Rice is a staple diet for many. But a recent study by Agricultural Research Service (ARS) under the United States department of agriculture has found that rising levels of carbon dioxide are causing natural transfer of genes from weedy rice to domesticated rice. This is worrisome because it can hit production of rice. Jyotika Sood talks to Lewis H Ziska, plant physiologist with ARS and lead author, about the implications
What are your key findings?
We have found that higher levels of atmospheric carbon dioxide facilitate the flow of genes between closely related wild or weedy rice plants and domesticated rice varieties. But this gene flow is not the same in both directions. Increased temperatures due to carbon dioxide levels leads to double flowering in wild rice varieties. Moreover, the weedy rice develops a greater height than the domesticated rice. Flowering and plant height are important factors in pollen sharing and impact gene flow. Transfer of wild genetic material to domesticated rice can result in the production of seed with weedy characteristics that would be undesirable in rice production.
How was the study conducted?
We carried out a two-year field study to document how atmospheric carbon dioxide concentrations affect growth in weedy and domesticated rice. We observed that weedy wild rice, often called red rice, transferred its various traits like red pericarp, greater shattering (falling of grain from the plant) and taller stands of weedy rice to domesticated species.
What implications does the study have for plant breeders and farmers?
For plant breeders, it is both good and bad news. Wild rice may respond more strongly to rising carbon dioxide, with greater seed yield. Consequently, understanding the basis of this response could help identify characteristics that could allow breeders to look for and incorporate those desirable characteristics in cultivated rice as a means to convert more carbon dioxide into seed yield. Conversely, breeders should be aware of a greater vulnerability of cultivated rice to undesired weedy characteristics with greater genetic mixing between wild and domesticated rice. For farmers, it suggests that rising carbon dioxide may enhance the competition from wild weedy rice in rice production and reduce consumable rice production.
What is your next step?
We wish to study wild weedy rice as a prototype to understand how rice can grow and yield more with increased atmospheric carbon dioxide.
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