科研之友
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摘要
The etiology of citrus sudden death (CSD) and its relationship with a severe variant of the citrus tristeza virus (citrus tristeza virus, CTV) is unknown. To discover a possible relationship, a study was made of five populations of 100 trees each one, in regions with and without CSD presence, in commercial groves of the states of Sao Paulo and Minas Gerais, Brazil. In the groves with CSD, foliar discoloration was observed, along with defoliation, reduced vegetative growth and eventually tree death. The objective of the present study was to characterize the population structure of CTV isolates present in both regions with the purpose of etiologically associating CTV with CSD. Only 96/500 amplified for the gene of the coat protein (CP) of the CTV, which were subjected to hybridation with specific probes and to an analysis of single-strand conformation polymorphism (SSCP). The percentages of hybridation with specific probes for severe CTV isolations were 79.60% and 84.67% in the region with and without CSD. Therefore, no definite association was found of severe isolations with CSD. The SSCP analysis determined the presence of up to five haplotypes; in a single tree in regions with MSC, and as many as seven in regions without CSD. A dominant pattern was not found. The analysis of molecular variance (AMOVA) showed a greater variation within populations than among regions, which indicates a heterogeneous population structure with local origin. With the data obtained, no direct relationship was determined between severe CTV isolates and CSD, but the possible involvement of CTV in the new syndrome was not discarded.
- 出版日期2008-2
