2017 ASHS Annual Conference

Australian limes are Citrus relatives belonging to the genera Microcitrus and Eremocitrus. These species are sexually and graft compatible with other Citrus cultivars and several hybrids between the two groups exist. A long-term field evaluation study recently concluded in Florida has identified several of these Australian limes to be resistant to Huanglongbing (HLB). HLB is a phloem-restricted disease, vectored by the asian citrus psyllid, that has had a significant negative impact on the Florida citrus industry. Most commercially cultivated sweet oranges, grapefruits and mandarins are highly susceptible to this disease. We have developed a large population of diploid, triploid and tetraploid Citrus X Australian lime hybrids using conventional and somatic cell fusion techniques. Diploid and triploid progeny were created by conventional breeding between selected monoembryonic citrus cultivars as the female parent with pollen obtained from Microcitrus accessions at the USDA-ARS National Germplasm Repository for Citrus and Dates in Riverside, CA and the Florida Department of Plant Industry Citrus Arboretum in Winter Haven, FL. Allotetraploid progeny were created using the process of somatic fusion while autotetraploid progeny were created following treatment in a 0.00044% oryzalin solution. In addition, several potential somaclonal variants were induced by treatment of seeds with ethyl methane sulphonate (EMS). Field testing is underway for these novel and potentially HLB tolerant hybrids.