Callus induction in Amaranthus tricolor and Amaranthus spinosus.
Amaranths are an agriculturally valuable crop, but tissue culture techniques for these species remain limited. A study was conducted at the Plant Tissue Culture Laboratory, Institute of Crop Science, College of Agriculture and Food Science from October to December 2009. This study sought to identify a combination of plant growth regulators (PGRs) to induce callus formation on hypocotyl segments of Amaranthus tricolor and Amaranthus spinosus. Amaranthus spp. calli were yellow to deep yellow with a few cultures exhibiting red pigmentation depending on the PGRs applied in the induction medium. PGRs also influenced the number of days before callus outgrowths became visible. Callus formation in both species was faster with a combination of 6-benzylaminopurine (BAP) and 2,4-dichlorophenoxyacetic acid (2,4-D) than with α-naphthaleneacetic acid (NAA). A. spinosus calli were induced in 10 days with Murashige and Skoog medium (MS) + 0.5 mg L-1 BAP + 0.5-1 mg L-1 2,4-D; callus induction took 12.5 days in MS + 1.0 mg L-1 BAP + 0.5 mg L-1 2,4-D in A. tricolor. In both species, BAP treatments caused profuse callus growth, but A. tricolor favored NAA, while A. spinosus was more responsive to 2,4-D. The A. tricolor calli scored with profuse growth also had the greatest mass. For A. spinosus, the calli with the greatest mass formed in MS + 0.5 mg L-1 BAP + 5.0 mg L-1 NAA, but the larger calli formed in BAP + 2,4-D-containing media.