Gladiolus breeding for rapid generation cycling for potted plant production and the discovery of gladiolus genes, UPSTREAM OF FLOWERING LOCUS C (UFC) and FLOWERING LOCUS C EXPRESSOR (FLX)

Abstract

Gladiolus (Gladiolus ×hybridus Rodigas) is a geophytic floriculture crop, cultivated for cut flower and garden ornamental uses. It is a perennial crop and is characterized to have a long juvenile period of up to 5 years, with tall plant height which is undesirable for potted production and poorly understood in flowering pathway. In this research, the constant selection in gladiolus breeding at the University of Minnesota for rapid generation cycling (RGC) resulted in reducing the juvenility time from 3 – 5 years into a range of 3 – 11 months from germinating seedlings, recurrent selection breeding method was significantly early in flowering time (21.63 weeks). Also, our gladiolus genotypes have reduced dormancy, are able to re-sprout after senescence, which is a new trait in gladiolus. These traits in RGC genotypes were tested further with the application of ancymidol, a gibberellin inhibitor to control height in potted plants. The high concentrations of ancymidol can inhibit flowering for commercial cultivars. However, the RGC lines had significant reductions in plant height to a more acceptable plant size within the aesthetic ratio and the ability to flower while commercial cultivar comparisons failed to flower at higher concentrations of ancymidol. All this knowledge drove us to test for the existence of flowering genes in gladiolus. Herein we were able to discover the existence of UPSTREAM OF FLOWERING LOCUS C (UFC) and FLOWERING LOCUS C EXPRESSOR (FLX) in gladiolus. UFC is an adjacent gene to FLOWERING LOCUS C (FLC), the floral repressor in Arabidopsis thaliana, while FLX gene upregulates FRIGIDA (FRI) which upregulates FLC expression. The amino acid sequence of UFC has up to 57% identity to Musa acuminata. The discovered FLX gene in gladiolus is partially completed which is missing 2 exons and shows up ~65% of identity of FLX to Ananas comosus. These two, newly discovered genes in gladiolus, can provide better understanding of the flowering and vernalization response in ornamental geophytes and begin clarification of the effects of breeding for RGC on flowering genes / alleles as well as the application of plant growth retardants for production of dwarf gladiolus for potted plant production