Making copies apomictic would permit development of superior-yielding apomictic hybrids that perpetuate hybrid vigor across seed generations. New evidence indicates that apomixis (asexual seed formation) is an intermediate hybrid phenotype and is polygenically controlled. Hence, interspecific introgression approaches mat face previously unforseen difficulties. The goals of this project are to elucidate the polygenic parental components of apomixis in sorghum. Apomixis has arisen several times in sorghum through the hybridization of ecotypically diverse lines. We propose to characterize variability in ovule development among sexual lines that have previously produced apomicts and correlate this reproduction variability with reproductive anomalies in hybrids produced from the divergent lines. Standard cytological procedures will be used to compare stages of megasporogenesis and embryo sac development with corresponding stages of ovule growth among diploids. Hybrids, involving parents with distinctly-different photothermal requirements and schedules of ovule development will be made and analyzed for apomixis and other anomalies. A successful demonstration of the cases of apomixis, through Phase I funding, will allow us to confer apomixis to at least some crops by selecting (or breeding) appropriate polygenic parental phenotypes followed by hybridization. Stabilizing and controlling the apomixis will require additional manipulations.
Anticipated Results/Potential Commercial Applications of Research: The primary goal of this proposal is to develop a model system composed of sexual parents and apomictic hybrids. With adequate funding, this goal should be readily obtained. It has occurred repeatedly in nature and in the plant breeding programs, including sorghum. F1 Technologies need only conduct similar experiments to validate these several findings and to further elucidate the underlying mechanisms. Once a model system is in place, we foresee no serious obstacles to precisely characterize parental traits responsible for apomixis. Introducing apomixis into sexual crops and being able to manipulate it will provide revolutionary opportunities for commercialization and crop improvement.
