United States Department of Agriculture, Agriculture Research Service, Forage and Range Research, Utah State University, Logan, UT, 84322, USA.
The Land Institute, 2440 E. Water Well Rd, Salina, KS, 67401, USA.
Theor Appl Genet. 2019 Aug;132(8):2325-2351. doi: 10.1007/s00122-019-03357-6. Epub 2019 Jun 6.
Allohexaploid (2n = 6x = 42) intermediate wheatgrass (Thinopyrum intermedium), abbreviated IWG, is an outcrossing perennial grass belonging to the tertiary gene pool of wheat. Perenniality would be valuable option for grain production, but attempts to introgress this complex trait from wheat-Thinopyrum hybrids have not been commercially successful. Efforts to breed IWG itself as a dual-purpose forage and grain crop have demonstrated useful progress and applications, but grain yields are significantly less than wheat. Therefore, genetic and physical maps have been developed to accelerate domestication of IWG. Herein, these maps were used to identify quantitative trait loci (QTLs) and candidate genes associated with IWG grain production traits in a family of 266 full-sib progenies derived from two heterozygous parents, M26 and M35. Transgressive segregation was observed for 17 traits related to seed size, shattering, threshing, inflorescence capacity, fertility, stem size, and flowering time. A total of 111 QTLs were detected in 36 different regions using 3826 genotype-by-sequence markers in 21 linkage groups. The most prominent QTL had a LOD score of 15 with synergistic effects of 29% and 22% over the family means for seed retention and percentage of naked seeds, respectively. Many QTLs aligned with one or more IWG gene models corresponding to 42 possible domestication orthogenes including the wheat Q and RHT genes. A cluster of seed-size and fertility QTLs showed possible alignment to a putative Z self-incompatibility gene, which could have detrimental grain-yield effects when genetic variability is low. These findings elucidate pathways and possible hurdles in the domestication of IWG.
异源六倍体（2n = 6x = 42）中间偃麦草（Thinopyrum intermedium），简称 IWG，是一种常异交多年生禾本科植物，属于小麦的三级基因库。多年生性对于粮食生产将是一个很有价值的选择，但将这个复杂特性从小麦-中间偃麦草杂种中导入的尝试尚未取得商业成功。将 IWG 自身作为一种兼用的饲料和粮食作物进行培育已经取得了有用的进展和应用，但粮食产量明显低于小麦。因此，已经开发了遗传和物理图谱来加速 IWG 的驯化。在此，使用这些图谱来鉴定与 IWG 谷物产量性状相关的数量性状位点 (QTL) 和候选基因，这些基因来自于两个杂合亲本 M26 和 M35 的 266 个全同胞后代的一个家系。在与种子大小、脱落、脱粒、花序容量、育性、茎大小和开花时间有关的 17 个性状中观察到了超亲分离。在 21 个连锁群中，使用 3826 个基于序列的基因型标记，在 36 个不同区域共检测到 111 个 QTL。最显著的 QTL 的 LOD 分数为 15，对种子保持和裸粒百分比的家系平均值分别具有 29%和 22%的协同效应。许多 QTL 与一个或多个 IWG 基因模型对齐，对应于 42 个可能的驯化直系同源基因，包括小麦 Q 和 RHT 基因。一个种子大小和育性 QTL 簇显示可能与一个假定的 Z 自交不亲和基因对齐，当遗传变异性低时，这可能对谷物产量产生不利影响。这些发现阐明了 IWG 驯化的途径和可能的障碍。
