As California joins the fight against citrus greening, they believe they have a trio of citrus trees that could hold the key to beating the disease.


Citrus greening, also known as HLB, was detected in a South Florida grove in 2005, and it has decimated the Sunshine State’s citrus harvests since then. Citrus greening has been detected in California a few times, and researchers and citrus growers there are trying to get out ahead of the disease. More scientists and researchers working towards the end of citrus greening can only be a good thing. Researchers with the University of California believe they have three citrus trees that may be able to contribute to the end of citrus greening, according to a University of California, Agriculture and Natural Resources release. Read a summary of the article below.

Citrus Greening in California


Citrus greening was first detected in California in 2012 in a residential citrus tree located in Hacienda Heights, and then again in a residential kumquat tree in San Gabriel in 2015. Both are areas around Los Angeles.

The disease is spread by the Asian citrus psyllid, and both trees were destroyed. Citrus officials believe it will only be a handful of years until the disease is detected in commercial citrus groves.

California’s Special Citrus Trees


There are three citrus trees located at the University of California’s Lincove Research and Extension Center (REC) that researchers believe may be resistant to citrus greening. They are the current focus of Mikeal Roose, a professor of genetics in the Department of Botany and Plant Sciences at UC Riverside, and one of the creators of the easy-peel mandarin, Tango. The trees, each over three decades old, are “crosses of sweet orange (two) and Rangpur lime (one) with Eremocitrus glauca, the desert lime, a wild Australian citrus relative,” according to the release.

Roose believes the trees could be resistant to citrus greening due to a project conducted by UC Riverside scientist Chandrika Ramadugu. Ramadugu tested 100 California accessions of citrus and closely related genera—like kumquats, for instance—from the National Clonal Germplasm Repository for Citrus and Dates, looking for citrus resistance.  An Australian citrus variety, Eremocitrus sp., was one of the few discovered to be resistant to the bacteria that cause citrus greening. Additionally, the resistance is transmitted genetically to hybrids.

Seedlings from those three trees are currently growing large enough to be tested for resistance to citrus greening. The trees could offer a wealth of information about resistance, in addition to their HLB-resistant DNA.

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