Methods of Auxin Application in Cutting Propagation: A Review of 70 Years of Scientific Discovery and Commercial Practice

Abstract

The discovery of auxins as plant growth regulating chemicals in the 1930s and their ability to stimulate adventitious rooting in stem cuttings marked a major milestone in the modern history of plant propagation. Basic and applied research conducted during the past 70 years has provided information regarding absorption and translocation of auxin in cuttings, as well as the effects of timing of auxin application, methods of auxin application, type of auxin, and concentration of auxin on the rooting response of cuttings. The basal quick-dip method, the powder application method, and the dilute soak method have been the most commonly used methods for applying auxin to cuttings in commercial horticulture over the past 7 decades, with the first two methods still in common use today. In addition, a wide variety of other auxin application methods have been reported beginning in the 1930s and continuing to the present. Some of these methods remain primarily of historical interest, several find limited use in commercial horticulture, and others show potential for greater use in the future. Opportunities exist for further development of auxin application techniques that can enhance plant quality, efficiency and productivity of the cutting propagation process, and worker safety. This review provides horticulturists, from the academic researcher to the commercial propagator, with an exploration of auxin application methods over the past 70 years, along with an examination of the physiological response of cuttings to applied auxin and an overview of issues leading to future opportunities.

Molecular Authentication, Propagation Trials and Field Establishment of Greek Native Genotypes of Sambucus nigra L. (Caprifoliaceae): Setting the Basis for Domestication and Sustainable Utilization

“…Asexual propagation via cuttings was conducted for Greek genotypes of S. nigra for the first time in the current study providing interesting data. High rates of rooting capacity among genotypes of softwood leafy cuttings taken in summer with the use of Indole-3-butyric acid (IBA) were observed, which are well above the commercially accepted threshold for propagation [43]. This observation is in agreement with similar work on this species elsewhere [31,44].…”

Molecular Authentication, Propagation Trials and Field Establishment of Greek Native Genotypes of Sambucus nigra L. (Caprifoliaceae): Setting the Basis for Domestication and Sustainable Utilization

“…Asexual propagation via cuttings was conducted for Greek genotypes of S. nigra for the first time in the current study providing interesting data. High rates of rooting capacity among genotypes of softwood leafy cuttings taken in summer with the use of Indole-3-butyric acid (IBA) were observed, which are well above the commercially accepted threshold for propagation [43]. This observation is in agreement with similar work on this species elsewhere [31,44].…”

Improved method for vegetative propagation of mature Pinus halepensis and its hybrids by cuttings

“…This was also demonstrated in the present study by the observations that relatively very low concentrations of 2-DP-Gly were required to stimulate rooting. A combination of IBA, which provides the auxin required for the initial stages of rooting, and 2-DP-Gly, which provides the auxin required for the later stages of rooting, proved to be more effective than each auxin alone (Table 2), as also reported for combinations of various other auxins applied to promote rooting (Blythe et al 2007).…”

Adventitious Rooting of Lavandula x intermedia Cuttings1

“…If required, selection of a PGR and PGR concentration to enhance rooting of cuttings is a critical, yet possibly a costly step (Baldwin andStanley 1981, Blythe andSibley 2001). Use of auxin-based PGRs at greater concentrations is known to produce negative, phytotoxic effects on cutting rooting percentage and root quality data (Andrade et al 1999, Blythe et al 2007, Blythe and Sibley 2009. Furthermore, our data indicates selection of the correct PGR and PGR concentration for propagation of lavandin by cuttings is essential to provide increased rooting, and greater root quality.…”

“…Additional research confirms cultivar differences frequently occur when asexually propagating plants through cuttings (Andrade et al 1999, Copes and Mandel 2000, Epstein and Ackerman 1993, Mabizela et al 2017, McIvor et al 2014, Noyszewski and Smith 2020, and interactions between genotype and rooting medium have been reported for a number of species (Bajaj 1986). When asexually propagating plants through cuttings, propagators are required to carefully select specific techniques and methods for each genotype (Blythe et al 2007). Therefore, when propagating lavandin tip cuttings, propagators should balance cultivar choice (genotype) with medium, PGR, and PGR concentration best suited for each particular cultivar.…”

Molecular Authentication, Propagation Trials and Field Establishment of Greek Native Genotypes of Sambucus nigra L. (Caprifoliaceae): Setting the Basis for Domestication and Sustainable Utilization

