L. Grimová

Reflects the coat protein variability of apple mosaic virus host preference

Apple mosaic virus (ApMV) is a widespread ssRNA virus which infects diverse species of Rosales. The phylogenetic analysis of complete capsid protein gene of the largest set of ApMV isolates discriminated two main clusters of isolates: one cluster correlates with Maloideae hosts and Trebouxia lichen algae hosts; a second with hop, Prunus, and other woody tree hosts. No correlation was found between clusters and geographic origin of virus isolates, and positive selection hypothesis in distinct hosts was not confirmed: in all virus populations, purifying selection had occurred. GGT→AAT substitution resulted in Gly→Asn change inside the zinc-finger motif in the capsid protein was revealed specific for discrimination of the clusters and we hypothesise that could influence the host preference.

DISTRIBUTION OF VIRUSES IN OLD COMMERCIAL AND ABANDONED ORCHARDS AND WILD APPLE TREES

Samples from apple trees in old commercial and abandoned orchards as well as in wild apple trees in the outskirts of Prague in the Czech Republic were surveyed for the presence of Apple mosaic virus (ApMV), Apple stem grooving virus (ASGV), Apple stem pitting virus (ASPV) and Apple chlorotic leaf spot virus (ACLSV) using conventional and quantitative RT-PCR. Results revealed that ACLSV was the most frequent virus (70%) in old apple cultivars. ASPV together with ASGV were present in approximately half of the tested trees, and ApMV was found at the lowest frequency. Unexpectedly, the occurrence of ApMV, ASGV and ASPV was confirmed in wild-growing apple trees although the incidence was low. Sequence of the coat protein coding gene from several of these apple virus isolates provided insights into their population structure in Central Bohemia. Together, our molecular findings extend our knowledge on the distribution of apple viruses in populations of old cultivated apple trees in the Czech Republic and provide the first evidence of the presence of ApMV, ASGV and ASPV in wild apple trees. The latter finding raises the question on the origin of viruses in wild apple trees because their spread without human intervention is not known.

Distribution of Two Formae Speciales of Polymyxa Graminis in the Czech Republic

Abstract It has been shown that two formae speciales of P. graminis, namely f. sp. temperata (ribotype Pg-I) and f. sp. tepida (ribotype Pg-II), are widely distributed throughout temperate areas of Europe. In this study, the presence of both forms of the temperate Polymyxa spp. was identified in soil samples from different locations of the Czech Republic during a survey performed in 2012 and 2013. Based on polymerase chain reaction results, of the total 58 tested samples, 67.2% contained at least one monitored forma specialis. Specifically, P. graminis f. sp. temperata was detected in 48.3% of soil samples, while P. graminis f. sp. tepida was detected in 44.8% of samples. Mixed populations were found in 25.9% of the tested areas. This plasmodiophorid was confirmed not only in crop fields but also in meadows and forests in all explored regions. Our results extend the knowledge on the distribution of both ribotypes of P. graminis and provide the first evidence of f. sp. tepida within the Czech Republic.

Occurrence of Several Viruses Infecting Wild Growing Stone Fruit Trees in Central Bohemia

Abstract The phytosanitary status of wild growing stone fruit trees and shrubs was examined in surveys conducted in 2013 and 2014 in the region of Central Bohemia, Czech Republic. A total of 159 leaf samples were collected (42 cherries, 77 bird cherries, 10 cherry plums, 13 blackthorns, 2 round plums, 15 plums) and tested for the presence of Plum pox virus (PPV), Prunus necrotic ringspot virus (PNRSV), Prune dwarf virus (PDV), Apple mosaic virus (ApMV), Apple chlorotic leaf spot virus (ACLSV), Cherry virus A (CVA), Cherry necrotic rusty mottle virus (CNRMV), Cherry green ring mottle virus (CGRMV), and Cherry leafroll virus (CLRV) using reverse transcription-polymerase chain reaction (RT-PCR). Totally 28.3% of the investigated trees and shrubs were infected by at least one monitored virus. Mixed infection occurred in 5 out of 159 trees (3.1%). PPV was the most widespread virus (13.2% of samples), followed by PDV (11.3%). Contrary to these two most relevant viral pathogens, the incidence of CLRV and CVA was negligible in individually growing trees of the genus Prunus and ApMV, ACLSV, CGRMV, and CNRMV were not detected at all.