First report of olive leaf scorch in Brazil, associated with Xylella fastidiosa subsp. pauca

Olea europaea (L.) trees displaying leaf scorching symptoms, identical to those recently reported for olive trees colonized by Xylella fastidiosa in Southern Italy and also in Argentina, were observed in commercial orchards of two counties in Southeastern Brazil. PCR-based diagnosis using conserved primers for X. fastidiosa strains (RST31/33) and also specific to X. fastidiaosa subsp. pauca (CVC1/272-2 int) were positive for all symptomatic tested samples (n = 8 of 9), but no template was obtained using twigs from asymptomatic trees (n = 20). Bacterial colonies were isolated from symptomatic tissues on culture medium and confirmed by PCR using the set of primers specific to X. fastidiosa subsp. pauca. Comparative sequence analyses of seven MLST loci amplified from one tripled passaged colony (MFG01) perfectly matched with sequences of alleles leuA #7, petC #6, malF#8, cysG#10, holC#11, nuoL#8, and gltT#8, the allelic profile of Sequence Type-ST16, which is represented by the strain COF0238 isolated from Coffea arabica (L.) in Brazil (http://pubmlst.org/xfastidiosa/). Phylogenetic analysis placed the ST16 into subspecies pauca, but genetically closer to ST11 and ST13, both obtained from Citrus sinensis (L.) trees with citrus variegated chlorosis. The results confirm the association of olive plants showing leaf scorching with the presence of X. fastidiosa subsp. pauca , and represent the first report of this bacterium in Brazilian olive orchards

The use of random amplified polymorphic DNA to evaluate the genetic variability of Ponkan mandarin (Citrus reticulata Blanco) accessions

RAPD analysis of 19 Ponkan mandarin accessions was performed using 25 random primers. Of 112 amplification products selected, only 32 were polymorphic across five accessions. The absence of genetic variability among the other 14 accessions suggested that they were either clonal propagations with different local names, or that they had undetectable genetic variability, such as point mutations which cannot be detected by RAPD

Genetic Structure and Molecular Variability Analysis of Citrus sudden death-associated virus Isolates from Infected Plants Grown in Brazil

Citrus sudden death-associated virus (CSDaV) is a monopartite positive-sense single-stranded RNA virus that was suggested to be associated with citrus sudden death (CSD) disease in Brazil. Here, we report the first study of the genetic structure and molecular variability among 31 CSDaV isolates collected from both symptomatic and asymptomatic trees in CSD-affected areas. Analyses of partial nucleotide sequences of five domains of the CSDaV genomic RNA, including those encoding for the methyltransferase, the multi-domain region (MDR), the helicase, the RNA-dependent RNA polymerase and the coat protein, showed that the MDR coding region was the most diverse region assessed here, and a possible association between this region and virus adaption to different host or plant tissues is considered. Overall, the nucleotide diversity (π) was low for CSDaV isolates, but the phylogenetic analyses revealed the predominance of two main groups, one of which showed a higher association with CSD-symptomatic plants. Isolates obtained from CSD-symptomatic plants, compared to those obtained from asymptomatic plants, showed higher nucleotide diversity, nonsynonymous and synonymous substitution rates and number of amino acid changes on the coding regions located closer to the 5’ end region of the genomic RNA. This work provides new insights into the genetic diversity of the CSDaV, giving support for further epidemiological studies

