Improvements to Pyrus rooting efficiency using floral foam as a substrate

Abstract Induction and development of healthy roots is necessary for both micropropagation and the successful rescue of in vitro genetically transformed or edited plants. Pear ( Pyrus ) genotypes are known to be recalcitrant to rooting treatments, and responses are highly genotype-dependent. Floral foam has been used successfully in some species to improve rooting, or de novo root regeneration (DNRR). In this study, the use of floral foam was assessed for effects on DNRR efficiency and root qualities, for five genetically diverse Pyrus genotypes. DNRR efficiency was compared between floral foam, agar, and covered agar containing the same rooting hormone composition to assess the role of darkening of the root zone during rooting. The effect of floral foam was genotype-dependent, and increased DNRR efficiencies in most genotypes. In the case of P. communis 'Tsarigradka', the delivery method of auxin (dipping in a high concentration solution, rather than receiving a low concentration dissolved in the medium) in combination with floral foam was necessary to increase DNRR efficiency. Rooting in agar with the root zone covered to impose darkness did not show improvements over uncovered agar, suggesting that darkening of the root zone is not sufficient to explain improvements from using floral foam. Together, these results suggest that use of floral foam can be an effective strategy for rooting plants produced from in vitro methods.