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What’s up with pecans?
In parts of Mexico, 40% of pecan harvests have been lost to vivipary, a condition that causes the nuts to germinate prematurely.
“What happens is that before the pecan comes off a tree, it begins to germinate, to make a whole new tree,” said Jennifer Randall of New Mexico State University. “There’s a little root coming out of the pecans. You can’t eat them. You can’t sell them. It is becoming quite a problem.”
She said the condition has started to show up in the United States, affecting pecan orchards in Texas and Arizona. It is one of a number of challenges facing pecan production that are linked to climate change.
Randall is a Ph.D. plant molecular biologist and plant pathologist in NMSU’s Department of Entomology, Plant Pathology and Weed Science. She is also the lead researcher in a group of scientists working to develop genetic tools to breed climate-adapted pecan trees.
“As climate is changing, it is important to get the genetic information growers need to have the right trees to grow in specific areas today, but also 50 years from now,” Randall said. “Vivipary is just part of it. We are looking at water quality, drought stress, salinity (salt-content) tolerance. We are looking at gene networks that determine flowering, pecan-nut composition and tree architecture, smaller trees because growers would like to be able to grow more trees per acre.
“We are looking at diseases caused by fungal and bacterial organisms and by insects. Damage caused by humidity, things we don’t see (in New Mexico). We will help our New Mexico growers, but the main goal is to help pecan growers across the United States.”
A lot to do
Work such as this is not new to Randall.
“We had a (U.S. Department of Agriculture) grant that started in 2016 and just ended this year,” she said. “We reported on the genomes (genetic material) in four varieties of pecans – the Pawnee, Lakota, Elliot and Oaxaca.”
There are hundreds of varieties of pecans, the most prevalent in New Mexico being the Wichita, Western and Pawnee. Randall said the pecan has a native region that spans from Oaxaca in Mexico to Illinois, an area with many different climates.
The new multistate research project directed by Randall is funded by a four-year grant from the National Institute of Food and Agriculture, part of USDA. An allocation of $3.9 million will pay for the first two years.
Randall is overseeing a team made up of faculty from NMSU, Texas A&M, the University of Arizona, the University of Georgia, the University of Oklahoma and the University of California. It also includes USDA scientists in Texas, Georgia and Louisiana.
“We have so many people working on it because we have a lot to do,” Randall said.
The group will work with the Alabama-based HudsonAlpha Institute for Biotechnology to analyze genetic mismatches that cause vivipary, budding that fails to adapt to environmental changes and other problems.
Randall said data collected will allow the development of vital genetic tools necessary for understanding regional adaptation and selecting improved cultivated plants and rootstocks for all major pecan regions.
Research will be done on the ground as well as in labs. There are research plots in Arizona, California, Texas, Oklahoma, New Mexico and other areas.
“Quite a bit of the work will happen in (New Mexico’s) Mesilla Valley,” Randall said. “We have pecan orchards at our Leyendecker Experimental Farm here in Las Cruces. Among the things we will be looking at there, due to precarious soil and constraints on water here, are rootstocks that are salinity tolerant.”
Building a picture
New Mexico is a major player in pecan production.
According to 2021 USDA figures, the most recent available, the state has 46,000 pecan-bearing acres, which ranks it fourth behind Georgia, Texas and Oklahoma. This does not count those acres planted with immature trees that are not yet producing pecans.
The 2021 USDA report also showed that New Mexico produced more than 78 million pounds of in-shell pecans, second after Georgia, for a value of nearly $189 million, which ranks first in the country.
Stats such as that are vital to Richard Heerema, a pecan specialist at NMSU and a member of Randall’s research team.
“We have people with expertise in economics, ecology, soil science, molecular biology and more,” Heerema said of the researchers. “My own area of expertise is in horticulture and plant physiology.”
Since he is based in New Mexico, it’s no surprise that Heerema’s focus is on how pecan plants fare in arid conditions.
“I’m interested in salinity tolerance because the build up of salt in irrigation water, or in the soil, can cause physiological stress in the (pecan) plant,” he said. “I’m pretty interested in tolerance to water stress (lack of moisture), how the root functions and how the leaf functions. I’m interested in the connection between the genetics of the plant and how it tolerates water stress.”
He wants to know how that works in existing varieties, but he’s also intrigued by the possibility of improving varieties.
“In a four-year grant, we will not have time to develop new varieties,” Heerema said. “But we may be able to identify genetic markers that could be used for new variety development down the road.
“We are going to build a picture of what makes these plants tick.”