ReDivia - Repositorio Digital de l'Instit Valencià d'Investigacions Agràries
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Competition between honeydew producers in an ant-hemipteran interaction may enhance biological control of an invasive pest
No full textAsian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is an invasive citrus pest in southern California, which secretes honeydew and has the potential to spread a lethal bacterial disease, huanglongbing, of citrus. In urban citrus, Argentine ant, Linepithema humile (Mayr) (Hymenoptera: Formicidae), also an invasive pest, tends honeydew-producing hemipterans. We used field data to determine whether the mutualistic relationship between L. humile and six established species of honeydew producers may hinder or favor the establishment of D. citri and its biological control with Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae) in citrus via competition or mutualism for ants, respectively. In the field, L. humile and D. citri are engaged in a mutualistic relationship. Ants harvest solid honeydew secreted by psyllid nymphs and tended more than 55% of observed D. citri colonies. Linepithema humile displayed a preference hierarchy when tending honeydew producers infesting citrus. It responded equally or less intensively to D. citri than to other honeydew-producing species. Consequently, the mutualism between L. humile and D. citri was affected by the presence of other honeydew-producing species, and the percentage of D. citri colonies tended by L. humile. The number of ants per D. citri colony also decreased as the number of other honeydew producers increased. Diaphorina citri density was also affected by the presence of other honeydew producers. Both colony size and the number of D. citri nymphs counted per tree decreased as the number of other honeydew producers increased. Our results indicate that competition between honeydew producers for the mutualist ant L. humile may hinder the establishment of D. citri by possibly facilitating increased biological control
Moderate plant water stress reduces fruit drop of "Rojo Brillante" persimmon (Diospyros kaki) in a Mediterranean climate
No full textSpring fruit drop is a crucial determinant for yield in persimmon trees. Several environmental and tree endogenous factors can determine the magnitude of this physiological phenomenon. In this sense, plant water status might play a pivotal role in persimmon fruit drop occurring during spring. The main purpose of this study was to establish and quantify the effects of plant water stress on fruit drop of the ‘Rojo Brillante’ persimmon cultivar. To achieve this goal, a field experiment was conducted during three consecutive seasons with mature trees. Three irrigation regimes were tested: Control, always well watered; and two deficit irrigation (DI) treatments where water was applied at 50% of the Control regime during May and June (DIearly) or during July and August (DIlate). Plant water stress was monitored by means of midday stem water potential (Ψstem) readings. The seasonal variation of fruit drop was quantified during the entire fruit abscission period. Both DI regimes led to lower fruit drop than the Control (31 and 12% lower fruit drop for DIearly and DIlate, respectively). In addition, in the last two experimental seasons, there was a highly significant relationship between the amount of fruit that dropped during the physiological fruit drop and the average Ψstem for the period of water restrictions. However, the timing of water stress also affected the existing relationships. Early season water stress had a greater effect on reducing fruit abscission during the second wave of fruit drop. In semi-arid climates, this knowledge can be used for increasing ‘Rojo Brillante’ persimmon fruit set by restricting irrigation applications during late spring
Effect of ground cover management on Thysanoptera (thrips) in clementine mandarin orchards
No full textConservation biological control by means of ground cover offers an interesting alternative to chemical control. A complex of Thysanoptera (thrips) species inhabits citrus, some of which are considered pests. This study investigated the effect of ground cover management on thrips species composition, distribution, and seasonal abundance in four commercial clementine mandarin (Citrus clementina Tanaka) orchards. Three soil management systems were compared: resident vegetation, Festuca arundinacea Schreber (Poales: Poaceae), and bare soil. Cover management affected thrips species diversity and abundance. Two of the main species causing fruit damage in Spanish citrus, Frankliniella occidentalis (Pergande) and Thrips tabaci Lindeman, were abundant in the resident ground cover. However, their abundance was strongly depressed in the F. arundinacea cover. The resident vegetation cover could provide a range of suitable host plants supporting populations of potential thrips pest species beyond the citrus blooming period. The F. arundinacea cover, which hosted Poaceae-specific thrips species, could also provide alternative food sources for Phytoseiidae mites. These predatory mites could reduce populations of potential thrips and other citrus pests below economic injury level. Our results confirm the suitability of F. arundinacea as a cover crop for clementine mandarins
