The dual nature of the grafted trees has allowed a 'divide and conquer' strategy for the achievement of higher yields by focusing breeding efforts on very different traits in the two constituent parts.
Since its domestication by pre-Columbian civilizations, sunflower has long been the focus of breeding efforts.
They have more recently been the focus of intensive breeding efforts, including, over the last few years, the development of molecular markers and the identification of genes responsible for various traits of agronomic interest (Paterson et al., 2005).
Breeding efforts focus on chilling tolerance during flowering to avoid male sterility and on the development of appropriate parental lines combining earliness and adequate height.
Many breeding efforts focus on further improvement of quality depending on the region where it is grown.
To achieve new breakthroughs in yield, breeding efforts have focused on expanding the yield sink capacity, mainly by increasing the number of grains per panicle and grain size.
However, in recent decades, internationally coordinated public wheat breeding efforts have focused on increasing resistance to disease and abiotic stress, while raising the genetic yield potential per se has received scant attention.
Over the years, breeding efforts increasingly focused on improving oil yield, and the germplasm that formed the basis of the modern oilseed gene pool was eventually brought back to North America, where commercial production commenced in the mid-twentieth century.
Traditional breeding efforts have been focused on the improvement of switchgrass as a forage crop [ 4], while the current bioenergy research is targeting high cellulose and starch content for bioethanol production and low ash content for combustion systems [ 5] combined with significantly increased biomass yield.
These findings clarify the history of European and Asian pears and have implications for breeding efforts.