Characterization of citrus genotypes (Citrus spp) using rapds markers

Em programas de melhoramento de citros, a caracterização adequada dos recursos genéticos disponíveis é de grande importância, principalmente devido às características biológicas da cultura, como a heterozigosidade, a embrionia nucelar e o longo ciclo reprodutivo. A facilidade com que ocorrem hibridações (interespecíficas e intergenéricas) e a embrionia nucelar favoreceram a formação e a preservação de novas combinações, classificadas como espécies. Neste estudo, marcadores RAPDs foram utilizados para analisar 15 acessos de Citrus spp., sendo quatro variedades de laranjeiras doce (C. sinensis Osbeck), quatro tangerineiras (C. reticulata Blanco, C. nobilis Loureiro, C. sunki Loureiro e C. deliciosa Tenore), uma laranjeira azeda (C. aurantium L.), um pomeleiro (C. paradisi Macf.), uma torangeira (C. grandis Osbeck), uma cidreira (C. medica L.), uma limeira ácida (C. latifolia) e dois híbridos (Citrus clementina T. x (C. tangerina T. x C. paradisi Macf.)). Doze sequências iniciadoras aleatórias foram utilizadas para estudar os 15 genótipos, encontrando-se um grau de similaridade mínimio de 0,81 ("Simple Matching") entre as tangerineiras. Os menores graus de similaridade foram encontrados entre as espécies de Citrus menos aparentadas (C. medica, C. grandis e C. latifolia). As quatro cultivares de laranjeiras doces não puderam ser diferenciadas pelos marcadores RAPD utilizados, apresentando similaridade máxima.In citrus improvement programs the characterization of the available genetic resources is of great importance, mainly concerning biological characteristics of the culture, as the heterozigosity, nucellar the embriony and long reproductive cycle. Favored by nucellar embriony interespecific and intergeneric hybridizations and genotypes preservation happen easily. RAPDs markers were used to analyze 15 Citrus spp., four sweet orange (C. sinensis Osbeck), (C. medica, C. grandis e C. latifolia), four mandarins (C. reticulata Blanco, C. nobilis Loureiro, C. sunki Loureiro e C. deliciosa Tenore), a sour orange (C. aurantium L.), a grapefruit (C. paradisi Marcf.), a pummelo (C. grandis Osbeck), a cidra (C. medica L.), a lime (C. latifolia) and two hybrids (Citrus clementina T. x (C. tangerina T. x C. paradisi Macf.)). Genetic similarities of 15 Citrus genotypes obtained with twelve random primers, indicated a minimum similarity degree of 0.81 (simple matching) among the mandarins. Lower similarity degrees were obtained among less related Citrus species (C. medica, C. grandis e C. latifolia). The four varieties of sweet oranges (C. sinensis Osbeck) could not be differentiated by RAPD markers, showing maximum similarity

First report of olive leaf scorch in Brazil, associated with Xylella fastidiosa subsp. pauca.

Olea europaea (L.) trees displaying leaf scorching symptoms, identical to those recently reported for olive trees colonized by Xylella fastidiosa in Southern Italy and also in Argentina, were observed in commercial orchards of two counties in Southeastern Brazil. PCR-based diagnosis using conserved primers for X. fastidiosa strains (RST31/33) and also specific to X. fastidiaosa subsp. pauca (CVC1/272-2 int) were positive for all symptomatic tested samples (n = 8 of 9), but no template was obtained using twigs from asymptomatic trees (n = 20). Bacterial colonies were isolated from symptomatic tissues on culture medium and confirmed by PCR using the set of primers specific to X. fastidiosa subsp. pauca. Comparative sequence analyses of seven MLST loci amplified from one tripled passaged colony (MFG01) perfectly matched with sequences of alleles leuA #7, petC #6, malF#8, cysG#10, holC#11, nuoL#8, and gltT#8, the allelic profile of Sequence Type-ST16, which is represented by the strain COF0238 isolated from Coffea arabica (L.) in Brazil (http://pubmlst.org/xfastidiosa/). Phylogenetic analysis placed the ST16 into subspecies pauca, but genetically closer to ST11 and ST13, both obtained from Citrus sinensis (L.) trees with citrus variegated chlorosis. The results confirm the association of olive plants showing leaf scorching with the presence of X. fastidiosa subsp. pauca , and represent the first report of this bacterium in Brazilian olive orchards.ISSN:0031-9465ISSN:1593-209