ReDivia - Repositorio Digital de l'Instit Valencià d'Investigacions Agràries
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Reproductive strategies and food sources used by Acerophagus n. sp near coccois, a new successful parasitoid of the invasive mealybug Phenacoccus peruvianus
No full textPhenacoccus peruvianus Granara de Willink (Hemiptera: Pseudococcidae) is a new invasive mealybug that causes important damages in ornamental plants in urban landscapes and nurseries in Southern Europe. Recently, a new species of genus Acerophagus Smith (Hymenoptera: Encyrtidae) has been recorded as the main parasitoid of P. peruvianus in Spain, displacing the native parasitoid Leptomastix epona Walker (Hymenoptera: Encyrtidae). In this work, we have determined some traits of the reproductive and feeding strategies of Acerophagus sp.: fecundity, immature developmental time, host instar suitability, and preference when parasitizing P. peruvianus, and the effect of natural occurring sugar sources on adult longevity. Acerophagus sp. egg load reached its maximum when it was 5 days old. Second and third nymphal instars and adults were suitable for parasitism and immature development (efficient encapsulation was low). Immature development lasted between 20 and 22 days. Acerophagus sp. developed as a solitary parasitoid in the second instar and as a gregarious parasitoid in older instars (2-4 parasitoids per host). All the emerged offspring were females. Acerophagus sp. always preferred older instars when different host instars were available. Finally, adults lived more than 20 days when fed on honey, but they lived fewer than 3 days when fed on naturally occurring sugar sources (host honeydew and host plant flowers, Bougainvillea glabra). The consequences of these characteristics on biological control and parasitoid rearing are discussed
Characterization of postharvest treatments with sodium methylparaben to control citrus green and blue molds
No full textThe curative antifungal activity of postharvest sodium methylparaben (SMP) treatments against citrus green (GM) and blue (BM) molds was characterized on different citrus species and cultivars artificially inoculated with Penicillium digitatum or Penicillium italicum and incubated at 20 °C and 90% RH for 7 d or stored at 5 °C and 90% RH for 8 weeks plus 7 d of shelf-life at 20 °C. Effective concentrations were selected in in vivo primary screenings with ‘Valencia’ oranges. SMP at 200 mM was tested at 20, 50 or 62 °C for 30, 60 or 150 s in small-scale trials to determine the best dip treatment conditions. Dips of 200 mM SMP at 20 °C for 60 s were selected and applied alone or in combination with 25 μL L−1 of the conventional fungicide imazalil (SMP + IMZ 25). Imazalil at the very low concentrations of 25 (IMZ 25) or 50 μL L−1 (IMZ 50) were also tested. Effectiveness of SMP alone at 20 °C for 60 s was significantly higher on oranges (cvs. ‘Valencia’ and ‘Lanelate’) than on mandarins (cvs. ‘Clemenules’, ‘Nadorcott’ and ‘Ortanique’), with GM and BM incidence reductions of up to 88% after 7 d at 20 °C. SMP was compatible with IMZ 25 and consistently improved its performance, irrespective of citrus cultivars and storage conditions. All treatments were less effective on ‘Clemenules’ mandarins. On ‘Valencia’ oranges stored for 8 weeks at 5 °C and 7 d at 20 °C, the combined treatment was significantly more effective than the single treatments (reductions of GM and BM incidence of about 50–60% and 90–95%, respectively). In additional tests, 200 mM SMP dips at 20 °C for 60 s did not prevent GM on ‘Valencia’ oranges wounded, treated, inoculated with P. digitatum 24 h later, and incubated at 20 °C for 7 d. In contrast, the treatments IMZ 25 and SMP + IMZ 25 showed significant preventive activity. It can be concluded from these results that SMP aqueous solutions, especially applied at room temperature, might be an interesting nonpolluting control alternative to be included in citrus postharvest disease control programs in the future
Molecular tools for sterile sperm detection to monitor Ceratitis capitata populations under SIT programmes
