Improvements to Pyrus rooting efficiencies using floral foam as a substrate

Authors: PIERCE, CLAIRE - Oregon State University; ANDERSON, DELANEY - Former ARS Employee; Waite, Jessica; GALIMBA, KELSEY - Oregon State University

Submitted to: In Vitro Cellular and Developmental Biology. Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/19/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary: Pears are notoriously difficult to root, which is an issue when it comes to generating plants through micropropagation, genetic transformation, or gene editing. In this study, we test the use of floral foam to determine its effect on rooting. We tested this in five different pear accessions (cultivars and species of pear). We found that floral foam increases the number of plants that produce roots for most accessions. We also tested whether the reason for this was simply due to having the roots grow in darkness: we attempted to root plants in agar-based media that was kept dark by covering it with foil. These tests didn't show any improvement, which means that darkness is not the main reason that the floral foam improved rooting. These results mean that using floral foam will be a good strategy for rooting various pear accessions in the future.

Technical 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 cultivar-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 its use 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 dissolve in the media) 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 may be an effective strategy for rooting plants produced from in vitro methods.