ReDivia - Repositorio Digital de l'Instit Valencià d'Investigacions Agràries
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Mapping the subgenomic RNA promoter of the Citrus leaf blotch virus coat protein gene by Agrobacterium-mediated inoculation
No full textCitrus leaf blotch virus has a single-stranded positive-sense genomic RNA (gRNA) of 8747 nt organized in three open reading frames (ORFs). The ORF1, encoding a polyprotein involved in replication, is translated directly from the gRNA, whereas ORFs encoding the movement (MP) and coat (CP) proteins are expressed via 3' coterminal subgenomic RNAs (sgRNAs). We characterized the minimal promoter region critical for the CP-sgRNA expression in infected cells by deletion analyses using Agrobacterium-mediated infection of Nicotiana benthamiana plants. The minimal CP-sgRNA promoter was mapped between nucleotides -67 and +50 nt around the transcription start site. Surprisingly, larger deletions in the region between the CP-sgRNA transcription start site and the CP translation initiation codon resulted in increased CP-sgRNA accumulation, suggesting that this sequence could modulate the CP-sgRNA transcription. Site-specific mutational analysis of the transcription start site revealed that the +1 guanylate and the +2 adenylate are important for CP-sgRNA synthesis. (C) 2010 Elsevier Inc. All rights reserved
Potential of an indigenous strain of the entomopathogenic fungus Beauveria bassiana as a biological control agent against the Red Palm Weevil, Rhynchophorus ferrugineus
No full textThe potential of a strain of Beauveria bassiana (Ascomycota: Clavicipitaceae) obtained from a naturally infected Rhynchophorus ferrugineus (Coleoptera: Curculionidae) pupa as a biological control agent against this weevil was evaluated both in the laboratory and in semi-field assays. Laboratory results indicate that this strain of B. bassiana can infect eggs, larvae and adults of R. ferrugineus (LC(50) from 6.3 x 10(7) to 3.0 x 10(9) conidia per ml). However, mortality was not the only indicator of treatment efficacy because adults of either sex inoculated with the fungus efficiently transmitted the disease to untreated adults of the opposite sex, with male-to-female and female-to-male rates of transmission of 55% and 60%, respectively. In addition, treatment with B. bassiana significantly reduced fecundity (up to 62.6%) and egg hatching (32.8%) in pairing combinations with fungus-challenged males, females or both sexes. Likewise, 30-35% increase in larval mortality was observed in larvae obtained from eggs from fungus-challenged females or from untreated females coupled with inoculated males, resulting in an overall 78% progeny reduction. Semi-field preventive assays on potted 5-year old Phoenix canariensis palms, with efficacies up to 85.7%, confirmed the potential of this strain as a biological control agent against R. ferrugineus. (C) 2010 Elsevier Inc. All rights reserved
Biological invasion of European tomato crops by Tuta absoluta: Ecology, geographic expansion and prospects for biological control
No full textThe tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a devastating pest of tomato originating from South America. After its initial detection in eastern Spain in 2006, it rapidly invaded various other European countries and spread throughout the Mediterranean basin. If no control measures are taken, then the pest can cause up to 80-100% yield losses in tomato crops in recently invaded areas and may pose a threat to both greenhouse and open-field tomato production. The exceptional speed and extent of T. absoluta invasion have called for studies documenting its biology and ecology, while indicating an urgent need for efficient and sustainable management methods. The development of approaches to manage T. absoluta would be facilitated through a detailed revision of information on this pest in its area of origin. This review combines information on the invasion by T. absoluta, its ecology, and potential management strategies, including data that may help the implementation of efficient biological control programs. These programs, together with a variety of other management tactics, may allow efficient integrated pest management of T. absoluta in Europe and Mediterranean Basin countries. © 2010 Springer-Verlag
Effects of Euseius stipulatus on establishment and efficacy in spider mite suppression of Neoseiulus californicus and Phytoseiulus persimilis in clementine
