2019 ASHS Annual Conference

Gladiolus ×hybridus is iconic cut flower in floriculture, producing a geophytic storage organ (corm) used as means of vegetative propagation. Gladiolus corms have deep dormancy and require a cold treatment to break it before flowering in the subsequent year. Gladiolus breeding is aimed to improve floral traits and disease resistance. However, the life cycle of gladiolus is typically 3-5 years from seed to flower; this long juvenile period slows the rate of progress. Our research aims to reduce juvenility and produce an annualized perennial for seed propagation. More than 20 years of selection for early seed germination and earlier flowering produced a cycle 1 flowering gladiolus which resulted in flowering from seed in the first year. The number of weeks to flower is ≤43 weeks from seed with 1-5 florets/stalk. The objective of this study was to determine the heritability of cycle 1 flowering. Recurrent selection was used for crossing two cycle 1 parents, which significantly increased the ratio of cycle 1 plants from 0.5% to 2.5%. After inbreeding (selfing) the parents, F₂ inbred lines failed to generate cycle 1 flowering inbreds and, instead, flowered later in cycles 2-3. However, inbreds originating from the recurrent selection progeny resulted in 1.47% of inbred cycle 1 plants. Due the precise selection for early seed germination and flowering, several genotypes show a pattern of reduced dormancy. These reduced dormant gladiolus corms were able to flower without a cold treatment, which contradicts the norm for commercial gladiolus production. This indicates that reduced dormancy is vernalization-independent and changes the Mediterranean type gladiolus into a subtropical type. In addition to reducing the juvenile period, cycle 1 gladioli have potential uses in potted plant production, as the plant height of cycle 1 plants is suitable for potted production. Future selection is still ongoing to increase the percentage of cycle 1 gladiolus in inbred and hybrid generations.