In vitro shoot propagation and regeneration of rocket (Eruca sativa Mill.) using organogenesis and somatic embryogenesis

Abstract

Eruca sativa (rocket, Brassicaceae), is known in traditional medicine for its therapeutic, while young plants are used as salad, vegetable, or green foods. Genetic improvement of the rocket has been limited due to the appearance of biennial plants and the requirement for isolation barriers. Plant tissue culture offers a platform to overcome existing barriers to improving this species. The present study aimed to achieve a feasible protocol for shoot regeneration and propagation of rocket cv. Domaća rukola and to evaluate the use of AgNO3 to improve regeneration efficiency. Proliferation of shoots from seedling epicotyl, shoot organogenesis from root, hypocotyl and cotyledon seedling explants, and somatic embryogenesis from immature zygotic embryos were studied. Murashige and Skoog (MS) basal medium in combination with a low KIN concentration of 0.1 mg l-1 with frequent subculture over a period of 3 weeks was found to be optimal for shoot multiplication with a multiplication index of almost 3 and only 9.3% of vitrified shoots without necrosis. Different concentrations of 2,4-D, BA or TDZ in combination with NAA and with or without AgNO3 were tested for shoot regeneration from seedling explants. As a result, the hypocotyl explants cultured on MS with a combination of TDZ 1.0+NAA 0.1+AgNO3 5.0 mg l-1 provided healthy shoots with a satisfactory regeneration rate of 25.4% and 2.2 mean number of shoots per regenerating explant. Immature zygotic embryos cultured on MS medium containing 1.0 mg l-1 2.4-D showed the highest regeneration frequency (78.76%) as well as the number of regenerated somatic embryos per explant (5.13) with low incidence of callusing and necrosis. KIN at 0.5 mg l-1 enabled the best conversion of somatic embryos into healthy plants (22.5%). The results provide an opportunity to use established regeneration protocols in rocket breeding improvement programs.