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

Abstract

Forest trees possess high genetic diversity and high heterozygosity which allow adaptation to changing environmental conditions. There is a tendency to propagate successful and unique genotypes, which are identified at their mature stage in the forests, for future improvement programs and conservation purposes. However, vegetative propagation of mature forest trees is still a challenge in many conifers. In this study, we focused on improving the rooting of cuttings of mature and old Pinus halepensis and its hybrids. We observed that storage of cuttings before rooting at 4°C for 4 weeks and prolong immersion of cuttings in a solution containing 400 mg/l of indole-3-butyric acid, 5 mg/l of the auxin conjugate 2-(2,4-dichlorophenoxy)propanoic acid-glycine methyl ester, and 0.01% of Amistar fungicide significantly improved rooting of mature cuttings. The active ingredient in Amistar is azoxystrobin, an uncoupler of respiration, which seems to directly promote rooting. Rooted cuttings of selected clones demonstrated unique and uniform growth performance, most likely delivering the intrinsic growth parameters of the mother trees. It was also observed that trees growing under drought stress possess improved rooting ability. By using rooted cuttings, it will be possible to study the relationship between growth rate and adaptation to semi-arid climate conditions. The ability to clonal propagate mature and old P. halepensis trees not only enables vegetative propagation of elite trees for improvement programs, but also provides an opportunity to preserve unique naturally occurring old P. halepensis genotypes.

Regeneration of Pinus halepensis (Mill.) through Organogenesis from Apical Shoot Buds

“…For many years, IBA has been applied to different plant species to induce adventitious roots [42], however, the use of 1-Naphthaleneacetic acid (NAA), combined with IBA or alone, has proved successful for inducing root meristem differentiation in Pinus species [41,43]. Also, a study focused on the rooting of cuttings of mature Pinus halepensis [44], has shown that pulses for four hours of IBA alone, auxin combinations, and the use of the quick-dip method with IBA alone, are efficient for root development and further acclimatization of the cuttings. Our plants were able to produce ex vitro roots and acclimatize successfully.…”

Enraizamiento de estacas de Pinus hartwegii de tres poblaciones naturales en ecosistemas de alta montaña del Estado de México y Veracruz

“…También menciona, que cuando el tejido pierde esta característica de competencia, el flujo polar de auxinas endógenas hacia el sitio de enraizamiento puede ser inhibido y afectar el proceso de inducción de raíces. Por lo que la aplicación de auxinas exógenas es necesaria para mejorar la respuesta al enraizamiento de las estacas de las especies de pino, ya que en ausencia de auxinas exógenas el porcentaje de enraizamiento es bajo (Cuevas-Cruz et al 2015, Rivera et al 2016, Riov et al 2020.…”

Slow release of a synthetic auxin induces formation of adventitious roots in recalcitrant woody plants

“…We envisioned that the inherent phytotoxicity and growth-inhibitory effect of synthetic auxins could be mitigated by their slow release in planta, maintaining a low yet functional level of the bioactive molecule over a prolonged time, thus opening the door to utilizations beyond their traditional role as herbicides 49 . Moreover, lengthy auxin treatments were reported to improve AR induction [50][51][52][53] , which could further enhance the effectiveness of a slow-release approach.…”