Phloroglucinol Improves Direct Rooting of In Vitro Cultured Apple Rootstocks M9 and M26

Abstract

Advances in micropropagation techniques have helped produce true-to-type clones of many horticulturally important plants. However, several cultivars of apple are difficult to root in vitro. In these cases, adventitious roots are induced together with undesirable formation of callus, which decrease the acclimatization rate of in vitro produced plantlets. In this study, two apple rootstocks, M9 and M26, were subjected to different concentrations of indole-3-butyric acid (IBA) to induce root formation. Although addition of IBA to the medium induced root formation, rhizogenesis was accompanied by the undesirable formation of callus in both cultivars. On the other hand, in gene expression analysis, the indole-3-acetic acid (IAA) synthase genes AAO1 and YUC1 were expressed more highly in M9 than in M26. This suggests that endogenous auxin levels may be higher in M9, which may explain why M9 plantlets are difficult to root and experience high levels of callus formation during propagation. In addition, rooting medium containing 0.1 mg·L−1 IBA was supplemented with different concentrations of phloroglucinol (0, 0.5, 1.0, and 2.0 mM) to examine whether direct rooting efficiency in the M9 could be improved. Addition of 1.0 mM phloroglucinol increased rooting percentage and decreased callus formation in the M9 rootstock. The rootstock M9 is a desirable cultivar but presents a problem with true-to-type direct rooting. Addition of phloroglucinol may improve direct rooting and eliminate callus formation during propagation.

In Vitro Propagation of Avocado (Persea Americana Mill.)

“…Moreover, De Klerk et al (2011) observed different effects of PG on rooting depending on the specific auxin applied. A positive rooting response using PG and IBA has been reported for several tree genera, including Diaspyros, Malus (Dobránszki and Teixeria da Silva, 2010), Jatropha (Daud et al, 2013), Juglans (Licea-Moreno et al, 2015) and apple rootstocks Ma and M26 (Kim et al, 2020). It has been reported that PG acts synergistically with auxin during the most sensitive phase of root initiation (Dobránszki and Teixeira da siva, 2010).…”

Role of Phenolic Compounds in Root Induction of Virus-free Apple Rootstocks and Scions

“…Regeneration of adventitious roots from shoots remains to be problematic for in vitro apple plantlet production (De Klerk et al, 2011;Kim et al, 2020a). Consequently, several attempts have been directed toward the choice and combination of growth regulators, root induction procedure, one-or multiple-step culturing, and treatment duration (De Klerk et al, 2011;Kim et al, 2020a;Souza et al, 2022).…”