Agriculture Research Service, Forage and Range Research Laboratory (FRRL), United States Department of Agriculture, Utah State University, Logan, UT, 84322-6300, USA.
Mol Genet Genomics. 2014 Jun;289(3):383-97. doi: 10.1007/s00438-014-0817-5. Epub 2014 Feb 9.
Rhizomes are prostrate subterranean stems that provide primitive mechanisms of vegetative dispersal, survival, and regrowth of perennial grasses and other monocots. The extent of rhizome proliferation varies greatly among grasses, being absent in cereals and other annuals, strictly confined in caespitose perennials, or highly invasive in some perennial weeds. However, genetic studies of rhizome proliferation are limited and genes controlling rhizomatous growth habit have not been elucidated. Quantitative trait loci (QTLs) controlling rhizome spreading were compared in reciprocal backcross populations derived from hybrids of rhizomatous creeping wildrye (Leymus triticoides) and caespitose basin wildrye (L. cinereus), which are perennial relatives of wheat. Two recessive QTLs were unique to the creeping wildrye backcross, one dominant QTL was unique to the basin wildrye backcross, and one additive QTL was detectable in reciprocal backcrosses with high log odds (LOD = 31.6) in the basin wildrye background. The dominant QTL located on linkage group (LG)-2a was aligned to a dominant rhizome orthogene (Rhz3) of perennial rice (Oryza longistamina) and perennial sorghum (Sorghum propinquum). Nonparametric 99 % confidence bounds of the 31.6-LOD QTL were localized to a distal 3.8-centiMorgan region of LG-6a, which corresponds to a 0.7-Mb region of Brachypodium Chromosome 3 containing 106 genes. An Aux/IAA auxin signal factor gene was located at the 31.6-LOD peak, which could explain the gravitropic and aphototropic behavior of rhizomes. Findings elucidate genetic mechanisms controlling rhizome development and architectural growth habit differences among plant species. Results have possible applications to improve perennial forage and turf grasses, extend the vegetative life cycle of annual cereals, such as wheat, or control the invasiveness of highly rhizomatous weeds such as quackgrass (Elymus repens).
根茎是匍匐于地下的茎，为多年生草本植物和其他单子叶植物提供了原始的营养繁殖、生存和再生机制。根茎的增殖程度在不同的禾本科植物中差异很大，在谷物和其他一年生植物中不存在，在丛生多年生植物中严格受限，或在某些多年生杂草中具有高度入侵性。然而，根茎增殖的遗传研究是有限的，控制根茎生长习性的基因尚未阐明。比较了源自根茎匍匐野燕麦（Leymus triticoides）和丛生 Basin 野燕麦（L. cinereus）杂种的正反交回交群体中控制根茎扩散的数量性状位点（QTL），它们是小麦的多年生近缘植物。两个隐性 QTL 是匍匐野燕麦回交所特有的，一个显性 QTL 是 Basin 野燕麦回交所特有的，一个加性 QTL 在 Basin 野燕麦背景下的正反交回交中具有高对数优势（LOD=31.6）可检测到。位于连锁群（LG）-2a 上的显性 QTL 与多年生水稻（Oryza longistamina）和多年生高粱（Sorghum propinquum）的显性根茎同源基因（Rhz3）对齐。31.6-LOD QTL 的非参数 99%置信区间定位于 LG-6a 的远端 3.8 厘摩区域，该区域对应于 Brachypodium 染色体 3 中包含 106 个基因的 0.7-Mb 区域。一个 Aux/IAA 生长素信号因子基因位于 31.6-LOD 峰处，这可以解释根茎的向地性和向光性行为。研究结果阐明了控制根茎发育和植物物种间结构生长习性差异的遗传机制。研究结果可能有助于提高多年生饲料草和草坪草，延长小麦等一年生谷物的营养生长周期，或控制高度根茎杂草如节节麦（Elymus repens）的入侵性。
