DNA content polymorphism and tissue culture regeneration in Caribbean pine

Abstract

The three varieties of Caribbean pine have significantly different amounts of nuclear DNA: Pinus caribaea var. caribaea, 11.5; P. caribaea var. hondurensis, 21; and, P. caribaea var. bahamensis, 25 pg. Dormant embryos of the three varieties had more nuclear DNA than germinating seedlings, and this extra DNA was spread through several classes from 2C to 7C; however, upon germination the seedling DNA rapidly reorganizes into the 2C–4C distribution typical of diploid plants. DNA content polymorphism of the dormant embryos among the three varieties was directly correlated with the diploid amount of DNA and with needle and cotyledon diversity. Buds regenerated from dormant embryo explants in tissue culture were genetically stable; however, the roots of regenerated plants had DNA contents ranging up to nine times the haploid amount. The instability is ascribed to the auxin content of the rooting medium, but buds regenerated or growing on this medium were stable. This bud stability and the production of buds on needle explants from 13-month-old regenerated seedlings are positive indicators for Caribbean pine biotechnology.