No full textBackground The success of an area-wide sterile insect technique (SIT) programme against Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) relies on the mating success of sterile males in the field. Limited information is available about the effectiveness of sterile males in achieving mates with wild females and how these matings contribute to reducing wild populations. To this end, firstly a mating competition test was performed in the laboratory with different release ratios (1:1:0, 1:1:1, 1:1:5, 1:1:10 and 1:1:20 for wild females:wild males:sterile VIENNA-8 males respectively) and different host fruit. Secondly, the same release ratios were evaluated under semi-natural conditions on caged trees and on sentinel host. Results By means of molecular markers, VIENNA-8 male sperm was positively detected in those females exposed to the male ratios 1:5, 1:10 and 1:20 in the laboratory. In the field test, sterile VIENNA-8 male matings and the C. capitata progeny on apples were positively correlated with the ratio of sterile males released and with the percentage of sterile matings respectively. Conclusions These results confirm the validity of using the molecular detection of VIENNA-8 male sperm to predict the C. capitata population under semi-natural conditions. Implications of these results in measuring the efficacy of an SIT programme are discussed. (c) 2012 Society of Chemical Industr
Effects of Hot Water Treatments on Antioxidant Enzymatic System in Reducing Flesh Browning of Persimmon
No full textThe flesh browning that appears during commercialization period is the main postharvest disorder that is limiting the market of "Rojo Brillante" persimmon in the Mediterranean area. Previous studies have suggested that mechanical damage suffered by the fruit during packing line operations is the trigger of this alteration when fruit is previously subjected to the required deastringecy treatment. In the present work, the effect of hot water treatments (HWTs) on flesh browning incidence of Rojo Brillante persimmon has been investigated. For that, fruits submitted to the commercial deastringency treatment were hot water treated at 45 A degrees C for 30 min or 50 A degrees C for 20 min and then subjected to different intensity of mechanical damage in packing line. Fruit bathed at 25 A degrees C for 25 min and fruit hand-packed acted as control treatments. Our results confirmed that mechanical damage during packing is a decisive factor in the incidence of flesh browning, and this alteration is found to increase the damage intensity. HWTs significantly alleviated flesh browning disorder by affecting the antioxidative system enzymes; the activity of catalase and ascorbate peroxidase was increased by HWTs while the activity of peroxidases was reduced. No changes were observed in polyphenol oxidase and phenylalanine ammonia lyase activity. Therefore, the application of HWTs may be a useful postharvest technology to reduce flesh browning of persimmon induced by packing line operations
Effects of high levels of zinc and manganese ions on Strategy I responses to iron deficiency in citrus
No full textThe aim of this work is to study the effect of elevated concentrations of either Zn2+ or Mn2+ in the culture media on the components of the system of iron acquisition by roots from Fe-deficient and Fe-supplied citrus seedlings. Seeds of Citrus aurantium (L.) were germinated in vitro. Nutrient solutions without iron, zinc or manganese were prepared for assays and then combinations of Fe-EDDHA, ZnSO4 center dot 7H(2)O or MnSO4 center dot H2O were added to obtain the following media: -Fe-Zn, +Fe-Zn, -Fe+Zn, +Fe+Zn, -Fe-Mn, +Fe-Mn, -Fe+Mn and +Fe+Mn. Data indicated that when either 100 mu M Zn2+ or 250 mu M Mn2+ were added to culture media containing 20 mu M Fe, iron concentration in roots and shoots was reduced with respect to the seedlings cultured in the same medium lacking Zn2+ or Mn2+. Reciprocally, the presence of iron in the medium lowered Zn and Mn levels in the plant. Addition of either 100 mu M Zn2+ or 250 mu M Mn2+ to the medium enhanced the transcription levels of FRO2, IRT1 and NRAMP3 genes in roots, this effect being more marked in Fe-starved plants. FC-R activity followed the same behaviour as the gene FRO2. Both Zn2+ and Mn2+ stimulated the activity of some genes (FRO2, IRT1 and NRAMP3) which was also induced by Fe-deficiency, although these effects appear to be independent of the inhibition of Fe uptake by these cations
Use or abuse of bioinformatic tools: a response to Samach
