High-density AFLP map of nonbrittle rachis 1 (btr1) and 2 (btr2) genes in barley (Hordeum vulgare L.)

Abstract

Wild relatives of barley disperse their seeds at maturity by means of their brittle rachis. In cultivated barley, brittleness of the rachis was lost during domestication. Nonbrittle rachis of occidental barley lines is controlled by a single gene (btr1) on chromosome 3H. However, nonbrittle rachis of oriental barley lines is controlled by a major gene (btr2) on chromosome 3H and two quantitative trait loci on chromosomes 5HL and 7H. This result suggests multiple mutations of the genes involved in the formation of brittle rachis in oriental lines. The btr1 and btr2 loci did not recombine in the mapping population analyzed. This result agrees with the theory of tight linkage between the two loci. A high-density amplified fragment-length polymorphism (AFLP) map of the btr1/btr2 region was constructed, providing an average density of 0.08 cM/locus. A phylogenetic tree based on the AFLPs showed clear separation of occidental and oriental barley lines. Thus, barley consists of at least two lineages as far as revealed by molecular markers linked to nonbrittle rachis genes.

Six-rowed barley originated from a mutation in a homeodomain-leucine zipper I-class homeobox gene

“…One of the main arguments in the debate over the evolution of barley relates to genetic changes between the brittle and nonbrittle rachis and between the two-and six-rowed spikes. We previously inferred the phylogeny of rachis brittleness (21) and of the number of rows of spikelets (22) based on molecular markers that are tightly linked to the btr1/btr2 and vrs1 genes. The genealogy based on each domestication gene (here, a domestication gene is one that motivates humans to domesticate a plant) allows adequate inferences about the origins of cultivated barley.…”

Characterization and Mapping of a Shattering Mutant in Rice That Corresponds to a Block of Domestication Genes

“…While we do not yet know the identity of the gene underlying the QTL, we infer that it may correspond to a different allele at the sh-h locus. We also investigated literature on genetic loci associated with the shattering habit in other grass crop species such as maize Stec 1991, 1993), sorghum (Paterson et al 1995b), pearl millet (Poncet et al 2002), wheat (Watanabe and Ikebata 2000;Jantasuriyarat et al 2004), barley (Komatsuda et al 2004), and American wild rice (Z. palustris var. interior L.) (Kennard et al 2002) along with comparative genetic maps (Devos 2005) to see whether any shattering loci have been reported in a homeologous region in other grasses.…”

“…Studies to determine the genetic basis of crop domestication in other grass species have identified genes and QTL associated with the shattering habit in maize Stec 1991, 1993), sorghum (Paterson et al 1995b), pearl millet (Poncet et al 2002), wheat (Watanabe and Ikebata 2000;Jantasuriyarat et al 2004), barley (Komatsuda et al 2004), and American wild rice (Zizania palustris var. interior L.) (Kennard et al 2002).…”

AB-QTL analysis in spring barley: II. Detection of favourable exotic alleles for agronomic traits introgressed from wild barley (H. vulgare ssp. spontaneum)

“…Indeed, several studies have reported segregation ratios for brittleness, which do not fit the two complementary gene models, but suggested the presence of additional loci (Matus et al 2003). Komatsuda et al (2004) detected two minor QTLs for brittleness on chromosomes 5H and 7H coinciding with the position of the QTLs QBrt.S42-5H.a and QBrt.S42-7H.a. The QTL on chromosome 5H may also be identical to the weak rachis QTL Hst-7L detected by Kandemir et al (2000).…”