No full textThe two-spotted spider mite, Tetranychus urticae, is one of the most problematic phytophagous pests in Spanish clementine orchards. The most abundant predatory mites in this ecosystem are Euseius stipulatus, Phytoseiulus persimilis and Neoseiulus californicus. Euseius stipulatus is dominant but poorly adapted to utilize T. urticae as prey. It mainly persists on pollen and citrus red mite, Panonychus citri. A recent study suggested that the more efficacious T. urticae predators P. persimilis and N. californicus are negatively affected by lethal and non-lethal intraguild interactions with E. stipulatus. Here, we investigated the potential of N. californicus and P. persimilis to colonize and thrive on young clementine trees infested by T. urticae in presence and absence of E. stipulatus. Presence of E. stipulatus interfered with establishment and abundance of P. persimilis and negatively affected the efficacy of N. californicus in T. urticae suppression. In contrast, the abundance of E. stipulatus was not affected by introduction of a second predator. Trait-mediated effects of E. stipulatus changing P. persimilis and N. californicus behavior and/or life history were the most likely explanations for these outcomes. We conclude that superiority of E. stipulatus in intraguild interactions may indeed contribute to the currently observed predator species composition and abundance, rendering natural control of T. urticae in Spanish clementine orchards unsatisfactory. Nonetheless, stronger reduction of T. urticae and/or plant damage in the predator combination treatments as compared to E. stipulatus alone indicates the possibility to improve T. urticae control via repeated releases of N. californicus and/or P. persimilis
Polyembryonyin Non-apomictic Citrus Genotypes
No full textAdventitious embryony from nucellar cells is the mechanism
leading to apomixis in citrus. However, singular cases
of polyembryony have been reported in non-apomictic
genotypes as a consequence of 2x×4x hybridisations and in
vitro culture of isolated nucellus. The origin of the plants
obtained as a consequence of these two processes is still
unclear. In this work, we systematically analyzed the
genetic structure (ploidy and allelic constitution at SSR
locus) of plants obtained from polyembryonic seeds arising
from 2x×4x sexual hybridisations or regenerated from
nucellus culture in vitro of different non-apomictic citrus
genotypes. Histological studies were also conduced to try to
identify the initiation process of polyembryony in nonapomictic
genotypes. We demonstrate that all plants
obtained from the same undeveloped seed in 2x×4x
hybridisations resulted from fission of the original zygotic
embryo. Also, the plants obtained from in vitro culture of
nucellus were recovered by somatic embryogenesis from
cells having the same genotype as the zygotic embryos of
the same seed. It appears that in non-apomictic citrus,
proembryos or embryogenic cells are formed by fission of
the original zygotic embryo and that the development of
these adventitious embryos, normally hampered, can take
place in vivo or in vitro as result of two different mechanisms that prevent the dominance of the initial
zygotic embryo
'Rafel' and 'Belgida', Two Apricot Cultivars Resistant to Sharka
Get PDF‘Rafel’ and ‘Belgida’ are mid- to earlyripening apricot cultivars (Prunus armeniaca L.) with good yield, excellent fruit quality, self-compatibility, and resistance to Sharka, a disease caused by the Plum pox virus, a serious limiting factor for apricot production in Europe. Their fruits have excellent organoleptic characteristics and are larger than the traditional Valencian cultivars. ‘Rafel’ and ‘Belgida’ are very well adapted to the climatic conditions of
the Valencia and Murcia areas
Chlorpyrifos Bioassay and Resistance Monitoring of San Joaquin Valley California Citricola Scale Populations
No full textThe responses to chlorpyrifos of six populations of citricola scale, Coccus pseudomagnoliarum (Kuwana) (Hemiptera: Coccidae), were tested using a leaf dip bioassay, and two- to nine-fold resistances were found. LC50 responses of nymphs ranged from 7.5 to 68.9 ppm and LC90 responses ranged from 20 to 222 ppm chlorpyrifos. A population tested monthly during August–October showed up to 3.5-fold differences in LC50 responses but no differences in LC90 responses as scale size increased. A diagnostic concentration of 178 ppm chlorpyrifos was used to test 93 populations from throughout the San Joaquin Valley California during 2006–2009 by using a leaf dip bioassay. Of the populations tested, 41% showed >20% survival after exposure to the diagnostic concentration of chlorpyrifos, indicating resistance problems. Research is needed to relate the level of survival of the scales in the bioassay to the field efficacy of the insecticide. Tulare County citrus growers applied a higher number of organophosphate and carbamate insecticides during the 15-yr period from 1994 to 2008, and these orchards showed a higher average scale survival of chlorpyrifos and a higher number of locations with resistant scale compared with the other San Joaquin Valley counties. Chlorpyrifos resistance is a significant issue for citricola scale management because biological control is ineffective in the San Joaquin Valley and the alternative neonicotinoid and insect growth regulator (IGR) insecticides require more frequent application
