Estrutura genética de uma população do badnavirus Dioscorea bacilliform alata virus (BDALV) que infectam inhame (Dioscorea spp.) no nordeste do Brasil

Abstract

The yam Dioscorea spp.)is a crop of great economic and social importance to the Northeast Brazil due its nutritional value and trade of tubers, highlighting its potential for export, mainly to Europe. Viral diseases are considered limiting factors to the yam production and germplasm movement. The knowledge of the dynamics of genetic variability in plant viral populations is an important step to understand how these populations evolve, as well as its implications for durability of control strategies based on host resistance. Studies for understand the genetic structure of dsDNA plant viruses (e.g., the members of Badnavirus)are scarce. Therefore, the aim of this work was determine the genetic structure of Dioscorea AL bacilliform virus (DBALV) populations that infect yam crop in Alagoas, Paraíba and Pernambuco States, by partial sequences of the RT/RNAseH region of the viral genome. A total of 150 leaf samples showing typical symptoms of viral infection were collected in Five yam-growing areas in 2012 and 2013. The presence of badnavirus DNA was confirmed by PCR amplification using the degenerate oligonucleotides Badna RP and Badna FP. The PCR products were purified and directly sequenced by MacrogenInc (Seoul, South Korea). Partial sequences of the RT/RNAseH region were initially analyzed with BLASTn algorithm and the GenBank non-redundant nucleotide database to determine the viral species with which they shared greatest identity. These similar sequences from GenBank were used to determine the taxonomic state of the viral isolates based on criterion established by ICTV. The phylogenetic analysis was performed using the MEGA v.5.0. Genetic variability analysis and inference about the population structure were performed using the DnaSPprogram v.5.10. Pairwise sequence comparisons and phylogenetic tree showed that all viral isolates obtained in this work belong to the same badnavirus species: DBALV. A DBALV population comprising 48 isolates showed high genetic variability, similar to those found in ssDNA viruses. Mutation and purifying selection were important evolutionary mechanisms acting on evolution of this badnavirus population. However, additional studies are necessary to elucidate the influence of other evolutionary process shaping the genetic variability in DBALV infecting yam in Brazil.