No full textIn a recent paper, we described for the first time the effects of fruit on the expression of putative homologues of genes involved in flowering pathways. It was our aim to provide insight into the molecular mechanisms underlying alternate bearing in citrus. However, a bioinformatics-based critique of our and other related papers has been given by Samach in the preceding Viewpoint article in this issue of Annals of Botany. The use of certain bioinformatic tools in a context of structural rather than functional genomics can cast doubts about the veracity of a large amount of data published in recent years. In this response, the contentions raised by Samach are analysed, and rebuttals of his criticisms are presented
Occurrence, Prevalence and Distribution of Citrus Viroids in Uruguay
No full textThe occurrence of Citrus exocortis viroid (CEVd), Citrus bent leaf viroid (CBLVd), Hop stunt viroid (HSVd), Citrus dwarfing viroid (CDVd), Citrus bark cracking viroid (CBCVd) and Citrus viroid VI (CVd-VI) in Citrus spp. cultivated in six provinces of Uruguay was surveyed in 20082009 and 2009-2010 growing seasons using Northern blot hybridization. Sixty two per cent of surveyed trees were infected with either single or mixed viroid inocula, the latter being more abundant. CBCVd and CVd-VI were not detected in the samples analyzed. HSVd showed the highest prevalence (92%) among infected plants followed by CDVd (50%), CEVd (23%) and CBLVd (19%). The most frequently observed viroid combination was HSVd+CDVd. Our results showed that CEVd, CBLVd, HSVd, CDVd are widespread throughout citrus orchards in Uruguay and highlight the presence of mixed viroid infections
Mini-review: Heat treatments for the control of citrus postharvest green mold caused by Penicillium digitatum
Get PDFPostharvest green mold, caused by the pathogen Penicillium digitatum (Pers.:Fr.) Sacc., is the most economically important postharvest disease of citrus fruits in Spain, areas with Mediterranean climate, and citrus production areas worldwide characterized by low summer rainfall. Economic losses due to this disease have been typically reduced through the application of synthetic chemical fungicides such as imazalil or thiabendazole. However, human health risks and environmental contamination associated with chemical residues and the proliferation of resistant strains of the pathogen are major problems associated with the use of these chemicals. There is, therefore, an increasing need to find and implement alternative antifungal postharvest treatments as part of integrated management programs for disease control. Among alternative physical decay control methods, heat treatments are the most common and popular because they are relatively effective, simple, cheap, and easy to apply and combine with other control systems. In this article, research work based on the evaluation of heat treatments used alone or in combination with other physical, chemical, or biological methods for the control of citrus green mold is reviewed. The most important postharvest heat treatments that have been tested against P. digitatum on fresh citrus fruits are curing, hot water dips (HWD), and hot water rinsing and brushing (HWRB). Typical citrus curing employs exposure of fruit for 2- 3 days to an air atmosphere heated to temperatures higher than 30°C at relative humidity higher than 90%. HWD are generally applied as relatively brief immersions (1-5 min) in water heated to 40-55 °C. HWRB consists basically in packingline machinery that treats the fruit by the application of hot water over rotating brushes at a relatively high temperature (55-65 °C) for a short time (10-60 s). Efficacy results, general performance, modes of action, limitations, advantages and disadvantages, and commercial feasibility of these heat treatments are discussed
Biological control of Rhynchophorus ferrugineus
Get PDFThe invasive red palm weevil, Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae), is one of the most destructive pests of palms in the world. To date, the control of this pest has been mainly based on the use of insecticides. However, this control method can result in environmental, social and economic problems. To improve management options against the weevil, the efficacy of the entomopathogenic nematode Steinernrema carpocapsae Weiser (Nematoda: Steinernematidae) and the potential of a strain of the entomopathogenic fungus Beauveria bassiana (Ascomycota: Clavicipitaceae) were evaluated in laboratory, semi-field and field assays. The use of these entomopathogenic microorganisms resulted highly efficient against R. ferrugineus