Project Grant 20237001641308

** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** HUANGLONGBING (HLB) OR CITRUS GREENING DISEASE IS CONSIDERED THE BIGGEST THREAT TO THE U.S. CITRUS INDUSTRY. GIVEN THE LOSS OF REVENUE BEING SUSTAINED BY CITRUS GROWERS DUE TO HLB, THERE IS A CRITICAL NEED FOR RESISTANT AND TOLERANT VARIETIES TO ALLEVIATE DISEASE MANAGEMENT COSTS, IMPROVE YIELD AND OFFSET PRODUCTION LOSSES. RESISTANCE HAS BEEN IDENTIFIED IN THE RELATED SPECIES EREMOCITRUS GLAUCA; HOWEVER INTROGRESSION OF RESISTANCE INTO COMMERCIAL VARIETIES TYPICALLY TAKES DECADES DUE TO THE LONG JUVENILITY OF CITRUS. WE HAVE AN E. GLAUCA SELECTION WITH PRECOCITY THAT FLOWERS AND SETS FRUIT WITH VIABLE SEEDS WITHIN A YEAR OF PLANTING. PORTIONS OF F1 AND BC1 HYBRIDS WITH THIS SELECTION ALSO SHOW PRECOCITY. WE ARE PROPOSING TO CREATE CROSSES AND BACKCROSSES (UP TO BC2) TO GENERATE VARIETIES OF COMMERCIAL QUALITY AND RESISTANCE/TOLERANCE TO HLB USING THE PRECOCIOUS SELECTION MUCH FASTER THAN WITH PREVIOUSLY AVAILABLE GENOTYPES. WE ARE ALSO PROPOSING TO DETERMINE THE HLB RESISTANCE, TOLERANCE, EARLY FLOWERING ANF FRUIT QUALITY OF THESE POPULATIONS FOTH UNDER GREENHOUSE (GRAFT-INOCULATED FOR WITH HLB) AND FIELD CONDITIONS (NATURAL INFECTION). WE WILL ALSO USE PREVIOUSLY E. GLAUCA X CITRUS BC1 POPULATIONS CHARACTERIZED FOR THE PAST 5 YEARS FOR HLB TOLERANCE/RESISTANCE TO GENERATE PCR MOLECULAR MARKERS BASED ON GBS ANALYSIS TO FACILITATE THE IDENTIFICATION AND FUTURE BREEDING OF TOLERANT/RESISTANT TYPES. SIMILARLY, PRECOCIOUS BC1 SEGREGATING POPULATIONS WILL BE USED TO PRODUCE MARKERS FOR EARLY FLOWERING. FINALY, E. GLAUCA X PONCIRUS TRIFOLIATA WILL BE PRODUCED AND EVALUATED FOR PHYTOPHTORA ROOT ROT AND HLB TOLERANCE TO DETERMINE THEIR POTENTIAL USE AS ROOTSTOCKS.