1 Southern Horticultural Laboratory, Agricultural Research Service, United States Department of Agriculture, P.O. Box 287, 810 Hwy 26 West, Poplarville, MS 39470
| 2 Floral and Nursery Plants Research Unit, U.S. National Arboretum, Agricultural Research Service, U.S. Department of Agriculture, Tennessee State University Otis L. Floyd Nursery Research Center, 472 Cadillac Lane, McMinnville, TN 37110
| 3 Floral and Nursery Plants Research Unit, U.S. National Arboretum, Agricultural Research Service, U.S. Department of Agriculture, 3501 New York Avenue, NE, Washington, DC 20002
Crapemyrtle (L. indica and L. indica × L. fauriei hybrids) is one of the most popular flowering landscape plants in the U.S. Although many cultivars have been developed through breeding efforts, little has been published on the reproductive biology of the genus. The objective of this study was to evaluate barriers to successful self-seed production in crapemyrtle. Self-compatibility was assessed by comparing pollen tube growth, fruit and seed production, and seed germination following controlled self- and cross-pollinations. Observations of pollen tube growth at intervals up to 24 hours after self- and cross-pollination indicated no barriers to self-fertilization acting at the stigmatic or stylar level in L. indica, L. fauriei or cultivars derived from inter-specific hybrids of these two species. Self-pollinations of `Catawba', `Whit IV', `Tonto' and `Tuscarora' had lower percent seed pod set and seed germination than did cross-pollinations of these cultivars. The number of seeds per pod was lower when `Catawba', `Whit IV' and `Tuscarora' were self-rather than cross-pollinated, but no difference between `Tonto' self- and cross-pollinations was observed. When decreased pod set is combined with much lower seed germination for self-pollinations, selfing of crapemyrtle is extremely unproductive when compared to cross-pollination. A late-acting self-incompatibility system or inbreeding depression is indicated for L. indica and inter-specific crosses with L. fauriei.