Approaches to generate herbicide resistant Taraxacum koksaghyz by directed and undirected mutagenesis of the acetohydroxyacid synthase
Taraxacum koksaghyz is an upcoming alternative bioresource for natural rubber. A major obstacle for extensive cultivation is the lacking weed management. Here, two different strategies were conducted to obtain herbicide resistant T. koksaghyz by targeting the essential enzyme acetohydroxyacid synthase (AHAS) as a well-studied locus for resistance-conferring mutations. For the diploid T. koksaghyz a single AHAS gene was identified with a range of highly homologous alleles in the considered selection of plants. Undirected EMS mutagenesis led to one putative imidazolinone tolerant and two resistant individuals. The resistant plants featured the same, well-described mutation (C572T causing Ala191Val) which was successfully inherited to vital and fertile progeny. Transcriptional studies gave little evidence of the involvement of a metabolic tolerance. Several gene regions of TkoAHAS1 were targeted successfully by CRISPR/Cas9 in vitro. In vivo targeting of two sites led to detection of InDels at the 3’ end. However, their influence on herbicide resistance remains to be conclusively assessed.