Transgenic Efforts Against HLB

Matthew Mattia recently provided an overview of work at the U.S. Department of Agriculture Agricultural Research Service (USDA ARS) transgenic test site in Fort Pierce. Transgenic refers to an organism that contains genetic material into which DNA from an unrelated organism has been artificially introduced. Scientists at the Picos Farm screen transgenics for suppression of citrus Candidatus Liberibacter asiaticus (CLas), the bacteria that causes the citrus disease huanglongbing (HLB). They seek tree resistance to or tolerance of HLB.

Mattia, a USDA ARS citrus research geneticist, said resistance means there is no CLas in the plant on replication, and no HLB ever. Tolerance means that the tree’s economic production is not affected when there is detectable CLas in the tree and HLB symptoms are present. Tolerance can only be verified after many field seasons.   

Scientists at Picos Farm conduct the testing in the lab, greenhouse and field. Lab testing is the fastest, with a two- to three-week turnaround time. Greenhouse testing data is available about a year after plants are inoculated with CLas. Field-plant testing takes the longest time but gives true confirmation of resistance/tolerance, Mattia said. Field testing yields initial data about a year after planting, but resistance data requires from four to six years to obtain. 

Testing at the 8-acre site began in 2015 with funding from the Citrus Research and Development Foundation. Scientists from other institutions, including the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS), perform transgenics work at the USDA ARS site.

Mattia’s presentation was the first of several by USDA ARS and UF/IFAS researchers during an Aug. 31 Citrus Transgenic Field Day at the testing site. More than 30 people attended either in person or via Zoom. Other topics discussed at the field day included:

• Identification of HLB-tolerant transgenic lines
• Mapping HLB responses in trifoliate orange to support breeding and transgenic improvements
• Transgenic rootstocks for HLB tolerance: A view on progress and limitations
• Evaluating systemic acquired resistance genes for inducing enhanced tolerance to HLB

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