Identification of a New Enamovirus Associated with Citrus Vein Enation Disease by Deep Sequencing of Small RNAs
No full textTo identify the causal agent of citrus vein enation disease, we examined by deep sequencing (Solexa-Illumina) the small RNA (sRNA) fraction from infected and healthy Etrog citron plants. Our results showed that virus-derived sRNAs (vsRNAs): (i) represent about 14.21% of the total sRNA population, (ii) are predominantly of 21 and 24 nucleotides with a biased distribution of their 5' nucleotide and with a clear prevalence of those of (+) polarity, and (iii) derive from all the viral genome, although a prominent hotspot is present at a 5'-proximal region. Contigs assembled from vsRNAs showed similarity with luteovirus sequences, particularly with Pea enation mosaic virus, the type member of the genus Enamovirus. The genomic RNA (gRNA) sequence of a new virus, provisionally named Citrus vein enation virus (CVEV), was completed and characterized. The CVEV gRNA was found to be single-stranded, positive-sense, with a size of 5,983 nucleotides and five open reading frames. Phylogenetic comparisons based on amino acid signatures of the RNA polymerase and the coat protein clearly classifies CVEV within the genus Enamovirus. Dot-blot hybridization and reverse transcription-polymerase chain reaction tests were developed to detect CVEV in plants affected by vein enation disease. CVEV detection by these methods has already been adopted for use in the Spanish citrus quarantine, sanitation, and certification programs
Characterization of Citrus sinensis transcription factors closely associated with the non-host response to Xanthomonas campestris pv. vesicatoria
No full textPlants, when exposed to certain pathogens, may display a form of genotype-independent resistance, known as non-host response. In this study, the response of Citrus sinensis (sweet orange) leaves to Xanthomonas campestris pv. vesicatoria (Xcv), a pepper and tomato pathogenic bacterium, was analyzed through biochemical assays and cDNA microarray hybridization and compared with Asiatic citrus canker infection caused by Xanthomonas citri subsp. citri. Citrus leaves exposed to the non-host bacterium Xcv showed hypersensitive response (HR) symptoms (cell death), a defense mechanism common in plants but poorly understood in citrus. The HR response was accompanied by differentially expressed genes that are associated with biotic stress and cell death. Moreover, 58 transcription factors (TFs) were differentially regulated by Xcv in citrus leaves, including 26 TFs from the stress-associated families AP2-EREBP, bZip, Myb and WRKY. Remarkably, in silico analysis of the distribution of expressed sequence tags revealed that 10 of the 58 TFs, belonging to C2C2-GATA, C2H2, CCAAT, HSF, NAC and WRKY gene families, were specifically over-represented in citrus stress cDNA libraries. This study identified candidate TF genes for the regulation of key steps during the citrus non-host HR. Furthermore, these TFs might be useful in future strategies of molecular breeding for citrus disease resistance
Characterization of Sour Cherry Isolates of Plum pox virus from the Volga Basin in Russia Reveals a New Cherry Strain of the Virus
No full textPlum pox virus (PPV) is the causal agent of sharka, the most detrimental virus disease of stone fruit trees worldwide. PPV isolates have been assigned into seven distinct strains, of which PPV-C regroups the genetically distinct isolates detected in several European countries on cherry hosts. Here, three complete and several partial genomic sequences of PPV isolates from sour cherry trees in the Volga River basin of Russia have been determined. The comparison of complete genome sequences has shown that the nucleotide identity values with other PPV isolates reached only 77.5 to 83.5%. Phylogenetic analyses clearly assigned the RU-17sc, RU-18sc, and RU-30sc isolates from cherry to a distinct cluster, most closely related to PPV-C and, to a lesser extent, PPV-W. Based on their natural infection of sour cherry trees and genomic characterization, the PPV isolates reported here represent a new strain of PPV, for which the name PPV-CR (Cherry Russia) is proposed. The unique amino acids conserved among PPV-CR and PPV-C cherry-infecting isolates (75 in total) are mostly distributed within the central part of P1, NIa, and the N terminus of the coat protein (CP), making them potential candidates for genetic determinants of the ability to infect cherry species or of adaptation to these hosts. The variability observed within 14 PPV-CR isolates analyzed in this study (0 to 2.6% nucleotide divergence in partial CP sequences) and the identification of these isolates in different localities and cultivation conditions suggest the efficient establishment and competitiveness of the PPV-CR in the environment. A specific primer pair has been developed, allowing the specific reverse-transcription polymerase chain reaction detection of PPV-CR isolates
Is Sperm Freezability Related to the Post-Thaw Lipid Peroxidation and the Formation of Reactive Oxygen Species in Boars?
