National Institute of Agrobiological Sciences, Tsukuba, 305-8602, Japan.
Faculty of Science, Plant Breeding Institute, The University of Sydney, Cobbitty, NSW, 2570, Australia.
Plant J. 2018 May;94(3):525-534. doi: 10.1111/tpj.13876. Epub 2018 Apr 6.
Wild barley forms a two-rowed spike with a brittle rachis whereas domesticated barley has two- or six-rowed spikes with a tough rachis. Like domesticated barley, 'agriocrithon' forms a six-rowed spike; however, the spike is brittle as in wild barley, which makes the origin of agriocrithon obscure. Haplotype analysis of the Six-rowed spike 1 (vrs1) and Non-brittle rachis 1 (btr1) and 2 (btr2) genes was conducted to infer the origin of agriocrithon barley. Some agriocrithon barley accessions (eu-agriocrithon) carried Btr1 and Btr2 haplotypes that are not found in any cultivars, implying that they are directly derived from wild barley through a mutation at the vrs1 locus. Other agriocrithon barley accessions (pseudo-agriocrithon) carried Btr1 or Btr2 from cultivated barley, thus implying that they originated from hybridization between six-rowed landraces carrying btr1Btr2 and Btr1btr2 genotypes followed by recombination to produce Btr1Btr2. All materials we collected from Tibet belong to pseudo-agriocrithon and thus do not support the Tibetan Plateau as being a center of barley domestication. Tracing the evolutionary history of these allelic variants revealed that eu-agriocrithon represents six-rowed barley lineages that were selected by early farmers, once in south-eastern Turkmenistan (vrs1.a1) and again in the eastern part of Uzbekistan (vrs1.a4).
野生大麦形成二棱小穗，穗轴易碎，而栽培大麦形成二棱或六棱小穗，穗轴坚韧。与栽培大麦一样，“agriocrithon”形成六棱小穗；然而，小穗像野生大麦一样易碎，这使得 agriocrithon 的起源模糊不清。对六棱小穗 1（vrs1）和非易碎穗轴 1（btr1）和 2（btr2）基因的单倍型分析推断了 agriocrithon 大麦的起源。一些 agriocrithon 大麦品种（eu-agriocrithon）携带的 Btr1 和 Btr2 单倍型在任何品种中都没有发现，这表明它们是通过 vrs1 基因座的突变直接从野生大麦中衍生而来的。其他 agriocrithon 大麦品种（pseudo-agriocrithon）携带来自栽培大麦的 Btr1 或 Btr2，这表明它们起源于携带 btr1Btr2 和 Btr1btr2 基因型的六棱地方品种之间的杂交，然后通过重组产生 Btr1Btr2。我们从西藏收集的所有材料都属于 pseudo-agriocrithon，因此不支持青藏高原是大麦驯化的中心。这些等位变异的进化历史表明，eu-agriocrithon 代表了被早期农民选择的六棱大麦谱系，一次是在土库曼斯坦东南部（vrs1.a1），另一次是在乌兹别克斯坦东部（vrs1.a4）。
