Dear Colleagues,

Plant propagation is the process of growing new plants from old plants by various methods, such as collecting seeds, cuttings, or other parts of plants. Research on plant propagation systems addresses difficult issues across commodity disciplines. Advances in biotechnology can create new opportunities for the rational use and regeneration of valuable plant material through the adoption of techniques such as in vitro culture and conservation. In vitro culture of plants is also a direct tool to obtain more productive and dynamic plants (including plants without diseases and pests), which is conducive to the production of more efficient and high-yielding plants in the field, especially through micro-propagation. This Special Issue will focus on new methods of in vitro culture and propagation, major innovations, advances, or improvements in existing technology, or elucidating new in vitro plant cultivation applications. These approaches can positively impact plant development, disease resistance, mineral nutrition, propagation, and germplasm conservation.

Prof. Dr. Jeffery Adelberg
Prof. Dr. Byoung Ryong Jeong
Guest Editors

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• propagation
• in vitro plant cultivation
• biotechnology
• plant tissue culture
• micropropagation
• rooting
• conservation
• in vitro propagation
• tissue culture
• transplants
• plant factory
• controlled environment agriculture

Title: Modified Media and Lighting for Repeated In Vitro Cutting Cycles of Cannabis Sativa without the use of cytokinin
Authors: Jeffrey Adelberg; Molly McKay
Affiliation: Clemson University
Abstract: Micropropagation is a technique used to propagate clean, high quality clonal stock plants. While most micropropagation protocols optimize the use of cytokinin plant growth regulators (PGR) in a single harvest batch system, this two part study uses an in vitro multiple harvest system “hedging” combined with the batch fed media process and observed (1) the effects of modified physical state media, and (2) LED light qualities in an effort to improve production. In Experiment 1, four genotypes of Cannabis sativa (Cherry 1, BaOx, T1, Peach) were observed in three different physical states : stationary agar (A), stationary Oasis® infused with liquid (OIL) and agitated Oasis® infused with liquid (AOIL). Fifteen explants (nodes and shoot tips) were planted in treatment physical states consisting of 120 mL DKW medium (liquid or agar) and later harvested on 3 week cycles. During time of harvest, 15mL was supplemented as a treatment factor; addition or no addition. The number of shoots harvested, shoot length, and dry shoot mass during 5 repeated 3-week cutting cycles was recorded. Some genotypes (T1 and Peach) could not produce enough shooots on multiple harvest cutting schedule and were eliminated from the experiment. Over multiple cycles, the remaining genotypes (BaOx and Cherry) showed that both types of OIL treatments (stationary or agitated) with media additions performed better than A regardless of additions. Shoots harvested increased from the initial 15 during cycle 1 to a maximum of 30 shoots per vessel in the third cycle, in OIL but not A. In A, both genotypes were less, (20 in Cherry 1 and 17 in BaOx). Shoot length was also highest in OIL for both genotypes, but AIOL resulted in more growth during cycle 1, especially for the genotype Cherry 1. By the third cycle, shoots harvested, shoot length, and dry mass were decreasing from 3mg to 1mg but vessels receiving media additions were able to produce at least seven shoot tips (half production of original input) in latter cycles (5). By the end of the experiment, the only vessels that produced greater than 7 shoots per vessel were OIL, but internodes were often too short (ex vitro planting hasa desired length of 10mm). In Experiment 2, blue and supplemental far-red light were observed to affect in vitro shoot growth with Cannabis sativa (BaoX and Cherry). Fifteen explants (nodal and apical) were cultured in RV750 vessels containing liquid infused Oasis® IVE foam (OIL) of 120 mL DKW medium and harvested every 2 weeks. Vessels also received 15mL liquid additions during time of harvest. Plants were placed into LED light treatments providing different spectral qualities (white, high red:blue and medium red:blue, white with 5% far-red, high red:blue 5% far-red, medium red:blue with 5% far-red, and low red:blue with 5% far-red). Treatments had similar light intensities (190-240 µMol/m2/s-1) for a 16 hour photoperiod. Shoot number, shoot length, leaf number, shoot fresh and dry mass were recorded at each two week harvest period. Five randomly selected shoot tips per vessel were rooted ex vitro on the greenhouse mist bench for 16 days. Over multiple cycles, 5% far-red treatments increased shoot number and their length, while higher blue light ratios increased dry shoot mass. Shoot numbers increased from initial 15 at cycle 1 to a maximum 28 in cycle 3 with far- red, and to 18 without far-red, before decreasing to 15 during cycle 5. The accumulated number of shoots over 5 cycles (10 week period) was 108 shoots with far-red, and 84 without. Shoot length in far-red-treated plants increased from 19 mm during cycle 1 to 25 mm in cycle 3. Plants without far-red had 15 mm length in cycles 1-3. By cycle 5, both far-red and non-far-red were reduced to 10 mm. Shoot dry mass during cycle 1, was greatest at 6mg for plants with most blue light before decreasing 50% in cycle 3 and remained around 3mg for the duration with most blue light. With least blue light, dry shoot was 3mg for all 5 cycles. Sixty eight percent of shoots rooted on mist bench, regardless of prior in vitro treatment.