Abstract:
The aim of any breeding process is to fully express the targeted, superior/desirable parent
characteristic in the progeny. Hybrids are often used in this dynamic, and complex process for which
homozygous parents—which may require up to eight generations of back crossing and selection—are
required. Doubled haploid (DH) technologies can facilitate the production of true breeding lines
faster and in a more efficient manner than the traditional back crossing and selection strategies.
Sunflower is the third most important oilseed crop in the world and has no available double haploid
induction procedure/technique that can be efficiently used in breeding programs. A reproducible
and efficient doubled haploid induction method would be a valuable tool in accelerating the breeding
of new elite sunflower varieties. Although several attempts have been made, the establishment of
a sunflower doubled haploid induction protocol has remained a challenge owing recalcitrance to
in vitro culture regeneration. Approaches for haploid development in other crops are often cultivar
specific, difficult to reproduce, and rely on available tissue culture protocols—which on their own are
also cultivar and/or species specific. As an out-crossing crop, the lack of a double haploid system
limits sunflower breeding and associated improvement processes, thereby delaying new hybrid
and trait developments. Significant molecular advances targeting genes, such as the centromeric
histone 3 (CenH3) and Matrilineal (MTL) gene with CRISPR/Cas9, and the successful use of viral
vectors for the delivery of CRISPR/Cas9 components into plant cells eliminating the in vitro culture
bottleneck, have the potential to improve double haploid technology in sunflower. In this review, the
different strategies, their challenges, and opportunities for achieving doubled haploids in sunflower
are explored.
