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

Abstract

AbstractSugar beet is hypothesized to have a narrowed genetic base due to its origin as White Silesian Beet and from numerous breeding selections and practices. High sugar quality, yield of recoverable sugar, cytoplasmic-male sterility system, monogermity, pests and disease resistance and bolting resistance constitute some of the adaptations that significantly influenced the existing genetic background of the crop. In this study we aimed to evaluate the extent of genetic diversity existing in wild beet representatives of Beta and Patellifolia and sugar beet cultivars, with a special focus on the complex Beta vulgaris. Another purpose was to determine the potential usefulness and conformity of selected molecular markers in different groups of materials in the context of rhizomania resistance. To reach these goals, molecular RAPD, ISSR techniques, literature-selected rhizomania resistance-segregating sequences as well as mitochondrial markers were used. The comparison of genetic diversity in wild and cultivated Beta forms shows that the population differentiation values and distance values are relatively high in cultivars. Moreover, the diversity component seemed to be compromised rather on the level of population (Hs) than in total (Ht) in cultivars. Our results shed a new light on the expected genetic bottlenecks existing in cultivars and revealed features specific for individual taxa (Patellifolia, Corollinae). Some degree of distinctiveness was suggested between genetic determinants of rhizomania resistance in modern cultivars in comparison with wild resistance sources. In addition, we document here an internal heterogeneity existing in selected wild/weedy accessions at the level of crucial sequences using high resolution melting.