Loss of crop genetic diversity due to modern plant breeding is an enduring global concern. The U.S. Pacific Northwest (PNW) is an important wheat (Triticum aestivum L.)‐producing region. We examined population structure and changes in genomic‐level and agroecosystem‐level genetic diversity of PNW wheat over the past 120 yr. Wheat varieties were slightly structured by spring and winter growth habit, but not by geographic origin or period of variety release. At the genomic level, we did not find long‐term shifts in gene diversity in either spring or winter wheat, but fluctuations were significant within market classes and within the most widely grown spring and winter varieties. Diversity in hard red spring (HRS) wheat peaked in 1970–1999 and since dropped below the level of varieties before 1930. Hard red winter (HRW) in 2000–2019 is more diverse than before 1930, whereas soft white spring (SWS) and soft white winter (SWW) are at the same level of diversity in 2000–2019 as they were before 1930. The most widely grown spring varieties had the lowest diversity in 1930–1969, whereas the most widely grown winter varieties had the lowest diversity in 2000–2019. At the agroecosystem level, Simpson's index of diversity (1 − D) has been on a rising trend since the 1990s as the dominance of acreages by a few varieties has become less common. Cultivation of multiple market classes and periodic incorporation of new germplasm by breeding programs have been able to maintain the quantitative level of genetic diversity in PNW wheat over time.

中文翻译：

---

美国西北太平洋地区历史和现代小麦品种的遗传多样性

由于现代植物育种而造成的作物遗传多样性的丧失是全球持续关注的问题。美国西北太平洋地区（PNW）是重要的小麦（Triticum aestivumL。）-产区。我们研究了过去120年中PNW小麦的种群结构以及基因组水平和农业生态系统水平的遗传多样性变化。小麦品种在春季和冬季的生长习性上略有结构，但不是按地理来源或品种发布时期构成。在基因组水平上，我们没有发现春小麦或冬小麦的基因多样性发生长期变化，但在市场类别和最广泛种植的春冬季品种中波动很大。硬红春（HRS）小麦的多样性在1970–1999年达到顶峰，此后降至1930年之前的品种水平以下。2000–2019年的硬红冬（HRW）比1930年之前更多样化。白色冬季（SWW）在2000–2019年的多样性水平与1930年之前相同。在1930–1969年，生长最广泛的春季品种的多样性最低，而在2000–2019年，生长最广泛的冬季品种的多样性最低。在农业生态系统层面，辛普森的多样性指数（1 −D）自1990年代以来一直呈上升趋势，因为少数品种占主导地位的土地变得不那么普遍了。通过育种计划的培育，多种市场类别的培育和新种质的定期整合已经能够长期保持PNW小麦遗传多样性的定量水平。