227 research outputs found
Life table analysis of Diaphorina citri (Hemiptera: Psyllidae) infesting sweet orange (Citrus sinensis) in SĂŁo Paulo
An ecological life table for eggs and nymphs of Diaphorina citri Kuwayama (Hemiptera:
Psyllidae) was constructed with data obtained from orange orchards (Citrus sinensis Osbeck) in 2 regions of the State of SĂŁo Paulo, over 4 generations in the period from XI-2006
to V-2007, comprising spring, summer, and fall seasons. Young growing shoots with D. citri
eggs present were identifed, and live individuals were counted until adult emergence. No
predatory arthropods were observed in association with D. citri eggs and nymphs during
the study. The mean parasitism of fourth- and ffth-instar nymphs by Tamarixia radiata
Waterston (Hymenoptera: Eulophidae) was 2.3%. The durations of the eggâadult period
were similar among the 4 generations, ranging from 18.0 to 24.7 d (at mean temperatures
ranging from 21.6 to 26.0 °C) and followed the temperature requirement models obtained
in the laboratory for D. citri. However, survival from the egg to the adult stage for the same
period varied considerably from 1.7 to 21.4%; the highest mortalities were observed in the
egg and small nymphal (frst- to thirdinstar) stages, which were considered to be key phases
for population growth of the pest.Uma tabela de vida ecolĂłgica foi construĂda para ovos e ninfas de Diaphorina citri Kuwayama (Hemiptera: Psyllidae) com dados obtidos em pomares de laranja (Citrus sinensis Osbeck) em 2 regiĂ”es do estado de SĂŁo Paulo, com 4 geraçÔes, no perĂodo de novembro de 2006
a maio de 2007, compreendendo as estaçÔes de primavera, verão e outono. Ramos jovens
em crescimento com a presença de ovos de D. citri foram identificados e os indivĂduos vivos
foram contados atĂ© a emergĂȘncia dos adultos. Nenhum predador foi observado associado a
ovos e ninfas de D. citri durante o estudo. A taxa média de parasitismo de ninfas de quarto
e quinto Ănstares por Tamarixia radiata Waterson (Hymenoptera: Eulophidae) foi de 2.3%.
A duração do perĂodo de ovo a adulto foi semelhante entre as quatro geraçÔes, variando de
18.0 a 24.7 dias (com temperaturas médias de 21.6 a 26.0 °C) e seguiram os modelos de
exigencias térmicas obtidas em laboratório para D. citri. Todavia, a sobrevivencia de ovo
atĂ© o estĂĄgio adulto variou consideravelmente para o mesmo perĂodo, de 1.7 a 21.4%, sendo
que as maiores mortalidades foram observadas nos estĂĄgios de ovos e ninfas pequenas (de
primeiro a terceiro Ănstares), as quais foram consideradas fases chaves para o crescimento
populacional desta praga.info:eu-repo/semantics/publishedVersio
Sampling and distribution pattern of Trioza erytreae Del Guercio, 1918 (Hemiptera: Triozidae) in citrus orchard
Developing efficient sampling protocols is essential to monitor crop pests. One vector of the citrus disease HLB, the African citrus psyllid Trioza erytreae Del Guercio, 1918 (Hemiptera: Triozidae), currently threatens the lemon industry throughout the Mediterranean region. In this work, a pool of sampling methods devoted to monitoring the population of T. erytreae was compared, its spatial distribution in the orchard was assessed, and the minimum sampling effort for the best sampling method was estimated. Three lemon orchards in North-western Portugal were sampled for one year using two types of yellow sticky traps (standard yellow and fluorescent Saturn yellow), B-vac sampling and sweep net sampling. The method that best performed, in terms of cost-efficiency, was the yellow sticky traps. The two colours of the sticky traps tested did not yield a significantly different number of catches. The spatial distribution throughout the orchards was found to be aggregated towards the borders. A minimum of three sticky traps per hectare was found to be enough to estimate the population at 90% accuracy for the mean during the outbreak. These results should help to monitor and anticipate outbreaks that may even colonize neighbour orchards. Studies on the local dispersion patterns of T. erytreae throughout the orchard are mandatory to further refine and optimize efficient monitoring protocols.The authors are grateful to the Foundation for Science and
Technology (FCT, Portugal), for financial support through national
funds FCT/MCTES to CIMO (UIDB/00690/2020) and to the project
PRE-HLB-Preventing HLB epidemics for ensuring citrus survival in
Europe (H2020-SFS-2018-2 Topic SFS-05-2018-2019-2020, proj. No. 817526).info:eu-repo/semantics/publishedVersio
Optimization of Pathogenicity Tests for Selection of Native Isolates of Entomopathogenic Fungi Isolated from Citrusgrowing Areas of MĂ©xico on Adults ofDiaphorina citriKuwayama (Hemiptera: Liviidae)
