Polyploid Induction for Developing Sterile, Non-Invasive Forms of Nandina

Nandina domestica, a commonly used plant in the landscape, has invaded natural areas in several states in the southeastern United States, including Florida.  Its invasiveness is primarily due to prolific seed production and dispersal by animals through ingesting the berry.  One approach to control the invasiveness of nandina is through ploidy manipulation and selection and use of sterile triploids.  Ploidy analysis indicates that all available nandina cultivars are diploids.  The objective of this study was to induce tetraploids that can be used as parents in inter-ploidy pollination to produce sterile triploids.  When shoot tips were treated with colchicine in vivo, the percentage of new growth containing polyploid cells varied between 0 and 80% among several cultivars.  The majority of the tetraploid cells were eliminated during further growth of the shoots, and only a small percentage (<10%) of the shoots became stable tetraploids due to strong competition between normal diploid and newly induced polyploid cells in nandina.  To lessen diplontic selection and promote tetraploid cells to develop into shoots, treated plants were monitored over time for ploidy level and diploid growth were selectively removed regularly.  When germinating seeds were used in colchicine treatment, 7% to 24% of seedlings contained tetraploid cells, and a higher percentage (54%) of tetraploid-containing seedlings appeared to be stabilized.  So far, a number of tetraploid shoots or seedlings have been obtained.  They are being evaluated for possible changes in morphology.  When coming into flowering, these tetraploids will be crossed with diploids to develop sterile triploid nandina.