Delhaize Emmanuel, Rathjen Tina M, Cavanagh Colin R
CSIRO Agriculture, GPO Box 1600, Canberra, ACT 2601, Australia
CSIRO Agriculture, GPO Box 1600, Canberra, ACT 2601, Australia.
J Exp Bot. 2015 Aug;66(15):4527-36. doi: 10.1093/jxb/erv223. Epub 2015 May 11.
Rhizosheaths comprise soil that adheres to plant roots and, in some species, are indicative of root hair length. In this study, the genetics of rhizosheath size in wheat was investigated by screening the progeny of multiparent advanced generation intercrosses (MAGIC). Two MAGIC populations were screened for rhizosheath size using a high throughput method. One MAGIC population was developed from intercrosses between four parents (4-way) and the other from intercrosses between eight parents (8-way). Transgressive segregation for rhizosheath size was observed in both the 4-way and 8-way MAGIC populations. A quantitative trait loci (QTL) analysis of the 4-way population identified six major loci located on chromosomes 2B, 4D, 5A, 5B, 6A, and 7A together accounting for 42% of the variation in rhizosheath size. Rhizosheath size was strongly correlated with root hair length and was robust across different soil types in the absence of chemical constraints. Rhizosheath size in the MAGIC populations was a reliable surrogate for root hair length and, therefore, the QTL identified probably control root hair elongation. Members of the basic helix-loop-helix family of transcription factors have previously been identified to regulate root hair length in Arabidopsis and rice. Since several wheat members of the basic helix-loop-helix family of genes are located within or near the QTL, these genes are candidates for controlling the long root hair trait. The QTL for rhizosheath size identified in this study provides the opportunity to implement marker-assisted selection to increase root hair length for improved phosphate acquisition in wheat.
根鞘由附着在植物根部的土壤组成，对于某些物种而言，根鞘可指示根毛长度。在本研究中，通过筛选多亲本高代杂交（MAGIC）群体的后代，对小麦根鞘大小的遗传学进行了研究。使用高通量方法对两个MAGIC群体进行根鞘大小筛选。一个MAGIC群体由四个亲本间杂交（四交）产生，另一个由八个亲本间杂交（八交）产生。在四交和八交MAGIC群体中均观察到根鞘大小的超亲分离。对四交群体的数量性状位点（QTL）分析确定了位于2B、4D、5A、5B、6A和7A染色体上的六个主要位点，这些位点共同解释了根鞘大小变异的42%。根鞘大小与根毛长度密切相关，并且在没有化学限制的情况下，在不同土壤类型中都很稳定。MAGIC群体中的根鞘大小是根毛长度的可靠替代指标，因此，所确定的QTL可能控制根毛伸长。先前已鉴定出拟南芥和水稻中基本螺旋-环-螺旋转录因子家族的成员可调节根毛长度。由于基本螺旋-环-螺旋基因家族的几个小麦成员位于QTL内或附近，这些基因是控制长根毛性状的候选基因。本研究中鉴定出的根鞘大小QTL为实施标记辅助选择提供了机会，以增加根毛长度，从而提高小麦对磷的吸收。
