Scientists seek out citrus plants with disease resistance

Citrus Greening Disease, also known as Huanglongbing (HLB), causes bitter, useless citrus fruit. Florida’s citrus industry has been decimated by the disease, which has now been discovered in California where 80 percent of the US’s citrus is grown. Over a quarter of a million oranges, grapefruits and mandarins are threatened. 

To combat this menace, a $1.5 million grant has been given to University of California Riverside (UCR) scientists to find disease resistant citrus plants. 

“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.”

To find tolerant plants, Seymour and UCR plant pathologist Philippe Rolshausen will study 350 citrus hybrids grown by collaborators in Florida. These plants are already infected with HLB but seem to be living longer, healthier lives and producing more fruit than other infected plants. This is what makes this project unique, in that it’s looking at infected plants in an area where the disease is endemic and the test size is quite large as well. 

“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,” said Seymour. “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.”

Beyond resistance to HLB, the scientists are also testing citrus plants for resistance to other diseases already found in California. 

“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,” said Seymour.

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By Zach Fitzner, Earth.com Staff Writer