Hybridization Studies Between the Australian Finger Lime and Conventional Citrus Cultivars for Germplasm Enhancement and New Cultivar Development

The finger lime (Microcitrus australasica) is native to Australia and is a thorny understory shrub producing finger-shaped fruit that contain compressed juice vesicles which tend to burst out when cut. These tart lime flavored juice vesicles have been termed as “citrus caviar” and are gaining popularity in restaurants as a garnish and as a component in mixed drinks. In addition, preliminary studies indicate finger limes to be tolerant to HLB. These cultivars can potentially be used as a source of HLB resistance and play a role in HLB management. We are creating new genetic combinations by hybridizing microcitrus with conventional citrus - using both conventional and somatic cell fusion techniques. A large population of diploid, triploid and tetraploid hybrids have been produced and their hybrid status confirmed using Random Amplified Polymorphic DNA (RAPD) and fluorescently labeled expressed sequence tag simple sequence repeat (EST-SSR) molecular markers. This germplasm will be screened for HLB tolerance and selected lines will be propagated for field trials. Field trials will also evaluate traits including plant growth and fruit / juice vesicle characteristics. Results from our research should generate useful hybrids that could be commercially cultivated as a niche specialty crop and also contribute to future citrus improvement and HLB tolerant cultivar development.