Diversity and evolutionary history of lettuce necrotic yellows virus in Australia and New Zealand

Abstract

Lettuce necrotic yellows virus (LNYV) is the type member of the genus Cytorhabdovirus, family Rhabdoviridae, and causes a severe disease of lettuce (Lactuca sativa L.). This virus has been described as endemic to Australia and New Zealand, with sporadic reports of a similar virus in Europe. Genetic variability studies of plant-infecting rhabdoviruses are scarce. We have extended a previous study on the variability of the LNYV nucleocapsid gene, comparing sequences from isolates sampled from both Australia and New Zealand, as well as analysing symptom expression on Nicotiana glutinosa. Phylogenetic and BEAST analyses confirm separation of LNYV isolates into two subgroups (I and II) and suggest that subgroup I is slightly older than subgroup II. No correlation was observed between isolate subgroup and disease symptoms on N. glutinosa. The origin of LNYV remains unclear; LNYV may have moved between native and weed hosts within Australia or New Zealand before infecting lettuce or may have appeared as a result of at least two incursions, with the first coinciding with the beginning of European agriculture in the region. The apparent extinction of subgroup I in Australia may have been due to less-efficient dispersal than that which has occurred for subgroup II - possibly a consequence of suboptimal interactions with plant and/or insect hosts. Introduction of subgroup II to New Zealand appears to be more recent. More-detailed epidemiological studies using molecular tools are needed to fully understand how LNYV interacts with its hosts and to determine where the virus originated.

Detection of genetic diversity among some species of Anthemis L. (Asteraceae) in Saudi Arabia by using RAPD-PCR analysis

“…Many studies conducted on other genus revealed similar results with insufficient molecular studies of Anthemideae (Matousek et al, 2007;Garcia et al, 2010;Riggins and Seigler, 2012). Similar results were obtained by other authors (Riggins and Seigler, 2012;Patil et al, 2016;Higgins et al, 2016;Kumar et al, 2016).…”

Diversity of partial RNA-dependent RNA polymerase gene sequences of soybean blotchy mosaic virus isolates from different host-, geographical- and temporal origins

“…Similarly, sequencing and phylogenetic analysis of the complete N gene of eight LNYV isolates from Australia also showed no temporal separation in subgroups [10]. However, this is in contrast to later studies of LNYV which reported the clustering of more recently collected isolates in a subgroup, with older isolates forming a distinct clade [23]. Table 1.…”

“…As an example, the high variability and absence of isolates from Lusikisiki in Groups A and C and the limited presence of isolates from Schoemanskloof in the other groups might be the result of competitive exclusion. Enhanced interactions of isolates in Groups A and C with plant or insect hosts may lead to their apparent dominance, as also described in Lettuce necrotic yellows virus (LNYV) [23]. Soybean cultivar selection varies greatly in different regions, as does the natural vegetation, which may serve as alternative hosts, and these may act in strain selection, furthermore insect vectors often select for specific genotypes adapted to plant-vector systems [24].…”

Geographic Distribution and Genetic Diversity of Rice Stripe Mosaic Virus in Southern China

“…In our study, all RSMV isolates showed low genetic variability (less than 1% at the nt level, Table 3; and the variation rates were mostly below 1.0%, Figure 3). However, lettuce necrotic yellow virus (LNYV) was found to form two subgroups and differed significantly between them (about 20% at the nt and 4% at the aa level) based on the analysis of the N gene (Higgins et al, 2016), whereas the N gene sequence of Taro vein chlorosis virus isolates differed significantly between them (19.3% at the nt and 6.3% at the aa level) (Revill et al, 2005). This may indicate some evidence that RSMV is a “new” pathogen that emerged and dispersed recently.…”