Genetic and Phenotypic Characterization Of Bolting Failure In Sugar Beet (Beta vulgaris)

In cool temperate climates, sugar beets are currently grown as a spring crop. They are sown in spring and harvested in autumn. Growing sugar beet as a winter crop with an extended vegetation period fails due to bolting after winter. To control this we are aiming to identify genes underlying bolting failure. Previously, we had identified a sugar beet accession which segregates for bolting failure. Fifty percent of the plants from this accession did not bolt after vernalization under field conditions. We hypothesized an oligogenic gene model responsible for the observed bolting failure. The respective sugar beet accession was crossed with a biennial sugar beet with regular bolting behavior to develop a structured mapping population. F2 and F3 generations were grown in consecutive years in the greenhouse and transplanted to the field after artificial vernalization at 5°C for 16 weeks. Bolting was recorded twice a week from mid of May until end of October. At the end of the experiment we observed non bolting plants in each generation. The statistical analysis of the replicated experiment with F3 families showed a significant genetic variation for bolting rate (p < 0.0001). Linkage mapping resulted in a first QTL termed nb1 (non bolting after vernalization 1) showing a LOD score of 15.46 and explained 34.2 % of the phenotypic variation of bolting failure.