of Cl- transport to leaves and to diminished Na+ loading in roots and leaves, thus favouring K+ uptake. Under both stresses, a minor negative impact on photosynthesis, nitrate reductase activity and lipid peroxidation in scion leaves grafted onto 12 and 14 rootstocks was observed.
In conclusion, the results of these works reinforce that the use of tolerant pepper rootstocks is a promising strategy to provide salinity and water stress tolerance and can consequently improve crop yield
Complete sequence of three different biotypes of tomato spotted wilt virus (wild type, tomato Sw-5 resistance-breaking and pepper Tsw resistance-breaking) from Spain
Get PDFTomato spotted wilt virus (TSWV) occurs worldwide and causes production losses in many important horticultural crops such as tomato and pepper. Breeding resistant cultivars has been the most successful method so far for TSWV disease control, but only two genes have been found to confer resistance against a wide spectrum of TSWV isolates: Sw-5 in tomato and Tsw in pepper. However, TSWV resistance-breaking isolates have emerged in different countries a few years after using resistant cultivars. In this paper, we report the first complete nucleotide sequences of three Spanish TSWV isolates with different biotypes according to their abilities to overcome resistance: LL-N.05 (wild type, WT), Pujol1TL3 (Sw-5 resistance breaking, SBR) and PVR (Tsw resistance-breaking, TBR). The genome of these TSWV isolates consisted of three segments: L (8913-8914 nt), M (4752-4825 nt) and (S 2924-2961 nt). Variations in nucleotide sequences and genomic RNA lengths among the different virus biotypes are reported here. Phylogenetic analysis of the five TSWV open reading frames showed evidence of reassortment between genomic segments of LL-N.05 and Pujol1TL3, which was supported by analysis with different recombination-detecting algorithms
Rootstock-mediated variation in tomato vegetative growth under drought, salinity and soil impedance stresses
Get PDFThere is increasing interest in using novel rootstocks to confer resistance to abiotic stresses in horticultural species, and to understand the physiological mechanism(s) conferring these responses. The same scion (Solanum lycopersicum ‘Boludo F1’, ‘Monsanto’) was grafted onto 144 different rootstocks: six accessions from S. lycopersicum (‘Cerasiforme’) and S. pimpinellifolium, selected for drought tolerance (sourced from AVRDC); nine introgression lines from S. lycopersicum × S. pennellii and × S. habrochaites, selected for high root/shoot ratio, salinity and drought tolerances (sourced from TGRC); and a population of 129 recombinant inbred lines (RILs) derived from a salt sensitive genotype of S. lycopersicum var. cerasiforme and a salt tolerant line from S. pimpinellifolium L. (sourced from IVIA). Plants were grown in greenhouses in hydroponics (salinity stress) or soil (soil drying or high soil mechanical impedance) for 2-5 weeks (during the vegetative stage), and shoot fresh weight (SFW) was recorded at the end of each experiment. Although rootstock effects on SFW were related for the soil drying and impedance assays, no relation was found between SFW under salinity and SFW under the other stresses. Indeed, the best rootstocks for drought stress were different to those that were the best for salinity and high soil impedance. For each abiotic stress, some graft combinations had higher SFW (up to 90% more) than the self-grafted commercial cultivar ‘Boludo F1’. The search for genetic factors contributing to this variation will be the objective of a future study
Untangling the aphid-parasitoid food web in citrus: Can hyperparasitoids disrupt biological control?
No full textMolecular techniques are irreplaceable to untangle the trophic links in communities where immature entomophagous species (either in the third or fourth level) develop inside the phytophagous. This is the case of aphid-parasitoid communities. Here, we develop a DNA-based approach to untangle the structure of the aphid-parasitoid food web in citrus, where Aphis spiraecola Patch. (Hemiptera: Aphididae) is a key pest and Binodoxys angelicae Haliday (Hymenoptera: Braconidae), its dominant primary parasitoid, is attacked by a complex of hyperparasitoids. Aphid populations and parasitism were followed at weekly intervals in 2012 and 2013. Parasitism rates were low (similar to 0.04 in the four sampled orchards). Simultaneously, colonies harboring aphid mummies were collected. Approximately half of the mummies were reared to adulthood and at least six hymenopteran hyperparasitoid species were identified by classical means: Syrphophagus aphidivorus (Mayr) (Encyrtidae), Alloxysta sp. (Forster) (Figitidae), Asaphes sp. (Walker) (Pteromalidae), Pachyneuron aphidis (Bouche) (Pteromalidae), Dendrocerus sp. (Ratzeburg) (Megaspilidae) and Phaenoglyphis villosa (Hartig) (Figitidae). The other half was subjected to a Taqman-based multiplex PCR to investigate trophic relationships in this food web. We confirmed that all six species hyperparasitized B. angelicae. The most abundant hyperparasitoids were S. aphidivorus and Alloxysta sp. Both were abundant from the beginning of the season, and hyperparasitism rates remained high (similar to 0.4) throughout the season in the two study years. Although these species could share the same mummy, S. aphidivorus and Alloxysta sp. were the most abundant species and dominated this food web. Finally, hyperparasitoids also increased the secondary sex ratio of B. angelicae. Thus, hyperparasitism probably explains the low impact of B. angelicae on A. spiraecola populations
Genetic mapping of centromeres in the nine Citrus clementina chromosomes using half-tetrad analysis and recombination patterns in unreduced and haploid gametes
