ABSTRACT
High throughput sequencing was performed on total pooled RNA from six Turkish trees of Pistacia showing different viral symptoms. The analysis produced some contigs showing similarity with RNAs of emaraviruses. Seven distinct negative-sense, single-stranded RNAs were identified as belonging to a new putative virus infecting pistachio. The amino acid sequence identity compared to homologs in the genus Emaravirus ranged from 71% for the replicase gene on RNA1, to 36% for the putative RNA7 gene product. All the RNA molecules were verified in a pistachio plant by RT-PCR and conventional sequencing. Although the analysed plants showed a range of symptoms, it was not possible to univocally associate the virus with a peculiar one. The possible virus transmission by mite vector needs to be demonstrated by a survey, to observe spread and potential effect on yield in the growing areas of the crop.
Subject(s)
Pistacia/virology , Plant Diseases/virology , Plant Viruses/classification , Plant Viruses/isolation & purification , RNA Viruses/classification , RNA Viruses/isolation & purification , Cluster Analysis , Computational Biology , High-Throughput Nucleotide Sequencing , Phylogeny , Plant Viruses/genetics , RNA Viruses/genetics , RNA, Viral/genetics , RNA, Viral/isolation & purification , RNA-Dependent RNA Polymerase/genetics , Reverse Transcriptase Polymerase Chain Reaction , Sequence Homology, Amino Acid , TurkeyABSTRACT
Several species of Septoria are associated with leaf and fruit spot of pistachio (Pistacia vera), though their identity has always been confused, making identification problematic. The present study elucidates the taxonomy of the Septoria spp. associated with pistachio, and distinguishes four species associated with this host genus. Partial nucleotide sequence data for five gene loci, ITS, LSU, EF-1α, RPB2 and Btub were generated for a subset of isolates. Cylindroseptoria pistaciae, which is associated with leaf spots of Pistacia lentiscus in Spain, is characterised by pycnidial conidiomata that give rise to cylindrical, aseptate conidia. Two species of Septoria s. str. are also recognised on pistachio, S. pistaciarum, and S. pistaciae. The latter is part of the S. protearum species complex, and appears to be a wide host range pathogen occurring on hosts in several different plant families. Septoria pistacina, a major pathogen of pistachio in Turkey, is shown to belong to Pseudocercospora, and not Septoria as earlier suspected. Other than for its pycnidial conidiomata, it is a typical species of Pseudocercospora based on its smooth, pigmented conidiogenous cells and septate conidia. This phenomenon has also been observed in Pallidocercospora, and seriously questions the value of conidiomatal structure at generic level, which has traditionally been used to separate hyphomycetous from coelomycetous ascomycetes. Other than DNA barcodes to facilitate the molecular identification of these taxa occurring on pistachio, a key is also provided to distinguish species based on morphology.
