Southern Gardens Citrus in Clewiston, Florida, an agricultural company, has
applied to the United States Department of Agriculture (USDA) in February
for permission to use the engineered version of the citrus tristeza virus
(CTV) to fight the bacterium that causes citrus greening. Citrus greening,
or huanglongbing, is a disease that has slashed orange production in the US
in half over the past decade, and threatens to destroy the US$3.3-billion
industry entirely. The application's comment period has ended, and the USDA
will now assess the possible environmental effects of the engineered virus.
Field trials of engineered CTV are being conducted and once the request is
approved, it would be the first time this approach has been used
commercially. It could also provide an opportunity to sidestep the
regulations and public stigma related to genetically engineered crops.
The engineered virus is not the only option being explored to tackle citrus
greening. Other projects aim to edit the citrus tree genome using
CRISPR-Cas9 to make them more resistant to the pest, or to engineer trees
that express defense genes or short RNA molecules that prevent disease
transmission. Local growers have also helped to fund an international
project that has sequenced citrus trees in the search for more weapons
against citrus greening.