THE PHENOLOGY OF EARLY FRUIT RIPENING IN PECAN

Abstract

Twenty-two pecan [Carya illinoinensis (Wangenh.) K. Koch] cultivars were monitored weekly for stage of fruit development to establish how differences in fruit phenology ultimately define time of ripening. Simple techniques for season-long, field assessment of fruit expansion, kernel fill and shuck dehiscence were developed to allow for the uniform evaluation fruit phenology independent of cultivar differences in fruit size and weight. The earliest fruit ripening cultivars in this trial entered into the period of rapid fruit expansion over two weeks before cultivars that ripen late in the season. Once rapid fruit expansion began, the pace of fruit development for early-ripening cultivars was faster than later maturing pecans. Early ripening cultivars took the least amount of time to fully expand their fruits and achieve maximum ovule expansion (the water stage). Early maturing cultivars were also quicker to split shucks (ripen fruit) once kernel deposition was completed. The time required to deposit solid kernel tissue inside a fully expanded ovule was roughly the same for all early ripening cultivars (two weeks). Only extremely late maturing cultivars, or those cultivars generally not adapted to the 200 day growing season at this study’s location, took longer to fill their kernels (18-21 days). Charting the key phenological events that define time of fruit ripening for all 22 cultivars studied in this test illustrates that pecan fruit phenology is a continuously variable genetic trait. In addition, the simple methods assessing fruit phenology developed in this study may become an important tool for screening a large number new pecan clones for adaptation to northern pecan growing regions.