embryogenic callus cultures of monoembryonic citrus
types. However, very recently we have combined nucellar
parents with monoembryonic parents, with the latter being
the leaf-derived protoplast donor. A few of these hybrids
have proven to be monoembryonic and are being utilized in
interploid crosses as females (for example ‘Succari’ sweet
orange ? ‘Hirado Buntan Pink’ zygotic pummelo). We are
still waiting for several other such hybrids to pass through
juvenility to flowering. Our program has generated more
than 12,000 triploid citrus hybrids from interploid crosses,
with a few thousand of these being fathered by somatic
hybrids (Gmitter and Grosser 1993, 2005; Viloria and
Grosser 2004; Grosser et al. 2000, 2006). Somatic hybrid
parents successfully used in these crosses are listed in
Table 3. Our first triploid hybrids are now overcoming
juvenility, and seedless triploid fruits have been obtained in
all three categories to provide proof of concept (Fig. 2).
For mandarin improvement, additional breeding objectives
beyond seedlessness include easy-peeling, good external/
internal color, good flavor, a range of maturity dates, and
good shipping ability/shelf-life. Our program is continuing
efforts to generate improved breeding parents, and we
recently reported 9 new somatic hybrids and 5 autotetraploids
produced by protoplast fusion, with focus on the
zipper-skin trait (Grosser et al. 2010).