Relationship between field performance, family, embryo morphology, and isozyme heterozygosity, and in vitro reactivity in jack pine

Abstract

The influence of field performance, family, embryo morphology, and isozyme heterozygosity level on in vitro reactivity of Pinus banksiana Lamb. was evaluated on embryos from five superior families, five inferior families, and a mixed seed lot. Embryo length, number of cotyledons, and isozyme heterozygosity were determined for each embryo. Seed germination and fresh weight were determined on a family level. On average, superior families showed higher percentages of embryos that formed buds in vitro. Within each performance class, the analysis based on initial number of embryos revealed differences among families for the percentage of green embryos and embryos with adventitious buds and shoots. When calculations were based on green embryos only, i.e., excluding embryos that remained white, there were no differences among families. Thus, the overall in vitro potential of a family appears to be strongly dependent upon the capacity of embryos to turn green. On a per family basis, seed germination was positively correlated with most in vitro characters, with the exception of mean shoot length per shoot-forming embryo. Small embryos had a lower probability of producing buds and shoots, and embryos with three cotyledons showed a higher mortality than embryos with four or more cotyledons. No significant relationships were observed between heterozygosity level and in vitro reactivity, with analyses performed on green embryos only.