Molecular assessment of genetic diversity in winter barley and its use in breeding

Abstract

During the last decades extensive progress has been achieved in winter barley breeding with respect to both, yield and resistance to fungal and viral diseases. This progress is mainly due to the efficient use of the genetic diversity present within high yielding adapted cultivars and -with respect to resistance -to the extensive evaluation of genetic resources followed by genetic analyses and introgression of respective genes by sexual recombination. Detailed knowledge on genetic diversity present on the molecular level regarding specific traits as well as on the whole genome level may enhance barley breeding today by facilitating efficient selection of parental lines and marker assisted selection procedures. In the present paper the state of the art with respect to virus diseases, i.e. Barley mild mosaic virus, Barley yellow mosaic virus, and Barley yellow dwarf virus is briefly reviewed and first results on a project aiming on a genome wide estimation of genetic diversity which in combination with data on yield and additional agronomic traits may facilitate the detection of marker trait associations and a more efficient selection of parental genotypes are presented. By field tests of 49 two-rowed and 64 six-rowed winter barley cultivars the genetic gain in yield for the period 1970-2003 was estimated at 54.6 kg ha −1 year −1 (r 2 = 0.567) for the six-rowed cultivars and at 37.5 kg ha −1 year −1 (r 2 = 0.621) for the two-rowed cultivars. Analysis of 30 SSRs revealed a nonhomogenous allele distribution between two and six-rowed cultivars and changes of allele frequencies in relation to the time of release. By PCoA a separation between two and six-rowed cultivars was observed but no clear cut differentiation in relation to the time of release. In the two-rowed cultivars an increase in genetic diversity (DI) from older to newly released cultivars was detected.

Plant Breeding: Assessment of Genetic Diversity in Crop Plants and its Exploitation in Breeding

“…The magnitude of the genetic gain achieved by these intensive breeding activities was determined in several studies (Riggs et al 1981;Wych and Rasmusson 1983;Bulman et al 1993;Jedel and Helm 1994;Muñoz et al 1998) and varies on average between 16 kg ha −1 y −1 for the period between −1 y −1 between 1960 and 1980 in Italy (Martiniello et al 1987). Results of field tests carried out on 64 six-rowed and 49 two-rowed winter barley cultivars that were registered in Germany during the last 40 years estimate the genetic gain in yield at 54.6 kg ha −1 y −1 (r 2 =0.567) for the six-rowed cultivars and at 37.5 kg ha −1 y −1 (r 2 =0.621) for the two-rowed cultivars (Ordon et al 2005). For the actual state of barley variety development in Europe, see also Friedt and Rasmussen (2003).…”

“…To get an even more detailed insight into the influences modern plant breeding had on the genetic diversity during the last 4 decades, 64 six-rowed and 49 two-rowed cultivars that were registered during this time in Germany and gained some importance were analysed using a set of 30 SSR markers distributed evenly over the whole genome (Ordon et al 2005). The 30 SSRs corresponded to 169 different alleles and the genetic similarity S D was estimated on average at 0.51 on the whole set and at 0.56 and 0.58 for the sixrowed and two-rowed cultivars, respectively.…”

Effects of Introgression and Recombination on Haplotype Structure and Linkage Disequilibrium Surrounding a Locus EncodingBymovirusResistance in Barley

“…Carriers of rym4 are resistant to BaMMV, BaMMV-Sil, and BaYMV-1, but are susceptible to BaYMV-2, while those carrying rym5 are resistant to BaYMV-1, BaYMV-2, and BaMMV, but not to BaMMV-Sil (Kanyuka et al 2004). Although at least seven independent loci conferring resistance to BYMV have been identified in barley to date (Ordon et al 2005), European breeding has relied heavily on rym4 and rym5, both of which originate from single germplasm accessions. The Dalmatian landrace Ragusa is the source of rym4 (Huth 1985), while rym5 derives from the Chinese landrace Mokusekko 3 (Konishi et al 1997;Graner et al 1999;Friedt et al 2000).…”

Marker assisted separation of resistance genes Rph22 and Rym16 Hb from an associated yield penalty in a barley: Hordeum bulbosum introgression line

“…To date, 18 resistance loci have been identified against these viruses, with 15 recessive genes and one dominant gene located in H. vulgare (Ordon et al 2005;Kai et al 2012), and two dominant genes (Rym14 Hb and Rym16 Hb ) from H. bulbosum (Ruge et al 2003;Ruge-Wehling et al 2006). Development of resistant cultivars is the only effective tool for controlling the effect of these viruses.…”