ASHS 2024 Conference

Invasive ornamental plants have been considered as a major contributor to the spread of invasive plant species in the United States and many other countries in the world. To mitigate the economic and ecological impacts of invasive ornamental plants, we have focused on genetic sterilization of four invasive ornamental plants that are commonly produced and widely used in Florida to develop sterile, triploid cultivars as alternatives to the invasive types. Toward this goal, we have made progress in (1) artificial induction of tetraploids in nandina, privet, and porterweed, 2) developing and releasing new sterile, non-invasive triploid lantana cultivars, 3) understanding the reproductive biology of lantana, 4) developing and applying new genomic and molecular tools, and 5) testing alternative breeding approaches. By applying the mitotic inhibitor agent colchicine to germinating seeds or seedlings, we have induced tetraploids in nandina, privet, and porterweed. Tetraploid nandina showed significantly reduction in pollen stainability and seed set. Tetraploid privet lines exhibited thicker leaves with darker green color. Induced tetraploid nandina, porterweed, and privet lines have come into flowering, and interploidy crosses are made to produce new triploids. Using existing tetraploids in lantana, we have generated hundreds of new triploids, evaluated their male and female sterility, and released five sterile, non-invasive triploid cultivars, three of which have become popular replacements of the invasive types. Ploidy and molecular marker analyses have revealed the production of unreduced female gametes and apomictic seeds in lantana and natural sexual polyploidization in lantana and several other lantana species. Genome and transcriptome analyses have uncovered candidate genes that are linked or directly involved in the production of unreduced female gametes in Lantana. A number of diploid and tetraploid lantana genotypes with male or female sterility have been identified, which are being used to generate new triploids through open pollination. Additional tools are needed to rescue triploid embryos and screen breeding populations for high female sterility. These new plant materials, genetic and genomic resources, and molecular tools are expected to facilitate the genetic sterilization of lantana, nandina, porterweed, and privet. The findings may guide similar genetic sterilization efforts in other invasive ornamental plants.