Effect of Advanced Cycle Breeding on Genetic Diversity in Barley Breeding Germplasm

Abstract

Plant breeding that emphasizes crosses among elite parents in a closed population (advanced cycle breeding) is presumed to decrease genetic diversity. To assess the effect of plant breeding on allelic diversity, we evaluated regional ancestors, parental lines, and cultivar candidates from the University of Minnesota six‐rowed barley (Hordeum vulgare L.) breeding program between 1958 and 1998 using pedigree information, 70 simple sequence repeat (SSR) markers, and a gene specific marker. Pedigree and SSR allelic diversity indices revealed a decrease in genetic diversity, from an average of 5.89 alleles per locus in the ancestors group to 2.34 alleles per locus in the fourth decade of breeding. A correspondence analysis showed differentiation in the germplasm with time. At specific loci, we detected both reductions and no change in the number of alleles over time. Several marker loci that demonstrated a reduction in number of alleles were associated with major loci for disease resistance or malting quality and were presumably under selection during breeding. Assessment of locus‐specific allelic variation across the genome in breeding germplasm should identify both the regions of the genome that should be conserved and the regions of the genome where there are opportunities to introgress new allelic diversity without disrupting desirable gene complexes.

Population structure and linkage disequilibrium in elite barley breeding germplasm from the United States

“…1), both of which are important genetic diversity (Cornuet and Luikart, 1996). The narrow gene pool of Midwest six-rowed spring barley (MN and N6) also was reported by other researchers (Wych and Rasmusson, 1983;Horsley et al, 1995;Condón et al, 2008;Mikel and Kolb, 2008;Hamblin et al, 2010). Another important statistic in population genetics is the number of rare polymorphisms (variants).…”

“…2 and also the highest background LD (r 2 =0.12) among all subpopulations. In contrast, Midwest six-rowed spring subpopulations (sp2, sp6, and sp9) with a very narrow genetic pool (Horsley et al, 1995;Condón et al, 2008;Hamblin et al, 2010) had a much lower background LD from 0.04 to 0.07. These results indicate that structure is an important confounding factor for LD estimation in CAP.…”

“…2). These programs have a very narrow gene pool and also share a large proportion of founders (Horsley et al, 1995;Condón et al, 2008;Hamblin et al, 2010). Because of gene recombination, each Midwest line has a different size and location of a founder's chromosomal segments, but the proportion of one founder's genetic material is likely to be constant.…”

One Century of Interactions Between Intensive Breeding and Genetic Diversity Conservation of Barley

“…Jedel and Helm (1994) detected average annual decreasing of grain protein content 0.01-0.02 g kg −1 yr −1 during over 77 years in western Canadian barley cultivars. The annual gain 0.065% in starch content in the extract detected Condón et al (2008).…”

“…According to the third conclusion, selection both by breeders and farmers resulted in loss of alleles, including microsatellite alleles, in the heterogeneous breeding materials due to selection against undesirable traits linked to these alleles (Fufa et al, 2007) and the plant breeding led to a narrowing of genetic diversity (Allard, 1996;Grausguber et al, 2002;Condón et al, 2008). This was observed also within barleys grown in northern Europe where the foundation genotypes, i.e.…”