Structural relation for acclimatization success for in vitro cultured avocado

J.C.A. Hiti-Bandaralage, A. Hayward, N. Mitter
Improving avocado (Persea americana Mill.) rootstock propagation has been a major industry and research challenge globally for many decades. Avocado is an outcrossing species; thus, clonal propagation is the only way to propagate proprietary rootstocks. At present, avocado clonal propagation involves ex vitro rooting of tree cuttings at very poor efficiency, long turn-around time and high expense. A suitable mass clonal propagation process through in vitro culture technology could potentially revolutionize the avocado industry globally. Over the last four years, we have been developing an in vitro mass propagation technology for avocado. We observed avocado cultivars to differ in their ability to acclimatize. We hypothesized that this difference may relate to the specific structural characteristics of the cultivars. To test this, histological investigation of the stems, leaves, and roots of tissue cultured plants of two avocado cultivars; ‘Reed’ and ‘Velvick’ was carried out. Quantitative parameters; stomatal index, stomatal density, trichome density, vein-islet density, and vein termination density were analysed for comparison. Acclimatization success correlated to the presence of fully differentiated secondary xylem in the root suggested to maintain high water availability. Meanwhile, the presence of smaller epidermal cells, high stomatal density, less amount of xylem vessels in stem and reduced vein termination density correlated to reduced acclimatization success. These findings will succour optimization strategies for in vitro culture of difficult-to-acclimate cultivars of avocado but also, other woody perennials experiencing similar problems.
Hiti-Bandaralage, J.C.A., Hayward, A. and Mitter, N. (2020). Structural relation for acclimatization success for in vitro cultured avocado. Acta Hortic. 1285, 269-280
DOI: 10.17660/ActaHortic.2020.1285.39
histology, avocado, in vitro culture, acclimatization

Acta Horticulturae