Genetic Engineering of Plum (Prunus domestica L.) for Plant Improvement and Genomics Research in Rosaceae

Abstract

Fruit trees are among the most recalcitrant of plants to regenerate adventitious shoots. In most woody fruit species, transformation and regeneration are difficult and often limited to a few genotypes or to seedlings (Petri and Burgos, 2005). This feature is the major limiting factor preventing the development of gene transfer technologies for fruit trees (Petri and Scorza, 2008). Such barriers slow the ability to relate the wealth of Prunus structural data, namely from peach, directly to testable questions of agricultural relevance. However, plum has been one of the more successful rosaceaous fruits to regenerate and transform, especially among Prunus species. A number of regeneration protocols have been reported from different tissues of European plum (Prunus domestica L.), such as leaf explants (Bassi and Cossio, 1991; Csanyi et al., 1999; Escalettes and Dosba, 1993; Mikhailov and Dolgov, 2007; Nowak et al., 2004), or seed-derived tissues (Mante et al., 1989, 1991) (Table 1). Agrobacterium tumefaciens-mediated transformation has been the principal technique applied to plum. One publication reported the use of Agrobacterium rhizogenes, but no transgenic shoots were recovered (Escalettes et al., 1994). There are few reports of regeneration of transformed plum shoots from clonal explants in European plum (Table 2). In these reports, transformation efficiencies are low and the varieties used as explant sources are generally of limited or local importance. Furthermore, in most cases, only marker genes were introduced into the plant genome, with few reports of modification of agronomically important traits (Escalettes et al., 1994; Mikhailov and Dolgov, 2007; Mikhailov et al., 2007; Yancheva et al., 2002). The most successful transformation/regeneration protocol reported in plum has been developed in the authors’ laboratory (USDA, Kearneysville), using embryonic