Nav: Home

Hiding in plain sight

September 16, 2019

Early rice growers unwittingly gave barnyard grass a big hand, helping to give root to a rice imitator that is now considered one of the world's worst agricultural weeds.

New research from Zhejiang University, the Chinese Academy of Sciences and Washington University in St. Louis provides genomic evidence that barnyard grass (Echinochloa crus-galli) benefited from human cultivation practices, including continuous hand weeding, as it spread from the Yangtze River region about 1,000 years ago.

Barnyard grass is a globally common invasive weed of cultivated row crops and cereals. The new study was published Sept. 16 in the journal Nature Ecology & Evolution.

"In Asia, rice farmers have traditionally planted and weeded their paddies by hand. Any weeds that stick out are easily detected and removed," said Kenneth Olsen, professor of biology in Arts & Sciences. "Over hundreds of generations, this has selected for some strains of barnyard grass that specialize on rice fields and very closely mimic rice plants. This allows them to escape detection."

Olsen collaborated on data analyses and interpretation for the new study. He is working with the study's corresponding author, Longjiang Fan of Zhejiang University, on other research related to rice evolutionary genomics and agricultural weed evolution.

This study sequenced the genomes of rice-mimic and non-mimic forms of the weed as a step towards understanding how this process has occurred.

This form of mimicry, called Vavilovian mimicry, is an adaptation of weeds to mimic domesticated plants. In the case of barnyard grass, the rice mimics grow upright like a rice plant instead of sprawling along the ground like most barnyard grass. They also have green stems like rice plants instead of the red stems more commonly found in the weed.

"With the advent of agriculture about 10,000 years ago, humans all over the planet began creating a wonderful habitat for naturally weedy plant species to exploit," Olsen said. "The most successful and aggressive agricultural weeds were those that evolved traits allowing them to escape detection and proliferate in this fertile new environment."

The researchers estimate that the mimic version of E. crus-galli emerged at about the same time that Chinese historical records indicate that the regional economic center was shifting from the Yellow River basin to the Yangtze River basin. During this period of the Song Dynasty, human populations were growing rapidly, demand for rice as the staple grain was paramount. This is also the time when a quick-maturing, drought-resistant variety of rice called Champa rice was introduced to the Yangtze basin from Southeast Asia -- to allow two harvests in a year. Weed management in paddies might have been intensified in the context of these conditions.

Traditional farming preserves diversity of Thai purple rice

However, while common barnyard grass is a major agricultural weed in the U.S., the rice mimic form has never become widespread in the main rice growing region -- the southern Mississippi valley.

Olsen speculates that this is because U.S. rice farmers rely on mechanized farming instead of hand labor.

"Without farmers out in the fields planting and weeding by hand, there's not such strong selection for weeds to visually blend in with the rice crop," he said.
-end-


Washington University in St. Louis

Related Rice Articles:

High-protein rice brings value, nutrition
A new advanced line of rice, with higher yield, is ready for final field testing prior to release.
Rice plants engineered to be better at photosynthesis make more rice
A new bioengineering approach for boosting photosynthesis in rice plants could increase grain yield by up to 27 percent, according to a study publishing January 10, 2019 in the journal Molecular Plant.
Can rice filter water from ag fields?
While it's an important part of our diets, new research shows that rice plants can be used in a different way, too: to clean runoff from farms before it gets into rivers, lakes, and streams.
Rice plants evolve to adapt to flooding
Although water is essential for plant growth, excessive amounts can waterlog and kill a plant.
Breeding better Brazilian rice
Rice production in Brazil is a multi-billion-dollar industry. It employs hundreds of thousands of people, directly and indirectly.
Breakthrough in battle against rice blast
Scientists have found a way to stop the spread of rice blast, a fungus that destroys up to 30% of the world's rice crop each year.
More rice, please: 13 rice genomes reveal ways to keep up with ever-growing population
Rice provides 20% of daily calories consumed globally. We will need more as population grows toward 9-10 billion by 2050.
Ancient rice heralds a new future for rice production
Growing in crocodile infested billabongs in the remote North of the country, Australia's wild rice has been confirmed as the most closely related to the ancient ancestor of all rices.
2-faced 2-D material is a first at Rice
Rice University materials scientists replace all the atoms on top of a three-layer, two-dimensional crystal to make a transition-metal dichalcogenide with sulfur, molybdenum and selenium.
Multi-nutrient rice against malnutrition
ETH researchers have developed a new rice variety that not only has increased levels of the micronutrients iron and zinc in the grains, but also produces beta-carotene as a precursor of vitamin A.
More Rice News and Rice Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Uncharted
There's so much we've yet to explore–from outer space to the deep ocean to our own brains. This hour, Manoush goes on a journey through those uncharted places, led by TED Science Curator David Biello.
Now Playing: Science for the People

#556 The Power of Friendship
It's 2020 and times are tough. Maybe some of us are learning about social distancing the hard way. Maybe we just are all a little anxious. No matter what, we could probably use a friend. But what is a friend, exactly? And why do we need them so much? This week host Bethany Brookshire speaks with Lydia Denworth, author of the new book "Friendship: The Evolution, Biology, and Extraordinary Power of Life's Fundamental Bond". This episode is hosted by Bethany Brookshire, science writer from Science News.
Now Playing: Radiolab

Dispatch 1: Numbers
In a recent Radiolab group huddle, with coronavirus unraveling around us, the team found themselves grappling with all the numbers connected to COVID-19. Our new found 6 foot bubbles of personal space. Three percent mortality rate (or 1, or 2, or 4). 7,000 cases (now, much much more). So in the wake of that meeting, we reflect on the onslaught of numbers - what they reveal, and what they hide.  Support Radiolab today at Radiolab.org/donate.