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A GIFT SEED

Objective 2

Pest Management & Climate Change

Leadership

Dr. Bert Cregg (Objective Leader), Dr. Jeremy Johnson, Dr. Gary Chastagner, Dr. Justin Whitehill, Dr. Jean Ristaino

Objective Goal & Deliverables

GOAL: Evaluate drought tolerance across environments using commercially important Abies species and identify resistance traits, mechanisms and genes against insect pests, Phytophthora infection, and deer browse.

DELIVERABLES

  1. Fraser complex, noble, and CoFirGE complex seedlings adapted to drought.
  2. A rapid in-field detection method to identify Phytophthora species.
  3. Deeper knowledge and identification of Abies spp. specific genes involved in climate, disease, insect, and deer resilience.

Objective Activities

Each of the following activities will contribute to the generation of the Objective 2 deliverables listed above.

The main focus of activity 2.1. is studying the effects of climate and climate variability on Abies spp. Christmas trees.

The Objective team is going to do this by analyzing drought tolerance traits of Fraser, noble, and CoFirGE complex families. Studies will be conducted for trees grown in containers under a range of water stress (Sub-Activity 2.1.1.), as well as for field-grown trees across a range of different environments (Sub-Activity 2.1.2.). Field-grown tree studies will be conducted on a plantation-scale and coupled with a retrospective genetic analysis.

The main focus of activity 2.2. is evaluating the impacts of Phytophthora on fir, including population characterization, identification of genes related to disease resistance, and in-field diagnostics.

The Objective 2 team plans to do this by identifying phylogenetic relationships between east vs west coast Phytophthora root rot isolates collected from infected fir Christmas trees across the US (Sub-Activity 2.2.1.), studying pathogenicity of Phytophthora species on fir under increasing temperatures (Sub-Activity 2.2.2.), identifying genes related to disease resistance in fir (Sub-Activity 2.2.3.), and testing the effectivity current diagnostic technology on in-field fir infected by Phytophthora spp. (Sub-Activity 2.2.4.).

The main focus of Activity 2.3. is identifying mechanisms of insect tolerance/resistance in Abies spp.

The Objective 2 team will develop genomic resources of insect-infested Abies needle tissues to facilitate genomic marker discovery and assist genome annotation efforts. Generation of these genomic resources will be done in Project Director Dr. Justin Whitehill’s laboratory, and downstream bioinformatic analysis will be performed with the Objective 1 team.

The main focus of Activity 2.4. is studying deer browse preference and aroma chemistry of Abies spp.

The Objective 2 team will be doing this by identifying and studying genetic relationships between deer browse preference and correlations with aroma chemistry of Abies spp. (Sub-Activity 2.4.1.), as well as developing genomic resources on Abies spp. resin-producing structures (Sub-Activity 2.4.2.).

Year 1 Progress

Activity 2.1: Climate Impacts

Co-I-s Johnson and Cregg recruited a Ph.D. graduate research assistant to work on the investigations of genotypic variation in drought resistance mechanisms in Abies spp. A field-plot trial and a container-tree trial of 12 genotypes was established in spring 2025 at the MSU Forestry Tree Research Center near East Lansing, MI. Samples were collected for DNA extraction from 65 trees in the Michigan State University Fraser fir seed orchard (with Jesse Hickman, Ph.D. candidate, NCSU) as well as 60 individuals from the NC State Fraser fir breeding program. Climate resilience traits were assessed for photosynthetic gas exchange and shoot water potential (pre-dawn and midday) on progeny from 4 open-pollinated families from the Michigan State University Fraser fir seed orchard.

Activity 2.2: Phytophthora Impacts

50 Phytophthora isolates from Abies spp. in the WSU Phytophthora culture collection that were collected between 2004-2024 were revived and inventoried. These cultures are being evaluated alongside an additional 151 isolates maintained by the Whitehill lab at NC State.

A series of greenhouse and field experiments related to pathogenicity of Phytophthora spp. on Abies spp. under various temperature/moisture regimes are underway at WSU Puyallup and NC State.

Candidate genes and mechanisms involved in Phytophthora resistance from momi fir have been identified through activities in the Whitehill lab. Artificial inoculation experiments of clonal plant materials revealed a suite of candidate genes that appear to be active in momi fir defense against infection.

A LAMP assay is being developed to identify Phytophthora cinnamomi from infected plants in the field.

Activity 2.3: Insect Resistance Mechanisms

The Whitehill lab used synchrotron imaging to understand how the elongate hemlock scale insect feeds within fir needles. This novel imaging technique provided high resolution x-ray images that were 3-D reconstructed to give a clear understanding of how the insect feeds on fir trees. This information is being used to help develop potential pest management strategies in the field.

Activity 2.4: Deer Browse and Aroma Chemistry

Whitehill lab PhD student Kaley Patton performed an experiment to assess terpene accumulation and identify the genes involved in their biogenesis.