Genetic diversity of contemporary North American barley

Crop diversity has important implications for genetic vulnerability and potential for crop improvement. Genetic diversity was estimated by coefficient of parentage (CP) among 363 contemporary North American barley (Hordeum vulgare L.) cultivars registered during the era of 1970 through 2006. This was facilitated by using pedigree lineage derived from U.S. Plant Variety Protection Certificates and/or registration articles. Overall diversity, as measured through CP, was estimated at 0.023 for this era. Diversity was greater among feed (CP = 0.020) than among malt barley (0.111) cultivars. The estimate of genetic diversity was much lower (CP = 0.141) among 23 widely grown cultivars that constituted 87% of the U.S. harvested barley hectarage from 2001 through 2005. Within these 23 elite cultivars, diversity was substantially lower for six-row malting barley (CP = 0.574) versus two-row malting barley (CP = 0.237). Most prevalent types of breeding populations used for development of the 363 North American barley cultivars registered from 1970 through 2005 were two-parent cross (used for 44% of new cultivars), complex cross (25%), and three-parent cross (14%). Barley breeding progress for grain yield improvement was estimated at 4.4% per breeding cycle using yield comparison of progeny and parents across environments. Barley germplasm available is genetically diverse, recycling leading commercial cultivars predominates and this breeding strategy has been successful.