State Plant Breeding Institute, University of Hohenheim, 70593, Stuttgart, Germany.
BMC Genet. 2019 Jul 29;20(1):64. doi: 10.1186/s12863-019-0768-2.
Heading time is an important adaptive trait in durum wheat. In hexaploid wheat, Photoperiod-1 (Ppd) loci are essential regulators of heading time, with Ppd-B1 conferring photoperiod insensitivity through copy number variations (CNV). In tetraploid wheat, the D-genome Ppd-D1 locus is absent and generally, our knowledge on the genetic architecture underlying heading time lacks behind that of bread wheat.
In this study, we employed a panel of 328 diverse European durum genotypes that were evaluated for heading time at five environments. Genome-wide association mapping identified six putative QTL, with a major QTL on chromosome 2B explaining 26.2% of the genotypic variance. This QTL was shown to correspond to copy number variation at Ppd-B1, for which two copy number variants appear to be present. The higher copy number confers earlier heading and was more frequent in the heat and drought prone countries of lower latitude. In addition, two other QTL, corresponding to Vrn-B3 (TaFT) and Ppd-A1, were found to explain 9.5 and 5.3% of the genotypic variance, respectively.
Our results revealed the yet unknown role of copy number variation of Ppd-B1 as the major source underlying the variation in heading time in European durum wheat. The observed geographic patterns underline the adaptive value of this polymorphism and suggest that it is already used in durum breeding to tailor cultivars to specific target environments. In a broader context our findings provide further support for a more widespread role of copy number variation in mediating abiotic and biotic stress tolerance in plants.
生育期是硬粒小麦的一个重要适应性特征。在六倍体小麦中，光周期 1（Ppd）基因座是生育期的重要调节因子，其中 Ppd-B1 通过拷贝数变异（CNV）赋予对光周期的不敏感性。在四倍体小麦中，D 基因组的 Ppd-D1 基因座缺失，而关于生育期遗传结构的知识普遍落后于普通小麦。
本研究利用 328 份来自欧洲的多样化硬粒小麦基因型进行了 5 个环境下的生育期评估。全基因组关联作图鉴定出了 6 个假定的 QTL，其中 2B 染色体上的一个主效 QTL 解释了 26.2%的基因型方差。该 QTL 与 Ppd-B1 的拷贝数变异相对应，其中似乎存在两种拷贝数变异。较高的拷贝数导致更早的抽穗，并且在纬度较低、易受热和干旱影响的国家更为常见。此外，还发现了另外两个 QTL，分别对应 Vrn-B3（TaFT）和 Ppd-A1，分别解释了 9.5%和 5.3%的基因型方差。
我们的研究结果揭示了 Ppd-B1 拷贝数变异作为欧洲硬粒小麦生育期变异的主要来源的未知作用。观察到的地理模式强调了这种多态性的适应价值，并表明它已经在硬粒小麦的育种中被用于根据特定的目标环境来调整品种。从更广泛的角度来看，我们的研究结果进一步支持了拷贝数变异在介导植物非生物和生物胁迫耐受性方面更广泛的作用。
