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U.S. Department of Agriculture USDA Forest Service Southern Regional Extension Forestry Southern Regional Extension Forestry

Genetic Analysis Of Putatively Apomictic Seed Fromamerican Sycamore

While conducting controlled pollinations of sycamore (Platanus occidentalis L.), it was observed that all six seed trees produced viable seed from the unpollinated flowers used as pollination controls. If the seeds proved to be of apomictic origin, exclusion of pollen would be an efficient means of cloning mature sycamore trees. We identified heterozygous loci in the five seed trees by screening for random amplified polymorphic DNA (RAPDs) markers that segregated in a 3:1 (band present:band absent) ratio in selfed progeny. Any individual seedling, or cohort, of apomictic origin should be band present for all heterozygous loci in the mother tree. We found no evidence for any of the five families of putative apomicts being of only asexual origin. Only five individuals out of 115 putative apomicts had the same RAPD banding patterns as the mother trees. Based on estimated gene frequencies, these five individuals are possibly of asexual origin and warrant further research. On average, these five individuals represent only 0.076% of all seeds (viable and nonviable), and only 4.3% of the viable seeds, from the unpollinated cohorts. The very low percentages of possible apomicts indicate that pollen exclusion is unlikely to be an efficient means of cloning mature sycamore trees. Keywords: Platanus occidentalis L., random amplified polymorphic DNAs, RAPDs, arbitrarily primed PCR, apomixis, clone.


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Author(s): K. Lei, Michael Stine, Samuel B. Land, Jr.

Publication: Tree Improvement and Genetics - Southern Forest Tree Improvement Conference - 1995