Phytoregulators and Explant Size in the in vitro Culture of Malva sylvestris

In vitro propagation of plants makes it possible to accelerate the process of plant multiplication, the study of secondary metabolite production and the cultivation of biotrophic fungi. The objective of this work was to study the combination of indoleacetic acid (IAA) and benzylaminopurine (BAP) and explant sizes in in vitro multiplication of M. sylvestris. Five concentrations of BAP (0, 0.5, 1.0, 1.5 and 2.0 mg L-1) and two of IAA (0 and 0.5 mg L-1) were used in explants of 4 to 9 mm and of 14 to 23 mm. Contaminated explants, oxidation, establishment, relative growth rate (RGR), sprouting, rooting and callus formation were evaluated. There was no interaction effect between BAP and IAA concentrations. At 28 days, explants were established at 32.76% and callus formation was 62.5% for explants associated with 0.0 mg L-1 of IAA. There was 32.14% establishment and 63.79% callus formation at 0.5 mg L-1 of IAA. Bacterial contamination at 28 days was 60.53%, twice as much the amount found at 14 days, suggesting that the explants presented endogenous contamination. It was found that explant size influences the subsequent meristematic development. The use of smaller explants (4 to 9 mm) allowed greater formation of calli and larger explants (14 to 23 mm) allowed greater formation of shoots. In conclusion, larger explants are preferable for production of M. sylvestris in vitro by organogenesis while smaller ones are preferable for embryogenesis.