Characterization of Beta vulgaris Alphanecrovirus-1, a putative Alphanecrovirus identified in sugar beet.

Abstract

Beta vulgaris Alphanecrovirus-1 (BvANV-1) was recently identified in our laboratory through RNA sequencing analysis of infected sugar beet roots. To determine the impact of BvANV-1 on sugar beet and other locally-grown rotational crops and weeds and to evaluate viral transmission by the Olpidium sp. vector, infectious clones were developed. Two variants of BvANV-1 were obtained; both clones share a similar sequence with the exception of three single nucleotide polymorphisms (one amino acid substitution and two silent mutations represented in the BvANV-1-7 clone) compared to the putative wild-type sequence found in BvANV-1-10 clone. Infection of Nicotiana benthamiana with BvANV-1-10 led to strong, systemic necrosis on all leaves and stunting of the plant, while plants inoculated with BvANV-1-7 exhibited infrequent necrotic lesions on inoculated leaves. To determine which mutation(s) were involved with the decreased virulence on BvANV-1-7-inoculated N. benthamiana, different combinations of point mutations were introduced reciprocally from BvANV-1-10 into BvANV-1‑7 clone and tested using mechanical inoculation of transcript RNA. The impact of the mutation on aggressiveness will be presented along with other data regarding characterization of this putative pathogen of sugar beet including host range and viral transmission by the vector.