MULTIPLE PATERNAL GENOTYPES IN EMBRYOGENIC TISSUE DERIVED FROM INDIVIDUAL IMMATURE LOBLOLLY-PINE SEEDS

Pine embryogenic tissue derived from immature zygotic embryos may consist of multiple genotypes due to simple polyembryony. To test this hypothesis, megagametophytes with intact zygotic embryos were cultured from immature loblolly pine (Pinus taeda L.) seeds of clone WV42 control pollinated with a 1:1:1 pollen mix of clones WV44, WV47, and WV48. Each pollen parent contained a marker allele at one or more of the following loci: aconitase, malic dehydrogenase, 6-phosphogluconate dehydrogenase, and shikimate dehydrogenase, allowing determination of the paternal parent. After two to four weeks in culture, embryogenic tissue derived from zygotic embryos extruded from megagametophytes was separated into individual embryos and sectors of embryogenic tissue. The paternal genotype of each resulting cell line was determined by starch gel electrophoresis. Three of thirty-six explants produced multiple cell lines with genotypic differences among the cell lines within each explant. Our results unequivocally show that it is possible to initiate embryogenic tissue from more than one zygotic embryo of a loblolly pine seed and that the resulting cell lines may be genetically different.