DOI: 10.5061/dryad.ht76hdrvt
title: Data from: Evaluating transgenic Darling 54 American chestnuts for reintroduction: Insights from survivorship, growth, and respiration in a common garden

description: Transgenic Darling 54 chestnuts, engineered with an OxO gene for blight
 tolerance, retain the native American chestnut’s genome and offer a
 potential restoration solution for this functionally extinct tree species.
 We compared the performance of three-year-old trees in a common garden
 experiment featuring nearly 500 trees across five chestnut types,
 including Darling 54 transgenic (OxO+, n = 198) and non-transgenic (OxO-,
 n = 201) full-siblings, hybrid chestnuts (B3F3 backcross hybrids, n = 34;
 F1 hybrids, n = 17), and Chinese chestnuts (n = 55). We measured
 survivorship, growth, crown morphology in August 2024 and dark respiration
 rates in May and August 2024 to determine the suitability of Darling 54
 transgenic trees for ecological restoration. Statistical analyses assessed
 the effects of transgene status and maternal lineage on growth performance
 and respiration. Darling 54 OxO+ trees exhibited strong survivorship and a
 favorable growth form comparable to related non-transgenic chestnuts,
 despite reduced growth rate and survival. Elevated leaf respiration was
 observed in OxO+ trees during late-season measurements, suggesting a
 potential metabolic cost associated with transgenesis. Overall, Darling 54
 OxO+ chestnuts maintain desirable traits, but reduced growth and
 intermittently higher respiration rates may indicate a trade-off. Although
 OxO+ chestnuts show promise as restoration trees, additional research is
 needed to assess blight tolerance, long-term performance under competitive
 forest conditions, and whether growth constraints persist over time.
description: # Data from: Evaluating transgenic Darling 54 American chestnuts for
 reintroduction: Insights from survivorship, growth, and respiration in a
 common garden Dataset DOI:
 [10.5061/dryad.ht76hdrvt](10.5061/dryad.ht76hdrvt) ## Description of the
 data and file structure This dataset was collected during a common garden
 experiment designed to evaluate the performance of transgenic and
 non-transgenic American chestnuts (*Castanea dentata*) alongside hybrid
 and Chinese chestnut controls. Nearly 500 trees were planted and monitored
 over three years to assess survivorship, growth, crown morphology, and
 leaf respiration. The data were used to test the effects of transgene
 status and maternal lineage on growth and physiology, with the aim of
 determining the suitability of Darling 54 transgenic chestnuts for forest
 restoration. ### Files and variables #### File: CG_Survival.csv
 **Description:** Dataset of original common garden plantings in 2021 used
 to assess survivorship in 2024 across the five chestnut types. Note: N/A
 means "not planted," and thus this variable is not applicable.
 ##### Variables * Row: Alphabetic location of trees (A through S) * Pos:
 Numeric location of trees (1 through 28) * TreeID: Unique tree identifier
 * Type: Chestnut type (5 variables: OxO-, OxO+, B3F3, Chinese, F1) *
 Mother: Maternal line (13 variables) * Status: Survival status (1 = alive,
 0 = dead) #### File: AugustGrowth_Dryad.csv **Description:** Dataset
 collected in August 2024 and used to evaluate tree grown and morphology
 ##### Variables * Row: Alphabetic location of trees (A through S) *
 Pos: Numeric location of trees (1 through 28) * TreeID: Unique tree
 identifier * Type: Chestnut type (5 variables: OxO-, OxO+, B3F3, Chinese,
 F1) * Mother: Maternal line (13 variables) * Height: Total tree height in
 2023 in meters (m) * NewHeight: Total tree height in 2024 in meters (m) *
 HeightDiff: NewHeight minus Height in meters (m) * CrownHeight: Height of
 tree crown in meters (m) * CrownWidth: First width of crown in meters (m)
 * CrownWidth2: Second width of crown measured perpendicular from
 CrownWidth in meters (m) * Crown: Average of CrownWidth and CrownWidth2 in
 meters (m) * Diamwidth: First basal diameter in centimeters (cm) *
 Diamwidth2: Second width of crown measured perpendicular to DiamWidth in
 centimeters (cm) * BasalDiam: Average of Diamwidth and Diamwidth2 in
 centimeters (cm) * 1stOrderBranch: Not analyzed * DomLeader: Not analyzed
 #### File: CGarden_Total_Dryad.csv **Description:** Dataset collected in
 December 2023 and used to evaluate tree heights ##### Variables * Plot:
 Common Garden * TreeID: Unique tree identifier * Type: Chestnut type (5
 variables: OxO-, OxO+, B3F3, Chinese, F1) * Mother: Maternal line (13
 variables) * Row: Alphabetic location of trees (A through S) *
 Pos: Numeric location of trees (1 through 28) * Height: Total tree height
