Screening for homozygous atwrky18 T-DNA knockouts using the 'Touch-and-Go' method. Seventy-two F2 progeny obtained by crossing of homozygous atwrky40 and atwrky18 mutants, were screened with primers flanking the T-DNA insertion site in the AtWRKY18 gene allowing detection of the wild-type AtWRKY18 allele. Amplification of a 644 bp size fragment indicates that F2 progeny are either wild type or heterozygous for AtWRKY18. No amplification suggests that the progeny are homozygous for the atwrky18 mutant allele. Controls, including DNA from the homozygous parental lines (knockout; KO), were replicated twice in pairs, giving a total of four independent control reactions. Primer control, lanes that contain no DNA template.