Domestication and Spread of Broomcorn Millet (Panicum miliaceum L.) Revealed by Phylogeography of Cultivated and Weedy Populations

Yue Xu,Xinyu Zhao,Fanshuang Meng,Chunxiang Li,Xingyu Zhu,Fengjie Sun,Hui Zhou,Fuzhou Wang,Xin Zhao,Mingyue He,Ping Lu,Minxuan Liu

doi:10.3390/agronomy9120835

Abstract

Cultivated broomcorn millet (Panicum miliaceum L.), one of the most ancient crops, has long been an important staple food in the semiarid regions of Eurasia. Weedy broomcorn millet (Panicum ruderale (Kitag.) Chang comb. Nov.), the companion weed of cultivated broomcorn millet, is also widely distributed throughout Eurasia and can produce fertile offspring by crossing with cultivated broomcorn millet. The evolutionary and genetic relationships between weedy and cultivated broomcorn millets, and the explicit domestication areas and detailed spread routes of this cereal are still unclear. The genetic diversity and population structure of 200 accessions of weedy and cultivated broomcorn millets were explored to elucidate the genetic relationship between weedy and cultivated broomcorn millets, and to trace the explicit domestication areas and detailed spread routes of broomcorn millets by using 23 simple sequence repeats (SSR) markers. Our results show that the weedy populations in China may harbor the ancestral variations that gave rise to the domesticated broomcorn millet. The population structure pattern observed in the wild and domesticated broomcorn millets is consistent with the hypothesis that there may be at least two independent domestication areas in China for the cultivated broomcorn millet, the Loess Plateau and the Northeast China, with both following the westward spread routes. These two westward spread routes of cultivated broomcorn millet coincide exactly with the prehistoric Oasis Route and Steppe Route, respectively.

Highlights

Broomcorn millet (Panicum miliaceum L.), known as common millet, proso millet, hog millet, or white millet, is one of the most ancient crops in the world [1]
Three questions were addressed: (1) Is weedy broomcorn millet the descendant of the wild ancestor of the cultivated broomcorn millet? (2) Where is the explicit domestication area of cultivated broomcorn millet in China? (3) Where are the spread routes of this cereal after being domesticated in China? Our results support our hypotheses that (1) the weedy populations in China may harbor the ancestral variations that gave rise to the domesticated broomcorn millet; (2) there may be at least two independent domestication areas of broomcorn millet in China—the cultivars domesticated in the Loess Plateau, while the cultivars domesticated in the Northeast China; and (3) the westward spread routes of broomcorn millets that we speculated in this study coincide exactly with the prehistoric Oasis Route and Steppe Route, respectively
The microsatellite loci in the present study show the levels of polymorphisms appropriate for analyzing the genetic diversity of broomcorn millets

Summary

Introduction

Broomcorn millet (Panicum miliaceum L.), known as common millet, proso millet, hog millet, or white millet, is one of the most ancient crops in the world [1]. It has long been an important staple food in the semiarid regions of Eurasia, mainly in Russia, Ukraine, China, and India, because of its short growing season and high tolerance to heat and drought [2]. The archaeological remains of domesticated broomcorn millet were discovered at the Xinglonggou and the Baiyinchanghan sites in Northeast China [1,3], the Dadiwan site in the Loess BC [1,3,4,5,6,7,8,9].

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Conclusion