Rapid generation cycling enhances selection rate of gladiolus ×hybridus

Geophytic floricultural crops, i.e., those with underground storage organs, are primarily vegetatively (asexually) propagated. During breeding, domestication, and continued crop improvement, sexual cycles are neceßary to study trait inheritance and select new genetic variation. The University of Minnesota Flower Breeding and Genetic program is breeding new phenotypes of Gladiolus, a cut flower and garden crop with corms. Typical generation cycles from seed to flower take 3-5 years. Our objectives were to create a rapid generation cycling proceß to select early flowering seedlings and enhance the rate of genetic improvement. Techniques under evaluation include germination (week) in the plug phase and correlation with flowering date, fast cycling of generations (2-3/year), along with selection of high leaf number and early stem stalk emergence in cycles 1-3. A total of 71 croßes and N=1,026 seedlings were evaluated in this study. Seedlings germinated primarily in weeks 2-4 after sowing although some croßes took until week 7. All seedlings had one leaf/plant in cycle 1; whereas in cycle 2, leaf counts ranged from one to seven. By cycle 2, 6% of the seedlings (primarily from six croßes) also had elongated stems with 1-4 leaves/stem. Stem elongation in cycle 2 is a highly heritable trait. Cycle 3 plants with elongated stems flowered, reducing generation time as much as 1-2 cycles. As many as three cycles (generations)/year could be accomplished consisting of reduced greenhouse growth, dry down and cold storage treatments.