The US Corn Belt and European maize owe their existence to a historic change: the ability of this plant, originally from the tropics, to flower early enough to avoid winter. Research led by Cornell University in New York and the Max Planck Institute (MPI) for Developmental Biology in Tuebingen, Germany reveals that indigenous people in the American southwest started the process of adapting maize to temperate growing seasons 4000 years ago and refined it over the following 2000 years.
From this point onwards, it grew well enough to provide a reliable source of subsistence, mainly in stews and soups. Its nutritional content was also improved - the study finds that some of the archaeological samples had high beta-carotene yellow kernels, the earliest evidence of people eating yellow corn. The kernels were also likely to be of the popping variety.
Farmers adapted it using the genetic diversity of domesticated varieties and wild grass relatives already present in Mexico. Over time, their selections meant that varieties became dominant for gene variants that drive early flowering, enabling them to cope with a shorter growing season and different day-lengths. This took millennia to accomplish.
“We see incredible genetic variation in maize, but it took a long time to accumulate enough of the early flowering variants in the same plant to adapt to short growing seasons. A trait like flowering time is so complex that it involves changes to hundreds of genes,” says Kelly Swarts from Cornell University and now at the MPI for Developmental Biology.
The samples reveal that the first maize successfully adapted to grow in a temperate climate was short, bushy and was likely a pop-type corn compared to modern varieties, or landraces. The authors find that it helped lead to all temperate US and European maize grown today.
“Our findings show that because of its genetic diversity maize has the ability to adapt to just about anything that’s thrown at it” says Swarts. “But we won’t have the luxury of millennia to adapt maize to the environmental challenge of global warming and will need precision breeding, for example with genome-edited crops, to rapidly develop new varieties. Maintaining diversity in traditional maize landraces is also important. Precision breeding holds great promise, as long as we have a good understanding of what to target by studying the widest possible diversity.”
The scientists studied 15 maize samples extracted from fossilized maize cobs discovered in a dry cave shelter known as Turkey Pen in Utah’s Grand Gulch canyon."It was very exciting to carry out the first genetic analysis of the samples since their excavation in the 1970s,” says Hernán Burbano from the MPI for Developmental Biology. “The samples were very well-preserved in this dry environment. Although DNA fragments were short, in some samples up to 80% of the retrieved fragments were maize DNA with only a minor fraction of microbial origin. Consequently, it was possible to characterize genetic variation in each sample across the whole genome,” he says.
The authors gathered information from thousands of modern inbred maize varieties. To predict flowering in the long-dead archaeological samples, they compared the genomes of ancient and modern strains. To test whether their predictions were accurate, they developed populations from descendants of the ancient varieties and grew them to observe when they flowered.
The validation showed that the initial predictions were highly accurate. Future studies of archaeobotanical crop samples could now use the same methods. “It wasn’t thought possible to pinpoint a trait like flowering time from archaeological samples and it’s only because of recent advances in both ancient and modern genomics that we’ve been able to generate these new insights,” says Swarts.
The study was funded by the National Science Foundation in the US and the Max Planck Society in Germany. It will be published on Friday 4th August in Science.
Sarah Hailer | Max-Planck-Institut für Entwicklungsbiologie
In focus: Peptides, the “little brothers and sisters” of proteins
12.11.2018 | Technische Universität Berlin
How to produce fluorescent nanoparticles for medical applications in a nuclear reactor
09.11.2018 | Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences (IOCB Prague)
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure
Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...
Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly
The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...
Scientists developed specially coated nanometer-sized vehicles that can be actively moved through dense tissue like the vitreous of the eye. So far, the transport of nano-vehicles has only been demonstrated in model systems or biological fluids, but not in real tissue. The work was published in the journal Science Advances and constitutes one step further towards nanorobots becoming minimally-invasive tools for precisely delivering medicine to where it is needed.
Researchers of the “Micro, Nano and Molecular Systems” Lab at the Max Planck Institute for Intelligent Systems in Stuttgart, together with an international...
09.11.2018 | Event News
06.11.2018 | Event News
23.10.2018 | Event News
12.11.2018 | Life Sciences
12.11.2018 | Materials Sciences
12.11.2018 | Physics and Astronomy