Get PDFBackground: Mapping centromere locations in plant species provides essential information for the analysis of genetic structures and population dynamics. The centromere's position affects the distribution of crossovers along a chromosome and the parental heterozygosity restitution by 2n gametes is a direct function of the genetic distance to the centromere. Sexual polyploidisation is relatively frequent in Citrus species and is widely used to develop new seedless triploid cultivars. The study's objectives were to (i) map the positions of the centromeres of the nine Citrus clementina chromosomes; (ii) analyse the crossover interference in unreduced gametes; and (iii) establish the pattern of genetic recombination in haploid clementine gametes along each chromosome and its relationship with the centromere location and distribution of genic sequences. Results: Triploid progenies were derived from unreduced megagametophytes produced by second-division restitution. Centromere positions were mapped genetically for all linkage groups using half-tetrad analysis. Inference of the physical locations of centromeres revealed one acrocentric, four metacentric and four submetacentric chromosomes. Crossover interference was observed in unreduced gametes, with variation seen between chromosome arms. For haploid gametes, a strong decrease in the recombination rate occurred in centromeric and pericentromeric regions, which contained a low density of genic sequences. In chromosomes VIII and IX, these low recombination rates extended beyond the pericentromeric regions. The genomic region corresponding to a genetic distance < 5cM from a centromere represented 47% of the genome and 23% of the genic sequences. Conclusions: The centromere positions of the nine citrus chromosomes were genetically mapped. Their physical locations, inferred from the genetic ones, were consistent with the sequence constitution and recombination pattern along each chromosome. However, regions with low recombination rates extended beyond the pericentromeric regions of some chromosomes into areas richer in genic sequences. The persistence of strong linkage disequilibrium between large numbers of genes promotes the stability of epistatic interactions and multilocus-controlled traits over successive generations but also maintains multi-trait associations. Identification of the centromere positions will allow the development of simple methods to analyse unreduced gamete formation mechanisms in a large range of genotypes and further modelling of genetic inheritance in sexual polyploidisation breeding schemes
Development and assessment of a network of water meters and rain gauges for determining the water balance. New SCADA monitoring software
No full textCurrently the scarcity of water resources in certain areas of the Mediterranean coast, specifically in southeastern Spain, make the irrigation efficiency a vital issue when it comes to cope with the high costs of water and contribute to an environmentally-sustainable and energy-efficient agriculture. The aim of this paper is to describe the design and assessment of a system to determine the water balance of an experimental planting of four rows of eight pots of vines (Vitis vinifera L. cv Bobal). This system consisted of a network of low cost water meters and rain gauges and a supervision, control and datalogging application (SCADA) running in a compact programmable automation controller. The water meters were installed at the beginning of the rows to measure the irrigation water. Due to the low flow rate in the drainage network and given the scarcity and high price of low-flow rate flowmeters, we decided to study the feasibility of using tipping bucket rain gauges to measure the drainage water. For this reason comprehensive calibration tests were conducted to ensure their proper operation under the desired flow rate taking into account possible tilt variations in its field deployment. Data from flow meters and rain gauges were processed in the compact controller that was responsible for monitoring and generating charts in real time providing an interface accessible from the Internet. The historical data were sent to a remote FTP to have a backup and make them available from anywhere through an Internet connection. The results obtained during the system operation showed that it provided acceptable accuracy in the determination of water balance. This makes it feasible for applications such as irrigation scheduling of potted crops at a lower cost than other systems that estimate crop evapotranspiration using climatic data such as Eddy-correlation and Bowen-ratio stations. (C) 2014 Elsevier B.V. All rights reserved
Acta Horticulturae
No full textCitrus trees, traditionally associated with Spanish Mediterranean agriculture, are particularly sensitive to water allocation fluctuations. In this area structural water resource deficits, as well as the gradual decline in citrus prices received by farmers, have promoted the co-plantation of other crops that are more resistant to water shortages, such as pomegranates, which have been grown in eastern Spain for decades. At present, demand for pomegranates is growing due to their associated nutritional benefits and functional food qualities. In this paper, we have analyzed technical-economic aspects of citrus and pomegranate cultivation in light of their increasing competition. The comparison of these two crops begins with an assessment, from a farm economy perspective, of the main results published in the scientific literature on Regulated Deficit Irrigation, which is one of the techniques used to address water shortage problems. Also, we have analyzed the trend in prices received by farmers for the orange ‘Lane late’, the mandarin ‘Clemenules’ and for the two main Spanish varieties of pomegranate, ‘Valenciana’ and ‘Mollar’. The economic outlook for these two crops (citrus and pomegranate) is rounded off by an investment analysis, which describes the profitability of individual farms
El cultivo del caqui
No full textLa fertilización es la técnica de cultivo que tiene como finalidad aportar a los suelos o a las plantas directamente los nutrientes necesarios para lograr una nutrición equilibrada capaz de generar un desarrollo adecuado de los órganos vegetales y una producción óptima (en rendimiento y calidad) con el mínimo riesgo de contaminación ambiental. Para lograr una nutrición mineral adecuada en el caqui, como en cualquier cultivo agrícola, se requiere la presencia en concentraciones variables de los nutrientes esenciales, unos en mayor concentración (macronutrientes): nitrógeno (N), fósforo (P), potasio (K), calcio (Ca), y magnesio (Mg), y otros en menor concentración (micronutrientes): hierro (Fe), cobre (Cu), manganeso (Mn), cinc (Zn), boro (B) y cloro (Cl)