Abstract
Crop domestication from wild ancestors has resulted in the wide adaptation coupled with improved yield and quality traits. However, the genetic basis of many domesticated characteristics remains to be explored. Upland cotton (Gossypium hirsutum) is the most important tetraploid cotton species, accounting for about 90% of world cotton commerce. Here, we reveal the effects of domestication on fiber and stress traits through comprehensive analyses of semi-domesticated races and cultivated cotton accessions. A total of 416 cotton accessions were genotyped, and a decrease in genetic diversity from races to landraces and modern cultivars was detected. Furthermore, 71 domestication selective sweeps (DSS) and 14 improvement selective sweeps (ISS) were identified, with the Dt sub-genome experiencing stronger selection than the At sub-genome during the both selection types. The more expressed genes and a delay in the expression peak of genes related to secondary cell wall (SCW) development in modern cultivars compared to semi-domesticated cotton races, may have contributed to long fibers in these plants. However, down-regulation of genes related to stress response was responsible for decreasing stress tolerance in modern cultivars. We further experimentally confirmed that silencing of PR1 and WRKY20, genes that showed higher expression in the semi-domesticated races, drastically compromised cotton resistance to V. dahliae. Our results reveal fiber improvement and decreased stress tolerance as a result of the domestication of modern upland cotton cultivars.
Highlights
Crop domestication of wild plants has resulted in a variety of physiological and economical improvements
Evolution and domestication of upland cotton has been extensively investigated through different methods, such as biochemical markers (Wendel et al, 1992), molecular markers (Brubaker and Wendel, 1994; Hinze et al, 2016), gene expression arrays (Hovav et al, 2008b), RNA-seq (Chaudhary et al, 2009; Yoo and Wendel, 2014), and whole genome resequencing (Fang et al, 2017a; Fang et al, 2017b; Wang et al, 2017; Ma et al, 2018)
We found that the G. tomentosum species were closely related to semi-wild upland cotton races which is consistent with that of a previous report (Wendel and Cronn, 2003)
Summary
Crop domestication of wild plants has resulted in a variety of physiological and economical improvements. The allotetraploids that were present 1–2 million years ago (MYA) originated from one hybridization event between an extinct progenitor of Gossypium herbaceum (A1) or Gossypium arboreum (A2) and another progenitor, Gossypium raimondii (D5) (Wendel, 1989). Fiber Improvement and Stress Tolerance and the Caribbean, upland cotton was first domesticated at least 4,000–5,000 years ago, and was subsequently subjected to directional selection (Wendel et al, 1992). In later evolution and domestication studies, upland cotton was often divided into three groups; wild or semi-domesticated races ( named semi-wild), landraces, and improved modern cultivars (Fang et al, 2017a; Fang et al, 2017b; Wang et al, 2017). The improved modern cultivars that are widely cultivated in nowadays and have a high fiber yield and superior fiber quality, are mainly derived from the landraces
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