ISHS Acta Horticulturae 636: XXVI International Horticultural Congress: Key Processes in the Growth and Cropping of Deciduous Fruit and Nut Trees
INSIGHT INTO ALTERNATE BEARING OF PECAN |
| Authors: | B.W. Wood, P.J. Conner, R.E. Worley |
| Keywords: | irregular bearing, flowering, yields, stress, breeding, phytohormones, assimilates |
| Abstract:
The fundamental cause of alternate bearing in pecan [Carya illinoinensis (Wangenh.) K. Koch] is unknown, but is closely linked to the size of the dormant season carbohydrate pool. Nut yields (over a period of up to 78 years) were evaluated, for 66 cultivars, in regards to alternate bearing intensity (I). Best-fit regression analysis indicates no association between I and fruit ripening date (FRD) or nut volume; although, there was moderate association with post-ripening foliation periods (PRFP) in that I tends to decrease as the length of the PRFP decreases. Multiple regression models indicated that FRD and nut volume were poor predictors of I, however PRFP possessed significant inverse predictive power. Late-season canopy health, as measured by percentage of leaflet retention, decreased as FRD approached early-season ripening. Late-season photoassimilation rate was higher on foliage of trees with late FRDs than those with mid- or early-season ripening dates. Sprays of either Alar or ProGibb to the canopy of either “On” or “Off” trees altered return bloom the following year. These data provide new insight into the complex nature of alternate bearing in pecan and are interpreted to indicate that alternate bearing in pecan is regulated by; a) gibberellins during the time of fruit development, and b) the size of the carbohydrate pool at about the time of bud break. | |
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