R plot in bold font

tiff("lnR-G-diploid-20130617.tif",width=480,heigh=480)
par(font=2)
plot( log(tb$a) ~ tb$b, pch=19, col='blue', xlim=c(0.05, 0.22),ylim=c(-8,-3.5),xlab="G",ylab="lnR") 
text( tb$b*1.02, log(tb$a*1.1), as.character(tb$strain ) )
dev.off()