Field trial of non-transgenic grapefruit on SCFV transgenic and control rootstocks.
Photo Credit: USDA Agricultural Research Service
Citrus greening [huanglongbing (HLB)] has emerged as
the most significant disease in citrus (Citrus sp.)
agriculture. The disease is associated with theCandidatus Liberibacter species of bacteria. The most
prevalent and virulent species in this group isCandidatus Liberibacter asiaticus. It is primarily vectored
by the asian citrus psyllid [ACP (Diaphorina citri)].
The bacteria and insect vector are present in many
citrus orchards worldwide, including the United States,
China, and Brazil. HLB often has a devastating impact on
infected citrus; causing a rapid decline, with loss of fruit
yield and quality and potentially leading to tree death.
The bacteria has had a significant negative impact on the
citrus industry, causing loss of fruit quality and yield, as
well as loss of root mass, leading to tree decline. Finding
a cure has been challenging due to the complexity of the
CLas bacteria interactions with the citrus host and the
asian citrus psyllid. Another factor that has made it hard
to recover from the disease is the tendency of the citrus
industry to focus on a small number of cultivars with
commercially desirable traits, but little genetic diversity.
Researchers who are working to find a citrus cultivar
that is HLB resistant have a choice of either adding
genetic variation through breeding with distant relatives
or modifying the trees transgenically. In an article
published this month in the Journal of the American
Society for Horticultural Science, scientists present
promising results from transgenic populations that
produce antibodies that can bind with CLas proteins and
reduce the bacteria’s ability to replicate.
This study advances the research needed to test the
durability and strength of any resistance conferred by
expression in rootstocks to a grafted tree and will
hopefully lead to the development of a novel protection
strategy for HLB.
According to Ed Stover, a Research Horticulturalist with
the USDA Agricultural Research Service, “The Florida
citrus industry desperately needs more HLB tolerant
trees. If sufficient tolerance can be conferred by a single
transgenic rootstock then it will greatly expedite
implementation. Any transgenic solution will require
extensive validation and analyses for non-target effects
and food safety.”
The complete article is available on the ASHS Journal of the American Society for Horticultural Science electronic journal web site:
About the American Society for Horticultural Science
Established in 1903, the American Society for Horticultural Science is recognized around the
world as one of the most respected and influential professional societies for horticultural
scientists. ASHS is committed to promoting and encouraging national and international
interest in scientific research and education in all branches of horticulture. Comprised of
thousands of members worldwide, ASHS represents a broad cross-section of the
horticultural community – scientists, educators, students, landscape and turf managers,
government, extension agents and industry professionals. ASHS members focus on
practices and problems in horticulture: breeding, propagation, production and
management, harvesting, handling and storage, processing, marketing and use of
horticultural plants and products. To learn more, visit .
