Apple stem pitting virus (ASPV) was detected in samples of European pear (Pyrus communis) cvs. Starkrimson and Abate Fetel, and Asian pear (P. pyrifolia var. culta) cvs. Kousui and Housui. The samples were collected in the beginning of autumn 2003 at the Experimental Station of Embrapa Uva e Vinho, Vacaria, RS. Using several combinations of primers, DNA fragments of 269 and 1554 bp were amplified, the latter containing the complete coat protein gene (1131 nt) of ASPV. Another amplified fragment of 291 bp comprised part of the viral polymerase gene. These fragments are excellent tools for the diagnosis of ASPV in pear. Comparison of the nucleotide sequences with sequences of the GenBank showed 89% identity with sequences from the German isolate of apple, and 85 to 88% with Polish isolates, both from pear. The herbaceous indicator Nicotiana occidentalis cv. 37B, mechanically inoculated with leaf extracts from cv. Housui, presented necrotic local lesions, marginal leaf necrosis and severe vein necrosis. ASPV was also detected by dot-ELISA in the cvs. Abate Fetel and Kousui, by imunoblot in the cv. Starkrimson and by indexing on Pyronia veitchii, graft-inoculated with buds of the infected cv. Abate Fetel.
Pyrus communis; P. pyrifolia; Malus spp.; Flexiviridae; ASPV; dot-ELISA; immunoblot; RT-PCR
