A phylogenetic analysis based on nucleotide sequence of a marker linked to the brittle rachis locus indicates a diphyletic origin of barley

Background and Aims Barley ( Hordeum vulgare ssp. vulgare) cultivation started between 9500 and 8400 years ago, and was a major part of ancient agriculture in the Near East. The brittle rachis is a critical trait in the domestication process. Methods A DNA sequence closely linked to the brittle rachis complex was amplified and resequenced in a collection of cultivated barleys, wild barleys ( H. vulgare ssp. spontaneum) and weedy brittle rachis varieties (H. vulgare ssp. vulgare var. agriocrithon). The sequence was used to construct a phylogenetic tree. Key Results The phylogeny separated the W- (btr1- carrying) from the E- (btr2-carrying) cultivars. The wild barleys had a high sequence diversity and were distributed throughout the W- and E- clades. Some of the Tibetan var. agriocrithon lines were closely related to the E- type and others to the W- type cultivated barleys, but an Israeli var. agriocrithon line has a complex origin. + Conclusions The results are consistent with a diphyletic origin of barley. The W- and E- type cultivars are assumed to have evolved from previously diverged wild barley via independent mutations at Btr1 and Btr2.