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Instal GAPIT

devtools::install_github("jiabowang/GAPIT")

Load GAPIT

library(GAPIT)

Before the gwaspr package can be used, we first need to run GWAS with GAPIT.

Genotype data (myG)

Our population, the LDP, was genotyped using an exome caputure array and filtered with the following criteria to yield a data set of 336,367 SNPs, stored in our object myG.

  • Only Bi-allelic = TRUE
  • Minimum Read Depth = 3
  • Minor Allele Frequency = >5%
  • Maximum Missing Frequency = 25%
  • Heterozygous = <25%

Note: header = T

# Load our genotype file in hapmap format (note: header = F)
myG <- read.csv("gwaspr_myG_hmp.csv", header = F)
# Map + marker Info
myG[1:10,1:11]
##                      V1      V2    V3     V4     V5       V6     V7       V8
## 1                    V1      V2    V3     V4     V5       V6     V7       V8
## 2                    rs alleles chrom    pos strand assembly center protLSID
## 3  Lcu.1GRN.Chr1p853882     A/G     1 853882   <NA>     <NA>   <NA>     <NA>
## 4  Lcu.1GRN.Chr1p854117     G/A     1 854117   <NA>     <NA>   <NA>     <NA>
## 5  Lcu.1GRN.Chr1p854159     A/C     1 854159   <NA>     <NA>   <NA>     <NA>
## 6  Lcu.1GRN.Chr1p854174     C/G     1 854174   <NA>     <NA>   <NA>     <NA>
## 7  Lcu.1GRN.Chr1p870836     A/G     1 870836   <NA>     <NA>   <NA>     <NA>
## 8  Lcu.1GRN.Chr1p870898     C/T     1 870898   <NA>     <NA>   <NA>     <NA>
## 9  Lcu.1GRN.Chr1p870903     G/A     1 870903   <NA>     <NA>   <NA>     <NA>
## 10 Lcu.1GRN.Chr1p871108     A/G     1 871108   <NA>     <NA>   <NA>     <NA>
##           V9   V10    V11
## 1         V9   V10    V11
## 2  assayLSID panel QCcode
## 3       <NA>  <NA>   <NA>
## 4       <NA>  <NA>   <NA>
## 5       <NA>  <NA>   <NA>
## 6       <NA>  <NA>   <NA>
## 7       <NA>  <NA>   <NA>
## 8       <NA>  <NA>   <NA>
## 9       <NA>  <NA>   <NA>
## 10      <NA>  <NA>   <NA>
# genotrype calls
myG[1:10,12:17]
##             V12             V13            V14            V15          V16
## 1           V12             V13            V14            V15          V16
## 2  X3156.11_AGL CDC_Asterix_AGL CDC_Cherie_AGL CDC_Glamis_AGL CDC_Gold_AGL
## 3             G               A              G              A            G
## 4             G               G              G              A            G
## 5             C               C              C              C            C
## 6             G               G              G              G            G
## 7             G               G              N              G            G
## 8             T               C              N              C            T
## 9             G               G              N              A            G
## 10            A               A              A              A            A
##                  V17
## 1                V17
## 2  CDC_Greenstar_AGL
## 3                  A
## 4                  G
## 5                  A
## 6                  C
## 7                  A
## 8                  C
## 9                  G
## 10                 A

Phenotype data (myY)

# Load our phenotype file
myY <- read.csv("gwaspr_myY.csv")
myY[1:15,]
##                 Name Cotyledon_Color Cotyledon_RedvsYellow DTF_Sask_2017
## 1    CDC_Asterix_AGL          Yellow                     0          54.7
## 2      CDC_Rosie_AGL             Red                     1          59.0
## 3       X3156.11_AGL             Red                     1          60.7
## 4  CDC_Greenstar_AGL          Yellow                     0          56.7
## 5     CDC_Cherie_AGL             Red                     1          54.3
## 6     CDC_Glamis_AGL          Yellow                     0          59.0
## 7       CDC_Gold_AGL          Yellow                     0          54.0
## 8       CDC_Imax_AGL             Red                     1          53.0
## 9    CDC_Impower_AGL          Yellow                     0          57.0
## 10      CDC_KR.1_AGL             Red                     1          57.0
## 11     CDC_LeMay_AGL          Yellow                     0          55.7
## 12     CDC_Maxim_AGL             Red                     1          54.3
## 13      CDC_QG.1_AGL           Green                    NA          57.7
## 14 CDC_Red_Rider_AGL             Red                     1          57.0
## 15   CDC_Redcoat_AGL             Red                     1          57.7
##    DTF_Nepal_2017
## 1           128.0
## 2           123.3
## 3           125.3
## 4           121.0
## 5           125.3
## 6           123.0
## 7           125.3
## 8           128.7
## 9           123.3
## 10          121.7
## 11          126.7
## 12          125.7
## 13          126.7
## 14          123.5
## 15          126.7
myY <- myY[,-2] 

Covariate data (myCV)

# Load our covariate file
myCV <- read.csv("gwaspr_myCV.csv")[,c("Name","b")]
myCV[1:10,]
##                 Name             b
## 1    CDC_Asterix_AGL -1.201707e-03
## 2      CDC_Rosie_AGL -1.752062e-03
## 3       X3156.11_AGL -1.114926e-03
## 4  CDC_Greenstar_AGL -5.607040e-05
## 5     CDC_Cherie_AGL -7.040853e-04
## 6     CDC_Glamis_AGL -1.234765e-03
## 7       CDC_Gold_AGL -9.853332e-05
## 8       CDC_Imax_AGL -1.210779e-03
## 9    CDC_Impower_AGL -1.396606e-03
## 10      CDC_KR.1_AGL -7.986330e-04

Run GWAS

Run GWAS on the 3 traits myY

# Run GWAS
myGAPIT <- GAPIT( 
  # Phenotype data
  Y = myY,
  # Genotype data
  G = myG, 
  # Set PCA number
  PCA.total = 4,
  # Select Models
  model = c("GLM","MLM","MLMM","FarmCPU","BLINK") )

GWAS with covariate

Run GWAS on the DTF_Sask_2017 trait with b as a covariate.

# Prep data
myY2 <- myY[,c("Name","DTF_Sask_2017")]
# Rename the trait to be rerun with a covariate
colnames(myY2)[2] <- "DTF_Sask_2017_b"
# Run GWAS with a covariate
myGAPIT <- GAPIT(
  # Phenotype data
  Y = myY2,
  # Genotype data
  G = myG,
  # Covariate data
  CV = myCV,
  # Set PCA number
  PCA.total = 0,
  # Select Models
  model = c("GLM","MLM","MLMM","FarmCPU","BLINK") )