No full textThe aim of the present study was to determine whether the levels of reactive oxygen species (ROS) substances production and the levels of lipid peroxidation of the sperm membrane were related to the quality that the ejaculates exhibited after cryopreservation in boars. Ejaculates from 42 healthy boars were used in this study and they were cryopreserved with the lactose-egg yolk extender (LEY). Several sperm quality parameters were assessed by flow cytometry in samples incubated for 30 and 150 min at 37°C after thawing: the percentage of sperm with intact plasma membrane (SIPM), intracellular reactive oxygen substances production through mean of DCF fluorescence intensity of total sperm (mean-DCF) and the percentage of viable and non-viable sperm containing oxidized BODIPY (VSOB and NVSOB). In addition, the percentages of total motile (TMS) and progressively motile sperm (PMS) were assessed at the same incubation times with a computer-assisted sperm analysis system. The classification of the ejaculates into good or bad freezers was performed through hierarchical cluster analysis from SIPM and TMS at 150 min post-thawing. The ejaculates of those males classified as good freezers exhibited higher (p 0.05) VSOB, NVSOB and mean-DCF. Therefore, these results show that lipid peroxidation and the amount of reactive oxygen substances in the sperm after cryopreservation are similar between boars classified as good or bad freezers
Efecto de la inmunocastración en el peso canal y las piezas nobles en cerdas Ibéricas de cebo
Get PDFA total of 192 Iberian females (Duroc*Iberian), with 110 days of age and 45 ± 3.41 kg BW, were used to study the effect of immunocastration in yield of carcass and prime lean cuts. There were three treatments: surgically castrated females (CC), entire females (CE), and inmunocastrated females (CI) the experimental design was a complete randomized blocks with 48 replicates total (4 pigs in each), 12 replicates per block and 16 per treatment. The feed, the same for all animals, was suministered ad libitum. After sacrifice, 31 pigs were selected for each treatment to assess the performance of carcass and main lean cuts. Treatment CI tended to improve slaughter and carcass weights (p0.05) and significantly less in the CC (p0.05) and significantly less in the CC (p55 %; p0.05) and quadratic for CE and CI (p<0.05). The immunocastration favors the growth of Iberian female; the surgical castration is the least interesting option
Assessment of drip irrigation sub-units using airborne thermal imagery acquired with an Unmanned Aerial Vehicle (UAV)
No full textThe proper maintenance of irrigation sub-units is a key aspect for efficient irrigation and for ensuring that the theoretical high drip irrigation application efficiencies are achieved. The performance assessment methods are based on the discharge measurements of some emitters sampled within the irrigation unit. The emitter selection is a key aspect for guaranteeing that plot heterogeneity is well represented. In this work, thermal images obtained by means of an Unmanned Aerial Vehicle over an irrigation district were used to determine irrigation performance. Four irrigation sub-units were assessed with standard methods. Canopy temperature showed a good correlation with the total flow discharge when plant water status variability in the sub-unit was high. When standard irrigation performance assessment protocols are used, the sample of emitters is small and so the large existing variability might not be taken into account. Aerial thermal images can quantify plant water status in large areas enabling the detection of some failures in the irrigation delivery system that might not be always detected with the standard irrigation performance assessment protocols
Treatment with cholesterol-loaded methyl-beta-cyclodextrin increased the cholesterol in rabbit oocytes, but did not improve developmental competence of cryopreserved oocytes
No full textMembrane cholesterol:phospholipids ratio is an important determinant of cell chilling sensitivity. At low temperatures, major membrane destabilisation occurs when the membrane undergoes a phase transition. To increase membrane fluidity and stability during cooling and thus increase oocyte cryoresistance, cholesterol has been added to the plasma membrane. This study was conducted to determine if cholesterol could be incorporated into rabbit oocytes by incubation with cholesterol-loaded methyl-beta-cyclodextrin (CLC) and if added cholesterol could improve the developmental ability of cryopreserved oocytes after parthenogenetic activation or intracytoplasmic sperm injection. Fresh, frozen and vitrified oocytes incubated with CLC containing 20% NBD-labelled cholesterol (NBD-CLC) were evaluated using confocal microscopy. Fluorescence intensity was higher in fresh oocytes than in cryopreserved ones. Pre-treating rabbit oocytes with 1 mg of NBD-CLC/mL did not improve cleavage and developmental rates after cryopreservation. Results showed that treatment with CLC increased the cytoplasmic cholesterol content, but did not improve cleavage rate and developmental competence of cryopreserved oocytes