In Vitro Production Methods for Harrisia aboriginium, an Endangered Florida Endemic Cactus

Abstract

Harrisia aboriginium is an endangered cactus endemic to Southwest Florida. This study developed a protocol for sterile micropropagation of this species. The disinfestation protocol this research determined as a best practice for seeds of this species included a 15-minute wash in soapy water followed by a quick dip in 95% ethanol. This was followed by a 15-minute wash in 1.875% sodium hypochlorite solution supplemented with Tween^® 20 and finished with three rinses in sterile deionized water. There was vigorous shaking of the vessel containing the seeds and various solutions at all times. Several hundred seeds were introduced into sterile culture successfully using this protocol with a 0% contamination rate and a 98.6% germination rate.

The H. aboriginium seedlings germinated and grew well on a medium containing half-strength modified version of the nutrients and vitamins described by Murashige and Skoog, supplemented with 15g/L sugar. The medium was solidified with a combination of 4.1g/L agar and 1.1g/L CP Kelco Gelzan^®. To induce shoot multiplication, H. aboriginium seedlings were transferred to the same medium supplemented with various types and concentrations of plant hormones; it was determined that the media supplemented with 6-BAP gave the best multiplication results. Increasing concentrations of 6-BAP in the medium caused increased shoot formation, with the highest rate of 6-BAP addition evaluated (3 mg/L), resulting in an average of 12.2 shoots being produced in four months. Whole shoot clusters or individual separated shoots readily formed roots without the need of supplemental rooting hormone. Plants with roots were transplanted into a substrate composed of half commercial potting soil mix and half perlite v/v. Plants were moved into greenhouse conditions, watered when dry, about once a week, and fed with a diluted Miracle-Gro® Water Soluble All Purpose Plant Food 24-8-16 fertilizer at a concentration of one teaspoon per liter with every watering. Acclimating plants from culture was straight-forward with a 100% survival rate.