Vol.:(0123456789) 1 3 Horticulture, Environment, and Biotechnology https://doi.org/10.1007/s13580-020-00269-z RESEARCH REPORT Hypoxis hemerocallidea cormlet production in response to corm cutting and exogenous application of plant growth regulators Motiki Meshack Mofokeng 1,2  · Hintsa Tesfamicael Araya 1,2  · Stephen Oluwaseun Amoo 1  · Christian Phillipus du Plooy 1  · Phatu William Mashela 2 Received: 10 September 2019 / Revised: 22 May 2020 / Accepted: 17 June 2020 © Korean Society for Horticultural Science 2020 Abstract The study was undertaken to understand the efect of plant growth regulators (PGRs) on cormlet production in Hypoxis hemerocallidea corm cuttings. In the frst experiment, conducted in spring and summer, whole corms and corms subjected to chipping into four or eight segments or to scooping were used. These were soaked in 1.0 g L − 1 indole-3-butyric acid (IBA), 0.5 g L − 1 α-naphthalene acetic acid (NAA), a combination of 1.0 g L − 1 IBA and 0.5 g L − 1 NAA, or distilled water (control) for 16 h. In the second experiment, corms cut by chipping into eight segments were soaked in 25, 50, or 100 mg L − 1 of 6-benzyladenine (BA) or gibberellic acid (GA 3 ), as well as their combinations (100 mg L − 1 GA 3 + 25 mg L − 1 BA, 100 mg L − 1 BA + 25 mg L − 1 GA 3 ) for either 30, 60, or 120 min. Soaking corm cuttings chipped into equal segments in distilled water signifcantly increased the number of cormlets compared to soaking in IBA or NAA. Chipping into eight segments and soaking in distilled water resulted in a signifcantly higher number of cormlets in the summer experiment. There were no signifcant diferences in the number of cormlets when the eight segments of corm cuttings were soaked in BA and GA 3 . Soaking the corm cuttings for 120 min in GA 3 at 25 mg L − 1 resulted in all eight segments of the cuttings producing one cormlet each. This is the frst report on vegetative propagation of H. hemerocallidea showing that PGRs’ had no positive efect on cormlet production. Keywords African potato · Benzyladenine · Gibberellic acid · Indole-3-butyric acid · Naphthalene-acetic acid · Vegetative propagation 1 Introduction Plant growth regulators (PGRs) are organic compounds applied in small quantities to promote, inhibit, or modify physiological processes in plants (Boldt 2008). They play an essential role in breaking dormancy, manipulating growth, sprouting, and promoting the production of good quality corms (Baskaran et al. 2009). Natural PGRs’ are important for plant growth and development, but they can be substituted by synthetic ones (Roy et al. 2017). Applica- tion of cytokinins, for example, can stimulate the growth of axillary buds (Sajjad et al. 2015), gibberellic acid (GA 3 ) can enhance cell division and elongation, and auxins can infu- ence adventitious root formation in plants (Štefančič et al. 2005). Indole-3-butyric acid (IBA) and naphthalene-acetic acid (NAA) are the most widely used auxins for promoting root development as they have shown to be more efective in some cases than the naturally occurring indole-3-acetic acid (IAA) (Blythe et al. 2007). Vegetative propagation methods applied on some bulbs, in combination with the use of PGRs’, can improve the pro- duction of bulblets to more than the natural multiplication rate (Solgi et al. 2015). However, the treatment efcacy of PGRs’ is dependent on the type of PGR used, the cultivar (Ram et al. 2002), and the application method, amongst other factors. Spraying of PGRs’ is easier and quicker but does not give uniformity of application, while media drenches can be more labour intensive (Boldt 2008). Soaking of bulbs Communicated by Tae-Ho Han, Ph.D. * Motiki Meshack Mofokeng mofokengm@arc.agric.za 1 Agricultural Research Council - Vegetable and Ornamental Plants (ARC-VOP), Private Bag X293, Pretoria 0001, South Africa 2 Green Technologies Research Centre, University of Limpopo, Private Bag X1106, Sovenga 0727, South Africa