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United States Department of Agriculture

Agricultural Research Service

Research Project: PECAN CULTIVATION AND DISEASE MANAGEMENT

Location: Fruit and Nut Research

Title: Influence of plant bioregulators on pecan flowering and implications for regulation of pistillate flower initiation

Author
item Wood, Bruce

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 3, 2011
Publication Date: June 1, 2011
Citation: Wood, B.W. 2011. Influence of plant bioregulators on pecan flowering and implications for regulation of pistillate flower initiation. HortScience. 46(6):870-877.

Interpretive Summary: Alternate bearing and control of flowering are the most important biological problems for the U.S. pecan industry. There is great need for improved strategies and tools for their control. This research substantially identifies how these processes are being regulated in pecan and identifies horticultural tools by which they can potentially be controlled in orchard enterprises. A new theory is also presented explaining flowering in pecan, and other tree crops, and therefore establishes a model for guiding future research on these problems. This research establishes the potential for manipulation of alternate bearing and flowering in pecan and many other tree crops by orchard managers.

Technical Abstract: Mitigation of alternate bearing (AB) through regulation of floral initiation of pistillate flowers is central to improving crop-load management of pecan [Carya illinoinensis (Wangenh.) K. Koch] trees and orchards. The present study examines the influence of key bioregulators {i.e., an auxin [as B-napththaleneacetic acid (NAA)], a cytokinin [6-benylamino purine (6-BA)], an ethylene generator (ethephon) and an auxin transport inhibitor [2,3,5-triiodobenzoic acid (TIBA)]} on subsequent season pistillate flowering. Gibberellic acid (i.e., GA3) and NAA inhibited; whereas, P-Ca (calcium 3-oxido-5-oxo-4-propionylcyclohex-3-enecarboxylate), ethephon, and BA+TIBA promoted floral initiation when topically applied to canopies prior to the kernel filling stage of seed development. These bioregulators exhibit potential for integration into a bioregulator based strategy to mitigate pecan AB by selective and timely use in “off” or “on” cycle years, depending on the bioregulator. Field studies provide evidence that a “cytokinin-gibberellin balance”, with partial modulation by auxin and ethylene, acts in the endogenous primordial environment of floral meristems as a “second-level-signal” regulating a key step in a three-step process for initiation of pistillate flowers in pecan. This establishes a new model for explaining pistillate flower initiation in pecan, and a basis for designing future research on the control and management of pistillate flowering and AB.

Last Modified: 9/20/2014
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