Host Effect on the Genetic Diversification of Beet necrotic yellow vein virus Single-Plant Populations

Abstract

Theoretical models predict that, under restrictive host conditions, virus populations will exhibit greater genetic variability. This virus response has been experimentally demonstrated in a few cases but its relation with a virus's capability to overcome plant resistance is unknown. To explore the genetic host effects on Beet necrotic yellow vein virus (BNYVV) populations that might be related to resistance durability, a wild-type virus isolate was vector inoculated into partially resistant Rz1, Rz2, and susceptible sugar beet cultivars during a serial planting experiment. Cloning and sequencing a region of the viral RNA-3, involving the pathogenic determinant p25, revealed that virus diversity significantly increased in direct proportion to the strength of host resistance. Thus, whereas virus titers were highest, intermediate, and lowest in susceptible, Rz1, and Rz2 plants, respectively; the average number of nucleotide differences among single-plant populations was 0.8 (±0.1) in susceptible, 1.4 (±0.1) in Rz1, and 2.4 (±0.2) in Rz2 genotypes. A similar relationship between host restriction to BNYVV root accumulation and virus genetic variability was detected in fields of sugar beet where these specific Rz1- and Rz2-mediated resistances have been defeated.

Genetic diversity and population structure of beet necrotic yellow vein virus in China

“…This result supported the evolutionary hypothesis for p25 tetrad motif proposed by Chiba et al (2011). In addition, the other newly found tetrads, which appeared to be minor, should also cause concern, as it has been hypothesized that low-frequency haplotypes collected from susceptible plants are most likely the founders of viral populations that go on to infect resistant plants ( Acosta-Leal et al, 2010). Thus, whether isolates containing these newly found tetrads are associated with RB should be further investigated.…”

Occurrence of resistance‐breaking strains of Beet necrotic yellow vein virus in sugar beet in northwestern Europe and identification of a new variant of the viral pathogenicity factor P25

“…Acosta‐Leal et al . () detected increased P25 tetrad diversity in resistant sugar beet plants, indicative of virus adaptation to restrictive host conditions. By means of competition experiments followed by P25 deep sequencing analysis, it was demonstrated that Rz1 genotypes selected RB strains that actually possessed reduced fitness in a susceptible genotype (Bornemann & Varrelmann, ).…”

Crop wild relative populations of Beta vulgaris allow direct mapping of agronomically important genes

“…Alleles that provide resistance show a dominant inheritance at both loci, and Rz2 confers a higher resistance level than Rz1 (ref. 8). Rz1 and Rz2 were mapped at a distance of about 20 cM on chromosome (Chr) 3 of the sugar beet6910.…”