Abstract
The Australian finger lime is a unique citrus species that has gained importance due to its unique fruit characteristics and perceived tolerance to Huanglongbing (HLB), an often-fatal disease of citrus trees. In this study, we developed allotetraploid finger lime hybrids and cybrids by utilizing somatic cell fusion techniques to fuse diploid ‘OLL8’ sweet orange or ‘Page’ tangelo callus-derived protoplasts with finger lime (FL) mesophyll-derived protoplasts. Six somatic fusions were regenerated from the ‘OLL8’ + FL fusion, while three putative cybrids were regenerated from the ‘Page’ + FL fusion. Ploidy levels and nuclear-expressed sequence tag derived simple sequence repeat (EST-SSR) markers confirmed the somatic hybrid production, and mitochondrial DNA primer sets confirmed the cybrid nature. Several trees produced by the somatic fusion remained HLB negative even after 6 years of growth in an HLB-endemic environment. Pathogenesis related (PR) and other genes that are often upregulated in HLB-tolerant trees were also upregulated in our somatic fusions. These newly developed somatic fusions and cybrids could potentially be used as breeding parents to develop the next generation of improved HLB-tolerant rootstocks and scions.
Highlights
IntroductionMuell) is an Australian native citrus species
Somatic fusion resulted in the production of allotetraploids Finger limes have been reported to be HLB-tolerant [3]
Sweet oranges are hybrids between pummelo and mandarin [32], and ‘OLL8’ is an improved sweet orange that was recently released from the citrus breeding program of the University of Florida [33]
Summary
Muell) is an Australian native citrus species. Finger lime trees likely originated in South Asia and migrated to Australia during the early Pliocene epoch, where they further developed into the modern-day finger lime. This species is characterized by its round to teardrop-shaped juice vesicles that burst into individual juice sacs when the fruit is cut.
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