Multistate Scientists Seek HLB Tolerance

Brian GermanCitrus, Research

A $1.5 million emergency grant is enabling scientists in citrus-producing states to find trees tolerant to the devastating citrus disease HLB. The disease has crippled Florida’s citrus industry and has already been detected in California, which grows 80% of America’s fresh citrus.

The National Institute of Food and Agriculture is supporting scientists at the University of California, Riverside (UCR); the University of Florida and the U.S. Department of Agriculture’s Agricultural Research Service in the search for plants with natural tolerance to HLB. 

HLB Tolerance
Asian citrus psyllids are responsible for spreading HLB disease. (USGS)

“If you find a disease affecting your crops, a good first step is to look for plants that are able to grow and produce despite infection,” said UCR geneticist Danelle Seymour. “Then you can start to identify the genetic basis of the disease tolerance and make sure the next generation of plants includes these genes.”

Seymour and UCR plant pathologist Philippe Rolshausen will examine a set of 350 citrus hybrids developed and grown by project collaborators in Florida. All trees in the set are already infected with HLB, yet they live longer, are healthier and yield more fruit than their infected relatives.

While numerous projects are searching for solutions to HLB, this one is different because the plants being tested were all grown in an environment endemic to the disease. Additionally, the number of plants that can be tested is unusually large. “The environment in which these plants were grown means we can be confident that these rootstocks will enhance tree health and yield in HLB-affected areas,” Seymour said. “Also, because our data set is so large, we’ve got the opportunity to identify plants with levels of tolerance that exceed current commercial varieties.”

In addition to searching for parts of the hearty hybrids’ genomes responsible for their tolerance to HLB, scientists will be checking for plants that have resistance to other pathogens that are already in California. Citrus in the state is also threatened by nematodes that chew up roots, preventing plants from taking up nutrients, and by phytophthora, a type of water mold that causes rotting roots. 

“This way, we’re making sure the next generation of rootstocks will include the right genes and that we’re being as efficient as possible in our breeding practices,” Seymour said. 

Source: University of California, Riverside