EXPERIMENTS ON TRANSFORMATION AND IN VITRO REGENERATION OF SQUASH VARIETIES

Squash is an important species in the Cucurbitaceae family. The development of genetic transformation offers the potential of introducing valuable traits into this crop. An efficient in vitro plant regeneration system is critical for plant transformation. The regeneration ability of three Cucurbita varieties (C. pepo convar. patissoniana ‘Óvári fehér’, C. pepo convar. giromontiina ‘Black Beauty’, C. maxima convar. maxima ‘Nagydobosi’) was tested as a first step for further transformation experiments. The cotyledon explants of the tested varieties were cultured on Murashige and Skoog medium supplemented either with indole-3-acetic-acid [IAA] (0.1-0.9 mg/L) and benzyladenine [BA] (0.6-1.2 mg/L) in twenty-five different hormone combinations. Shoot induction via organogenesis was achieved in the tested varieties. Our second objective was to develop an efficient transformation method. The cotyledon explants were cut and soaked in Agrobacterium tumefaciens strain LBA4404 suspension containing ZYMV CP gene (zucchini yellow mosaic virus coat protein gene) After co-cultivation, the explants were put on selection media, which contained the same hormones as the regeneration media, supplemented with claforan (500 mg/L) and kanamycin (100 mg/L). Leafy shoots were transferred to root induction media supplemented with kanamycin (100 mg/L) for further selection. Regenerated plantlets with roots were transferred to sterile soil. Transformation was confirmed by PCR amplification of ZYMV CP gene in transgenic plants.