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University of West Indies PhD award-winning student, UF visiting scholar

While she was a graduate student at the University of the West Indies in Jamaica, Sasha-Kay Clarke and her adviser, Dr. Sherline Brown, were hopeful they would find a research scientist who would accept Clarke as a visiting doctoral student. Brown and Clarke sought a laboratory where Clarke would be able to learn and conduct research using entomological and molecular techniques.

Brown and Clarke found Jawwad Qureshi, a University of Florida assistant professor of Horticultural Entomology, and sent him an email message expressing their interest in having Clarke visit his lab. Qureshi asked for more information about Clarke’s work and her plans for doctorate research. After a review of Clarke’s qualifications and exemplary academic performance, Qureshi offered Clarke a position as a Visiting Research Scholar in his laboratory for one year and in collaboration with Dr. Wayne Hunter laboratory, Research Entomologist at neighboring U.S. Department of Agriculture U.S. Horticultural Research Laboratory.

In August 2017, Clarke boarded a plane in Jamaica bound for Florida. She moved into the dormitory at the UF Institute of Food and Agricultural Science’s Indian River Research and Education Center in Fort Pierce and began work in Qureshi’s Citrus Entomology Laboratory on management of Asian citrus psyllid using biological and molecular techniques.

In Fort Pierce, Clarke has been conducting research to isolate genes inside the Asian citrus psyllid. The insect vectors pathogens that cause huanglongbing (HLB), or citrus greening disease. The infection is responsible for reducing Florida’s signature crop to half of what it once was. Clarke said the opportunity at IRREC was auspicious because she is working with a team of scientists using the latest scientific knowledge to solve a pressing issue with an internationally important crop.

Clarke, Qureshi, Hunter, and a number of scientists who work in the center of the state’s celebrated grapefruit production region devote most of their work to resolve citrus greening.

Clarke said her skill set as a research scientist had grown considerably for the time she has worked at IRREC. She said citrus greening is also a problem in Jamaica, where citrus is an important crop.

“RNA interference is a highly sequence-specific approach to modulating gene expression at the post transcriptional level,” said Clarke. “In Dr. Qureshi’s Citrus Entomology Laboratory, I have been working with RNA interference using double-stranded RNA triggers to suppress vital genes in the HLB insect vector, the Asian citrus psyllid.”

Clarke said her goal is to find a way to help manage the psyllid with the RNA interference by altering genes vital to the insect’s survival. If the scientists are able to “interfere” with the insect’s genes, then they can reduce its population in the region where citrus is produced and control the citrus greening pathogen.

“The best thing about this work is that double-stranded RNAi is very specific. We are able to target a specific insect—it’s inexpensive to do—it affects only the targeted insect, and the effect decreases naturally over time, thus, safe for the environment.”

Clarke explained that with RNA interference, her work is to knockout a specific gene within the insect that will reduce it as a carrier of the bacteria that causes the disease, citrus greening.

“When we find the correct gene and RNAi technique, we can use $4 to treat up to 200 trees,” said Clarke. “Right now, we are looking at how the citrus trees absorb this treatment to effectively deliver it to the psyllid.”

Clarke published a research paper in Journal of Economic Entomology about her work with genetic variance of said citrus psyllid in Jamaica citrus production habitats. Her work characterized the genetics of the psyllids in the Caribbean and its endosymbiont Wolbachia sp.

“The Asian citrus psyllid is a global problem because its dispersal is easily influenced by anthropogenic activities,” said Clarke. “Humans help the psyllid to move globally and now the insect and the pathogen it carries are problems everywhere in the world where citrus is produced.”

During the last year, Clarke’s work has been recognized three times with prestigious awards. During the Florida Academy of Science meeting held in Miami Shores in March this year, her work as the lead scientist on a research project won the Best Graduate Student Poster Presentation. The project title was: Assessment of Psyllids RNA Off-Target Effects on a Ladybeetle Predator. Florida Scientist Abstracts.

For Clarke’s oral presentation delivered at the Florida State Horticultural Society meeting in June, in Fort Lauderdale, she was recognized with a First Place award, Best Graduate Student Oral Presentation. The title presentation was: Factors Affecting Citrus Tree Absorption and RNAi Delivery to Asian Citrus Psyllid. Florida State Horticultural Society Abstracts.

Clarke has also written a research paper for the above presentation which is expected to be published in one of the Society’s journals this year.

This year in July, during the Florida Entomology Society’s annual meeting, Clarke was recognized with a Second Place award, the Best Graduate Student Oral Presentation. The title for the award-winning work was Assessment of Psyllid-dsRNA Off-Target Effects (Predator: Prey).

In a week, Clarke’s position with UF as a Visiting Scholar will culminate. Her plans are to return to Jamaica and complete a Ph.D. in molecular biology and then seek a post doctorate position. She said she wants to gain more skills in bioinformatics and genetic variations.

“So many diseases affect vital crops and food, we need to ensure their safety and availability. I want to help in this way,” said Clarke. “I enjoy when new discoveries are made, and I can participate in the help it gives food production.”

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