Genetic variation and recombination of RdRp and HSP 70h genes of Citrus tristeza virus isolates from orange trees showing symptoms of citrus sudden death disease

<p>Abstract</p> <p>Background</p> <p>Citrus sudden death (CSD), a disease that rapidly kills orange trees, is an emerging threat to the Brazilian citrus industry. Although the causal agent of CSD has not been definitively determined, based on the disease's distribution and symptomatology it is suspected that the agent may be a new strain of <it>Citrus tristeza virus </it>(CTV). CTV genetic variation was therefore assessed in two Brazilian orange trees displaying CSD symptoms and a third with more conventional CTV symptoms.</p> <p>Results</p> <p>A total of 286 RNA-dependent-RNA polymerase (RdRp) and 284 heat shock protein 70 homolog (HSP70h) gene fragments were determined for CTV variants infecting the three trees. It was discovered that, despite differences in symptomatology, the trees were all apparently coinfected with similar populations of divergent CTV variants. While mixed CTV infections are common, the genetic distance between the most divergent population members observed (24.1% for RdRp and 11.0% for HSP70h) was far greater than that in previously described mixed infections. Recombinants of five distinct RdRp lineages and three distinct HSP70h lineages were easily detectable but respectively accounted for only 5.9 and 11.9% of the RdRp and HSP70h gene fragments analysed and there was no evidence of an association between particular recombinant mosaics and CSD. Also, comparisons of CTV population structures indicated that the two most similar CTV populations were those of one of the trees with CSD and the tree without CSD.</p> <p>Conclusion</p> <p>We suggest that if CTV is the causal agent of CSD, it is most likely a subtle feature of population structures within mixed infections and not merely the presence (or absence) of a single CTV variant within these populations that triggers the disease.</p

Aplicação de silicato de potássio e crescimento foliar da cana-de-açúcar

The objective of this study was to evaluate the effect of increasing doses of potassium silicate on the leaf growth of sugarcane under controlled conditions. The experiment was conducted in a completely randomized design, with six replications and six treatments consisting of doses of potassium silicate (0, 40, 80, 160, 200 and 240 g L -1). The leaf application of potassium silicate quadratically increased the leaf growth of sugarcane. The maximum growth of the leaf area and dry matter production of leaves were obtained with doses of 66.6 and 40.0 g L -1 of potassium silicate, respectively. With a dose of 51.0 g L -1 of potassium silicate, the maximum estimated value of leaf area ratio was obtained. The content of potassium (K) present in the dry matter of the leaf +1 responded linearly to the doses of potassium silicate. However, the high concentration of K in function of the application of high doses of potassium silicate reduced the leaf growth of sugarcane. Therefore, to obtain the maximum leaf growth of sugarcane the dose of potassium silicate to be applied should be between 40.0 and 66.6 gL -1.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Genetic variation and recombination of RdRp and HSP 70h genes of isolates from orange trees showing symptoms of citrus sudden death disease-1

<p><b>Copyright information:</b></p><p>Taken from "Genetic variation and recombination of RdRp and HSP 70h genes of isolates from orange trees showing symptoms of citrus sudden death disease"</p><p>http://www.virologyj.com/content/5/1/9</p><p>Virology Journal 2008;5():9-9.</p><p>Published online 16 Jan 2008</p><p>PMCID:PMC2244595.</p><p></p>6 are represented by blue, green and red dots respectively. Multiple dots on particular branches represent identical sequences. Whereas branches with more than 75% bootstrap support are labeled with filled black diamonds, those with between 50 and 74% support are labeled with unfilled black diamonds. Sequence lineages H1, H2, and H3 are indicated. (B) The mosaic structures of obviously recombinant sequences excluded from the phylogenetic analysis. The mosaics are colour coded according to the main sequence lineages from which they have probably been derived. Coloured dots beside the schematic representations of the recombinant sequences represent the numbers and origins of recombinant sequences sharing similar mosaics. (C) The relative population representation of different major HSP70h lineages identified in A

Genetic variation and recombination of RdRp and HSP 70h genes of isolates from orange trees showing symptoms of citrus sudden death disease-0

<p><b>Copyright information:</b></p><p>Taken from "Genetic variation and recombination of RdRp and HSP 70h genes of isolates from orange trees showing symptoms of citrus sudden death disease"</p><p>http://www.virologyj.com/content/5/1/9</p><p>Virology Journal 2008;5():9-9.</p><p>Published online 16 Jan 2008</p><p>PMCID:PMC2244595.</p><p></p>ith CSD) and C6 (without CSD) are represented by blue, green and red dots respectively. Multiple dots on particular branches represent identical sequences. Whereas branches with more than 75% bootstrap support are labeled with filled black diamonds, those with between 50 and 74% support are labeled with unfilled black diamonds. Sequence lineages R1a, R1b, R2, R3 and R4 are indicated. (B) The mosaic structures of obviously recombinant sequences excluded from the phylogenetic analysis. The mosaics are colour coded according to the main sequence lineages from which they have probably been derived. Grey areas represent sequence tracts that were not clearly derived from one of the five identified sequence lineages in A. Coloured dots beside the schematic representations of the recombinant sequences represent the numbers and origins of recombinant sequences sharing similar mosaics. (C) The relative population representation of different major RdRp lineages identified in A