 in 2023 #### File: AugustRespforR_Dryad.csv **Description:** Foliar
 respiration dataset generated by an open gas exchange system (LI-6400) in
 August 2024 for 100 OxO full-sibling American chestnut trees #####
 Variables * Row: Alphabetic location of trees (A through S) * Pos: Numeric
 location of trees (1 through 28) * TreeID: Unique tree identifier *
 Family: Maternal line (13 variables) * Type: Transgene status (2
 variables: OxO-, OxO+) * Obs: Order of respiration measurements * HHMMSS:
 Hour/minutes/seconds * PhotoAreaNeg: Respiration on an area basis
 expressed as a negative number (μmol CO~2~ m ^-2^ s ^-1^) * PhotoArea:
 Respiration on an area basis corrected to a positive number (μmol CO~2~ m
 ^-2^ s ^-1^) * PhotoMass: Respiration on a mass basis (nmol CO~2~ g ^-1^ s
 ^-1^) * Cond: Conductance to H~2~O (mol H~2~O m ^-2^ s ^-1^) * Ci:
 Intercellular CO~2~ concentration (μmol CO~2~ mol ^-1^) *
 Trmmol: Transpiration rate (mmol H~2~O m ^-2^ s ^-1^) * VpdL: Vapor
 pressure deficit based on Leaf temp (kPa) * CTleaf: Computed leaf temp (C)
 * Area: Total leaf surface area * SLA: Specific leaf area (cm^2^g ^-1^) *
 StmRat: Stomatal ratio * BLCond: Total boundary layer conductance for the
 leaf (includes stomatal ratio) (mol m ^-2^ s ^-1^) * Tair: Temperature in
 sample cell (C) * Tleaf: Temperature of leaf thermocouple (C) *
 TBlk: Temperature of cooler block (C) * CO2R: Reference cell CO~2~ (μmol
 CO~2~ mol ^-1^) * CO2S: Sample cell CO~2~ (μmol CO~2~ mol ^-1^) *
 H2OR: Reference cell H~2~O (mmol H~2~O mol-^1^) * H2OS: Sample cell H~2~O
 (mmol H~2~O mol ^-1^) * RH_R: Relative humidity in the reference cell (%)
 * RH_S: Relative humidity in the sample cell (%) * Flow: Flow rate to the
 sample cell (μmol s ^-1^) * PARi: In-chamber quantum sensor (μmol m ^-2^ s
 ^-1^) * PARo: External quantum sensor (μmol m ^-2^ s ^-1^) #### File:
 CGRespforR_Dryad.csv **Description:** Foliar respiration dataset generated
 by an open gas exchange system (LI-6400) in May 2024 for 100 OxO
 full-sibling American chestnut trees ##### Variables * Row: Alphabetic
 location of trees (A through S) * Pos: Numeric location of trees (1
 through 28) * TreeID: Unique tree identifier * Family: Maternal line (13
 variables) * Type: Transgene status (2 variables: OxO-, OxO+) * Date: Date
 of measurements * Obs: Order of respiration measurements * HHMMSS:
 Hour/minutes/seconds * PhotoAreaNeg: Respiration on an area basis
 expressed as a negative number (μmol CO~2~ m ^-2^ s ^-1^) * PhotoArea:
 Respiration on an area basis corrected to a positive number (μmol CO~2~ m
 ^-2^ s ^-1^) * PhotoMassNeg: Respiration on a mass basis expressed as a
 negative number (nmol CO~2~ g ^-1^ s ^-1^) * PhotoMass: Corrected positive
 respiration on a mass basis (nmol CO~2~ g ^-1^ s ^-1^) * Cond: Conductance
 to H~2~O (mol H~2~O m ^-2^ s ^-1^) * Ci: Intercellular CO~2~ concentration
 (μmol CO~2~ mol ^-1^) * Trmmol: Transpiration rate (mmol H~2~O m ^-2^ s
 ^-1^) * VpdL: Vapor pressure deficit based on Leaf temp (kPa) *
 CTleaf: Computed leaf temp (C) * Area: Total leaf surface area (cm^2^) *
 SLA: Specific leaf area (cm^2^g ^-1^) * StmRat: Stomatal ratio *
 BLCond: Total boundary layer conductance for the leaf (includes stomatal
 ratio) (mol m ^-2^ s ^-1^) * Tair: Temperature in sample cell (C) *
 Tleaf: Temperature of leaf thermocouple (C) * TBlk: Temperature of cooler
 block (C) * CO2R: Reference cell CO~2~ (μmol CO~2~ mol ^-1^) *
 CO2S: Sample cell CO~2~ (μmol CO~2~ mol ^-1^) * H2OR: Reference cell H~2~O
 (mmol H~2~O mol ^-1^) * H2OS: Sample cell H~2~O (mmol H~2~O mol ^-1^) *
 RH_R: Relative humidity in the reference cell (%) * RH_S: Relative
 humidity in the sample cell (%) * Flow: Flow rate to the sample cell (μmol
 s ^-1^) * PARi: In-chamber quantum sensor (μmol m ^-2^ s ^-1^) *
 PARo: External quantum sensor (μmol m ^-2^ s ^-1^) ## Code/software The
 data files are provided in comma-separated values (.csv) format, which can
 be opened using any free or open-source software such as *R* (R Core Team,
 2025), or more generally in spreadsheet programs. All analyses for this
 project were conducted in R version 4.4.3 (R Core Team, 2025). Within R, I
 primarily used the tidyverse collection of packages (Wickham et al.,
 2019), including `readr` for importing CSV files, `dplyr` for data
 wrangling, and `ggplot2` for visualization. Additional packages used
 were `lme4`, `emmeans`, `car`, `doBy`, `grid`, `gridExtra`, and
 `multcomp`.  The workflow involved importing each CSV file into R using
 `read.csv()`, performing data cleaning and transformation steps,
 conducting statistical analyses (e.g., ANOVA and Tukey’s HSD tests), and
 generating figures.