Submitted to: Pecan South
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2006
Publication Date: N/A
Citation: N/A Interpretive Summary: The USDA conducts the largest pecan breeding and genetics program in the world. The program is divided into two main parts: the BBP (Basic Breeding Program) and NPACTS (National Pecan Advanced Clone Testing System). Controlled crosses are made and these seedlings are evaluated for a 10 year period on their own roots or grafted to large trees. Based upon initial performance in the BBP, a very few clones are selected to be tested in NPACTS. NPACTS tests are planned to be 15 year tests, and to duplicate the best commercial production practices for the location of the test. This is needed to identify clones that will increase orchard profitability, which is the primary goal of the USDA scion breeding program. This paper reports the performance of many of the released USDA cultivars as to their blooming habits in three diverse environments. This information is needed by growers to know which cultivars to plant in adjacent rows in the orchards to insure good cross pollination and adequate pecan production.
Technical Abstract: Pecan (Carya illinoinensis (Wangenh.) K. Koch) is a heterodichogamous anemophilous species that expresses severe inbreeding depression. This study compared pollen shed and pistil receptivity patterns for commercial pecan cultivars commonly grown in Durham, California and in Brownwood and College Station, Texas. Earliest pollen shed occurred at College Station, followed by Brownwood, and then Durham. Pollen shed at Durham was delayed likely by lower April temperatures, while pistil receptivity was delayed very little. The disproportionate effect of cool April temperatures on pollen shed dates, compared to dates of pistil receptivity are discussed. Growing degree days (10o C base) for flower development at Durham and Brownwood were similar compared to those measured in College Station, which were much higher for both staminate and pistillate temporal development parameters. Improved orchard designs in environments that experience cool April temperatures should include very early pollen-shedding cultivars to insure adequate pollination of cultivars with early pistil receptivity.