Low Infection of Phelipanche aegyptiaca in Micro-Tom Mutants Deficient in CAROTENOID CLEAVAGE DIOXYGENASE 8

Strigolactones (SLs), a group of plant hormones, induce germination of root-parasitic plants and inhibit shoot branching in many plants. Shoot branching is an important trait that affects the number and quality of flowers and fruits. Root-parasitic plants, such as spp., infect tomato roots and cause economic damage in Europe and North Africa-hence why resistant tomato cultivars are needed. In this study, we found defective mutants of Micro-Tom tomato ( ) by the "targeting induced local lesions in genomes" (TILLING) method. The mutants showed excess branching, which was suppressed by exogenously applied SL. Grafting shoot scions of the mutants onto wild-type (WT) rootstocks restored normal branching in the scions. The levels of endogenous orobanchol and solanacol in WT were enough detectable, whereas that in the mutants were below the detection limit of quantification analysis. Accordingly, root exudates of the mutants hardly stimulated seed germination of root parasitic plants. In addition, SL deficiency did not critically affect the fruit traits of Micro-Tom. Using a rhizotron system, we also found that infection was lower in the mutants than in wild-type Micro-Tom because of the low germination. We propose that the mutants might be useful as new tomato lines resistant to .