In vitro regeneration of Pinus pinaster adult trees

Regeneration of adult conifer trees by means of in vitro culture has been the subject of intense study during the last 20 years. Propagation by tissue culture may become the best method for obtaining multiple identical trees and for capturing the genetic gain in breeding programs. However, the method has several problems related to phase change of trees (juvenile-adult) that limit its practical applications. In this study, shoot buds were collected from 20 maritime pine (Pinus pinaster Ait.) adult trees (> 20ayears old) from November to March. Buds were cut transversely into 0.5-1.0acm slices and cultured on several media (DCR, WP and modified LP) supplemented with cytokinins (6-benzyladenine, metatopolin, or zeatin) at two concentrations (25 or 50a mu mol/L). The highest organogenic response (axillary shoots formation ability) occurred on DCR medium supplemented with 25a mu mol/L zeatin and metatopolin, and 25 or 50a mu mol/L 6-benzyladenine. All shoots that regenerated on DCR medium with 25a mu mol/L 6-benzyladenine developed healthy and well rooted plantlets. The ability to micropropagate adult trees represents a significant progress in the application of biotechnology to forest tree improvement programs, and it opens the possibility of using select trees in agroforestry areas under biotic or abiotic stress.