Bitter orange trees taste yucky to bugs

CORNELL (US) — Orange trees engineered to leave a bitter taste in the mouths of bugs may protect Florida’s $9 billion citrus industry from a deadly bacterial disease.

Scientists engineered the trees to provide a natural resistance to the Asian citrus phyllid, the insect responsible for spreading the deadly bacterial disease huanglongbing—also known as citrus greening because it causes perpetually immature green fruit that tastes bitter, medicinal, and sour.

First confirmed in Florida in 2005, the disease has spread to all citrus growing counties in the state. Citrus growers have faced a costly regime of cutting out dying trees and spraying insecticides to reduce the psyllid populations.

To find a solution, scientists at at Cornell University’s New York State Agricultural Experiment Station turned to a model system: tomatoes.

Plant pathology and plant-microbe biology faculty members Kerik Cox and Herb Aldwinckle first identified a handful of naturally occurring insecticides produced by bacteria, fungi, and plants known to fend off other types of insects.

Then research support specialist Ewa Borejsza-Wysocka and technicians Peggy Abbott and Shirley Kuehne used genetic engineering to insert candidate genes individually and in groups into tomato plants. They found some transgenic lines were very effective in making the tomato leaves unappealing to tomato psyllid insects and inserted the most promising genes into the Hamlin orange variety.

The diminutive transgenic orange plants await the opportunity to prove themselves against the Asian citrus psyllid on its home turf in Florida while the required permits and approvals are being secured. Aldwinkle says he hopes to have some results of the trials within a year.

Rick Kress, president of Southern Gardens Citrus Inc., one of the largest citrus growers and processors of not-from-concentrate orange juice in Florida, is in the process of continuing the overall research in Florida through evaluation of disease resistance on a commercial basis and is optimistic that the work will have tremendous economic benefits.

“It would also have a positive environmental impact by reducing insecticide sprays, because in Florida, trying to eliminate the Asian citrus psyllid is as daunting as trying to get rid of mosquitoes.”

More news from Cornell University: