Insight Into Alternate Bearing of Pecan

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.

Influence of Cluster Thinning on Return Bloom, Nut Quality, and Concentrations of Potassium, Nitrogen, and Non-structural Carbohydrates

“…Hypotheses for alternate bearing have undergone modification as more data became available. The current theory supports a two-level control with inhibitors and promoters determining induction during the previous growing season and the dormant season carbohydrate pool influencing pistillate flower development (Smith et al, 1986;Sparks, 2000Sparks, , 2003aWood, 2003;Wood and McMeans, 1981;Wood et al, 2003Wood et al, , 2004.…”

“…Alternate bearing is the most significant horticultural problem facing pecan producers. Several reviews have been published on the subject (Barnett and Mielke, 1981;Monselise and Goldschmidt, 1982;Smith, 2005;Sparks, 1974Sparks, , 1975Sparks, , 1979Sparks, , 1986Sparks, , 2000Sparks, , 2003aWood, 1991;Wood et al, 2004). Initial research (Smith and Waugh, 1938) and later work suggested that stored carbohydrate concentrations during the winter markedly affected subsequent flowering (Malstrom, 1974;Wood, 1989Wood, , 1991Worley, 1979aWorley, , 1979b.…”

Influence of fungicides on gas exchange of pecan foliage

“…The natural trait of alternate bearing by pecan (Carya illinoinensis) trees is accentuated by environmental stresses interacting with hormonal and energy reserves related to flowering physiology (Worley, 1979a,b;Wood, 1995Wood, , 2011Wood et al, 2004). Some environmental factors reduce photoassimilation by trees sufficiently to impact dormant season energy reserves (Smith & Waugh, 1938;Sparks, 1975;Wood, 1989Wood, , 2014Smith et al, 2007) and, thus, availability of sucrose at the onset of the subsequent growing season (Wood, 2014); therefore orchard management strategies are required that maximize the photoassimilative capacity of the canopy.…”

Influence of Nitrogen Application Time on Nitrogen Absorption, Partitioning, and Yield of Pecan

“…(Wood, 1993), as well as in other fruit crops (Monselise and Goldschmidt, 1982). Studies suggest the amount of nonstructural carbohydrates stored during winter may be closely linked to the flowering potential of pecan (Lockwood and Sparks, 1978;Smith and Waugh, 1938;Wood, 1988Wood, , 1989Wood, , 1991Wood, , 1995Worley, 1979aWorley, , 1979b. Nitrogen depletion by large crops occurs in pistachio (Pistacia vera L.) (Brown et al, 1995;Rosecrance et al, 1998;Weinbaum et al, 1994a), citrus (Citrus reticulata Blanco) (Golomb and Goldschmidt, 1987) and prune (Prunus domestica L.) (Weinbaum et al, 1994b).…”