Huanglonbing (HLB), es considerado una de las mĂĄs letales enfermedades de los cĂtricos alrededor del mundo, y ha alcanzado las principales ĂĄreas de producciĂłn de limĂłn Mexicano (Citrus latifolia Tanaka) en la costa del pacifico de MĂ©xico. Los productores han iniciado el uso de insecticidas para controlar las poblaciones del psĂlido asiĂĄtico de los cĂtricos, Diaphorina citri Kuwayama (Hemiptera: Liviidae), el vector del patĂłgeno âCandidatus Liberibacter asiaticusâ asociado con el HLB. Actualmente los costos de los insecticidas y los efectos secundarios de su uso son las principales preocupaciones, ya que podrĂan perjudicar la estrategia de manejo contra el vector; y por lo tanto, alternativas ecolĂłgicas y econĂłmicamente viables a los insecticidas convencionales serian necesarias a corto plazo. Por tanto, el objetivo de este estudio fue evaluar la patogenicidad de 27 aislados nativos y 3 cepas de hongos entomopatĂłgenos para determinar su potencial como agentes de control biolĂłgico sobre Diaphorina citri usando 2 diferentes mĂ©todos de bioensayo. Los bioensayos fueron realizados bajo condiciones de laboratorio (26 ± 2 °C, 60 ± 5% H.R y 16:8 h L:O) mediante la exposiciĂłn de insectos adultos a una concentraciĂłn de 1 Ă 108 conidios por mililitro utilizando 2 diferentes mĂ©todos de aplicaciĂłn, es decir, por asperjado de esporas en las plĂĄntulas de cĂtricos y por asperjado directo a los psĂlidos adultos. Los resultados mostraron que para el asperjado directo a los adultos los aislados HIB-24 (B. bassiana) y HIB-32 (I. fumosorosea) mostraron el mayor porcentaje de mortalidad (60.66%). Respecto al asperjado de plĂĄntulas el aislado HIB-19 (I. fumosorosea) mostrĂł el mayor porcentaje de mortalidad (62.02%). Los resultados de este estudio demuestran el potencial para el uso de hongos entomopatĂłgenos en el manejo de D. citri en MĂ©xico.
ABSTRACT
Huanglongbing (HLB), considered one of the most lethal diseases of citrus worldwide, has reached the main areas of Mexican lime (Citrus latifolia Tanaka) fruit production on the Pacific coast of MĂ©xico. Growers have initiated intensive use of insecticides in order to control populations of the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), the vector of the pathogen, âCandidatus Liberibacter asiaticusâ associated with huanglongbing. Presently, costs of insecticides and the side effects of their use are major concerns, because they could impair the management strategy against the vector; and thus, ecologically and economically viable alternatives to conventional insecticides are required in the short term. Therefore the goal of this study was to evaluate the pathogenicity of 27 native isolates and 3 strains of entomopathogenic fungi and determine their potential as biological control agents of D. citri by using 2 different bioassay methods. Bioassays were performed under laboratory conditions (26 ± 2 °C, 60 ± 5% RH and 16:8 h L:D) by exposing adult insects to a concentration of 1 Ă 108 conidia per milliliter using 2 different application methods, i.e., spraying the spores onto the citrus seedlings and spraying the spores directly onto the adult psyllids. The results showed that by direct spraying the adults, HIB-24 (B. bassiana) and HIB-32 (I. fumosorosea) isolates showed the highest mortality (60.66%). Regarding spraying of the seedlings, HIB-19 (I. fumosorosea) showed the highest percentage of mortality (62.02%). The results from this study demonstrate potential for using entomopathogenic fungi in the management of D. citri in MĂ©xico
Conservation of Gene Order and Content in the Circular Chromosomes of âCandidatus Liberibacter asiaticusâ and Other Rhizobiales
âCa. Liberibacter asiaticus,â an insect-vectored, obligate intracellular bacterium associated with citrus-greening disease, also called âHLB," is a member of the Rhizobiales along with nitrogen-fixing microsymbionts Sinorhizobium meliloti and Bradyrhizobium japonicum, plant pathogen Agrobacterium tumefaciens and facultative intracellular mammalian pathogen Bartonella henselae. Comparative analyses of their circular chromosomes identified 514 orthologous genes shared among all five species. Shared among all five species are 50 identical blocks of microsyntenous orthologous genes (MOGs), containing a total of 283 genes. While retaining highly conserved genomic blocks of microsynteny, divergent evolution, horizontal gene transfer and niche specialization have disrupted macrosynteny among the five circular chromosomes compared. Highly conserved microsyntenous gene clusters help define the Rhizobiales, an order previously defined by 16S RNA gene similarity and herein represented by the three families: Bartonellaceae, Bradyrhizobiaceae and Rhizobiaceae. Genes without orthologs in the other four species help define individual species. The circular chromosomes of each of the five Rhizobiales species examined had genes lacking orthologs in the other four species. For example, 63 proteins are encoded by genes of âCa. Liberibacter asiaticusâ not shared with other members of the Rhizobiales. Of these 63 proteins, 17 have predicted functions related to DNA replication or RNA transcription, and some of these may have roles related to low genomic GC content. An additional 17 proteins have predicted functions relevant to cellular processes, particularly modifications of the cell surface. Seventeen unshared proteins have specific metabolic functions including a pathway to synthesize cholesterol encoded by a seven-gene operon. The remaining 12 proteins encoded by âCa. Liberibacter asiaticusâ genes not shared with other Rhizobiales are of bacteriophage origin. âCa. Liberibacter asiaticusâ shares 11 genes with only Sinorhizobium meliloti and 12 genes are shared with only Bartonella henselae
