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Apr 4, 2012

Spinach Genes Provide Cure For Citrus Greening Disease - Lead to Development of New GM Citrus Crops in Texas


Dr. Erik Mirkov, 

plant pathologist at
Texas AgriLife 

Research and Extension
Photo: Texas AgriLife Research 
Texas AgriLife Research scientists have discovered that two spinach genes can make a citrus tree resistant to the Huanglongbing (HLB), a citrus greening disease that can ruin citrus orchards.  Citrus greening is a bacterial disease that affects the vascular system of the tree.  According to Dr. Erik Mirkov, a Texas AgriLife Research plant pathologist, "it basically shuts off the tree's ability to take up and use water and nutrients, causing the tree to die."

Using biotechnology, Mirkov's research team inserted two spinach genes into a gene-modified (GM) citrus tree creating the first HLB virus resistant citrus tree. One of the spinach genes is more effective than then other but they work better together than alone.  Mirkov inserted the two spinach proteins because he knew that they had broad-spectrum resistance against multiple bacteria and fungi.

Initial funding for the research was provided by the U.S. Department of Agriculture (USDA).  Additional support has been donated by Florida citrus producer Southern Gardens Citrus to develop third and fourth generation trees that are immune to HLB. The trees include Rio Red and Ruby Red grapefruit, Hamlin and Marrs sweet oranges, and three rootstocks – Flying Dragon, C22 and Carrizo.  This could take up to three or four years to complete.  Regulatory approval would be necessary from the USDA following this to ensure that these new GM citrus crops are safe for human consumption.  Currently Mirkov is meeting several times a year with federal agencies to keep them abreast of his progress. This includes the Food and Drug Administration (FDA), the Environmental Protection Agency (EPA), and the U.S. Department of Agriculture (USDA).

HLB disease is spread by two species of psyllid insects.  has been devastating the citrus orchards in the Americas, Asia, and parts of Africa.  According to Mirkov, if some type of solution is not found for HLB, "the world’s entire citrus industry is at risk. ... Citrus greening is a citrus grower’s worst nightmare because at this point, there is no cure. It can spread for years before it can be detected, so it’s insidious, to say the least."  It is thought to have originated in China in the 1900s.  Greening was detected in Florida in 2005 and earlier in 2012 in the Lower Rio Grande Valley of Texas.

According to Ray Prewett, president of Texas Citrus Mutual, a commodity group in Mission, “the entire U.S. citrus industry is placing a lot of hope and faith on the outcome of this research. Our industry is using all of the currently available tools to fight the disease recently found in Texas, but we are counting on disease-resistant trees as our best long term solution.”

For more see:

"Spinach Genes May Stop Deadly Citrus Disease," Crop Biotech Update, 4 April 2012.

"U.S.: GM citrus trees show HLB disease resistance," GreenBiotech News, 2 April 2012.

Santa Ana, Rod. "Spinach genes may stop deadly citrus disease," Texas AgriLife Research and Extension Center Press Release, 26 March 2012.

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About Margaret


CEO and Curator (The Food Museum) | Managing Director and Chief Editor (GR2 Global LLC) | Educator (UCLA PhD) | Researching and writing on global food issues, nutrition and health, sustainability, history (preservation), conservation (natural resources), and design.
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