Absract Alternate bearing has been and still is a major problem in fruit trees. From the point of view of a horticulturist it is a tree productivity syndrome which must be addressed by agro-technical means in order to eliminate or, at least, mitigate the alternation cycle. ‘Masting’ is a widespread forest tree irregular sexual reproduction pattern that has attracted ecologists who wonder about the survival-advantage of this behavior. From an evolutionary perspective alternate bearing and masting seem to be related and may share a common bio-evolutionary mechanism, responsible for ‘yield alternation’. A recently developed resource budget model, based on nonlinear chaos dynamics, seems to account for a broad spectrum of yield alternation patterns. From an evolutionary standpoint, one may envision a domestication-evolutionary continuum from extreme masting, through intermediate alternate bearing, down to regular yield of fully-managed fruit trees. Domestication records of pecan (Carya illinoiensis) support this hypothesis. The alternate bearing of fruit trees appears to be mediated by a ‘fruit overload’ signal but resource depletion still plays a critical role in the alternate bearing of numerous tree crops. © 2018 International Society for Horticultural Science. All Rights Reserved.

The group of evergreen fruit trees includes numerous horticulturally and economically important crops, the best known of which are probably date palm, olive, Citrus spp., mango, coconut and avocado. Citrus is the only member of the group discussed in detail in the present volume. It seems appropriate, therefore, to give some thought to general attributes of this group and consider their relevance to source-sink relationships. © 1996 by Marcel Dekker, Inc. All Rights Reserved.