Assessing Abies nordmanniana & Abies bornmuelleriana Seed Quality Factors.

Open Access
Author:
Curry, Amanda Christine
Graduate Program:
Horticulture
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
August 11, 2017
Committee Members:
  • Ricky M Bates, Thesis Advisor
  • James C Sellmer, Committee Member
  • Robert Berghage Jr., Committee Member
Keywords:
  • Abies
  • Seed Quality Factors
  • Horticulture
  • Seed Germination
  • Abies Seed
  • Christmas Trees
  • Nordmann fir
  • Turkish fir
Abstract:
A lack of Christmas tree species diversity in the United States has led to the rise of several pest and disease problems. Fraser fir (Abies fraseri) is one of the most popular tree species, due to its superior postharvest characteristics and overall general appearance. Unfortunately, it is highly susceptible to Phytophthora root rot and has a mortality rate considered too high for many Christmas tree growers. Likewise, Douglas-fir (Pseudotsuga menziesii) is in production regularly, but is prone to Rhabdocline Needlecast (Rhabdocline pseudotsugae). Several control management strategies exist. However, overall species care and general decline in popularity is making maintenance expensive. Growers are interested in introducing exotic Mediterranean firs, particularly Nordmann (Abies nordmanniana) and Turkish (Abies bornmuelleriana), due to their resistance to Phytophthora root rot and marketable Christmas tree characteristics. However, many problems occur with storage practices, as seed viability only lasts two years at most. The goal of this research project was to examine possible reasons for decline of seed viability, and to identify potential solutions for improving germination in individual seedlots. Standard germination tests were performed on seed of Nordmann fir from seedlots collected in 2011, 2013 and 2015. Germination test results suggest that Nordmann fir seed quickly lose viability using conventional Abies storage methods. Seed moisture content in Turkish fir seed collected in 2015 was altered prior to stratification to determine if the moisture content percentage influenced seed germination. Results indicated that a change in seed moisture was not significant in germination rate. However, seed moisture fluctuated during prechilling. Thus, by determining a solution to stabilize seed moisture during the stratification protocol, experiment results may differ. Furthermore, changes in seed moisture content were monitored after a 12-week period to determine adequate methods for seed storage. Seed was stored in three types of media; a refrigerator, freezer, and an airtight container containing zeolite beads. Results indicated that seed in the refrigerator had absorbed the iv most moisture, while the seed stored in the freezer and zeolite drying beads had insignificant changes in moisture content. Seed stratification method in Nordmann, Turkish and Fraser fir was also tested to determine any differences in seed germination. While seed that underwent the stratification-redry method had slightly higher total germination by the end of the experiment, they were not statistically significant. Nevertheless, seed moisture content changed during the stratification period. Finally, wasp larvae from the genus Megastigmus is making importing Nordmann and Turkish firs seed a challenge for industry leaders. An incubation treatment exists for Douglas-fir (Pseudotsuga menziesii) that successfully kills the insects inside seed while not affecting germination. The objective was to determine if the same treatment had influence on overall seed germination for Nordmann and Turkish fir. Results concluded that seed was significantly affected by the incubation, meaning that seed that underwent the prolonged heat treatment had a lower germination rate compared to that of the control. These results suggest that Nordmann and Turkish fir seed have higher sensitivities to traditional storage and germination methods compared to other true fir species.