ASHS 2015 Annual Conference

Magnolia sieboldii K. Koch ‘Colossus’(2n=2x=38) is a deciduous shrub or small tree and Magnolia grandiflora L. ‘Kay Parris’(2n = 6x = 114) a densely pyramidal evergreen tree. In May 2013, several controlled crosses were performed between 2 individuals of these species. Seeds were harvested in August 2013 and subjected to a float test to determine viability. Aril tissue was removed from the 25 viable seeds. Following a brief rinse in 10% NaClO, seeds were stratified in slightly moist spaghnum peat for 5 months. Twenty-one seeds had germinated by March 2014 and 9 seedlings survived in early production after transplanting to 1 gallon containers. ISSR markers were used to analyze genetic variations and assessed inheritance of the remained 9 F₁ seedlings. Plants were accessioned and assigned a letter, with A being the most vigorous and H being the least vigorous individuals. A total of 584 bands were generated from 10 primers, in which 463 bands (79.3%) were polymorphic. UPGMA tree revealed that all the seedlings were much closer to their hexaploid pollen parent (M. grandiflora ‘Kay Parris’) and more distant from their diploid seed parent (M. sieboldii ‘Colossus’), supporting early foliage morphology. Seedling C is most similar to the pollen parent, both in regard to foliage proportions, margin undulation, and proximity. Seedling G is unique among the F1, displaying lanceolate leaves. Other seedlings grouped within the tree have slight morphological variations that may be analyzed for correlation to the UPGMA tree as they continue to mature and growth habit variations become evident. Further studies will include verification of the putative 2n=4x=76 ploidy level and selection of the best individuals for future controlled crosses and determination of reproductive fecundity.