This indicates that the root storage was an already existing trait that predisposed the plant for cultivation and not solely the result of human domestication, as previously thought. This discovery, published today in Nature Plants is part of a comprehensive monographic study of morning glories, the largest study of this group of plants to date, which also contributes important insights to the taxonomy and evolution of this megadiverse group of plants.
The researchers also discovered that sweet potato is not the only species of morning glory that produces storage roots. In fact at least 62 other species in the group also produce these underground organs, some of them as large as those of the sweet potato and many also edible.
Dr Pablo Muñoz, from Oxford's Department of Plant Sciences, whose PhD thesis formed a significant part of the paper said: 'Most other studies trying to understand the evolution of sweet potato assumed that its root storage is a product of domestication by humans. This study demonstrates that storage roots evolved many times independently in different species including sweet. potato before humans. '
The plant genus Ipomoea commonly known as morning glories, is one of the largest groups of flowering plants in the world. It includes over 800 species, including many ornamental plants and one of the most important crops for human consumption: the sweet potato ( Ipomoea batatas ). However, despite their importance and widespread distribution, most species of morning glories are very poorly known and have never been studied across their entire geographical range, hindering the understanding of this important group of plants.
Researchers at the University of Oxford's Department of Plant Sciences has the first comprehensive monographic study of morning glories at a global scale. It is a long-term collaboration with colleagues at the International Potato Center in Peru, Oregon State and Duke Universities in the US and the Royal Botanic Garden of Edinburgh. Their results include the description of 63 new species (almost 1
Their methods could offer a solution to the massive backlog in documenting and describing the bulk of the world's plant species.
The scientists demonstrated how a monographic taxonomic study carried out at a global scale could make massive contributions to ours understanding of diversity existing in poorly known groups of organisms. By working out the evolution of morning glories, they were also able to investigate several issues pertaining to the origin and evolution of sweet potato.
The research uses herbarium specimens – dried plants preserved in botanical gardens, museums and other institutions – for both morphological comparative studies and molecular analyzes. Herbarium specimens comprise an unparalleled resource to address the study of inadequately known plant groups and is the only feasible way to study megadiverse tropical groups across their entire distribution.
Lead author, Professor Robert Scotland, said: 'We hope this study acts as a catalyst in demonstrating the scale of progress that can be achieved. Taxonomy has often been perceived as simply descriptive science, and the continuation of work carried out by 18th and 19th century naturalists and no longer necessary.
'However, we believe that an accurate, up-to-date taxonomy is necessary to tackle the biodiversity crisis. A large percentage of tropical plant species are poorly known that, in practice, they are invisible to conservation studies. Taxonomy is the science that underpins biology and provides our basic knowledge of what species are there and where they live. Our study demonstrates the potential of taxonomy, through the integration of morphological studies and molecular analyzes, to contribute to understanding much of plant diversity existing on Earth. '
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