“…Asexual propagation via cuttings was conducted for Greek genotypes of S. nigra for the first time in the current study providing interesting data. High rates of rooting capacity among genotypes of softwood leafy cuttings taken in summer with the use of Indole-3-butyric acid (IBA) were observed, which are well above the commercially accepted threshold for propagation [43]. This observation is in agreement with similar work on this species elsewhere [31,44].…”

Improved method for vegetative propagation of mature Pinus halepensis and its hybrids by cuttings

“…This was also demonstrated in the present study by the observations that relatively very low concentrations of 2-DP-Gly were required to stimulate rooting. A combination of IBA, which provides the auxin required for the initial stages of rooting, and 2-DP-Gly, which provides the auxin required for the later stages of rooting, proved to be more effective than each auxin alone (Table 2), as also reported for combinations of various other auxins applied to promote rooting (Blythe et al 2007).…”

Adventitious Rooting of Lavandula x intermedia Cuttings1

“…If required, selection of a PGR and PGR concentration to enhance rooting of cuttings is a critical, yet possibly a costly step (Baldwin andStanley 1981, Blythe andSibley 2001). Use of auxin-based PGRs at greater concentrations is known to produce negative, phytotoxic effects on cutting rooting percentage and root quality data (Andrade et al 1999, Blythe et al 2007, Blythe and Sibley 2009. Furthermore, our data indicates selection of the correct PGR and PGR concentration for propagation of lavandin by cuttings is essential to provide increased rooting, and greater root quality.…”

“…Additional research confirms cultivar differences frequently occur when asexually propagating plants through cuttings (Andrade et al 1999, Copes and Mandel 2000, Epstein and Ackerman 1993, Mabizela et al 2017, McIvor et al 2014, Noyszewski and Smith 2020, and interactions between genotype and rooting medium have been reported for a number of species (Bajaj 1986). When asexually propagating plants through cuttings, propagators are required to carefully select specific techniques and methods for each genotype (Blythe et al 2007). Therefore, when propagating lavandin tip cuttings, propagators should balance cultivar choice (genotype) with medium, PGR, and PGR concentration best suited for each particular cultivar.…”

Molecular Authentication, Propagation Trials and Field Establishment of Greek Native Genotypes of Sambucus nigra L. (Caprifoliaceae): Setting the Basis for Domestication and Sustainable Utilization

“…Asexual propagation via cuttings was conducted for Greek genotypes of S. nigra for the first time in the current study providing interesting data. High rates of rooting capacity among genotypes of softwood leafy cuttings taken in summer with the use of Indole-3-butyric acid (IBA) were observed, which are well above the commercially accepted threshold for propagation [43]. This observation is in agreement with similar work on this species elsewhere [31,44].…”

Improved method for vegetative propagation of mature Pinus halepensis and its hybrids by cuttings

“…This was also demonstrated in the present study by the observations that relatively very low concentrations of 2-DP-Gly were required to stimulate rooting. A combination of IBA, which provides the auxin required for the initial stages of rooting, and 2-DP-Gly, which provides the auxin required for the later stages of rooting, proved to be more effective than each auxin alone (Table 2), as also reported for combinations of various other auxins applied to promote rooting (Blythe et al 2007).…”

Adventitious Rooting of Lavandula x intermedia Cuttings1

“…If required, selection of a PGR and PGR concentration to enhance rooting of cuttings is a critical, yet possibly a costly step (Baldwin andStanley 1981, Blythe andSibley 2001). Use of auxin-based PGRs at greater concentrations is known to produce negative, phytotoxic effects on cutting rooting percentage and root quality data (Andrade et al 1999, Blythe et al 2007, Blythe and Sibley 2009. Furthermore, our data indicates selection of the correct PGR and PGR concentration for propagation of lavandin by cuttings is essential to provide increased rooting, and greater root quality.…”

“…Additional research confirms cultivar differences frequently occur when asexually propagating plants through cuttings (Andrade et al 1999, Copes and Mandel 2000, Epstein and Ackerman 1993, Mabizela et al 2017, McIvor et al 2014, Noyszewski and Smith 2020, and interactions between genotype and rooting medium have been reported for a number of species (Bajaj 1986). When asexually propagating plants through cuttings, propagators are required to carefully select specific techniques and methods for each genotype (Blythe et al 2007). Therefore, when propagating lavandin tip cuttings, propagators should balance cultivar choice (genotype) with medium, PGR, and PGR concentration best suited for each particular cultivar.…”