Recipient Organization
UNIVERSITY OF FLORIDA
G022 MCCARTY HALL
GAINESVILLE,FL 32611
Performing Department
CITRUS RESEARCH & EDUCATION CENTER, LAKE ALFRED
Non Technical Summary
Citrus tristeza virus (CTV) continues to be a threat to the citrus industries in the mainland U.S., because there are many isolates that if introduced would destroy the economic viability of our industries. CTV presently is a major constraint to citrus production in Hawaii. Isolates of CTV cause two different disease syndromes. Decline isolates kill citrus varieties on the sour orange rootstock, which unfortunately is the most desirable rootstock for many areas. Isolates that cause stem-pitting diseases, which result in reduced growth and production of small, unmarketable fruit, regardless of rootstock, present the greatest threat potentially eliminating the commercial production of sweet oranges or grapefruit. Lime production in the U.S. already is limited by existing lime stem-pitting isolates of CTV. The probability is high that severe stem-pitting isolates will be introduced into the U.S., by accident, by bioterrorism, or by emerging from a `hidden' component of an
existing population. In that event, we need to be capable of managing the disease. Cross protection, the immunization of trees with mild strains to prevent induction of disease by severe strains, is a strategy that is complementary to development of resistant trees to manage CTV-induced diseases. We propose to engineer isolates of CTV that will effectively protect trees against stem-pitting diseases.
Animal Health Component
90%
Research Effort Categories
Basic
10%
Applied
90%
Developmental
(N/A)
Goals / Objectives
This proposal has two parts. The first is to develop an understanding of how CTV causes stem pitting and how cross protection of CTV works. We will identify viral sequences that affect the production of sweet orange stem pitting, grapefruit stem pitting, and lime stem pitting. We examine the relationship of infection and distribution of CTV to the induction of stem pits, and we will examine the roles of sequence similarity, RNA silencing suppressors, and movement and distribution in cross protection. The second part of this proposal is to use this understanding to create effective cross-protecting viruses and disease-specific detection reagents to manage any stem-pitting diseases in the U.S.
Project Methods
Citrus tristeza virus (CTV) continues to be a threat to the citrus industries in the mainland U.S., because there are many isolates that if introduced would destroy the economic viability of our industries. CTV presently is a major constraint to citrus production in Hawaii. Isolates of CTV cause two different disease syndromes. Decline isolates kill citrus varieties on the sour orange rootstock, which unfortunately is the most desirable rootstock for many areas. Isolates that cause stem-pitting diseases, which result in reduced growth and production of small, unmarketable fruit, regardless of rootstock, present the greatest threat potentially eliminating the commercial production of sweet oranges or grapefruit. Lime production in the U.S. already is limited by existing lime stem-pitting isolates of CTV. The probability is high that severe stem-pitting isolates will be introduced into the U.S., by accident, by bioterrorism, or by emerging from a `hidden' component of an
existing population. In that event, we need to be capable of managing the disease. Cross protection, the immunization of trees with mild strains to prevent induction of disease by severe strains, is a strategy that is complementary to development of resistant trees to manage CTV-induced diseases. We propose to engineer isolates of CTV that will effectively protect trees against disease. We have an ongoing research program on CTV that has focused on decline isolates that are problematic in Florida. Using procedures proposed here we already have identified viral gene products involved in production of disease symptoms by the Florida decline strain and have disarmed it to a mild phenotype. This isolate is under tests to protect trees from the decline isolate. This is a proposal to develop similar information concerning stem-pitting isolates of CTV - information that will allow an effective defense in the event that severe stem-pitting isolates of CTV are introduced into the U.S.