Biological Control in Citrus in Spain: From Classical to Conservation Biological Control
No full textThe status of citrus pest management in Spain and of biological control, including classical biological control strategies, is reviewed. The augmentative versus inoculation-based control, and the use of invertebrate biological control agents in citrus orchards and nurseries are described. Fortuitous and conservation biocontrol strategies, as well as exploitation of resident species, either native or naturalized, are discussed. Pesticide side-effect testing on natural enemies, presence of alternative hosts and use of banker plants are described, together with ground cover mangement strategies
Enfermedades de poscosecha de la granada en la zona de Elche
Get PDFEspaña es el primer productor y exportador de granadas de la Unión Europea. Más del 90% de las plantaciones comerciales de este frutal están situadas en la zona de Elche (Alicante). La industria de la granada está actualmente interesada en prolongar el período de almacenamiento de los frutos para alcanzar el mercado más allá del período actual de comercialización. Las pérdidas de peso, los daños por frío y las enfermedades de poscosecha son los principales problemas que limitan la frigoconservación de la granada. En este trabajo se determinaron la etiología y la incidencia de estas enfermedades en nuestras condiciones ambientales. Se utilizaron granadas cv. ‘Mollar de Elche’ de dos parcelas distintas para determinar la incidencia tanto de patógenos de herida (infecciones en poscosecha) como de patógenos latentes (infecciones en campo). Para ello, frutos sanos se hirieron en la piel o se desinfectaron con hipoclorito sódico y se colocaron en cámaras húmedas a 20ºC durante 2 meses. Se determinaron también las enfermedades en granadas conservadas a 5ºC durante 6 meses. Los hongos causantes de enfermedad se incubaron en medio patata dextrosa agar (PDA) a 25ºC para su aislamiento y posterior identificación. Los principales agentes causales de infecciones de herida y latentes fueron respectivamente Penicillium spp. (podredumbre azul) y Botrytis cinerea (podredumbre gris). P. expansum, P. sclerotiorum y P. glabrum fueron especies patogénicas de Penicillium identificadas. Las podredumbres azul y gris fueron también las más frecuentes en granadas conservadas en frío. Otros patógenos relativamente frecuentes en frutos almacenados a 20 y 5ºC fueron respectivamnete Aspergillus niger y Pilidiella granati
Comparison of chemical treatments for reducing epiphytic Pseudomonas savastanoi pv. savastanoi populations and for improving subsequent control of olive knot disease
No full textThe economic impact of the olive knot disease caused by Pseudomonas savastanoi pv. savastanoi (Psv) has dramatically increased in recent years, especially in high-density plantations. Here we report chemical control trials, performed in an olive grove planted with two susceptible cultivars, Arbequina and Picudo, over a four-year period. The effect of treatments made with copper oxychloride, cuprocalcic sulfate plus mancozeb or acibenzolar-S-methyl on the Psv populations and subsequent appearance of the disease were evaluated. Both copper treatments reduced the proportion of samples where Psv was isolated, and greatly reduced Psv populations in trees of cv. Picudo. The effect of copper on Psv populations was observed after the first application, but the greatest differences between copper-treated and untreated plants were observed in the third year, after five copper applications. No resistance to copper was detected in the remaining epiphytic Psv populations in treated plants. The average number of knots per plant was significantly lower in copper-treated plants than in untreated plants. By contrast, acibenzolar-S-methyl did not reduce either Psv populations or the disease during the study. These results support the usefulness of copper treatments for olive knot management. Results indicate that two copper treatments should be performed regularly under an integrated control program, especially in high-density groves, since their efficiency was demonstrated not only in decreasing olive knot incidence, but also in reducing Psv populations. (C) 2010 Elsevier Ltd. All rights reserved