Politics of nanotechnologies in food and agriculture
The chapter discusses the reasons for the delay in the regulatory intervention
concerning nanotechnologies used in the agriculture and food sectors. The
main finding is that unregulated introduction of nanoinnovation into the food system
is due to the current neoliberal food policy and to the power struggles that
characterize the economic, social and political dynamics within the global supply
chain. Therefore, it is necessary to put the âquestion concerning technologyâ at the
center of the regulatory debate in order to implement a regulatory system able to
face nanorisks. Which means looking at the way in which technology controls
power relationships within society. Attention should be shifted from efficiency to
power issues, and new technologies should be assessed from a political rather than
an economic or ethical perspective
Comparison of the âCa. Liberibacter asiaticusâ Genome Adapted for an Intracellular Lifestyle with Other Members of the Rhizobiales
An intracellular plant pathogen âCandidatus Liberibacter asiaticus,â a member of the Rhizobiales, is related to Sinorhizobium meliloti, Bradyrhizobium japonicum, nitrogen fixing endosymbionts, Agrobacterium tumefaciens, a plant pathogen, and Bartonella henselae, an intracellular mammalian pathogen. Whole chromosome comparisons identified at least 50 clusters of conserved orthologous genes found on the chromosomes of all five metabolically diverse species. The intracellular pathogens âCa. Liberibacter asiaticusâ and Bartonella henselae have genomes drastically reduced in gene content and size as well as a relatively low content of guanine and cytosine. Codon and amino acid preferences that emphasize low guanosine and cytosine usage are globally employed in these genomes, including within regions of microsynteny and within signature sequences of orthologous proteins. The length of orthologous proteins is generally conserved, but not their isoelectric points, consistent with extensive amino acid substitutions to accommodate selection for low GC content. The âCa. Liberibacter asiaticusâ genome apparently has all of the genes required for DNA replication present in Sinorhizobium meliloti except it has only two, rather than three RNaseH genes. The gene set required for DNA repair has only one rather than ten DNA ligases found in Sinorhizobium meliloti, and the DNA PolI of âCa. Liberibacter asiaticusâ lacks domains needed for excision repair. Thus the ability of âCa. Liberibacter asiaticusâ to repair mutations in its genome may be impaired. Both âCa. Liberibacter asiaticus and Bartonella henselae lack enzymes needed for the metabolism of purines and pyrimidines, which must therefore be obtained from the host. The âCa. Liberibacter asiaticusâ genome also has a greatly reduced set of sigma factors used to control transcription, and lacks sigma factors 24, 28 and 38. The âCa. Liberibacter asiaticusâ genome has all of the hallmarks of a reduced genome of a pathogen adapted to an intracellular lifestyle
Sequencing of diverse mandarin, pummelo and orange genomes reveals complex history of admixture during citrus domestication
Cultivated citrus are selections from, or hybrids of, wild progenitor species whose identities and contributions to citrus domestication remain controversial. Here we sequence and compare citrus genomes-a high-quality reference haploid clementine genome and mandarin, pummelo, sweet-orange and sour-orange genomes-and show that cultivated types derive from two progenitor species. Although cultivated pummelos represent selections from one progenitor species, Citrus maxima, cultivated mandarins are introgressions of C. maxima into the ancestral mandarin species Citrus reticulata. The most widely cultivated citrus, sweet orange, is the offspring of previously admixed individuals, but sour orange is an F1 hybrid of pure C. maxima and C. reticulata parents, thus implying that wild mandarins were part of the early breeding germplasm. A Chinese wild 'mandarin' diverges substantially from C. reticulata, thus suggesting the possibility of other unrecognized wild citrus species. Understanding citrus phylogeny through genome analysis clarifies taxonomic relationships and facilitates sequence-directed genetic improvement. (Résumé d'auteur
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