Understanding factors influencing peach fruit development and growth

Abstract

I have spent the majority of my career focused on studying the physiology and growth of fruit trees. A central theme of that research was developing an understanding of how environmental and management practices influence fruit growth. The inverse relationship between crop load and mean fruit size on peach trees was recognized more than a century ago. However, the dynamics of this relationship and why these relationships vary among seasons and in response to management were less well understood. Fruit growth responses can best be understood by recognizing that fruit growth involves two separate but dependent processes: fruit development and fruit growth (or expansion). Fruit development is a necessary precursor to fruit growth and creates the potential for growth. Rates of fruit development are particularly important during early stages of development when cells are dividing and differentiating to form specific tissues. Fruit development is highly dependent on heat accumulation during the early stages of growth. Development dictates fruit growth potential of a given cultivar at any given time during fruit growth via a relative growth rate (compound interest rate) function. Potential increases in fruit size during any given interval of time are dictated by relative growth rate functions, but actual increases in fruit size are governed by the ability of a tree to supply the resource needs of its fruit for a given growth interval. If the resource demands of the fruit are not met, the fruit will not grow to their potential for that growth interval. That deficit in actual growth will affect all future potential growth because future growth is compounded based on the growth that is actually attained in previous growth intervals. This presentation will further elaborate on how these principles of fruit development and growth can be used to understand fruit growth responses to multiple environmental and management factors, such as timing and amount of fruit thinning, seasonal differences in date of fruit maturity, and fruit sizing.