Carrots and Strawberries, Genetics and Phylogenetics

This is the fifth in a series of posts reviewing the 17 articles found in the October 2014 Special Issue of American Journal of Botany, Speaking of Food: Connecting Basic and Applied Science.

As expected, some of the articles in this issue get into pretty deep discussions about genetics and phylogenetics. Advancements in sequencing and analyzing DNA have not only led to better understanding of genes and their functions but have also given us greater insight into how species are related and their proper place on the phylogenetic tree.  While I have some background in these things and can follow along at a basic level, I certainly don’t feel confident in authoritatively summarizing such findings . I also question whether or not a high level discussion of phylogenetics makes for an interesting and engaging blog post. Plant systematics geeks are aggressively nodding “yes”; other readers’ eyes have glazed over by this point.

I am certainly not arguing that this is not important stuff. When a species we have become familiar with is suddenly given a new scientific name, it is not too annoy those of us who are trying to learn the names of things, rather it is because something novel has been discovered about the way living things are organized, about their life history – the way they came to be.  We should be celebrating advancements that allow us to look back over the millions of years of life on earth and see how various species emerged, evolved, disappeared, were replaced, and ultimately arrived at what we view today. And we should be humbled to know that these present forms are not the climax, that we are simply getting a glimpse in the evolutionary trajectory of the organisms around us. Perhaps it will prompt us to protect them, understanding that every scrap of biodiversity is important and worth conserving. After all, who are we to decide how the story goes?

The sixth and seventh articles in “Speaking of Food” are about carrots and strawberries respectively. Discussion about the genetics and phylogenetics of these plants dominates the articles, with the application being that we can improve these crops by better understanding their genetics, and we can gain insights into plant evolution by better understanding their phylogenetics.  Rather than give you a thorough overview of each of these articles (for reasons stated above), I am offering you bullet points of a few of the things that I learned while reading them.

Phylogenomics of the Carrot Genus (Daucus, Apiaceae) by Carlos Arbizu, Holly Ruess, Douglas Senalik, Philipp W. Simon, and David M. Spooner

  • The domesticated carrot (Daucus carota subsp. sativus) is “the most notable cultivated member of Apiaceae [a family consisting of 455 genera and over 3,500 species] in terms of economic importance and nutrition.”
  • Carrots are our primary source of vitamin A (due to high levels of alpha and beta carotenes), “accounting for about half of dietary intake.”
  • Wild carrot species can be used to improve the domesticated carrot by providing genes that will help with pest and disease resistance, yield increases, better nutrient value, etc.
  • “The taxonomy of D. carota is particularly problematical. It undergoes widespread hybridization experimentally and spontaneously with commercial varieties and other named subspecies.”
  • The researchers, upon examining more than half of the known Daucus species and 9 species that are very closely related, identified several Daucus spp. that “may be easily incorporated in carrot breeding programs.”
  • This study determined “misidentifications in germplasm collections” and highlighted “the difficulty of defining subspecies of D. carota.”
Flowers of Daucus carota (photo credit: www.eol.org)

Flowers of Daucus carota (photo credit: www.eol.org)

Fragaria: A Genus with Deep Historical Roots and Ripe for Evolutionary and Ecological Insights by Aaron Liston, Richard Cronn, and Tia-Lynn Ashman

  •  Fresh strawberries are fifth on the list of fresh fruit consumption in the United States.
  • “Resistance to a Fragaria-specific powdery mildew has been demonstrated in F. x ananassa [domesticated strawberry] transformed with a peach locus, and the cultivation of such transgenic plants could reduce pesticide usage in strawberry.” Commercial production awaits, though, “due to public resistance, a lack of industry support, and concerns over gene flow to the wild species of Fragaria.”
  • “The modern cultivated strawberry, Fragaria x ananassa, originated in the 18th century in Europe from hybridization between two species imported from North and South America. The parental species, F. virginiana and F. chiloensis, also hybridize naturally in northwestern North America, but there is no evidence that they were ever cultivated by the native Americans in this area.”
  • The stolons of strawberry plants can be used as dental floss!? So said Antoine Nicolas Duchesne in his 1766 book about strawberries. I guess I’ll have to read his account to get more insight into this interesting detail.
  • F. x ananassa has flowers that are self-compatible, but it is “derived from the hybridization of two wild species that show gender dimorphism,” which is common in the genus. For this reason, Fragaria, is “proving to be an exceptional model system for understanding the sexual system and sex chromosome evolution.”
  • Fragaria species occur across a broad range of temperate habitats and elevations from sea level sand dunes to moist, productive meadows to high, dry, mountain summits.” They are adapted to a wide variety of environmental conditions. “This variation represents a potential source of genetic variation for climatic tolerance, disease/pest resistance, and yield-associated traits.”
  • The Fragaria genus, like virtually all genera of flowering plants, includes polyploid species. Researchers conclude that Fragaria is an “ideal system for exploring relationships between ploidy formation, ploidy level, and the coordination of transcriptomic control.” They also believe that continued studies of “ecological and evolutionary genomics in Fragaria has the potential to provide further insights into hybridization.”
  • Finally, the researchers advise that the “familiarity of strawberries provides an opportunity to engage and educate the public about botanical research.”
Broadpetal Strawberry, Fragaria virginiana supsp. platypetala (photo credit: wikimedia commons)

Broadpetal Strawberry, Fragaria virginiana supsp. platypetala (photo credit: wikimedia commons)

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2 thoughts on “Carrots and Strawberries, Genetics and Phylogenetics

  1. Pingback: Your Food Is a Polyploid | awkward botany

  2. Pingback: Speaking of Food: A Recap | awkward botany

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