INBREEDING DEPRESSION IN SEED-PROPAGATED LILIUM X-FORMOLONGI INBREDS

Lilium longiflorum, Easter lily, remains among the top ten potted flowering plants in the United States. L. formosanum is a closely related white trumpet lily. Currently one Easter lily cultivar predominates in the U.S. market, ‘Nellie White’. In an effort to increase the crop germplasm base, interspecific hybrids were generated. Commercial, interspecific seed-propagated hybrids, from crossing L. formosanum (female) x L. longiflorum (male), were used in this study. Hybrids segregated for self incompatibility (SI) and self compatibility (SC). SC hybrids were self pollinated to generate 11 F₂ inbred populations (N=151). F₂ seedlings were grown to anthesis under glasshouse conditions of 21°C and long day photoperiods. Data were collected on % pollen stainability, no. days to visible bud, no. days to anthesis (flowering date), plant height, inflorescence length, no. of leaves, internode length, flower bud count, no. of shoots/bulb, stem color, and any morphological abnormalities. A single, dominant gene may control SC. Pollen stainability was significantly lower than the parents in two inbred families, but not significantly different in all others. The no. of days to visible bud ranged from 175 to 253 days, while flowering ranged from 196 to 283 days. All other traits showed significant inbreeding depression and varied depending on the inbred population. Additional abnormal symptoms indicating inbreeding repression included malformed flowers with petals/tepals becoming leaves, lack of anthers or pollen dehiscence. While inbreeding depression is severe, several early flowering inbreds with reduced depression could be selected to continue inbreeding in future generations.

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