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There has been very little work on genetic transformation of Annona spp. Early and preliminary studies of Agrobacterium tumefaciens-mediated genetic transformation of atemoya and cherimoya were attempted in 2001 (Botella and Encina, unpublished data). A protocol for A. tumefaciens-mediated transformation for cherimoya ‘Fino de Jete’ hypocotyl explants has been developed (Padilla et al., unpublishedFig. 3.1.3b). The putative transgenic lines obtained with different Agrobacterium strains and different plasmids, containing the neomycin phosphotransferase (NPTII) and β-glucuronidase (GUS) marker genes, are being evaluated to assess the transformation efficiency. Using this protocol, cherimoya has been transformed with three different antisense constructions to silence the INO gene and thereby obtain seedless fruits. These putative seedless lines are under evaluation in a greenhouse for further verification (Padilla et al., unpublished data). Transient gene expression of transformed cherimoya leaf protoplasts using a polyethylene glycol (PEG)-mediated protocol and the green fluorescent protein (GFP) gene as a reporter gene is being investigated (Padilla et al., 2018).

Genetic engineering of Annona spp. has focused on control of fruit ripening to extend shelf life and fruit quality (seedlessness). Different strategies that have been adopted to achieve these goals include: (i) control of the expression of genes related to growth and development of seeds; and (ii) blocking the biosynthesis of ethylene by transformation with ACC synthase genes in antisense. Improvement of orchard management, e.g. the development of dwarfing root-stocks by blocking GA3 biosynthesis, could possibly be addressed.