Haploid facultative parthenogenesis in sunflower sexual reproduction

Flowering plant sexual reproduction requires double fertilization, yielding embryo and endosperm seed compartments: the latter supports embryo growth and seed germination. In an experiment to generate haploid embryos through inhibition of pollen phospholipase activity in sunflower (Helianthus annus), we serendipitously discovered that emasculated sunflowers spontaneously form parthenogenic haploid seed. Exploration of genetic, chemical and environmental factors demonstrated that a specific genotype background enabled high parthenogenesis and that full spectrum high-intensity light supplementation boosted parthenogenesis, yielding hundreds of haploid seeds per head. Induction of doubled haploid plants can greatly accelerate plant breeding efficiency; however, despite successful engineering of haploid induction in many crops, few reported systems are commercially scalable¹. Here we report efficient methods of chemical emasculation and genome doubling to produce fertile plants and enable a scalable sunflower doubled haploid system.