Embryo explant influence on callus initiation frequency for loblolly pine

The objective of this study was to compare callus initiation frequency in response to different culture methods of loblolly pine (Pinus taeda) embryo explants. Cones were collected at the end of August and September, 1992, from trees in Arkansas. The seeds were isolated, disinfected in 70% ethanol for 30 s and in 30% Clorox for 15 min, and rinsed in sterilized water. Seed coat was removed, and the embryos were inoculated either attached to or separated from the megagametophytes. The separated megagametophytes were also cultured to test their potential to produce callus. These explants were cultured on half-strength modified MS medium adjusted to pH 5.8 and supplemented with 11 mg/L 2,4-D, 4.5 mg/L kinetin, and 4.5 mg/L BAP. The cultures were maintained in the dark at 20+3°C for 4 weeks, after which callus formation was recorded. Callus initiation frequencies from seeds collected in August and in September, respectively, were 78.3% and 92.5% for embryos, 13.7% and 27.2% for megagametophytes, and 29.9% and 48.6% for embryos attached to the megagametophyte. These differences indicate that callus initiation frequency from isolated embryos was higher than the frequency obtained from the other explants. These results suggest that the presence of megagametophyte tissue may restrict callus initiation from the embryo.

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Author(s): Feng H. Huang, H. Y. Yan, J. M. Al-Khayri, Xin Y. Li

Publication: Tree Improvement and Genetics - Southern Forest Tree Improvement Conference - 1993

Section: Concurrent Session 3: Softwood Propagation