Tall fescue (Lolium arundinacea Schreb.) and perennial ryegrass (Lolium perenne) are common cool-season turfgrass species. They are widely utilized in home lawns, athletic fields, golf courses, and roadsides. However, these grasses require frequent mowing to maintain lawn quality. Developing low-mowing frequency varieties is highly desirable because it can significantly reduce maintenance costs and fuel consumption. Gibberellin 20-oxidases (GA20ox) are key genes in the gibberellic acid (GA) biosynthesis pathway, mutations in which can induce a dwarf phenotype in plants and, therefore, reduce mowing frequency, as demonstrated by our dwarf turf varieties developed using conventional mutagenesis techniques. We have recently employed CRISPR/Cas9 technology to create knockout or knockdown mutations in the GA20oxidase1 gene to develop dwarf tall fescue and perennial ryegrass lines. The CRISPR/Cas9 construct used for editing LaGA20ox1 and LpGA20ox1 has ZmUbi and OsU6a promoters controlling the expression of Cas9 and sgRNA, respectively. We have delivered the CRISPR/Cas9 construct into tall fescue and perennial ryegrass via Agrobacterium-mediated transformation. We have observed a 35-50% reduction in plant height compared to the parental wild-type plants. Furthermore, the leaf widths in these mutants are reduced by 30-60%. Some mutants display a smoother leaf texture compared to the wild type. The T2 homozygous mutant progenies will undergo field evaluation for mowing frequency and fertilizer requirements. We anticipate that some of these gene-edited lines should exhibit a significant reduction in mowing frequency and fertilizer input.
