Evaluation of rhizomaniaresistance segregating se

Authors: Anna Litwiniec Maria Gośka Beata Choińska Kamilla Kużdowicz Aleksander Łukanowski Barbara Skibowska

Publish Date: 2015/10/07

Volume: 207, Issue: 3, Pages: 685-706

PDF Link

Abstract

Sugar 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 cytoplasmicmale 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 literatureselected rhizomania resistancesegregating 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 meltingSugar beet Beta vulgaris L ssp vulgaris is a crop with great economic importance especially in temperate climate zones where it constitutes a valuable sucrose source It contributes about one fifth to the global sugar production which for the 2007–2011 period reached approximately 157 million metric tons Koo and Taylor 2012 Crop rotation is necessary in beet production due to disease problems Koo and Taylor 2012 which may also be effectively eliminated by resistance breeding approachesBreeding contributed above all to the increase in sugar yield Some hybrids of fodder beets selected for relatively high sugar content ie “White Silesian” constituted the origin for all subsequently developed sugar beet varieties Fischer 1989 Biancardi et al 2010 At the same time other breeding practices and directions for example cytoplasmic male sterility and genetic monogermity systems used throughout the history of the modern crop’s development are supposed to impinge significantly on its genetic structure and as a consequence to result in genetic bottlenecks thus reducing available diversity and hampering in a way the progress in genetic combinations for new cultivars’ releases Biancardi et al 2010A considerably higher genetic diversity is expected to exist in wild relatives of sugar beet serving thus as a reservoir of potentially useful traits and genes such as those determining tolerance to biotic and abiotic stresses yield parameters or other advantageous morphological and physiological features Van Geyt et al 1990 Stevanato et al 2013 Hybridization between B vulgaris and exotic germplasm belonging to Beta is possible often providing fertile progeny fully compatible at the chromosomal level This phenomenon has been employed in sugar beet enhancement programs since the beginnings of the twentieth century as growth in cultivated acreage and expanding distribution areas were inevitably related to increased pathogen pressure and disease spread Panella and Lewellen 2007 Biancardi et al 2010 From this time on many directed and internationally coordinated initiatives have been undertaken by research and breeding communities especially in France and the USA aiming not only at the introgression of selected valuable traits into the sugar beet crop but also at broadening of its genetic base Such an integrated approach although requiring further selection cycles is at the same time expected to stimulate more rational and flexible management of genetic resources in the future Frese et al 2001 Additionally as a result of interfertile B vulgaris coexisting in seed production areas spontaneous outcrossings between wild and cultivated beets promote the origin of weed beets Boudry et al 1993 Despite its stochastic nature and basically unwanted effects in that particular case the phenomenon itself may also have some positive implications via increasing the variability level in the available gene poolOne of the best examples for implementing desired characters successfully in wild sea beet Beta vulgaris ssp maritima during breeding is rhizomania resistance genes Early partially resistant sugar beet cultivars were developed based on Munerati’s pool of these accessions selected in the Po estuary for Cercospora leaf spot resistance Van Geyt et al 1990 Presently it is believed that all the resistance sources identified thus far designated from Rz1 to Rz5 originate most probably from some wild sea beet ancestors Biancardi et al 2002 although their identity and independence from each other has not been fully confirmed yetIn this study we aimed to evaluate the extent of genetic diversity existing in wild beet representatives belonging to the genera Beta and Patellifolia as compared to sugar beet cultivars with a special emphasis on the complex Beta vulgaris using molecular RAPD ISSR techniques and literatureselected putative rhizomania resistancesegregating markers as well as mitochondrial markersOur results not only shed a new light on the expected genetic bottlenecks existing in cultivars and revealed some features specific for individual taxa Patellifolia Corollinae but also suggest that some degree of distinctiveness may exist between genetic determinants of rhizomania resistance in modern cultivars when compared with wild resistance sources

Keywords: