1) Trees have been in the ground for 4 years in a trial of 50 selections and cultivars on US-802 following no-choice ACP inoculation and several months in an ACP house. Standard growth measurements and disease ratings were initiated in July 2014 and will continue on a semi-annual basis. HLB is now widespread and the trees looking healthiest include a full sib of our best mandarin selection (unfortunately not in this trial), and several of our best grapefruit-like hybrids. The one true grapefruit is the least healthy selection in the trial. The best performers include hybrids containing Poncirus, and conventional hybrids which are predominately mandarin or pummelo. It may take 2-3 more years to clearly distinguish tolerant material. These trees are cropping this year, though Irma dropped a lot of fruit, and fruit will be used in a complementary project exploring synthesis of orange-like juice from HLB-tolerant types. The 5 selections with the highest percent of full canopy volume ratings had 46% to 57% increase in canopy volume over the last year while the 7 with the lowest percent of full canopy volume ranged from 0 to 23% increase. The r2 for percent of full canopy volume vs. last year�s % growth was 0.37 across the entire planting. Several selections that had looked good last year suddenly dropped to a very low canopy increase, and it appears this may be a relatively early indicator of HLB tolerance. 2) In June 2015 a field planting was established of: seedling trees of 133 Fortune x Fairchild hybrids from an earlier mapping study, seedlings of 27 Ponkan-like accessions, budded trees of 10 advanced ARS selections that are predominately mandarin, and budded trees of Fortune, Fairchild and Valencia. Data collection is underway. A NIFA grant proposal was submitted and funded to mobilize tolerance for industry use, and this planting will contribute. It is a collaboration between ARS, UF and UC Riverside. 3) Replicated trials in multiple locations are established of our best sweet-orange-like cultivars and mandarin-types. Volatiles from sweet-orange-like hybrids are so similar to sweet orange that likely can be legally named sweet orange. 4) RNA-seq compared transcriptome responses in HLB moderately tolerant �Sun Chu Sha� mandarin and susceptible �Duncan� grapefruit, to Xcc-flg22 and CLas-flg22 (most active epitope from the pathogen flagella; project initiated with Gloria Moore at University of Florida). Differential expression of a number of genes occurred between tolerant and susceptible citrus infected with CLas, suggesting their involvement in HLB tolerance. In addition, several genes were similarly regulated by CLas-flg22 and CLas treatments. Genes identified were recently published and are valuable for studying HLB tolerance mechanisms and potential for screening for HLB-tolerant citrus using CLas-flg22 as a pathogen proxy. A population of mandarin hybrids from a 2015 cross was used to test for CLas-flg22 responsiveness. Leaf injections of CLas-flg22 and Xcc-flg22 were conduct on about 60 seedlings, and 8 randomly selected plants were subject to expression analysis of marker genes identified by transcriptomics previously. CLas-flg22 injection induced marker genes in several plants, although the number of markers induced was inconsistent. The analysis of the remaining 50 plus plants is underway. 5) A group of CLas effector (28) was predicted using bioinformatics tools. The study of transcriptional level of these effectors in infected citrus samples was initiated. Many of the effectors were successfully detected by RT-qPCR in citrus RNA, suggesting their roles in pathogen virulence and host response modulation. The initial detection was achieved from 2 weeks to 10 weeks after inoculation in multiple citrus genotypes. A comparison between root and leaf CLas expression was carried out. Results indicated different deployment of effectors between above- and underground CLas infections. Using a detached leaf assay for ACP-mediated inoculation, we also detected the expression the effector as early as 6h after ACP exposure, and observed continuous expression of effectors by CLas from 6h to 7 days. In addition, expression patterns of effectors were different between HLB susceptible and tolerant/resistant citrus hosts, which was validated by testing, although only a few genotypes were tested. Correlation between effector expressione and host tolerance/susceptibility is underway analyzing citrus types with various genetic backgrounds. The number of effectors detected has a positive linear relationship with bacterial titer, but less association with infection stage within the first week of CLas inoculation. Consistently detected effectors may have important roles in pathogen virulence. Citrus transformation for expression of CLas effectors will permit investigation of host modulation and discovery of binding targets in citrus. 6) Seedlings with a range of pedigree contributions from Microcitrus have been received in a collaboration with M. Smith, Queensland Aus. citrus breeder, are being grown, and will be planted soon for field testing of HLB resistance. 7) Our putative chimeras have not proven to be successful. We identified a chimera (Satsuma and Poncirus) from the Citrus genebank, arranged its importation, and we finally got permission to accept this material and maintain it in a quarantine death house. Cuttings of the chimera and each separate component (Owari and Poncirus) have been rooted and will be challenged by hot ACP feeding in the next quarters.