2012 Annual Report 1a.Objectives (from AD-416): 1. To screen citrus species and related species in the USA and China for resistance to the Asian citrus psyllid. 2. To identify plant traits which impart resistance to the psyllid, traits that could be used to develop commercial citrus varieties with psyllid resistance for the purpose of reducing incidence of huanglongbing disease. 1b.Approach (from AD-416): Subject candidate citrus species and related species in free-choice infestation studies and determine species that are avoided by the psyllid for food and reproduction. Evaluate these apparently resistant plant species in no-choice studies to confirm they are avoided by the psyllid. Plant resistant species in the field and monitor them over time to determine if they develop huanglongbing. 3.Progress Report: This project is related to inhouse project objective 3c: Investigate basic biology and ecology of the Asian citrus psyllid and its natural enemies in Florida citrus. The objective of this project is to discover citrus germplasm with resistance to the Asian citrus psyllid. We have identified genotypes of Poncirus trifoliata and xCitroncirus sp. (hybrids of P. trifoliata and another parent species) that have resistance to the psyllid. We are now trying to identify the genotypic and phenotypic traits that promote resistance. Clear differences exist in the volatile profiles of susceptible and resistant plants. A project is being planned to analyze the amino acids, sugars, flavenoids, carrotenoids, isoprenoids, and sterols in phloem contents of germplasm that differs in psyllid susceptibility. This will provide information about the underlying reasons why some germplasm is psyllid-resistant and help identify traits that can be used in citrus breeding programs to confer psyllid resistance. Citrus that has been genetically transformed to express a plant defense protein is being evaluated for psyllid resistance.