Fruit Tree Domestication: The Evolution of Productivity

Studies of fruit tree domestication are rather scarce and productivity issues have been barely addressed. In the present study fruit tree productivity has been analyzed in the broader, biological context of trees’ sexual reproduction. The survival of individual trees does not depend upon regular, year-by-year flowering and fruiting. The irregular, fluctuating "masting" habit of forest trees probably represents the natural pattern of trees’ sexual reproduction. In the wild, trees seldom reach their fruiting potential; environmental stresses and endogenous resource constraints preclude regular fruiting and limit fruitfulness.  Consistent, year-by-year fruiting has been established in domesticated fruit tree crops through unconscious and conscious human selection. Advanced crop management eliminates or, at least, minimizes biotic and abiotic stresses, thereby enabling trees to approach their full fruiting potential. Examination of a broad range of wild, semi-domesticated, recently domesticated, and fully domesticated fruit tree species enables reconstruction of the evolutionary course of fruit tree productivity. Trees with a striking alternate bearing habit (olive, pistachio) represent, in our opinion, an intermediate position between wild and fully domesticated species. Alternate bearing appears to be a survival strategy for balancing reproductive and vegetative tree growth, in particular under sub-optimal conditions. The underlying genetic mechanisms are still greatly unknown. An evolutionary model of fruit tree productivity will be presented.