Project Number: 5310-21000-008-11
Project Type: Trust

Start Date: Nov 01, 2007
End Date: Oct 31, 2008

Objective:
Determine if thermotherapy and/or shoot tip grafting (STG) eliminates HLB in budwood.; Determine seasonal fluctuations in the infectivity of psyllids in Florida; Determine the incidence of HLB occurring in Murraya in areas where HLB is endemic in Brazil, evaluate Murraya species to determine genetic relationships between M. paniculata and M. exotica; Determine if HLB infected fruit can serve as a source of inoculum for psyllid vectors; Determine if sources of tolerance exist in diverse germplasm of Citrus and citrus relative.

Approach:
All research in Florida where plants are deliberately infected with HLB or are known to be HLB infected must be done in high security containment facilities. In cooperation with Lisa Williams, Florida DPI, we will monitor themotherapy and shoot tip grafting progeny plants for presence of HLB. Evaluations will be done by testing from plants and from psyllids from a clean colony forced to feed on the ¿therapied¿ plant, then testing the psyllids by PCR for presence of HLB and conducting transmission experiments. As new diagnostic methods are developed in other labs and made available, they will be utilized in the testing for HLB. Similar experiments will be conducted in cooperation with S. Lopes, Fundecitrus, Brazil. Susan Halbert, Florida DPI, will collect psyllids from the same locations on a regular basis. The psyllids will be preserved in alcohol, and sent to Lee and Manjunath in Riverside where they will be tested for HLB. As space in the containment facilities permits, some psyllids will be transferred to receptor plants which will then be monitored for HLB. Susan Halbert and Peggy Sieburth, FL Budwood Bureau, will monitor the trees in the arboretum for psyllids which will be preserved in alcohol and tested for HLB in Riverside. Sieburth and Lee will collect plant samples at 6 month intervals for testing for HLB by real time PCR. The California researchers will work cooperative with S. Lopes, Fundecitrus, Brazil, who will collect suspect (symptomatic) Murraya plants, as well as psyllids from the plants, from dooryards in areas near groves which harbor HLB. The HLB infested area of Sao Paulo State will be systematically sampled and about 300 samples in total will be collected. DNA extractions will be made to permit analyses by SSR markers to determine the genetic relatedness of the Murraya, and also extractions for real time PCR assay for HLB. DNA extracts from sources of Murraya from California, Florida as well as extracts from authentic M. exotica plants, will be analyzed using SSR markers. Transmission attempts from HLB infected fruit will be performed in Brazil in cooperation with S. Lopes. Psyllids from a clean colony will be used, confined to fruit for at least 10 days, then half will be tested by real time PCR and the remainder used for transmission to receptor plants. Documents Trust iwth CAlifornia Citrus Research Board. Log 35888.