Mutagenesis of in vitro material from Pseudotsuga menziesii and obtaining mutant lines

Abstract

Objective: To generate mutant lines of smaller size of Pseudotsuga menziesii, by starting from seminal and vegetative material exposed to different doses of gamma rays.
Design/methodology/approximation: A completely randomized design was used; seeds and embryos isolated from P. menziesii were irradiated with a source of gamma-ray; the LD50 was determined for each tissue type 150 and 18 Gy, respectively. A total of 750 explants were irradiated, their growth was evaluated at 60 days, selecting the individuals that showed a growth reduction greater than 30%. In order to multiply the in vitro lines, the optimal medium recommended for the species was evaluated with the combination of two growth regulators and three concentrations to determine which generated the highest number of shoots per explant. The growth was measured and compared to the control by the Tukey test at a level of 5% confidence.
Results: It was found that the dose of 12 Gy in vegetative tissues propagated in vitro allows to generate mutations that can give rise to mutant lines of interest according to the objective of the selection, which for this study was the reduction of growth; three mutant lines were selected and a means to multiply the generated lines was determined.
Limitations of the study/implications: Genetic improvement programs in forest species should be projected in the long term; mutagenesis is random, in addition to generating chimeras that can make it difficult to fix the selected character. Findings/conclusions: The dose of 12 Gy gave rise to three mutant lines with growth reduction greater than 30% in relation to the control, and the DCR medium BA 0.25 mg L?1+ANA 0.1 mg L?1 allowed generating an average of 9.1 shoots per explant on average at 60 days.