Resistance gene analogues are clustered on chromosome 3 of sugar beet and cosegregate with QTL for rhizomania resistance

Abstract

Worldwide, rhizomania is the most important disease of sugar beet. The only way to control this disease is to use resistant varieties. Four full-length resistance gene analogues (RGAs) from sugar beet (cZR-1, cZR-3, cZR-7, and cZR-9) were used in this study. Their predicted polypeptides carry typical nucleotide-binding sites (NBSs) and leucin-rich repeat (LRR) regions, and share high homology to various plant virus resistance genes. Their corresponding alleles were cloned and sequenced from a rhizomania resistant genotype. The 4 RGAs were mapped as molecular markers, using sequence-specific primers to determine their linkage to the rhizomania resistance locus Rz1 in a population segregating for rhizomania resistance. One cZR-3 allele, named Rz-C, together with 5 other molecular markers, mapped to the Rz1 locus on chromosome 3 and cosegregated with quantitative trait loci for rhizomania resistance. After screening a bacterial artificial chromosome (BAC) library, 25 cZR-3-positive BACs were identified. Of these, 15 mapped within an interval of approximately 14 cM on chromosome 3, in clusters close to the Rz1 locus. Rz-C differentiates between susceptible and resistant beet varieties, and its transcripts could be detected in all rhizomania resistant varieties investigated. The potential of this RGA marker for cloning of rhizomania resistance genes is discussed.

Evaluation of rhizomania-resistance segregating sequences and overall genetic diversity pattern among selected accessions of Beta and Patellifolia. Potential implications of breeding for genetic bottlenecks in terms of rhizomania resistance

“…On the contrary, such sequences were found by us in wild accessions. For example, the presence of one of resistance gene analogues that was previously shown to be common and universal for different resistance sources (Lein et al 2006) was not documented here for the cultivar group, but was typical for resistant B. vulgaris ssp. maritima accessions (Fig.…”

“…In case of rhizomania resistance there are many reports concerning identification of potentially useful molecular markers that turned out to segregate with the feature in different segregating populations and, as such, they may be potentially efficient tools for breeders (Barzen et al 1997;Giorio et al 1997;Scholten et al 1997;Gidner et al 2005;Lein et al 2006;Nouhi et al 2008;Amiri et al 2009;Feghhi et al 2012). However, functional significance for most of them is poorly understood yet, and all the more so because most of them may not necessarily be located within a single major gene.…”

Molecular mapping of a gene conferring resistance to Aphanomyces root rot (black root) in sugar beet (Beta vulgaris L.)

“…This suggests that Acr1, Rz1 and, hence, Rz2 may be clustered on chromosome III. Showing organizational similarity to known resistance genes in other plants, a number of resistance gene analogues (RGAs) have been cloned from sugar beet, amongst which some have been mapped to clusters on chromosome III (Lein et al 2007). This situation is reminiscent of the hypothesis proposed by Michelmore and Meyers (1998), where clustered RGAs facilitated the evolution of resistance to diverse pathogens, in this case to Aphanomyces and BNYVV.…”

Traditional Breeding in Sugar Beet

“…Virus infection causes a reduction of up to 50% in root yield, and negatively affects sugar yield and processing quality (Büttner et al 1995). A typical symptom of virus infection is the formation of fibrous, hairy roots (Lein et al 2006). A widely used source of resistance to BNYVV is the qualitative gene, Rz1 (Lewellen et al 1987).…”